(a) The above diagram represents an animal cell because cell is bounded by cell membrane and cell wall is absent.
(b) The above diagram represents a eukaryotic cell as it has a well-organised nucleus and other cell organelles in it.

Earth
The various cycles on earth like water, oxygen, carbon dioxide are disturbed due to deforestation. Also, the fertile land of earth is converted into dry land, i.e. desertification occurs by deforestation.

If the child is suffering from diarrhoea, the polio drops that are orally given vaccine may be excreted out because of frequent motions and thus becomes ineffective.

Weeds are the undesirable (unwanted) plants that may grow naturally along with the crop. They are hazardous to the crops as they compete with the crop for food, nutrients, water and sunlight. Hence, they must be controlled. The process of controlling or removing weeds from the field is known as weeding. There are several methods to remove weeds such as tilling in which weeds are uprooted. They are removed manually by cutting with the help of khurpi. They are also controlled by chemicals known as weedicides which kill the weeds, e.g. 2,4-D.

There is an outer thick layer in cells of plants called cell wall. It is required by plant for protection. Plants cells need protection against variations in temperature, high wind speed, atmospheric moisture etc.

No, the Red Data Book keeps record of only those species that are threatened, i.e. either critically endangered, endangered or vulnerable.

Forest conservation maintains the balance in nature. It acts as carbon sinks absorbing CO₂ and keeps global warming at bay.

Three main differences between plant and animal cells are as follows:

Chickenpox and ringworm are diseases that can spread through direct contact with infected person.

Baking bread/manufacturing of alcoholic drinks is the commercial use of yeast.

The process of rearing animals by providing them proper food, shelter and care is called animal husbandry. Some food materials provided by animals are eggs, milk, meat, honey, etc.

The rabi crops are known as winter crops because they are grown in winter season, e.g. wheat, gram, etc.

Uses of Bacteria:
(i) They are used to increase soil fertility by fixing nitrogen.
(ii) Some bacteria are used to produce antibiotics.
(iii) Lactobacillus bacterium converts milk into curd.
(iv) Some bacteria help in many functions of our body.
Uses of Fungi:
(i) Yeasts are used to prepare alcohol and vinegar by fermentation.
(ii) Mushrooms are eaten as food.
(iii) Penicillin is an antibiotic formed by a fungus called Penicillium.
Uses of Algae:
(i) Algae are used to make jellies.
(ii) Chlorella is used to obtain proteins.
(iii) Silicafrom diatoms are used in toothpastes.