Questions Related to NCERT

Phototropism is the growth of a plant in response to light. It happens because of a plant hormone called auxin. When light comes from one side, auxin moves to the shaded side of the plant. This causes the cells on that side to grow faster, making the plant bend towards the light.

Function of receptors:
Receptors are specialized cells present in sense organs (like eyes, ears, skin, nose, and tongue). They detect different types of stimuli from the environment such as light, sound, smell, touch, and taste. These receptors send messages as electrical signals to the brain or spinal cord for processing and response.

If receptors do not work properly:

1. The body will not be able to sense changes in the environment.
2. It may not respond correctly to danger or other stimuli.
3. For example, if touch receptors in the skin are damaged, the person may not feel pain from a hot object and may get injured.

Correct answer: (d) All of the above
The brain controls thinking, heartbeat regulation, and body balance, so all the given functions are correct.

Correct answer: (b) Synapse
The synapse is the gap between two neurons where signals are passed using chemical messengers.

Correct answer: (d) Cytokinin
Cytokinin is a plant hormone that helps in cell division and growth.

Some patients of diabetes are treated with insulin injections because their pancreas does not produce enough insulin or does not produce it at all.
Insulin is a hormone that helps control the level of sugar (glucose) in the blood. Without enough insulin, sugar builds up in the blood, which can be harmful.

When adrenaline is released into the blood (during fear, stress, or danger), it prepares our body to face the situation. This is called the "fight or flight" response.
The body shows the following changes:

1. The heart beats faster to send more oxygen to muscles.
2. Breathing becomes faster to take in more oxygen.
3. More energy is released by breaking down stored sugar.
4. Blood is sent more to muscles and less to skin and digestive system.

The use of iodised salt is advisable because iodine is essential for the proper functioning of the thyroid gland, which produces the hormone thyroxine. This hormone regulates the body’s metabolism.
A lack of iodine in the diet can cause a disease called goitre, where the thyroid gland in the neck becomes swollen.

In animals, chemical coordination is carried out by hormones, which are chemical messengers. These hormones are produced by special glands called endocrine glands.
Hormones travel through the bloodstream to different parts of the body and control various functions like growth, metabolism, reproduction, mood, etc.

When a tendril (a thin, curling part of a climbing plant) touches a support, the cells on the side away from the support receive more auxin.
Auxins promote cell elongation, so the cells on the outer side grow faster than those on the side touching the support. This unequal growth causes the tendril to bend and curl around the support.

Auxins are plant hormones that help in the growth of stems, root development, and bending of plants towards light (phototropism). They play a key role in cell elongation and overall plant growth.

Sensitive plant movement is quick, temporary, due to touch, and does not involve growth.

Shoot movement is slow, permanent, due to light, and involves growth.

Plant hormones are natural chemical substances made by plants that help in controlling and coordinating their growth, development, and responses to the environment. They are also called phytohormones.

Main types of plant hormones:

1. Auxins – Help in growth of stem and bending of plant toward light.
2. Gibberellins – Help in growth of stems, seed germination, and flowering.
3. Cytokinins – Help in cell division and growth of new leaves.
4. Abscisic acid – Stops growth and helps plant survive during stress (like lack of water).
5. Ethylene – Helps in ripening of fruits.

The brain does not control reflex actions, but it receives information after the action is done. Reflex actions are controlled by the spinal cord for a quick response.

When an agarbatti burns, it releases smell particles into the air. These particles enter our nose when we breathe. Inside the nose, there are special smell-detecting cells called olfactory receptors. These receptors send signals to the brain through the olfactory nerve. The brain then understands the signal and we recognize the smell.

The cerebellum is the part of the brain that maintains posture and equilibrium of the body.

At the synapse (the small gap between two neurons), the following steps take place:

• An electrical impulse reaches the end of the first neuron.
• This causes the neuron to release chemicals called neurotransmitters into the synaptic gap.
• These chemicals cross the gap and reach the second neuron.
• They trigger a new electrical impulse in the second neuron.

Reflex Action:- It is an automatic, quick response to a stimulus. Example: Pulling your hand away from a hot object.

• It happens without thinking.
• It is controlled by the spinal cord.
• It protects the body from harm.

Walking:- It is a voluntary action that you do with conscious control. Example: Walking to school or the market.

• It requires thinking and coordination.
• It is controlled by the brain.
• It helps in movement and daily activities.

We are given:
Two APs have the same common difference
The difference between their 100th terms is 100
We are asked to find the difference between their 1000th terms

Let the first terms of the two APs be:
First AP: a
Second AP: b

Common difference: d (same for both)

The 100th term of the first AP = a + 99d
The 100th term of the second AP = b + 99d

According to question:
(a + 99d) − (b + 99d) = 100
=> a − b = 100
=> (a + 999d) − (b + 999d) = 100

Hence the difference between their 1000th terms is 100.

Given AP: 3, 15, 27, 39, ...

First term a = 3
Common difference d = 15 − 3 = 12

We are told that a certain term is 132 more than the 54th term.
So, aₙ = a₅₄ + 132
=> a + (n − 1) × d = a + 53 × d + 132
=> (n − 1) × d = 53 × d + 132
=> (n − 1) × 12 = 53 × 12 + 132
=> (n − 1) × 12 = 636 + 132 = 768
=> (n − 1) = 768 ÷ 12 = 64
=> n = 64 + 1 = 65

Hence the 65th term is 132 more than the 54th term.