Selina Concise Biology Class 8 ICSE Solutions – Ecosystems

Selina Concise Biology Class 8 ICSE Solutions – Ecosystems

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 4 Ecosystems. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 4 Ecosystems

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

a. The term “ecosystem” is derived from the Greek word “Oikos” meaning.

  1. Body weight
  2. Food
  3. House
  4. Size

b. Rat in any food chain would occupy the position of

  1. Tertiary consumer
  2. Secondary consumer
  3. Primary consumer
  4. Producer

c. Evergreen broad-leaved trees are characteristic of

  1. Tropical rain forests
  2. Temperate deciduous forests
  3. Coniferous forests
  4. All of the above types of forests.

Short Answer Type:

1. Mention if the following statements are true (T) or false (F).
(a) Snakes are primary consumers (T/F)
(b) Some humans are strictly primary consumers & some others are of other types of consumers also (T/F)
(c) No ecosystem can survive without light (T/F)
(d) Cattle go to ponds for drinking water, so they are a constituent of pond ecosystem (T/F)

Answer:

(a) Snakes are primary consumers (F)
No the snakes are not primary consumers as snakes eat rats and frogs as these are primary consumers which eat plant products. As snakes eat the primary consumers so the snakes are secondary consumers.

(b) Some humans are strictly primary consumers and some others are of other types of consumers also (T)
It is true that humans are vegetarians and eat plants or plant products. So these humans are vegetariBut there are certain humans which eat the flesh or eggs of other animals. These are carnivores and humans living plants are called Herbivores.

(c) No ecosystem can survive without light (T)
The plants and animals and micro-organisms present at a place and interacting with the atmosphere like sun light, air, water, soil and warmth and dwelling at a place like, pond, desert, forest, rock form the ecosystem as pond ecosystem, desert ecosystem forest ecosystem. So ecosystem cannot survive without the presence of light. As the flora (plants) living in that ecosystem can only make food in the presence of light and the animals (Fauna) living in that ecosystem get the food from the plants of that ecosystem. So flora in that area cannot survive in that area without light and animals living in that area will not get the food and the plants and animals will perish and the ecosystem cannot survive.

(d) Cattle go to ponds for drinking water, so they are a constituent of pond ecosystem (F)
Cattles likes tigers, lions, cows, deers, buffaloes, go to take water from the pond and return to their dwellings as tigers, deers etc. come to the forest so they form a forest ecosystem. But plants like hydrilla, vallineria, lotus etc. and animals like frogs, beetles, fish live in the pond and form the pond ecosystem. But animals like buffalo which come only to take~water cannot form a part of the pond ecosystem.

2. Match the items in Column I with as many items as possible in Column II.
Selina Concise Biology Class 8 ICSE Solutions – Ecosystems 1
Selina Concise Biology Class 8 ICSE Solutions – Ecosystems 2
Answer:

Selina Concise Biology Class 8 ICSE Solutions – Ecosystems 3
3. Rewrite the following in their correct sequence in a food chain:
(a) Snake → Grasshopper → Grass → Frog
(b) Grass → Tiger → Deer
(c) Snake → Peacock → Rat → Wheat

Answer:

(a) Grass → Grasshopper → Frog → Snake
(b) Grass → Deer → Tiger
(c) Wheat → Rat → Snake → Peacock

Long Answer Type:

Question 1.
Differentiate among primary, secondary and tertiary consumers. Give one example of each in a food chain.
Answer:
All plants produce food through photosynthesis and are categorised as self food producers i.e. these are autotrophs. There are plant eating animals called herbivores as Rabbits, deers, pigeons, cows, buffaloes etc. and insects like grasshoppers, bees, butterflies and crickets also eat plants or plant products as fruits, flowers, pollen grains and plant juices. Such animals are called primary consumers.
Animals like tigers, lions, wolves, lizards, frogs eat the primary consumers. Birds vultures, kites, eagles eat the primary consumer, (i.e. These birds are well eat the flesh of many birds like pigeons, sparrows.) These animals or birds are called secondary consumers.
Animals like snakes are eaten by the peacocks, they eat the secondary consumers and are called tertiary consumers.
Owls, eagle are top carnivore. So it is quaternary consumer.

Question 2.
Define the term (a) flora and (b) fauna.
Answer:
Flora: Plants occurring in a particular is called flora of that area i.e. vegetative growth forms flora. Flora deals with plants.
Fauna: The animals occurring in a area form the fauna of that area. Fauna deals with animals.
Flora and fauna of an area is the plants and animals found in that area.

Question 3.
List any three members each of the flora and fauna of tropical rain forests.
Answer:
Tropical rain forest are on western coast of India and in the north, east.
Flora: bamboos, ferns, shrubs (Evergreen trees).
Fauna: leopards, jungle cats, monkeys, snakes, flying squirrels, insects, snails, centipedes, millipedes.

Question 4.
Define the following terms and give two examples in each case.
(a) Symbiosis
(b) Parasitism
(c) Predation
Answer:
(a) Symbiosis: It refers to relationships between organisms of different species that show on intimate association with each other. Symbiotic relationships provide atleast one of the participating species with a nutritional advantage.
Examples of Symbiosis Relationships are of Fungus and photosynthestic alga and Microbes and cattle.

(b) Parasitism: Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Examples of Parasitism are 4 tapeworms, flukes, the plasmodium species and mosquitoes.

(c) Predation: A predator is any consumer that kills and eats another living organism in order to obtain energy. The organism being eaten is called the prey.
Examples are Lions, Deer, Wolves, Eagles.

Selina Concise Biology Class 8 ICSE Solutions – Food Production

Selina Concise Biology Class 8 ICSE Solutions – Food Production

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 9 Food Production. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 9 Food Production

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(i) Which one of the following is an indigenous breed of dairy cows ?

  1. Jersey
  2. Frieswal
  3. Sahiwal
  4. Dangi

(ii) Which one of the following is the common breed of buffalo found in Gujarat ?

  1. Surti
  2. Murrah
  3. Gir
  4. Mehsana

(iii) Identify the indigenous breed of poultry of India:

  1. White leghorn
  2. HH-260
  3. Aseel
  4. B-77

(iv) Which one of the following is a rabi crop

  1. Mustard
  2. Pea
  3. Rice
  4. Wheat

(v) Identify the Kharif crop:

  1. Barley
  2. Mustard
  3. Rice
  4. Wheat

(vi) One of the following is a bacterial disease of sheep and goat. Identify it.

  1. Sore mouth
  2. Rinderpest
  3. Goat pox
  4. Brucellosis

(vii) Which one of the following is a bacterial disease of cattle in which the animal gets swelling on body parts, especially on the neck ?

  1. Cow pox
  2. Anthrax
  3. Salmonellosis
  4. Rinderpest

(viii) The plants that live for more than two years are called:

  1. Annuals
  2. Perennials
  3. Biennials
  4. Triennials

(ix) Which one of the following is a viral disease of poultry?

  1. Ranikhet disease
  2. Cholera
  3. Coryze
  4. Aspergillosis

Short Answer Questions:

1. Fill in the blanks:

  1. Cattle feed made from cereals and wheat is called concentrates.
  2. Rearing of birds for egg and meat is called poultry.
  3. Animal food is rich in proteins.

2. Name the following:

  1. The popular indigienous breed of poultry of India …..
  2. Rearing of honey bee …..
  3. Architect of white revolution in India …..
  4. A kashmiri goat which gives expensive wool ….
  5. Scientist responsible for green revolution in India ……

Answer:

  1. The popular indigienous breed of poultry of India Aseel.
  2. Rearing of honey bee is called apiculture.
  3. Architect of white revolution in India Mr. Verghese Kurien.
  4. A kashmiri goat which gives expensive wool kashmiri pashmina.
  5. Scientist responsible for green revolution in India M.S. Swaminathan.

3. Match the columns

Selina Concise Biology Class 8 ICSE Solutions - Food Production 1

Answer:

Selina Concise Biology Class 8 ICSE Solutions - Food Production 2

4. Answer the following questions:

Question 1.
Name any four animals which provide us food.
Answer:
Buffalo, goat, pig, hen, fish give us food.

Question 2.
Name any two dual purpose breeds of cattle.
Answer:
Dangi and Tharparkar are dual purpose breeds of cattle.

Question 3.
Give two examples of milch animals.
Answer:
Cows, buffaloes, goat are milk yielding animals.

Question 4.
Name any two high-yielding indigenous breeds of cow.
Answer:
Gir, Sahiwal, Red sindhi are high yielding breeds of cow.

Question 5.
Name four varieties of edible fishes of India.
Answer:
Eel, Hilsa, Salmon, Sardine, Pomphret are edible fishes.

Question 6.
Name two breeds of buffaloes.
Answer:
Murrah, surti, mehsana are breeds of buffaloes.

Question 7.
Name any two diseases of cattle caused by viruses.
Answer:
Cow pox, foot and mouth disease.

Question 8.
Name any two bacterial iiseases of cattle.
Answer:
Anthrax and rinderpest are bacterial diseases of cattle.

Question 9.
What are the symptoms of foot and mouth disease ?
Answer:
Blisters on the foot and mouth, high body temperature, reduced appetite are symptoms of foot and mouth disease.

Question 10.
Name two bacterial diseases of poultry.
Answer:
Fowl cholera, salmonellosis, coryze are bacterial diseases.

5. Briefly explain the following terms:
Answer:

  1. Animal husbandry: The branch of Biology which deals with feeding, shelter, caring and breeding of domesticated animals is called animal husbandry.
  2. Sericulture: Artificial rearing of silk worm and getting of silk from the silk worms is called sericulture.
  3. Aquaculture: The production and farming of aquatic animals as fishes, prawns, shrimps, molluscs, lobsters etc. is called aquaculture.
  4. Hatcheries: We raise small nurseries where water is stored in small pits where we put fish seeds (fish eggs). From these fish eggs very small fish come out after hatching. Then these small fish are transferred to big ponds. These small nurseries where eggs hatch to give small fish are called hatcheries.
  5. Pisciculture: It deals with production and management of fishes. It is a scientific, systematic way of raising of fishes, their multiplication, their production and management. So it is used as food in a sensible way.

6. What is organic farming?
Answer:

Organic farming is the practice of raising crops without using inorganic fertilisers and pesticides. Farmers use organic manure that has been prepared scientifically. In order to maintain soil fertility, and for weed and pest control, they use a combination of crop rotation, hand weeding, mixed cropping and biological control.

Long Answer Questions:

Question 1.
Differentiate between an egger and a broiler.
Answer:
Following are the differences between the egger and the broiler:
Egger

  1. Egg laying chickens are called eggers or egg layers.
  2. The chicks are given calcium (bones, seeds) and are reared to produce eggs.
  3. Eggers should give large number of eggs as white leghorns give many eggs. Rhode island red breeds like HH-260, IBL-80, B-77.

Broiler

  1. Chickens which give us meat are called broilers.
  2. Those chicks are reared on a diet of fats so that they gain flesh on their body and these are used as broilers.
  3. Broilers should give flesh. Indigenous variety Aseel give high yield of meat and less number of eggs.

Question 2.
Name any two exotic breeds of fowl in India, and mention their usefulness
Answer:
Exotic breeds of fowl in India are as:

  1. White leghorn: Its size is small and needs less feed for maintenance. So to raise it is economical. It lays oval white eggs.
  2. Rhode island red: It serves both the purposes as it is a good egg layer and also provide enough of meat. It was raised on a farm in Rhode island of U.S.A. So it is named as Rhode island red.

Selina Concise Biology Class 8 ICSE Solutions - Food Production 3

Question 3.
What are “milch animals”? Give three examples of exotic breeds of cow.
Answer:
Milk-producing animals are known as “milch animals” e.g. cows, buffaloes, goats and camels. The milk from goats is nutritious and is sometimes preferred to cow milk. But the production of goat milk is much less than that of cows and buffaloes. Cow milk is quite nourishing and easy to digest, but as compared to buffaloes, cows produce less quantity of milk. Buffaloes are the major source of milk in our country.
Exotic (Foreign) breeds. For example. Jersey, Holstein- Friesian, and Brown Swiss.

Question 4.
What is the meaning of the term “aquaculture”? Name any three animals which can be cultured by this method.
Answer:
The term “aquaculture” is used for production or farming of useful aquatic animals in various types of water bodies. The animals which can be cultured by this method are: fish, prawns, lobsters, molluscous, etc.

Question 5.
Differentiate between food crops and cash crops and give two examples of each:
Answer:
Differences:
Food crops

  1. These are crops which are grown for food such as cereals: wheat, rice, maize, pulses, oil seeds.
  2. These grow in the plains generally.
  3. These are annuals and complete their cycle in one season as in case of wheat, rice maize, gram, beans, peas.

Cash crops

  1. These are crops which are cultivated for commercial purposes such as tea, coffee, rubber, coconut, spices.
  2. These grow in the hilly areas on the slopes as water of rain should not stand in the roots as in case of tea.
  3. These plants are perennials. These plants live for more than two years. Tea, coffee require pruning before winter.

Question 6.
What are Kharif crops ? Give the name of the most important cereal plant of such crops. Briefly describe any three methods for cultivation of Kharif crops.
Answer:
Kharif crops generally grow in rainy season. Rice is the most important cereal Kharif crop growing in India. It occupies the largest area in India. It needs rainfall from 150 to 200 cms. It requires flooded fields during its growth. It requires alluvial loamy soil.

Cultivation methods of Kharif crops:

  1. Broadcasting: After preparing the fields for growing the rice crop the seeds are thrown in the fields. This method is adopted in the areas where there is less of rain. The fields are not flooded with water. This method is being adopted in China and Japan.
  2. Dibbling: In this method seeds are dropped at regular interval in the furrows made by the plough.
  3. Transplantation: Here the seeds are soaked for 24 hours. The seeds get sprouted. Then these seeds are transferred to nurseries. Here the seeds grow and attain a height of 6” to 9” and then these seedlings are transferred to specially prepared flooded fields which have been properly ploughed. Then those seedlings start growing in the fields. Then the fields are watered and manured from time to time. Then the crop matures and ultimately for ripening they require a temperature ranging from 16°C to 20°C. When the crop become fully ripe and plants become golden yellowish, then the crop is harvested manually or with the help of combines.

Question 7.
Name the two main crop seasons of India. Give three examples of the crops grown during each season.
Answer:
The two main crops seasons in India are:

  1. Kharif season: The rainy season is from July to October and is known as the Kharif Season. The chief kharif crops are the milles, known as Bajra and Jowar, Paddy, Maize, Cotton.
  2. Rabi season: The winter season is from November to April and is known as rabi season. Wheat, Gram, Peas, Linseed and Mustard are important rabi crops.

Question 8.
List the uses of bacteria in the food industry.
Answer:
The bacterial action is involved in the following industrial processes.

  1. In the manufacture of vinegar, butter and cheese.
  2. The process of tanning hides in leather making and preparing sponges.
  3. The separation of flax and hemp fibres which are used for making linen cloth and ropes.
  4. Fermentation of green plants for the production of ensilage for animal food.
  5. Bacteria are used for forming lactic acid, vinegar, citric acid, and vitamins.
  6. For formation of antibiotics, serums and vaccines, vitamin B complex.

Question 9.
Name any one variety of edible mushrooms.
Answer:
White button mushroom (Agaricus bisporous) and paddy straw mushroom (Volvariella) the two varieties of edible mushrooms.
Five major steps in cultivation of the common edible mushroom are as below:

  1. Composting: The compost is prepared by mixing the following in certain proportions.
    • Wheat or paddy straw,
    • Chicken manure
    • Some organic and inorganic fertilizer
      This compost is kept at about 50°C for a week.
  2. Spawning: “mushroom seed” consisting of mycelium of the selected type of mushroom is introduced into the compost, and allowed to spread for a couple of days.
  3. Casting: A thin layer of soil is spread over the compost to give support to the mushroom and provide humidity. It also prevents quick drying of the compost and helps to regulate temperature.
  4. Cropping and Harvesting: The growth occurs in three stages:
    (a) Mycelium (a network of fibrous mass) grows within 2 to 6 weeks.
    (b) Tiny pin heads.
    (c) Button stage which grows bigger attaining marketable size.
    The full grown mushrooms are taken out.
  5. Preservation: Mushrooms are highly perishable. Their shelf life is increased by a variety of processes
    (a) Vacuum cooling
    (b) Giving gamma radiation and storing at 15°C
    (c) Freeze drying in a solution of citric acid, ascorbic acid and brine, etc.

Question 10.
Mention the benefits of “Green revolution” in our country.
Answer:
Green revolution: Knowledge of science has brought about manifold increase in the production of grains, pulses and other crops and led to green revolution. Factors leading to it are:

  1. development of high – yielding varities.
  2. development of early – maturing varities.
  3. disease – resistant varities.
  4. using of fertilizers and pesticides.
  5. development of drought – resistant and dwarf varities.

Dr. M.S. Swaminathan is known as the father of green revolution in India which has led to manifold increase in the production of wheat and rice using hybrid varities (wheat – Kalyan Sona and Sonalika, Rice – IR – 8 Padma, Jaya and Pusa 215, Maize – Ganga 101 and Rankit).

Question 11.
Mention the benefits of “White revolution” in our country.
Answer:
The benefits of “White Revolution” in our country:

  1. The purpose of this programme was to link the rural producer (dairy farmer) with the urban consumer.
  2. Rural farmer co-operatives were organized at the village level and connected to the urban consumer.
  3. It ensured that the dairy farmer got a major share of the price of milk which consumers pay.

The “Operation flood” ensured thre objectives:

  1. increased milk production
  2. strengthened the dairy farmer’s income.
  3. easy availability of milk at a fair price to all.

Question 12.
Write briefly the processes of

  1. wine (alcohol) making and
  2. bread making.

Answer:

The steps for making

  1. Wine (alcohol): Wine is usually made from grapes. The grapes are crushed and the juice is extracted. The juice contains sugar and wild yeast.The yeast ferments the sugar and gradually turns it into alcohol.
  2. Bread: Mix some flour and water with a small amount of sugar and yeast. This makes dough. Then leave the dough for an hour or so in a warm place. During this period the living yeast cells multiply and fermenting sugar to form alcohol give off carbon dioxide gas. The gas so produced makes the dough rise, more or less doubling its size. Then when you bake the dough in a hot oven: the heat kills the yeast and evaporates the alcohol.

Question 13.
Give any five features of good shelter for milch animals.
Answer:

  1. Animal shelter should be very clean, well ventilated and well-lit.
  2. Cattle should have proper sheds, so that animals are safe from rain, cold and heat.
  3. The floor should have a proper sloping so that urine and excreta can be disposed of easily.
  4. Animals should have proper feeding and drinking tubs.
  5. Animal shelter should be spacious and there should not be over crowding.
  6. It should have arrangements for clean fresh drinking water.
  7. The shelter should give protection from predators.
  8. Shelter should be located away from the residential areas and waste disposal sites.

Question 14.
What type of food you would suggest for cattle in order to get good quality of milk ?
Answer:s
Cattle should be given good quality type of food which is proper for their growth, development, health and for their maintenance. Animal food is feed.
This cattle feed has two types of substances.

  1. Roughage: The animals get roughage from hay (straw of cereals), berseem, cowpea, lucerne, silage, maize, bajra and other green plants.
    These plants generally provide fibrous substances and other minerals.
  2. Concentrates: These are rich in carbohydrates, proteins, fats, minerals, and vitamins, concentrates are given by.
    • Grains and seeds of bajra, maize, rye, gram, cotton, jowar, barley. These provide carbohydrates.
      Legume seeds and cotton seeds provide proteins and fats.
    • Oil cakes: These oil cakes are very good feed for the animals. These are formed from the remains of oil seeds after we get the oil from the seeds. We get oil cakes from the seeds of cotton, mustard.
    • Molasses are rich in proteins.
    • Wheat bran, rice bran, and gram bran also give concentrates.

Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Humans

Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Humans

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 3 Reproduction in Humans. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 3 Reproduction in Humans

REVIEW QUESTION

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) The testes are located within the:

  1. Penis
  2. Scrotum
  3. Ureter
  4. Urinary bladder

(b) Amoeba is most commonly reproduced by:

  1. Budding
  2. Regeneration
  3. Binary fission
  4. Multiple fission

(c) Identify the stage which is formed after the fertilisation of the egg by the sperm?

  1. Ovule
  2. Foetus
  3. Embryo
  4. Zygote

(d) Internally, the uterus opens into:

  1. Urethra
  2. Vagina
  3. Oviduct
  4. Vulva

(e) Which one of the following represents the correct sequence in the life history of a butterfly ?

  1. Egg → Larva → Adult → Pupa
  2. Egg → Pupa → Adult → Larva
  3. Egg → Larva → Pupa → Adult
  4. Egg → Pupa → Larva → Adult

Short Answer Questions:

Question 1.
Distinguish between the following pair of terms:
(a) Egg and sperm.
(b) Sexual reproduction and asexual reproduction.
(c) Budding and Regeneration.
Answer:
(a) Egg and sperm
Egg Sperm

  1. Egg is produced in the ovaries.
  2. Egg is spherical in shape with a nucleus.

Sperm

  1. Sperm is produced in the testes.
  2. Sperm has head with nucleus, middle piece and tail.

(b) Sexual reproduction and asexual reproduction.

Sexual reproduction

  1. In sexual reproduction the two sexes i.e., male and female produce special type of reproductive cells sperms in the male and eggs in the female.
  2. To produce a new individual the sperm has to reach the ovum and fuse with it. e.g. Humans, bird, reptile, etc.

Asexual reproduction:

  1. It involves the production of an offspring from a single parent without the fusion of reproductive cells (gametes).
  2. It is a rapid mode of multiplication, e.g. Lower plants and animals {Amoeba).

(c) Budding and Regeneration

Budding: Budding is a process in which buds grow on the outside of the parent body. The buds detach themselves when they are large enough.
Example: Hydra
Regeneration: Regeneration is the process that uses cell division to regrow lost body parts.
Example: Starfish, sponges

Question 2.
Define the following terms:
(a) Fetilization
(b) Implantation
(c) Puberty
Answer:
(a) Fetilization: When sperms and eggs from the opposite partners (males and females) fuse to form Zygote. It is called fertilization.
(b) Implantation: The fertilised egg (zygote) soon starts developing and by the time it reaches the uterus, a small ball of numerous cells is already formed. This is a kind of embryo which forms a pit in the wall of the uterus and gets fixed in it. This natural way of fixing of the embryo in the wall of the uterus is called implantation. This produces the state of pregnancy.
(c) Puberty: Puberty is the period during which the reproductive systems of boys and girls mature. In girls, it starts at the age of about ten and the first sign of puberty is the development of breasts. In boys, it starts at about 11 years of age of the^enlargement of the testes is its first sign. Sudden spurt in growth, shoulder girdle grows more than hip girdle.

Question 3.
State the reason why testes lie outside the abdomen in a scrotum?
Answer:
Both the testes remain in the scrotum because normal body temperature are to high, scrotum has smooth muscle tissues that keeps the testes at a cooler temperature than the body temperature 2°C to 3°C lower than the body temperature which is the most suitable temperature for sperm production.

Question 4.
Why is it important that a very large number of sperms should be present in the semen ?
Answer:
Single ejaculation of semen has 20,000,000 to 40,000,000 sperms. But only 1 or 2 sperms go into oviduct and fertilise the egg to form the Zygote. It forms embryo that forms an individual. It is the sperm in the semen that are of importance, and therefore semen quality involves both sperm quantity and quality.

Question 5.
List the structures, in their correct sequence, through which the sperms must pass from the time they are produced in the testes to the time they leave the urethra.
Answer:
Sperms are produced in testes. They pass as follows:
The testes consist of a mass of sperm producing tube. The tubes join to form ducts leading to the epididymis which in.turn leads into a muscular sperm duct. The two sperm ducts, one from each testes, open at the top of the urethra.

Question 6.
State the functions of the following:
(a) Ovary
(b) Testes
(c) Fallopian tubes
(d) Seminal vesicle
(e) Uterus
Answer:
(a) Ovary: Ovaries produce ova (eggs) and secrete female sex hormones, oestrogen and progestrone.
(b) Testes: A pair of testes are present in human male. The testes produce sperms.
(c) Fallopian tubes: There are two fallopian tubes in the human female reproductive system. Fertilization occurs in the fallopian tube. It also conveys fertilized egg to the uterus.
(d) Seminal vesicle: The function of seminal vesicle is to store sperms and to secrete seminal fluid.
(e) Uterus: The inner lining recieves, protects and nourishes embryo. Contractions of muscular wall expel baby during birth.

Question 7.
Given here is a section of the female reproductive system of human beings.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 1
(a) Name the parts labelled 1 to 4
(b) Name the part where fertilisation occurs in human beings.
Answer:
(a)

  1. Ovary
  2. Fallopian tube (Oviduct)
  3. Uterus (Inner lining or Muscular wall)
  4. Vagina

(b) Fertilisation occurs in the upper part of the oviduct. Sperm fuses withthe egg and zygote is formed this is called fertilisation.

Question 8.
Given alongside is a diagram of male reproductive system in humans. Label the parts indicated by numbers 1 to 5, and state their functions.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 2
Answer:

  1. Seminal vesicle: The seminal vesicles produce a secretion which serves as a medium for the transportation of the sperms.
  2. Prostate gland: Prostate gland which pours an alkaline secretion into the semen as it passes through the urethra.
  3. Testes: Sperms are produced in the testes.
  4. Urethra: Urethra passes through the penis and carries either urine or semen.
  5. Sperm duct: The sperm pass through the sperm ducts.

Long Answer Questions:

Question PQ.
Define the term metamorphosis. Briefly describe the various stages occurring in the life-cycle of a butterfly.
Answer:
Metamorphosis: A change in the form and often habits of an animal during normal development after embryonic stage complete transformation from an immature form to an adult form in two or more distinct stages.

Life cycle of butterfly: The butterfly lays its eggs on the leaves of the plants. The new born that comes out of the egg is called larva. It passes through various stages of development. The larva of butterfly is also called Caterpillar. It is very active. It is very voracious. It feeds and moves actively and gains size.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 3

It stops moving and eating and it is called pupa. It is a resting stage. The pupa spins thread around itself and thus is enclosed in a covering. It is called cocoon. This cocoon covers the pupa and is protective in function. During this stage it forms the features of an adult. After attaining adulthood the pupa comes out of the cocoon after breaking it as an adult butterfly. The wings of emerged butterfly are wrinkled and soft. After an hour these are fully stretched and it starts flying.

Question PQ.
What is fertilization? Describe the process in human beings.
Answer:
Fertilization: The fusion of male (sperm) and female (ova) gamete is called fertlization.

As the male performs sexual act with the female and as a result of it the semen is deposited in the vagina of the female. Thus the semen has millions of sperms. Only a few of these sperms are able to reach the upper part of the oviduct. If there is an egg in the oviduct it is fertilized by the sperm. As sperm enters the egg and this leads to the formation of zygote, this act is called fertilisation.

During fusion only the head part of the sperm, which has nucleus, enters the egg. The tail is left behind. The nucleus of the sperm and egg fuse and form the zygote. Soon this zygote becomes many called embryo and reaches the uterus and implants on the wall of the uterus and forms the foetus. Baby develops with in the gestation period of 280 days. After this the baby is delivered.

Question 1.
How does a single called fertilized egg grows into an adult in human beings?
Answer:
Fertilised egg i.e., zygote divides and redivides and forms a ball of cells. This is a kind of embryo and it reaches the uterus and gets attached to the wall of the uterus. This fixing of embryo to the uterus is called implantation. Now the embryo undergoes a process “specialisation of cells’’. It leads to the formation of different parts of the body. This process is called differentiation. It leads to the formation of various tissues and other organs and thus organ systems are formed. Organ system lead to the formation of an individual. Thus the zygote forms an embryo, it forms a baby and it forms an adult.

Question PQ.
Tabulate the important physical changes in the boys and girls that take place during puberty.
Answer:
Reproductive system of boys and girls mature during puberty. Puberty starts at 10 in girls and at 11 in boys. Testes enlarge in boys and breasts develop in girls. The following table shows the physical changed in boys and girls that take place during puberty.

Boys

  1. Testes become large
  2. Scrotal sac grows and penis becomes long.
  3. Length increases and shoulder girdle grows becomes more.
  4. Hair grow on the chest arm pits and on the sex organs.
  5. Facial hair and moustaches grow.
  6. Voice becomes hoarse and deep.

Girls

  1. Breasts become large.
  2. Ovaries become large and these release eggs. Size of uterus and vagina grows. Menstruation cycle starts.
  3. Sudden grow th takes place in length. Hip girdle becomes trough shaped, it larger than the shoulder girdle.
  4. Chest and abdomen do not have hair. But hair arise on the sex organs and the arm pits.
  5. No moustaches and facial hair.
  6. High pitch voice.

Question 2.
Describe the human female reproductive system with a labelled diagram.
Answer:
On each side of the uterus two white oval bodies lie. These are called ovaries. Eggs are produced in the ovaries. Nearer to the ovaries there lies expanded funnel shaped oviducts or fallopian tubes. The eggs go into the oviducts when released by the ovaries. The two oviducts open into the uterus. The walls of the uterus are muscular. The growing embryo lodges to the wall of the uterus. It is supplied by the food and blood through the placenta w hich is a connection betw een the growing embryo and the mother. The uterus joins the vagina. It is the vagina in which semen is lodged during sexual act. From here sperms go up into the oviduct and fertilise the egg. The urethra which brings urine from the urinary bladder opens into the.vulva just in front of the vaginal opening.
Selina Concise Biology Class 8 ICSE Solutions - Reproduction in Humans 4

Question PQ.
‘Adolescence is a crucial stage’. Justify this statement.
Answer:
During adolescence physical and emotional changes takes place in the body of boys and girls. This is period between the age of 10 to 19 and this is very critical period. Boys bear facial hair, muscular body, hair in the arm pits and on the sex organs, and have hoarse voice. The girls also have beautiful contours, raised breasts, wide lips and high pitch voice. The body increases in length in both cases. Boys and girls becomes conscious about the growth of the body. They become hesitant and shy to each other. They become body conscious and spend lot of time on dressing up and grooming. Hormonal level increases in their body and become restless.

Hormones affect their brains and control their emotions and moods. They cherish the company of their own sexes and show the attraction for the opposite sex. Thus it is very strange and crucial stage in their life. So adolescence is a very crucial stage in the life of the boys and the girls.

Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants

Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 1 Transportation in Plants. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 1 Transportation in Plants

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Diffusion occurs when molecules move:

  1. from lower concentration to higher concentration.
  2. from higher concentration to lower concentration through a membrane.
  3. from higher concentration to lower concentration.
  4. when energy is used.

Answer: (3) from higher concentration to lower concentration.

(b) Ascent of sap in plants takes place through:

  1. Cortex
  2. Epidermis
  3. Xylem
  4. Phloem

Answer: (3) Xylem

(c) If the xylem vessels of a plant are plugged:

  1. The leaves will turn yellow
  2. No food will be made
  3. The plant will wilt (shrivel)
  4. The plant will continue to grow

Answer: (3) The plant will wilt (shrivel)

(d) Force responsible for the ascent of sap is:

  1. Capillary force
  2. Root pressure
  3. Transpirational pull
  4. All the three

Answer: (4) All the three

(e) Raisins swell when put in:

  1. Rain water
  2. Tap water
  3. Mustard oil
  4. Saturated sugar solution

Answer: (1) Rain water

(f) The root-hairs are suited for absorbing water from the soil because:

  1. They have a large surface area
  2. They have a semi-permeable membrane
  3. They contain a solution of higher concentration than the surrounding water.
  4. All the three.

Answer: (4) All the three.

(g) Transpiration is defined as:

  1. the rise of water up to the stem of a plant.
  2. the elimination of water with dissolved water products.
  3. the loss of water as water vapour from the aerial parts of a plant.
  4. the loss of water as water vapour from the roots as well as the leaves of the plant.

Answer: (3) the loss of water as water vapour from the aerial parts of a plant.

(h) Which one of the following favours the fastest transpiration rate ?

  1. A cool, humid, windy day,
  2. A hot, humid, windy day,
  3. A hot, humid, still day,
  4. A hot, dry, windy day.

Answer: (4) A hot, dry, windy day.

Short Answer Questions:

Question 1.
An experiment was set up as shown in the figure below. After some time, the Water level in test tube A fell down but not in test tube B.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 1
Why was there a fall in the water level of test tube A and not in that of test-tube B ?
Answer:
In test tube A the water level falls because the water was absorbed by the plant through its roots dipped in water. Here no water loss occurs due to evaporation from the water surface due to presence of oil.
In test tube B the water level remains unchanged as it does not contain a rooted plant. Due to the presence of oil on surface no water loss occurs due to evaporation.

Question 2.
How are roots useful to the plants? Give any two points.
Answer:
Roots are useful to the plants in the following way:

  1. It absorbs water and minerals from the soil and transport it upward to various parts of a plant.
  2. Roots fix the plant firmly in the ground.

Question 3.
What do xylem vessels carry?
Answer:
The xylem vessels carry the water and minerals absorbed by the roots to the stem and leaves.

Question 4.
Name the plant tissue which helps in carrying the food to different parts.
Answer:
Phloem.

Question 5.
Define the terms:
(a) semi-permeable membrane
(b) osmosis.
Answer:

(a) Semi-permeable membrane: It is a membrane that allows the movement of solvent molecules (e.g. water molecules) through it but prevents the movement of solute particles (e.g. sugar or salt molecules).
For example: Egg membrane, parchment membrane, cellophane paper etc. are semi-permeable membranes.

(b) Osmosis: The diffusion of water molecules through a semi-permeable membrane from a region where water is more concentrated to a region where it is less concentrated is called osmosis.
In other words, osmosis is the diffusion of water from its pure state or dilute solution into a stronger or concentrated solution through a semi-permeable membrane.

Question 6.
Under what conditions do plant transpire (a) more quickly and (b) most slowly?
Answer:
(a) Transpiration is faster on hot summer days as compared to cold winters.
(b) Transpiration is reduced if the air is humid. Air cannot hold any water molecules when it is already laden with moisture (humidity).

Question 7.
Given here is an enlarged diagram of a part of the root. Draw arrows on the diagram to show the movement of water passing through different parts.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 2
Answer:
Path of water through the root hair to the xylem vessels.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 3

Question 8.
Why is the structure of the root hair is quite suitable for absorbing water from the soil ?
Answer:
The root hair are suitable for absorbing water from the soil in the following three ways:

  1. The root hairs present a large surface area. More the surface area, greater is absorption.
  2. The cell wall is of cellulose nature and forms permeable membrane and the plasma membrane around the vacuole forms the semi-permeable membrane.
  3. Root hairs have solution (cell sap) of a higher concentration than the surrounding soil water.

Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 4
Fig. Unicellular root hairs through the soil particles

Question PQ.
In an experimental set-up, a dye was placed at the bottom of a beaker filled with water as shown in figure A, below. After some time, the entire water in the beaker got coloured uniformly as shown in figure D.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 6
Answer:
(a) Name and define the phenomenon shown in the experiment.

Answer: The phenomenon is diffusion. Diffusion is the movement of the molecules or atoms of a substance (whether in a solid, liquid or gaseous state) from the region of higher concentration to the region of lower concentration.

(b) In all the four figures, two kinds of molecules are shown symbolically – larger and smaller. Which molecules are of the solute and which are of the solvent?
(a) Larger: ………… (b) Smaller: …………..
Answer: (a) The larger molecules are of the solute (dye)
(b) The smaller molecules are of the solvent (water)

(c) If all the dark shaded molecules in A are tightly enclosed in a cell membrane, what will be the nature of movement of the molecules, if any ?
Answer: As the concentration of solvent molecules is more in the left side of the figure A. The cell membrane will act as semi permeable membrane and will allow only the solvent molecules of water to move towards the solute particles. So the solvent molecules will move towards the solute particles. This will show the phenomenon or process of osmosis.

Question 9.
Briefly explain, how transpiration helps in upward conduction of water in plants? (a) ………… (b) ……………
Answer:
(a) Plants continuously absorb water through their roots. This water is sent up through the stem to all parts of the plant, including the leaves. Only a little amount, of water is retained in the plant or utilised by it in photosynthesis. The rest of it gets evaporated into the atmosphere as water vapour through the stomata present in the epidermis of the leaves and other aerial parts of the plant. This creates a suction pressure which pulls up water from xylem of the roots to the stem and then to the leaves.

(b) Xylem tissues are in the form of capillary tubes (tracheids and fibres) where narrower the diameter, greater will be the force. Whenever the xylem vessels lay empty, such as during the loss of water by transpiration, the water from below rises into them by a capillary force.
During day time, water is lost from the surface of the leaves by the process of transpiration. In this process, more and more water molecules are pulled up due to their tendency of rentainingjoined (cohesion). Such pulling force created by the leaves is very important in the case of tall trees where an upward conduction of water takes place.

Question 10.
How does temperature, light intensity and wind affect transpiration?
Answer:
Temperature: Transpiration is faster on hot summer days as compared to cold winters.
Light intensity: The transpiration rate is increased due to the increase in light intensity. During daytime in the sunlight, the rate of transpiration is faster. This is because the stomata remain open to allow the inward diffusion of carbon dioxide for photosynthesis. During dark, the stomata are closed, and hence transpiration hardly occurs at night.
Wind: Transpiration is more when the wind is blowing faster as water evaporates faster from the leaves.

Question 11.
The set up shown alongside was kept in sunlight for an hour. It was observed that drops of water appeared on the inside of the polyethylene bag.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 7
(a) Name the process which is being demonstrated.
(b) Why was the pot and its soil left uncovered by the polythene bag ?
(c) Why was the pot left in the sunlight?
(d) Suppose the pot in this experiment was placed inside a dark room instead of placing it in sunlight for some time. What difference will be noticed?
Answer:
(a) The process demonstrates the loss of water that has appeared in the polythene bag is transpiration.
As the potted plant covered with polythene bag is kept in the sunlight there will be loss of water through the stomata present on the leaves. The water drops will appear inside the polythene bag as a result of loss of water from the stomata. This is due to transpiration.

(b) As the potted plant is kept in the sun. The water vapours will also be given by the pot and the wet soil. These vapours (water drops) will also go inside the polythene if it covers the pot and the soil. We left the pot and soil uncovered by the polythene so that we may find the loss of water from the aerial parts of the plant covered with polythene bag. This shows that the water gets deposited in the polythene bag has come from the aerial parts of plant.

(c) As we keep the pot in the sunlight the stomata will open and the loss of water i.e., transpiration takes place from the aerial parts of the potted plant and the stomata. The loss of water will be more (transpiration) in the sun, and water vapours will appear in the polythene bag very soon.

(d) As we keep the pot inside the room, the stomata will not open fully and the rate of loss of water will be very-very less, and no water vapours will appear in the polythene bag. By keeping the pot in the room the loss of water will be very less and as a result the transpiration will be very less.

Question 12.
State whether the following statements are true or false. Rewrite the false statements correctly.
(a) Water absorption mainly occurs through the root-hair.
True
(b) Water enters the root-hair by osmosis.
True
(c) Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant.
True
(d) A semi-permeable membrane allows larger molecules to pass through, but prevents the smaller ones.
False. A semi-permeable membrane allows smaller molecules to pass through, but prevents the smaller ones.
(e) Transpiration is the loss of water from the roots of the plant.
False. Transpiration is the loss of water from the aerial parts of the plant.
(f) Transpiration cools the plant when it is hot outside.
True
(g) During transpiration, the leaves lose more water from their upper surface.
False. During transpiration, the leaves lose more water from their lower surface.

Question 13.
Fill in the blanks with suitable terms given below: (Fast, Leaves, Stomata, Conducting, Ascent, Humid)
(a) Transportation in plants is carried out by a conducting system.
(b) The upward movement of sap that contains water and minerals is called ascent of sap.
(c) Transpiration is more when the wind is blowing fast.
(d) Most water gets evaporated from the plant from its leaves.
(e) Transpiration is reduced if the air is humid.
(f) The leaves have more stomata on their lower surface.

Long Answer Questions:

Question 1.
Draw a magnified view of the root-hair, and describe, how it helps in the absorption of water from the soil.
Answer:
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 8
Give above is a magnified view of a root-hair. It is a long protuberance of a cell. This cell contains a fluid called cell sap which is more concentrated than the surrounding soil water.
The root hair is covered by a very thin ceil membrane that allows water molecules to pass through, but prevents the larger molecules. So the water from the soil passes into the root hairs by osmosis.

Question PQ.
“Raisins swell in water, and grapes shrink in syrup.” Explain this phenomenon briefly.
Answer:
When we put some raisins in a bowl containing water, after 10-12 hours, we will notice that the raisins have swelled up. The raisins have absorbed water.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 9
But when we put some soft-skinned grapes in another bowl containing thick syrup of sugar. After 10-12 hours we will notice that grapes have shrunk. The grapes have lost water.
Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 10
In both cases the gain or loss of water is through the peel acting as a kind of semi-permeable membrane. This membrane has very minute pores which allow water molecules to pass through, but prevent the larger ones of sugar.

Question 2.
How does transpiration help the roots absorb water and minerals from the soil?
Answer:
Transpiration process in plants creates a suction pressure which pulls up water from xylem of the roots to the stem and then to the leaves.
Xylem tissues are in the form of capillary tubes (tracheids and fibres) where narrower the diameter, greater will be the force. Whenever the xylem vessels lay empty, such as during the loss of water by transpiration, the water from below rises into them by a capillary force.
Due to transpirational pull more and more water molecules are pulled up due to their tendency of remaining joined (cohesion). Such pulling force created by the leaves is very important in the case of tall trees where an upward conduction of water takes place.

Question 3.
Define the three processes by which plants absorb water and minerals from the soil.
Answer:
Following are the tree processes which help the plants to absorb water and minerals from the soil.

  1. Diffusion: Soil water moves into the root hairs through the process of diffusion from higher concentration to lower concentration as we put sugar in the milk and the sugar molecules are evenly distributed in the milk and occupy inter molecular spaces of milk.
  2. Osmosis: The cell sap and the cell walls act as semi- permeable membranes and permeable membranes. The concentration of the cell sap is more as compared to the water + minerals present in the soil. So the water and dissolved minerals enters the roots by the process of osmosis.
  3. Active transport: Root hairs absorb water and minerals from the soil. Water diffuses into the root hairs as the concentration of water is more as compared to root hair.
    But in case of minerals these move from lower concentration to molecules of higher concentration. So the minerals from the soil along with water move into the roots. So this is active transport in the opposite direction which needs energy.

Question 4.
How water absorbed by the roots is important for the plants?
Answer:
The water absorbed by the roots is important for the plant in three main ways:

  1. Transportation: The water in the plant body transports substances in solution from one part to another.
  2. Food production: Water is used in producing food (photosynthesis) by combining it with carbon-dioxide from the air in the presence of sunlight.
  3. Cooling: Water is used to cool the plant by evaporation through leaves when it is hot outside.

Question 5.
Name the factors which affect the rate of transpiration? State their role in each case.
Answer:
The following are the main factors that affect the rate of transpiration:

  1. Sunlight: During daytime, the rate of transpiration is faster. This is because the stomata remain open to allow the inward diffusion ofcarbondioxide for photosynthesis.
    During dark, the stomata are closed, and hence transpiration hardly occurs at night.
  2. Temperature: Transpiration is faster on hot summer days as compared to cold winter.
  3. Wind: Transpiration is more when the wind is blowing faster as water evaporates faster from the leaves.
  4. Humidity: Transpiration is reduced if the air is humid. Air cannot hold any water molecules when it is already laden with moisture (humidity).
  5. Low atmospheric pressure: The rate of transpiration increases when the pressure is low.

Question 6.
Mention the two ways in which transpiration helps the plants.
Answer:
Transpiration helps the plants in the following ways:

  1. Cooling effect: In transpiration, water gets evaporated from the plant. The heat required for this evaporation is obtained from the plant itself (latent heat) and thus the plant is able to cool itself w’hen it is hot outside.
  2. Transpiration helps in maintaining the concentration of the sap inside the plant body: The roots continue to absorb water from the soil. If excess water is not evaporated out, the sap would become dilute, preventing further absorption of water along with the minerals required by the plant.

Question 7.
Describe an experiment to show that the plant loses water through its leaves.
Answer:
Experiment: To demonstrate that the plants lose water through its leaves.

  • Take one small-sized, well-watered potted plant having a few branches. Place a polythene bag over its one branch as shown in A and tie it with a rubber band.
    Selina Concise Biology Class 8 ICSE Solutions – Transportation in Plants 11
  • Remove all the leaves from another branch (B) of the same plant, cover this too with a polythene bag and tie it with a rubber band.
  • Place the plant in sunlight, and observe it after 4-6 hours. You will notice that drops have appeared on the inner surface of the polythene bag over branch A, while no water drops appear on branch B.
  • This set-up indicates that most water gets evaporated from the plant through its leaves.

Question 8.
Name any three minerals whose deficiency causes diseases in plants. Give the symptoms of each deficiency.
Answer:
The nutrient elements i.e. minerals are essential for the plants to grow well and complete their life-cycle properly. The minerals are divided into two main categories:

(i) Macro-Nutrients: They are required in larger concentrations and they are obtained from soil.
The three macro-nutrients (minerals) whose deficiency causes diseases in plants are:

  1. Nitrogen (N) – Yellowing of leaves,wrinkling of cereal grains.
  2. Phosphorus (P) – Purple and red spots on leaves, delay in seed germination.
  3. Potassium (K) – Poor Growth

(ii) Micro Nutrients: They are required in small amounts and they are also obtained from soil.
The three micro-nutrients(minerals) whose deficiency causes diseases in plants are:

  1. Iron (Fe) – Yellowing of Leaves.
  2. Manganese (Mn) – Yellowing of leaves, with grey spots.
  3. Zinc (Zn) Desphaped leaves, yellowing of leaves, stunted plant growth.

Question 9.
List out the differences between xylem and phloem.
Answer:
The Xylem tissue consists of four types of cells:

  1. Tracheids: They are elongated dead cells with tapering ends. Their main function is in upward conduction of water and provide mechanical support.
  2. Vessels: They are like tube-like structures placed one above the other forming long channels. They provide mechanical support and also transport water and mineral salts laterally and vertically upward.
  3. Fibres: They are long, narrow and tapering at both ends. They provide only mechanical support.
  4. Parenchyma: They are living cells and helps in the conduction of water and minerals, and serve for the storage of food.

The Phloem tissue consists of four types of cells:

  1. Seive tubes: They are formed of seive cells and form the main conducting part of the phloem. These are cylindrical cells arranged in vertical rows, joined end to end. Their end walls are perforated by pores and are called seive plates. Seive piates helps in passing food material from cell to cell.
  2. Companion Cells: They are associated with seive tubes. It help sieve tubes in the conduction of food material.
  3. Parenchyma: It is formed of thin-walled unspecialized parenchymatous cells and these cells store food.
  4. Phloem fibres: They are dead sclerenchyma fibres formed of elongated cells. These provide mechanical strength.

Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence

Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 5 Endocrine System and Adolescence. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 5 Endocrine System and Adolescence

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Cortisone hormone is secreted by:

  1. Medulla of adrenal
  2. Cortex of adrenal
  3. Pancreas
  4. Thyroid

(b) Which one of the following hormones stimulates the breakdown of glycogen in the liver into glucose:

  1. Insulin
  2. Adrenaline
  3. Glucagon
  4. Thyroxine

(c) Which one of the following hormones converts excess of glucose into glycogen:

  1. Glucagon
  2. Thyroxine
  3. Insulin
  4. Adrenaline

(d) Which one of the following glands is also called master gland:

  1. Pituitary gland
  2. Adrenal gland
  3. Thyroid gland
  4. Ovary

(e) The emergency hormone to face the danger or to fight is secreted by:

  1. Islets of Langerhans
  2. Adrenal cortex
  3. Pituitary
  4. Adrenal medulla

(f) Which one of the following endocrine glands produces its hormone in large quantities as a result of emotional stimulation?

  1. Thyroid
  2. Islets of Langerhans
  3. Adrenal medulla
  4. Adrenal cortex

Adrenal medulla produces its hormone in large quantities as a result of emotional stimulation.

(g) In humans, increased thyroxine production results in (tick the correct answer):

  1. Increased metabolism
  2. Decreased metabolism
  3. Dwarfism
  4. Cretinism

Short Answer Questions:

Question 1.
What is a hormone?
Answer:
The secretions of the endocrine glands are called Hormones, which are poured directly into the blood and are carried to the target organs.

Question 2.
In table given below, fill in the blanks by naming endocrine glands, the hormones they secrete, and the function they perform, in a normal person.
Answer:

S.No. Name of the gland produced Function
1. Thyroid Thyroxine Control of metabolic rate
2. Pancreas Insulin Regulation of sugar in blood.
3. Adrenal Adrenaline and cortisone Preparing the body for action
4. Pituitary (i) Growth hormone
(ii) Thyroid stimulating hormone
(i) For growth
(ii) Stimulates thyroid gland to secrete thyroxine

Question 3.
Match the items in Column A with those in Column B. Column A Column B
Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence 1

Answer:

Selina Concise Biology Class 8 ICSE Solutions – Endocrine System and Adolescence 2

Question 4.
Name the source and the function of each of the following hormones:

Hormone Source Function
(a) Glucagon
(b) Thyroxine
(c) Adrenaline
(d) Insulin
(e) Cortisone

Answer:

Hormone Source Function
(a) Glucagon Pancreas Breakdown of glycogen to glucose. Raises sugar in the blood.
(b) Thyroxine Thyroid gland Control of metabolic rate
(c) Adrenaline Adrenal gland Prepare the body to face emergency, stress
(d) Insulin Pancreas Regulation of sugar in blood.
(e) Cortisone Adrenal cortex Regulates carbohydrate metabolism. Its deficiency causes Addison’s disease.

Question 5.
What is the difference between an exocrine gland and an endocrine gland?
Answer:
The salivary glands, pancreas, etc., are exocrine glands, they send their secretions through ducts directly to the target orgOn the other hand, the endocrine glands are ductless glands. Their secretions are called hormones, which are poured directly into the blood and are thus carried to the target organs.

Question 6.
Why is pitnitary gland is called “master gland”?
Answer:
The pituitary gland is called “master gland” because it produces hormones that control other glands and many body functions including growth (growth hormone, Thyroid and Gonad stimulating hormone).

Question 7.
Briefly write about the importance of physical hygiene during adolescence.
Answer:
Physical hygiene also named as Personal hygiene plays a crucial role in maintaining healthy during adolescence. The teenager should follow the below mentioned activities to promote their health:

  1. Proper and Safe Food: Adolescence is a stage of rapid growth and development. Hence, a teenager should take proper care of their diet. They should take proper balanced diet that provides protiens, carbohydrates, fats, minerals and vitamins. They should take freshly prepared food and avoid stale food. They should take milk, fruits and fresh vegetables.
  2. Proper life Style: Regular Exercise and sleep are necessary for maintaining good health. Teenager should avoid long hours of continous table work, television watching. Teenager should not consume alcohol, drugs or smoking.
  3. Cleanliness: Teenager should take bath regularly. They should always wash their hands before and after having meals. Brushing up teeths after every meal. They should always change and wear washed clothes especially undergarments. Regular toilet habits should be adopted for maintaining good health. Teenager must keep their feet cleaned and protected. Injuries due to bacteria like tetanus, hookworms and insects may be issued if barefoot walk is undertaken. They must wash and comb their hairs regularly. All body parts must be washed and cleaned everyday. If cleanliness is not maintained there may occur chances of catching bacterial infection. Girls should take special care of cleanliness during the time of menstrual period.
  4. Physical Exercise: Inorder to keep the body fit and healthy, teenager’s should walk, exercise and play outdoor games regularly in fresh air. Playing Outdoor games reduces the stress and strain of adolescence.

Question 8.
Briefly discuss any four activities which can be practiced to overcome stress.
Answer:
Stress is a state of mental or emotional strain and in simple terms it is called as tension.
The stress can be controlled or reduced by following the below mentioned steps:

  1. Yoga: It is a mind-body practice that combines physical poses, controlled breathing, and meditation or relaxation. Yoga helps in reducing steps by:
    (a) Increasing Flexibility
    (b) Increasing muiscle strength and tone.
    (c) Improving respiration, energy and vitality.
  2. Exercise: Exercise or Running or Jogging for 30 to 45 minutes at least three times a week reduce stress and keep’s the body much healthier.
  3. Proper sleep schedule: Improving your sleep schedule also helps in reducing the stress.
  4. Reading is a great way to calm your mind and to gain more knowledge.
  5. Practice Hobbies of your interest: One should must keep practicing their hobbies as it helps in reducing the stress. Enjoy playing guitar, paino or listening music or doing riddles.

Selina Concise Biology Class 8 ICSE Solutions – Nervous System

Selina Concise Biology Class 8 ICSE Solutions – Nervous System

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 7 Nervous System. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 7 Nervous System

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Medulla oblongata controls

  1. Smelling
  2. Beating of heart and respiratory movement
  3. Intelligence and will power
  4. Balancing the body

(b) Balance of body is controlled by:

  1. Spinal cord
  2. Cerebellum
  3. Cerebrum
  4. Medulla

(c) The smell of good food causes watering of your mouth. It is a

  1. Natural reflex
  2. Acquired relfex
  3. Inborn reflex
  4. Ordinary reflex

(d) The structural and functional unit of nervous system is a

  1. Axon
  2. Nephron
  3. Neuron
  4. Texon

Short Answer Questions:

Question 1.
Name the two types of coordination which take place in our body.
Answer:
(a) Nervous coordination: By nerves and brain
(b) Chemical coordination: By hormones

Question 2.
Your are driving your bicycle at a fast speed. Suddenly, a small boy comes in front of your cycle and, without wasting any time in thinking, you immediately apply the brakes and accident is avoided. What name is given to such an action?
Answer:
Reflex action (acquired).

Question 3.
Given below is the diagram of a neuron. Name the parts numbered 1-5.
Selina Concise Biology Class 8 ICSE Solutions – Nervous System 1
Answer:

  1. Dendrite
  2. Nucleus
  3. Cell Body (Nyton)
  4. Axon (Nerve fibre)
  5. Node of Ranvier

Question 4.
Write one word in the space provided to complete the second pair of the related words pertaining to nervous system.
Memory : cerebrum : : breathing :
Balance : cerebellum : : reasoning :
Answer:
Memory : cerebrum : : breathing: medulla oblongata
Balance : cerebellum : : reasoning : cerebrum

Question 5.
Differentiate between the following pair of terms:
(a) Stimulus and impulse
(b) Receptor and effector
(c) Motor nerve and sensory nerve
Answer:
(a) Stimulus: Any change in the environment that usually results in change in the activity of the body.
Impulse: A wave of electrical disturbance that runs through the nerves.

(b) Receptor: The nerve cell on receiving the stimulus sets up the waves of impulses towards the central nervous system.
Effector: Any muscle or gland on receiving the impulse from the brain (or the spinal cord), contracts or secretes.

(c) Motor nerve: It contains only motor neurons,
Example: Nerves going to the muscles of the eyeball.
Sensory nerve: It contains only sensoiy neurons.
Example: optic nerve of the eye.

Question 6.
(a) Name the three major divisions of the human nervous system.
(b) Name the three main parts of human brain.
Answer:
(a)

  1. The central nervous system (brain and spinal cord)
  2. The peripheral nervous system
  3. The autonomic nervous system

(b)

  1. Cerebrum
  2. Cerebellum
  3. Medulla oblongata

Question 7.
Give the function of each of the following:
(a) Olfactory nerve:
(b) Optic nerve:
(c) Facial nerve:
Answer:
(a) Olfactory nerve: The sense of smell is present in the epithelial layers of the nasal chambers. The sense of smell is carried to the brain by the olfactory nerve. They arise from the anterior ends of the olfactory lobes and are distributed to lining of nasal chambers.
(b) Optic nerve: It carries the reflection of the object from the retina to the brain. The image formed on the retina is in a reverted position and the correct picture is formed in the brain as the object is. The optic nerves arise from the side of diencephalon. They innervate the retina of the eye and are sensory in nature.
(c) Facial nerve: It carries message and all expressions of the face, mastication work alone by the teeth, movement of the neck and the activities of the salivary glands to the brain. It arises from the side of medulla. On the whole facial nerves are mixed in nature.

Long answer questions

Question 1.
With the help of a suitable diagram describe the structures of a neuron.
Answer:
Nervous system consists of special cells called nerve cells or neurons. It has a main cell body called cyton. It gives out many processes called dendrites. From it a very long process is given out. It is called axon or nerve fibre.
Selina Concise Biology Class 8 ICSE Solutions – Nervous System 2
The cell body has a nucleus. The dendrites get the message from the organs and send this message to the axon through the cell body. Then the axon sends the message to muscles to contrast or to the gland for secretion.
The neurons make contact with one another through their processes. The axon at its end branches and meets the dendrites of another neuron. The meeting point is called synapse. The message is passed on from one axon to the dendrites of another neuron. How the message goes ? It is like this:
Organ → Message goes to dnedrites → Cell body → Axon → Muscles or glands

Question 2.
Briefly describe the structure of the cerebrum in human brain and mention its functions.
Answer:
Brain consists of main three parts and lies in the cranial cavity of skull.

  1. The cerebrum
  2. The cerebellum
  3. The medulla oblongata

Cerebrum: It is very large and form two third of the whole brain. The two hemispheres are separated from each other by a deep longitudinal groove, the median fissure. The outer surface is folded with ridges and grooves. The hemispheres are hollow from inside and their walls have outer and inner portions. The outer portion has cell bodies of the neurons and it is called grey matter.
The wavery edges of the folded layer has large number of neurons to the extent of nine billion. The inner portion of the cerebrum has axons and it is called white matter.

Functions:

  1. It controls all the voluntary activities.
  2. It is the seat of intelligence, consciousness and will power.

Question 3.
Mention the three functions of spinal cord.
Answer:
Spinal cord has the following functions.

  1. It is the centre of reflex actions below the neck.
  2. It carries messages from the skin and muscles to the brain.
  3. All the stimuli and responses are passed from and to the brain through the spinal cord.

Question 4.
With the help of suitable example, describe reflex action.
Answer:
Reflex action: Reflex actions are automatic responses to stimuli. These actions are not under the control of the animal. They are of definite and mechanical type. Peripheral nervous system and spinal cord both control certain action and the brain is not in action.
Some examples of reflex actions are:

  1. Pupil becomes narrow when strong light falls on it.
  2. The aroma of the food makes the mouth watering.
  3. The hand is withdrawn as we touch the hot plate.
  4. Flow of bile from the gall bladder into the duodenum.
  5. A loud thud may lead to opening of the mouth.

In a reflex action brain is not involved, removing the hand on touching a hot plate is a reflex action. The impulse of heat goes from the hand to the spinal cord and the order is sent back to the muscles of the hand to remove the hand from the hot plate.

Question 5.
Describe three kinds of nerves, giving the example of each.
Answer:
A nerve is formed by a group of nerve fibres (axons) encased by tubular medullary sheath. The medullary sheath acts as insulation and do not allow mixing up of impulses of the neighbouring axons (nerve fibres) We have three kinds of nerves:

Selina Concise Biology Class 8 ICSE Solutions – Nervous System 3

  1. Sensory nerve: It brings impulses from sense organs as these have sensory fibres. These nerve carry the impulses from the sense organs to the brain or to the spinal cord as optic nerve of the eye.
  2. Motor nerves: These carry impulses to muscles or glands from the brain or spinal cord. These nerves have only motor fibres as nerves to the muscles of the eye ball.
  3. Mixed nerve: It has both sensory and motors fibres as nerve going to the tongue.

Question 6.
Differentiate between natural reflex and conditioned reflex. Give examples to illustrate your answer.
Answer:
Natural reflex: It is one in which no previous experience or learning is required. These reflexes are inborn i.e. inherited from the parents.
Examples are

  1. Blinking, coughing, sneezing as these are protective reflexes
  2. Salivation, swallowing, peristalsis as it provides functional efficiency.
  3. Dilation of the eyes pupil to look in the dark and vice versa. It is muscular movement.
  4. Pushing along of swallowed food through the food canal. It is muscular movement.

Conditioned Reflex: It is one which develops during lifetime due to experience or learning.
Examples are:

  1. Watering of mouth (Salvination) at the sight of a tasty food.
  2. Surfing the channels while watching the television.
  3. Typing of a keyboard of a computer.
  4. Playing a musical instrument.

Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System

Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 6 The Circulatory System. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 8 Biology Chapter 6 The Circulatory System

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) The only artery which carries deoxygenated blood is called,

  1. Hepatic artery
  2. Pulmonary artery
  3. Aorta
  4. Renal artery

(b) Pulmonary vein carries

  1. Oxygenated blood
  2. Deoxygenated blood
  3. Glucose-deficient blood
  4. CO2 laden blood

(c) Function of WBCs is to

  1. Transport oxygen
  2. Help in clotting of blood
  3. Provide immunity
  4. Provide storage of food.

(d) Blood Capillary is a

  1. Broad tube
  2. Artery with thick wall
  3. Vein with large lumen
  4. Narrow tube made up of endothelium only.

(e) Nucleus is absent in 

  1. RBCs
  2. WBCs
  3. All blood cells
  4. Liver cells.

(f) Sphygmomanometer measures

  1. Pulse rate
  2. Heart beat
  3. Blood pressure
  4. Brain activity

(g) The blood tastes saltish due to the presence of dissolved:

  1. Sodium chloride
  2. Potassium chloride
  3. Ammonium nitrate
  4. Sodium nitrate

Short Answer Questions:

Question 1.
1. Differentiate between the following pair of terms:
(a) Pulmonary artery and pulmonary vein.
(b) Vena cava and aorta.
(c) Platelets and WBC.
(d) RBC and WBC Ans.
Answer:
(a) Pulmonary artery and pulmonary vein.

Pulmonary artery Pulmonary vein
1. This involves circulation of blood from the heart to the lungs. 1. This involves circulation of blood to the heart from the lungs.
2. It carries deoxygenated blood. 2. It carries oxygenated blood.

(b) Vena cava and Aorta

Vena Cava Aorta
1. Vena Cava is a large vein. 1. Aorta is the large artery.
2. It carries deoxygenated blood from the upper and lower parts of the body i.e. head and shoulders. 2. It carries oxygenated blood to all parts of the body through its branches.

(c) Blood platelets and blood group.

Platelets WBC
1. These are colourless, oval or round, cytoplasmic fragments 1. WBC are colourless and lack haemoglobin, larger in quantity, and have distinct oval and lobed nucleus.
2. These play a major role in blood clotting. 2. They prevent body from disease causing germs by providing immunity
3. Their life span is 3-5 days and it is called thrombocytes. 3. Their life span is short i.e. 5 to 20 days.

(d) RBC and WBC

RBC WBC
1. They do not have nucleus at maturity. 1. They have a large characteristic nucleus.
2. They possess haemoglobin and are red. 2. They are colourless as they have no pigment.
3. They help in transport of respiratory gases. 3. They help in defence mechanism.

Question 2.
Give any three differences between an artery and a vein:
Answer:
Following are the differences between the artery and a vein:

Artery Vein
1. Arteries carry blood from the heart to various body parts. 1. Veins carry blood from different body parts to the heart.
2. These carry oxygenated blood (except the pulmonary artery). 2. These carry deoxygenated blood (except the pulmonary vein).
3. B lood flows with h igh speed and under high pressure. 3. Blood flows with low speed and under low pressure.

Question 3.
Fill in the blanks with suitable words given below:
Answer:
a. The two lower chambers of the heart are called ventricles.
b. The pulmonary artery takes the blood from the ventricles to the lungs.
c. The blood loaded with carbon dioxide from the body comes into the right auricle of the heart.
d. The oxygen-rich blood from the lungs comes into the left ventricle of the heart.
e. The oxygen-rich blood is pumped into different parts of the body through aorta.
f. The carbon dioxide loaded blood from right ventricle is pumped into the lungs through pulmonary artery.
g. The instrument used to find out the blood pressure is known as sphygmomanometer.
h. The colour of a red blood cell is due to haemoglobin.
i. The blood plasma contains a dissolved substance called fibrinogen.
j. The liquid part of coagulated blood is known as serum.

Question 4.
In which organ of our body does blood get oxygenated?
Answer:
Blood becomes oxygenated in the lungs. The oxygenated blood is returned to left verticles by the pulmonary vein.

Question 5.
Which side of the heart (left or right) contains oxygenated blood?
Answer:
The left side of the heart contains oxygenated blood.

Question 6.
What is the role of haemoglobin in the blood ?
Answer:
The haemoglobin is the respiratory pigment which is formed of the iron containing part known as haemin and protein part known as globin. It helps to transport respiratory gases (oxygen).

Question 7.
Name the disease in which the number of platelets reduces to 25,000 – 30,000 per cubic mm of blood. State its major symptoms.
Answer:
Dengue fever is one such disease in which the number of platelets get reduced to as low as 25-30 thousands per cubic mm of blood. The major symptoms of dengue are high fever, rashes or red spots on body, nausea or vomiting, pain in abdomen, back, or back of the eyes and muscles.

Long Answer Questions:

Question 1.
Given alongside is a diagram of human heart showing its internal structures. Label the parts marked 1 to 6, and answer the following questions.
Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System 1
(a) Which type of blood is carried by the blood vessel marked 2?
(b) Name the main artery which takes the blood from heart to different parts of the body?
(c) Which chamber of the heart receives deoxygenated blood from the body?
Answer:

  1. Left pulmonary artery
  2. Superior vena cava
  3. Left pulmonary vein
  4. Right auricle
  5. Left auricle
  6. Left ventricle

(a) Deoxygentated blood.
(b) Aortic arch (Aorta).
(c) Right Atrium

Question 2.
You can see some blood vessels on the outside of the hands specially in older people. Are those veins or arteries ? How can you confirm your answer ?
Answer:
In older persons the skin becomes loose as the fat below becomes less with age and the vessels passing through these areas especially on the outside of the hands become prominent. These are veins as they flow superficially. The veins are thin and less muscular. These carry the blood to the heart veins are placed superficially so they are easily visible to the eye and are prominent.
The blood in the veins will be carrying CO2 and will have many substances like sugar, amino acids, chemicals and bacteria.

Question 3.
Give the functions of lymph. Differentiate between Blood and the lymph.
Answer:
Functions of lymph are:

  1. Nutritive: It supplies nutrition and oxygen to those parts where blood cannot reach.
  2. Drainage: It drains away excess tissue fluid and metabolites and returns proteins to the blood from tissue spaces.
  3. Absorption: It absorbs the fats from the intestine through lymphatics.
  4. Defence: Lymphocytes and monocytes of the lymph function to protect the body. The lymphatics also remove bacteria from the tissues.

Difference between Blood and Lymph

Lymph Blood
1. It contains blood plasma without blood proteins and some RBC. 1. It contains blood plasms with proteins and all three types of blood cells namely RBC, WBC and blood platelets.
2. They are light yellow in colour and does not contain RBC and haemoglobin. 2. They are red in colour due to presence of haemoglobin in RBC,
3. It doesnot carry Oxygen. 3. It carries oxygen in the body.
4. It is the part of open circulatory system. 4. It is the part of closed circulatory system.

Question 4.
Name any two heart conditions that occur commonly. Briefly explain each of them.
Answer:

  1. Palpitations: Sometimes, one may experience the heart beating too hard or too fast or sometimes even skipping a beat. This can be frightening, but not serious or harmful and often this condition goes away on its own. Most of the time it is caused by stress or anxiety. Sometimes certain types of food may also cause palpitations.
    In rare cases, palpitations may be an indication of a more serious heart condition, specially if it is accompanied by shortness of breath, dizziness or chest pain.
  2. Hypertension: This is a condition that occurs in a person when blood flows through the blood vessels with a force greater than normal. This is also called High Blood Pressure. Hypertension can strain the heart, damage blood vessels and increase the risk of a heart attack or stroke.

Question 5.
During surgical operations or during accidents, the patient may be given blood from outside to save his life. What is the technical name of this process ? Briefly explain the precautions to be observed and taken in this process.
Answer:
During surgical operation or an accident when excess of bleeding takes place, the patient may be given blood from outside to save his life.
The transfer of blood from the donor to the recipient is called blood transfusion.
The following precautions are taken before the blood is given to the needy person:

  1. Matching of the donor’s blood with that of the recipient should be done.
  2. It should be made sure clinically that blood of donor is free from any infection.
  3. Sterilization of all the instruments to be used during the operation is must.

Question 6.
State briefly, the difference between white blood cells and the red blood cells.
Answer:
Difference between white blood cells and the red blood cells:

RBC WBC
1. They do not have nucleus at maturity. 1. They have a large characteristic nucleus.
2. They possess haemoglobin and are red. 2. They are colourless as they have no pigment.
3. They help in transport of respiratory gases. 3. They help in defence mechanism.
4. Life span is 120 days. 4. WBC have a short life span of 5 to 20 days.
5. They are about 5 million/mm3 of blood. 5. They are about 7000/ mm3 of blood.
6. In the embryonic stage the RBC are formed in the liver and spleen. But after birth, they are formed in the red bone marrow. 6. WBC are formed in the red bone marrow.

Question 7.
Answer very briefly, the following:
(a) Red Blood cells have no nucleus, then why do we call them cells?
(b) Why is it necessary to know The blood groups of the donor as well as the recipient ?
(c) Why should the blood going away from the stomach and intestines pass through the liver and not directly to heart?
Answer:
(a) RBC are formed in the liver and spleen when the organisjn is foetus. After birth these are formed in the red bone marrow. At the time of formation of RBC’s they have nucleus but later on they loose nucleus. Those enucleated cells perform all the functions of a cell so these are called cells.
RBC’s are surrounded by semipermeable plasma membrane. It contains homogenous cytoplasm and it is without the nucleus, endoplasmic reticulum, mitochondria, ribosomes and centrioles. RBC’s get advantage due to this condition. Corpuscles have more space to hold haemoglobin. It can as well give more oxygen by the haemoglobin to the tissue cells. So the enucleated condition is more useful to the tissue cells. The necessity of work has made them without nucleus and perform all the functions of the cells so they are called cells.

(b) Before transfusion of blood, it is most essential to determine the blood group of the donor and the recipient. The blood group of the donor and the recipient must match with each other, otherwise the RBC’s will stick to each other and thus the life of a recipient may be in danger as the blood groups are different. The sticking is due to the antigens (proteins) found in the blood of the donor and the antibodies found in the blood of the recipient.

(c) The blood from the stomach and the intestine goes to liver before going to the heart. Liver monitors the substances before passing into the body. Excess of glucose is retained by the liver in the form of glycogen and the excess amino acids are broken down by the liver. Harmful chemicals are detoxified and bacteria are destroyed and excess minerals, water and vitamins are stored in the liver.

Question 8.
Name the three kinds of blood vessels found in human beings. With the help of suitable diagrams, differentiate between them.
Answer:
The three kind of blood vessels found in human beings are arteries, veins and capillaries.

  1. Arteries are the blood vessels that carry blood from the heart to the various parts of the body.
  2. Veins are the blood vessels that carry blood from the body parts to the heart.
  3. Capillaries: These are the terminal branches of an artery, which rejoin to form a vein. A capillary is a very narrow tube whose walls have a single layer of cells with no muscles. Although the wall of a capillary is veiy thin, yet an exchange of nutrients, waste products and gases take place between the blood and the body fluids.Selina Concise Biology Class 8 ICSE Solutions – The Circulatory System 2

Differences:

Arteries

  1. Carry blood away from the heart.
  2. Have thick and more muscular walls.
  3. Carry oxygenated blood (except pulmonary artery which carries deoxygenated blood).
  4. The blood flows with jerks and under great force.

Veins

  1. Carry blood towards the heart.
  2. Have thin and less muscular walls.
  3. Carry deoxygenated blood (except pulmonary vein which carries oxygenated blood).
  4. The blood flows smoothly and under little pressure.

Capillaries:

  1. Arteries after entering an organ divide into number of smaller branches called arterioles which further divide repeatedly to form a network of fine branches called capillaries.
  2. The walls of the capillaries are very thin and are one cell deep.
  3. The Capillaries after the metabolic exchange unite to form larger vessels called venules, which again unite to form a vein.

Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants

Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 8 Biology Chapter 2 Reproduction in Plants. You can download the Selina Concise Biology ICSE Solutions for Class 8 with Free PDF download option. Selina Publishers Concise Biology for Class 8 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 8 Biology ICSE SolutionsChemistryPhysicsMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 8 Biology Chapter 2 Reproduction in Plants

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements

(a) Pollen is produced in the:

  1. Filament
  2. Style
  3. Pistil
  4. Anther

(b) Reproductive whorls of a flower are:

  1. Stamens and carpels
  2. Sepals and petals
  3. Sepals and stamens
  4. Petals and carpels

(c) Grafting is a method of:

  1. Artificial vegetative propagation
  2. Sexual reproduction
  3. Artificial pollination
  4. Cross-pollination

(d) Which one of the following is a false fruit ?

  1. Tomato
  2. Apple
  3. Potato
  4. Pea

Short Answer Questions:

Question 1.
Write two ways in which pollination may occur in plants.
Answer:
The two ways in which pollination may occur in plants are:
(a) Self-pollination.
(b) Cross-pollination.

Question 2.
Name the three agents of pollination.
Answer:
The three agents of pollination are:
(a) Insect
(b) Wind
(c) Water

Question 3.
Give two features of flowers which favour pollination by insects.
Answer:
Specialities of insect-pollinated flowers:
(a) These flowers are large with coloured petals to attract insects.
(b) These are scented so that insects locate the flowers by smell.

Question 4.
Name two characteristics of flowers in which pollination occur by wind.
Answer:
Special features of wind-pollinated flowers:
(a) They produce light pollen so that it is easily carried away.
(b) They produce a large quantity of pollen.

Question 5.
What is a “false fruit” ? Give one example:
Answer:
In false fruits the base of the flowers (thalamus) becomes the main fleshy part of the fruit, while the ovary remains a small central part containing seeds. Example: Apple and Pear.

Question 6.
Name any three agencies for dispersal of seeds.
Answer:
a. Wind
b. Water
c. Man and animals, birds, bats, squirrels.

Question 7.
Fill in the blanks by selecting suitable words:
(unisexual, fertilisation, fruit, stamen, anther, bisexual, pollination, seed, ovary)
Answer:
a. A flower that bears both the male and the female parts is known as bisexual flower.
b. A flower bearing only male or female parts is known as unisexual flower.
c. Transfer of pollen grains from the anther to the stigma is known as pollination.
d. Fusion of male cell with the female cell is called fertilisation.
e. The ovule develops into a seed.
f. The ovary of the flower develops into a fruit.

Long Answer Questions:

Question 1.
What is vegetative reproduction?
Answer:
Vegetative reproduction: In this method, new plants are produced by the vegetative parts of the plants. The vegetative part mean the leaf, stem and root. Potato, mint, ginger, banana etc. are reproduced by this method.
Vegetative propagation can occur by natural methods as well as by artificial methods.
Natural method includes reproduction by stem, by roots and by leaves.
Artificial method include reproduction by cutting, layering, grafting and tissue culture.

Question 2.
Briefly explain why a gardener prefers to grow certain plants vegetatively?
Answer:
Gardener prefer to grow certain plants by vegetative method. The advantages in doing so are as follows:

  1. Reproduction by vegetative parts takes place in a shorter time.
  2. New plants, thus produced, spread very fast in a small area.
  3. It is a surer method.
  4. All the characters of the mother plant are retained by the daughter plants.

Question 3.
Why is it disadvantageous to grow plants vegetatively?
Answer:
It is disadvantageous to grow plants vegetatively because of following:

  1. As all plants developed by vegetative propagation are identical, they are likely to be affected simultaneously if a disease spreads in the farm.
  2. Dispersal of plants does not take place on its own. Daughter plants, so developed, tend to remain nearby and are restricted to a particular area leading to competition for resources.

Question 4.
What is meant by pollination? Explain the structure of germinating pollen grain with the help of a labelled diagram.
Answer:
Pollination: Pollination is the process in which the pollen grains from the anthers are transferred to the stigma.
Structure of the pollen grain: After pollination pollen grains are deposited on the stigma of the carpel. Under suitable conditions pollen grains produce a tube known as pollen tube. This tube grows down through the stigma and style towards the ovary.
Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 1
The nucleus of the pollen grains divides by mitosis and forms two male gametes. The tip of the pollen tube after entering ovary discharges the two male gametes into the embryo sac.
One of the male gametes fuses with the egg to form the zygote. This fusion is called fertilization. Another male gamete fuses with the diploid secondary nucleus and forms the endosperm, a food storing tissue.

Question 5.
Imagine all the seeds produced by a plant happen to fall under the same plant and sprout into new plants. Mention any two problems that will be faced by the new plants. –
Answer:
If all the seeds produced by a plant happen to fall under the same plant and sprout into new plants then in this situation plants will face the following problems:

  1. A large number of plants will grow in a small limited space. The water and the minerals available to them in the soil will be limited.
  2. The air surrounding them will not be enough and less sunshine will be available to them. As a result, most of these sprouted plants will die.

Question 6.
What is a flower ? Draw a neat labelled diagram showing the L.S. of a typical flower.
Answer:
A flower is a reproductive part of a plant. It helps in sexual reproduction as it has male parts and female parts. A fully opened flower has the following parts:
Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 2

Stalk—A flower is attached to the shoot by means of stalk or pedicel stalk. The tip of the stalk is swollen or flattened. This is called torus or thalamus or receptacle.
The different parts of a flower are inserted on the thalamus. There are usually four whorls as

Calyx (Sepals)
Corolla (Petals)
Androecium (stamens)
Gynoecium (Carpels) Present on the thalamus

  1. Sepals (Calyx): These are the outermost part of the flower. These are leaf like and green in colour. This is the outer covering of the flower and form outer whorl in a flower. The Calyx (sepals) enclose the inner parts of the flower when it is a bud. It is protective in function.
  2. Corolla (Petals): Petals form the second whorl inner to the sepals. These are usually coloured, gaudy, or white in colour and scented and give sweet smell. The value of a flower is due to the attractive colour of the petals. These attract the insects for pollination.
  3. Stamens (Androecium): The third whorls inner to the petals are stamens. This third whorl is called Androecium. These are the male parts of the flower. Each stamen is formed of a long narrow, hair like structure called filament. On its tip it bears, a rounded broad sac like structure called anther. Each anther has two anther lobes. Each anther lobe has two pollen sacs which have powdery mass called pollen grains.
  4. Carpels (Gynoecium): Carpels are the inner most or fourth whorl in a flower. It is lodged on the thalamus and forms the female part of a flower. This whorl of carpels is called gynoecium. Each carpel or pistil has three parts.
    (a) The lower most, swollen part is ovary. It is attached to the thalamus.
    (b) The middle part is style which is narrow, thread like.
    (c) Stigma: The style ends in a knob like, rounded structure which is sticky in nature to receive the pollen grains.
    The ovaries contain ovules which later turn into seeds after fertilization and the ovary wall forms the fruit sometimes the thalamus also becomes a part of the fruit as in apple.

Question 7.
Write short notes on the following:
(a) Micro propagation
(b) Bryophyllum
(c) Vegetative reproduction
(d) Grafting
Answer:
(a) Micro propagation: This is the propagation of plants involving cell and tissue culture. If vegetative propagation is not possible in a crop, then buds, shoot apex or any other part of the plant can be used as explant for micropropagation.
Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 3

  1. The explants are treated with sterilisation chemicals to prevent microbial growth, and then cultured in a particular nutrient medium.
  2. Cells grow and divide to form a cell mass called callus Some growth regulators (Plant hormones) are added.
  3. The callus differentiates into plant parts looking like plant (plantlet). After 4-6 weeks the plantlets transferred to the soil.

(b) Bryophyllum: It is a beautiful plant grown in gar xerophyte plant and can grow in any type soil or container. It requires sun and watering time to time. We can grow it vegetatively.
Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 4
When a leaf is put on the soil or falls off accidentally from the parent plant. It starts giving out buds in the notches of the leaves. These buds start growing when in touch with soil having moisture. They give out adventitious roots which go into the soil and small aerial shoots which go into the air. So these adventitious buds form many plants from a single plant. Thus we can get many plants from a single leaf. We can grow these tiny plants into separate pots to get independent plants. This is one of the vegetative mode of reproduction.

(c) Vegetative reproduction: This is method of producing new plants from the vegetative parts of the plants. The vegetative part means the leaf, stem, root. As potato, mint, ginger, banana, sugar beet, gul-e-daudi, asparagus, sugar cane, are produced by this method.

(d) Grafting: In plants like mango, zizyphus (ber), guava apples, fruits, roses, a small bud is fixed on the stem. Many types of apples on a single plant thus a small orchard on a single plant. So we can have different types of roses and chrysanthemums on a single plant.
Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 5

Question 8.
How artificial pollination is useful to plant breeders ? Discuss briefly.
Answer:
Artificial pollination means transfer of pollen to the stigma artificially. In ancient times, it was a common practice to sprinkle “male flowers of palms on the “female flowers”. However, in modem era, plant breeders use artificial pollination for developing new varieties. The breeders remove the anthers in young flowers and cover such flowers by plastic bags. Such flowers are then pollinated with pollen from the plants of the desired variety.

Question 9.
With the help of suitable diagrams, describe
(a) Binary fission in plants
(b) Budding in yeast cell
Answer:
(a) Binary fission: This is one of the asexual mean of reproduction. In lower plants like bacteria reproduction takes place by this process. In this process the nucleus of the cell divides into two. Then the cell wall splits across the middle of the cell. Thus each part has a nucleus. Thus each part is an independent bacterium.Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 6
Later on these two parts of the cell get separated from each other and form two independent individuals called daughter cells and lead independent life.

(b) Budding in yeast cell: Budding is the most common method in yeast. The Parent cell produces an outgrowth called a bud. The bud grows, and then gets detached from the parent body to lead an independent life.
Selina Concise Biology Class 8 ICSE Solutions – Reproduction in Plants 7

Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid

Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid

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Selina Concise ICSE Solutions for Class 8 Biology Chapter 9 Diseases and First Aid

REVIEW QUESTIONS

Multiple Choice questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) A mosquito is a vector for

  1. Typhoid
  2. Cholera
  3. Malaria
  4. Jaundice

(b) Dengue is caused by a

  1. Protozoan
  2. Virus
  3. Worm
  4. Fungus

(c) The idea of vaccination was conceived by

  1. Charles Darwin
  2. Alexander Flemming
  3. Issac Newton
  4. Edward Jenner

(d) Which one of the following is not a psychotropic drug ?

  1. Morphine
  2. Cocaine
  3. Heroin
  4. Penicillin

(e) Which one of the following is a communicable disease ?

  1. Measles
  2. Cancer
  3. Heart stroke
  4. Allergy

(f) Cataract is a disease of: –

  1. Ears
  2. Nose
  3. Eyes
  4. Throat

(g) Infectious diseases can be prevented by:

  1. Medicines
  2. Proper food
  3. Immunisation
  4. Exercise

(h) Which one of the following is a genetic disease ?

  1. Scurvy
  2. Leukemia
  3. Goitre
  4. Haemophilia

(i) Which one of the following is a degenerative disease ?

  1. Thalassemia
  2. Beri-beri
  3. Cataract
  4. Diabetes

(j) Pellagra is one disease caused by the deficiency of:

  1. Vit. B3
  2. Vit. B1
  3. Vit. C
  4. Vit. D

(k) Hay fever and asthma are

  1. Deficiency diseases
  2. Genetic diseases
  3. Organic diseases
  4. Allergy diseases

(I) Which one of the following vitamin deficiency diseases can be cured by eating a diet which includes carrot, yellow fruits, vegetables, butter, milk, fish ?

  1. Beri-beri
  2. Dermatitis
  3. Night blindness
  4. Scurvy

Short Answer Questions:

Question 1(a).
What is a non-communicable disease ?
Answer:
The diseases which are caused due to improper functioning of the body organs e.g. diabetes, heart attack. They are not caused by germs and not transmitted from one to another.

Question 1(b).
What are communicable diseases ?
Answer:
Those disease which spread from one person to another by the entry of microorganisms are known as communicable diseases.

Question 1(c).
How can we control spreading of diseases by mosquitoes and houseflies ?
Answer:
We can control spreading of diseases by mosquitoes and houseflies by using repellants, throwing garbage in covered bins, avoiding stagnation of water and checking breeding of these insects.

Question 1(d).
Public hygiene is equally important as personal hygiene. Give reasons.
Answer:
Keeping oneself clean is personal hygiene. But public hygiene is equally important as dirty surrounding may lead to more of houseflies, mosquitoes and other insects which are major vectors of many communicable diseases. Clean surrounding also provides good mental health as it soothes our mind.

Question 1(e).
What is a deficiency disease ?
Answer:
These disease are caused by lack of nutrients, vitamins, minerals as a anaemia, goitre.

Question 1(f).
Biting nails should be strictly avoided. Give reason.
Answer:
Nail biting may cause many disease as the dirt has many bacteria causing diseases. Nails should be cut from time to time to save from diseases.

Question 1(g).
Regular exercise and proper rest is a must. Give reason.
Answer:
Regular exercise keeps our body strong and immune to many diseases, rest refreshes our body.

Question 1(h).
Children eating more of fast food tend to suffer from obesity (overweight). Comment.
Answer:
Fast food like pizza, burger, patty, oily foods etc. have much carbohydrates and fats. Children eating these become more and more fat and gain weight soon as they do not do much of physical work.

2. Name the following:

Question 2(a).
A viral disease caused due to unhealthy sexual contact
Answer:
AIDS.

Question 2(b).
A disease caused due to Plasmodium
Answer:
Malaria.

Question 2(c).
A disease caused by the bite of female Anopheles mosquito
Answer:
Malaria.

Question 2(d).
Two viral diseases caused by mosquito bites
Answer:
Dengu, Chikungunya.

Question 2(e).
Any droplet — borne disease.
Answer:
Amoebiasis, Cholera, Hepatitis A.

Question 2(f).
A viral disease caused by the bite of a dog
Answer:
Rabies/Hydrophobia

Question 2(g).
A disease due to choking of coronary artery
Answer:
Atheraosclerosis.

Question 2(h).
Two diseases caused due to deficiency of protein in the diet of a child.
Answer:
Kwashiorkor and marasmus.

3. Write short (2-3 sentences) notes on the following:
Disease, immunisation, pathogen, AIDS, vaccination, vector.

Answer:

Disease: Disease is a departure from normal health due to structural or functional disorder of the body. Disease may be due to deficiency of nutrients or malfunctioning of organs or 1 genetic disorders, improper metabolic activity, or allergies, or cancer and mental illness as diabetes, haemophilia, leukemia, schizophrenia.

Immunisation: It means, we make the body immune to certain diseases by introducing respective weakened germs into the body. Thus we develop resistance to the concerned disease this process is called immunisation. The germs or the material introduced into the body to make it resistant to the concerned disease is called vaccine. This produces antibodies in the body of the person and the person can be saved by these antibodies. The vaccine can be given by the injection or orally as polio drops, tap vaccine for typhoid, BCG vaccine for tuberculosis.

Pathogens: The germs that cause diseases to human beings and to other animals and plants are called pathogens. They spread the diseases from person to person or through the air or through the articles of the diseased persons. Pathogens may be different kinds of bacteria, viruses, fungi, protozoans or worms.

AID’S (Acquired Immune Deficiency Syndrome): It is a viral disease caused by the virus called HIV (Human immuno deficiency virus) This virus makes the defence mechanism of the human body very weak. The immune system in the body as W.B.C. becomes weak. Thus the person catches the infectious diseases very easily. This disease spreads through sexual contact as one of the partner may be carrier of the disease. It may spread through the blood transfusion and infected syringes, blades of the barbers, it may infect the developing baby through the blood by the mother. It is very deadly disease.

Vaccination: Vaccination is a method of making the body immune to a particular disease by injecting killed or weakened disease causing microbe into a body to stimulate the formation of antibodies and develop immunity to that disease causing microbe.

Vector: A vector is an organism that carries disease causing microbes (pathogens) from one host to another. They are the carriers of infection. Example: Mosquito, housefly, etc.

P.Q. Fill in the blanks by selecting suitable words given below:
(clotting, goitre, insuline, rickets, iron, proteins)

(a) Anaemia is caused due to the deficiency of iron.
(b) Deficiency of Vit. D causes rickets in children.
(c) Deficiency of iodine in the diet may cause goitre.
(d) Diabetes is caused due to undersecretion of insulin.
(e) Kwashiorkor is caused due to the deficiency of proteins.
(f) Haemophilia is a disease caused due to slow clotting of the blood.

P.Q. Find the odd one out:

(a) Typhoid, cholera, jaundice, tuberculosis, tetanus.
Jaundice is odd one
(b) Cold, AIDS, plague, malaria, measles.
Malaria is odd one.
(c) Scurvy, rickets, haemophilia, pellagra, night blindness.
Haemophilia is odd one.
(d) Proteins, carbohydrates, fats, minerals, cancer.
Cancer is odd one.

P.Q. Fill in the blank in the following table:
Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid 1
Answer:
Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid 2
Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid 3

Long Answer Questions:

Question 1.
What is vaccination? Mention the four ways in which vaccine’s are prepared, giving the name of one disease for which each type of vaccine is used.
Answer:
For developing resistance in the body we introduce germs or germ substances in the body to develop resistance in the body against a particular disease. The material introduced into the body is called vaccine, this practice is called prophylaxis.
The germ or the germ substance is put into the body orally as polio drops or it is introduced by injection as TAB vaccine. Vaccine or vaccination was attached with small pox, but it is now used in a general sense.

Preparation:

  1. Killed germs are introduced into the body These act as vaccine for TAB, vaccine for typhoid, Salk’s vaccine for poliomyelitis. Rabies vaccine for dog bite.
  2. Living weakened germs: The living germs are treated in such a way that they become very weak and as such, they cannot cause the disease. They can induce antibody formation such as the vaccine for measles and the freezed dried BCG vaccine for tuberculosis.
  3. Living fully virulent germs: These virulent germs in small doses are introduced into the body as vaccine and these produce antibodies in the body and these do not allow the germs of particular type to cause that disease: In this vaccination the person is inoculated with cowpox virus. It is very similar to small pox virus.
  4. Toxoids: Toxoids are prepared from the extracts., of toxins secreted by bacteria. These toxins are poisons and these are made harmless by adding formalin into them. They retain their capacity and as a result when introduced into the body they produce antibodies into the body and do not allow the germs to grow in the body as vaccines for diphtheria and tetanus.

Question 2.
Burns can be superficial burns, deep burns or chemical burns. What emergency care you would suggest in each case.
Answer:
When one gets burnt up accidentaly one should not pull clothes from the burnt area and one should not cut the blisters. One should apply butter, vaseline or ointment.

  • Superficial burns: When there are superficial bums, put cold water on it and apply some oily substance, bumol, castor oil, vaseline, butter etc.
  • Deep burns: When there are deep bums do not put cold water on the burnt area. Seek the help of hospital and one should be kept under the treatment of some expert doctor of skin.
  • Chemical burns: In case of chemical burns i.e., due to acid and other chemicals, wash with running water for 10 minutes and then cover with dressing.

Question 3.
Describe the ways in which communicable diseases are transmitted through various indirect methods.
Answer:
Indirect methods of transmission of communicable diseases:

  1. Using items used by the infected persons: The healthy persons may be infected by using the articles like towel, hankey, utensils, bedding used by the patient infected by the communicable diseases. Diseases like tuberculosis, ring worm; common cold, influenza are transmitted by this method.
  2. Contaminated food and water: Diseases like dysentery, cholera spread through the contaminated food and water. Flies sitting on the food, if taken by a healthy person may be infected by the germs which may cause vomiting and loose motions. Similarly water and food infected by entamoeba may cause dysentery to persons who may take contaminated food.
  3. Vectors or carriers: Organisms like mosquitoes and house flies, ticks carry germs from the source of infection and pass on the germs to the normal persons and thus they are infected by diseases like malaria, cholera, plague. These organisms which carry the disease are called vectors and are not infected themselves.
    Mosquitoes suck blood and carry the disease causing protozoans from infected persons to healthy persons.
    Similarly houseflies carry the germs from garbage and sewage to the food. If this food is taken by the persons they become prey to typhoid and other diseases.
  4. Air: One sneeze from a person infected by cold may give billions of germs which are carried by air and may infect the healthy person. Tuberculosis passes from one person to other by coughing or sneezing of the infected person.
    These germs remain suspended in the air and persons may be infected by these spores or germs. Common cold, measles, diptheria, chicken pox.

Question 4.
Given a crossword puzzle. Read the clues across and clues downward, and fill up the blank squares. Check up your performance with the correct solution given at the end.

Clues across

  1. Category of pathogen that causes diseases, like common cold and mumps.
  2. These may readily grow in your hair, if you do not wash it regularly.
  3. This is the vaccine for preventing tuberculosis.
  4. Cover this part of your body by a handkerchief while sneezing to prevent droplet infection to others.
  5. The disease pertussis is popularly known as whooping
  6. One of the most common insects which visits our exposed foods and contaminates them.
  7. A disease that weakens body’s defence system
    Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid 4
  8. Germ or germ – substance introduced into the body to prevent occurrence of an infectious disease.
  9. A disease in which the eyes, the skin and the urine turn yellow.
  10. An organ usually affected by tuberculosis.
  11. A disease caused by the bite of an infected dog, and which affects the central nervous system.

Answer:
Selina Concise Biology Class 8 ICSE Solutions – Diseases and First Aid 5