Explanation

Q. 3. (a) (i) Why are the bat and whale considered mammals?

Bats and whales are considered mammals because they share several characteristics, including:

Warm-blooded: 

Mammary glands:

Live birth: 

Complex brains: 

Backbone: 

(ii) Write a note on liver juice ‘Bile’. (5)

(b)How the urine is formed? Describe the role of the kidney in excretion. (5)

Urine Formation:
Urine is formed through three main processes in the kidneys: filtration, reabsorption, and secretion.

Blood is filtered in the glomerulus, removing waste and excess substances, which pass into the tubules.

Role of Kidney in Excretion:
The kidneys filter waste, excess ions, and toxins from the blood to produce urine, which is then excreted. 

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(c) (i) How is a bacterial cell different from a plant cell?

Bacterial Cell vs. Plant Cell:
A bacterial cell is a prokaryote, meaning it lacks a defined nucleus and membrane-bound organelles, while a plant cell is a eukaryote with both a nucleus and organelles.

Plant cells have a rigid cell wall made of cellulose and contain chloroplasts for photosynthesis, whereas bacterial cell walls contain peptidoglycan, and bacteria lack chloroplasts.

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(ii) What do you think low temperatures slow down cold-blooded animals? (5)

Low temperatures slow down cold-blooded animals because their body temperature depends on the external environment.

As temperatures drop, their metabolic processes, which control energy and movement, slow significantly, causing them to become less active or even enter a dormant state. This helps them conserve energy until temperatures rise.

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(d)What is hepatitis, its types, causes, prevention, and cure? (5)

Hepatitis:
Hepatitis is an inflammation of the liver, commonly caused by viral infections, but it can also result from toxins, alcohol, or autoimmune diseases.

Types:
The main types are Hepatitis A, B, C, D, and E, differing in transmission modes, severity, and long-term effects.

Prevention and Cure:
Vaccines (for Hepatitis A and B), practicing good hygiene, safe food, and water consumption prevent hepatitis; treatment varies by type, including antiviral medications and lifestyle changes for management.