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Solutions for Biology, Class 8, ICSE
Assertion (A): Some bacterial cells have an outermost slimy gelatinous layer in the form of a capsule.
Reason (R): Capsule protects the bacterium from desiccation and toxic compounds.
Both A and R are true.
Explanation — A bacterial cell has an outermost slimy, gelatinous, protective layer in the form of a capsule to protect it from desiccation and toxic compounds.
Assertion (A): Lactobacillus is a kind of bacteria which can convert milk into curd and curd into cottage cheese.
Reason (R): Lactose (milk sugar) can be converted into lactic acid by the action of Lactobacillus and different types of milk products like curd and cheese can be prepared.
A is false and R is true.
Explanation — Lactobacillus indeed helps convert milk into curd, however curd is converted to cottage cheese by processing it further which does not need the help of the bacteria Lactobacillus.
Assertion (A): Tea leaves and tobacco leaves are cured by bacteria to obtain specific flavours and aroma.
Reason (R): Curing is the process during which leaves are roasted at a very high temperature along with bacteria and some edible colours.
A is true and R is false.
Explanation — Curing is not about roasting leaves at a very high temperature with bacteria and edible colours. Instead, it involves controlled drying, fermentation, or aging, often at moderate temperatures, to enhance flavour naturally.
Assertion (A): The process of recovery of threads from the killed larvae of silkworm is called as reeling.
Reason (R): Threads are recovered from the larval stages of silkworm because this stage is the most active and productive stage in its life-cycle.
A is true and R is false.
Explanation — Threads are recovered from the cocoon, which is spun by the larva. The cocoon is harvested, and silk threads are extracted from it, not directly from the larva.
Assertion (A): Draught animals are mostly found in regions of prolonged shortage of rainfall.
Reason (R): Draught animals such as bullocks, horses and bulls are reared for doing heavy work.
A is false and R is true.
Explanation — Draught animals are those animals which are reared for doing heavy work such as bullocks, camels, elephants, horses, donkeys and mules. However, they are not specifically found only in regions with prolonged rainfall shortages.
Fill in the blanks:
Cattle feed made from cereals and wheat is called ...............
Rearing of birds for eggs and meat is called ...............
Animal food is rich in ...............
............... is an example of root crop.
Cereals are rich in ...............
............... are chemical substances used to destroy pests.
............... ia an example of a tuber crop.
Pig farming is termed as ...............
Cattle feed made from cereals and wheat is called concentrates.
Rearing of birds for eggs and meat is called poultry.
Animal food is rich in proteins.
Sweet potato is an example of root crop.
Cereals are rich in carbohydrates.
Pesticides are chemical substances used to destroy pests.
Potato ia an example of a tuber crop.
Pig farming is termed as piggery.
Difference between Eggers (or Layers) and Broilers:
| Egger | Broiler |
|---|---|
| The egg laying chickens are called Eggers | Chickens reared for obtaining meat are called Broilers |
| Eggers need food rich in vitamins, minerals and micronutrients. | Broilers require food rich in proteins, fats and vitamin A & K. |
| Eggers require enough space and adequate lighting for proper growth. | Broilers require conditions to grow fast with low mortality. |
Difference between Food crops and Cash crops:
| Food crop | Cash crop |
|---|---|
| Food crops are cultivated for the production of food. | Cash crops are cultivated for commercial purposes. |
| Examples — Wheat, Pulses | Examples — Cotton, Rubber |
Difference between Green revolution and White revolution:
| Green revolution | White revolution |
|---|---|
| The Green Revolution involved the development and application of high-yielding crop varieties, enhanced irrigation, and the use of chemical fertilisers and pesticides to increase agricultural productivity. | The White Revolution focused primarily on milk production, aiming to increase dairy yield and improve rural livelihoods through cooperative milk unions and dairy farming advancements. |
| Father of Green Revolution was M.S. Swaminathan. | Father of White revolution was Verghese Kurien. |
Difference between Milch animals and Draught animals:
| Milch animals | Draught animals |
|---|---|
| Milch animals are those who are kept for the purpose of milk production. | Draught animals are those whose males are used for ploughing and carriage purpose. |
| Example: Cow, Buffalo | Example: Ox, Camel, Horse |
Difference between Kharif crops and Rabi crops:
| Kharif crops | Rabi crops |
|---|---|
| Kharif crops are sown in early May – usually at the beginning of the first monsoon rains. | Rabi crops are sown around mid-November, preferably after the monsoon rains. |
| They are known as autumn crops. | They are winter crops. |
| Example: Rice | Example: Wheat |
Briefly explain the following terms :
(a) Animal Husbandry
(b) Sericulture
(c) Aquaculture
(d) Hatcheries
(e) Pisciculture
Answer
(a) Animal Husbandry — The branch of biology which deals with feeding, shelter, caring and breeding of domesticated animals is called animal husbandry.
(b) Sericulture — The technique of artificial rearing of silkworm for production of silk is called sericulture.
(c) Aquaculture — Aquaculture is the term used for production or farming of useful aquatic animals like fish, prawns, lobsters, molluscs, etc.
(d) Hatcheries — A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish or poultry.
(e) Pisciculture — Pisciculture is the production and management of fishes. It involves breeding and raising fish commercially in tanks or enclosures mainly for food.
Some of the uses of bacteria in the food industry are:
Following are the benefits of "Green Revolution" in our country:
Following are the benefits of "White Revolution" in our country:
Draw a neat and labeled diagram of the life cycle of a silk moth and answer the following questions.
(a) What are the four stages in the life cycle of a silk moth?
(b) Write the specific names for the larva and pupa of the silk moth.
(c) Name the process of recovering threads from the killed cocoons.
(d) Name a suitable plant on which these insects grow and develop successfully.
(e) Which kind of fibres can be made by using the threads from the cocoons ?
Labeled diagram showing the life cycle of a silk moth is given below:
(a) The four stages in the life cycle of a silk moth are:
(b) The specific names for the larva and pupa of the silk moth are Caterpillar and Chrysalis.
(c) Reeling.
(d) Mulberry
(e) Silk fibre can be made by using the threads from the cocoons.
Draw a neat and labeled diagram of the 'Internal structure of yeast'. Answer the following questions.
(a) Name the kingdom to which the yeast belongs.
(b) Is it unicellular or multicellular?
(c) Write the specific mode of nutrition in this organism.
(d) What are the suitable medium/places where yeast can grow successfully?
(e) Name two vitamins which are found in yeast.
(f) Write the economic importance of yeasts in two points.
Labeled diagram showing the ‘Internal structure of yeast’ is given below:
(a) Fungi
(b) Unicellular
(c) Yeast has a heterotrophic mode of nutrition.
(d) Yeast can grow successfully in moist and warm conditions in presence of sugar.
(e) Yeast is a source of vitamin B and vitamin E.
(f) Two points highlighting the economic importance of yeasts are:
Draw a neat and labelled diagram of a bacterium showing its internal structure. Answer the following questions.
(a) Name the kingdom to which bacteria belongs.
(b) Are they prokaryotes / eukaryotes?
(c) What are the four kinds of bacteria on the basis of their shape? Write the specific terms with their shapes.
(d) Name the outermost protective covering of a bacterium.
(e) What are the four suitable conditions required for the growth and development of bacteria?
(f) Name two kinds of respiration which can take place in bacteria.
(g) Mention the locomotory structure of bacteria which can help them to move.
Labeled diagram showing the internal structure of a bacterium is given below:
(a) Monera.
(b) They are prokaryotes.
(c) Bacteria can be classified into four types based on their shape:
(d) Slime Capsule.
(e) Four suitable conditions required for the growth and development of bacteria are:
(f) Two kinds of respiration which can take place in bacteria are:
(g) The locomotory structure of bacteria that helps them move is called the flagellum.
Match the terms given in column A with those in column B.
| Column A | Column B |
|---|---|
| (a) Rabi crop | (i) Transplantation |
| (b) Rice crop | (ii) Winter crop |
| (c) Orchards | (iii) Kharif crop |
| (d) Apiculture | (iv) Fishes |
| (e) Sericulture | (v) Cows |
| (f) Pisciculture | (vi) Honey bees |
| (g) Livestock | (vii) Dogs |
| (h) Pet | (viii) Silkworms |
| Column A | Column B |
|---|---|
| (a) Rabi crop | (ii) Winter crop |
| (b) Rice crop | (iii) Kharif crop |
| (c) Orchards | (i) Transplantation |
| (d) Apiculture | (vi) Honey bees |
| (e) Sericulture | (viii) Silkworms |
| (f) Pisciculture | (iv) Fishes |
| (g) Livestock | (v) Cows |
| (h) Pet | (vii) Dogs |
(a) Aseel
(b) Apiculture
(c) Mr. Verghese Kurien
(d) Kashmiri Pashmina
(e) M. S. Swaminathan
Yeast is a kind of microscopic organism which readily grows in all kinds of sugary solutions and in plant exudations containing sugar. Yeast is economically important in many ways. Some are given below:
P. In breweries
Q. In bakeries
R. Curing of tobacco
In which of the following processes/ways does yeast not play an important role ?
Only R
Reason — Yeast readily grow in all kinds of sugary solutions and in any plant exudations containing sugar. Yeast are widely used in breweries and bakeries. However, curing of tobacco is the action of certain bacteria, not yeast.
Amit and Sumit studied different kinds of microbes like viruses, bacteria, algae, fungi and protozoa. Which of the following statements does not match with the characteristic features of fungi ?
Fungi help in biological nitrogen fixation and improve the soil fertility.
Reason — Fungi are saprophytic in nature, i.e. they feed on dead and decaying organic matter and are called the natural cleaners of environment. They do improve soil health through decomposition but not by fixing nitrogen directly.
Name the following :
(a) Four animals which provide us food.
(b) Two dual purpose breeds of cattle.
(c) Two examples of milch animals.
(d) Two high-yielding indigenous breeds of cows.
(e) Four varieties of edible fishes in India.
(f) Two breeds of buffaloes.
(g) Two exotic breeds of Fowl
(h) Two exotic (Foreign) breeds of cows
(i) Two indigenous breeds of pigs
(a) Goat, Sheep, Pig, Hen
(b) Dangi and Tharparkar
(c) Cows, Goats
(d) Gir, Sahiwal
(e) Bombay Duck, Eel, Hilsa, Salmon
(f) Murrah, Surti
(g) White leghorn, Rhode Island red
(h) Jersey, Brown Swiss
(i) Desi and Ghori
The two main crop seasons of India are:
Organic farming is the practice of raising crops without using synthetic fertilisers and pesticides.
The main aim of organic farming is to enhance soil fertility, grow crops in an eco-friendly environment, free from chemical pollution (pesticides) and thus produce crops with high nutritional value.