Cell Cycle and Cell Division — BIOLOGY STD 11 Science — Question

While teaching cell division in the class, teacher told that during meiosis, the chromosome number is reduced to half of the parent, whereas during mitosis, the number remains the same. Seema was not able to recognise what teacher explained in the class and asked her elder brother, a botany student, the need of reducing chromosomes during gamete formation and what will happen if chromosome number will not reduced to its half. He explained the concept in detail to Seema.

1. In which part of the organisms does meiosis occur?
2. How does meiosis help in evolution?
3. Give the significance of meiosis.
4. What value is expressed in the behaviour of Seema's elder brother?

What do you understand by occupational respiratory disorders?

Make a comparative account of the five kingdoms ole (in Whittaker's classification) on the following characters:

1. Cell wall
2. Body organisation.

If one debarks a tree, what parts of the plant is being removed?

The bulk of a plant is made up of dead tissues so that physical strength can be attained and resources can be utilized in a better way. What lesson can be learnt from this strategy of plants? How does focusing on something help us in our life?

1. We should learn to save money so that it can be utilized for better purposes.
2. Instead of wasting our energy on trivial matters, we should focus on more E productive works.
3. Physical exercise is good for a strong body, while mental exercise is good for a strong mind.

Mention the layers of body wall of earthworm.

On the basis of characteristics describe how closely or distantly related following species are:
Human, Chimpanzee, Cats, Tigers, Rabbits, Mouse, Crocodiles and Lizards.

What are root hairs? Which region of the root do they arise from? What is their function?

Discuss “The respiratory pathway is an amphibolic pathway.”

Give the location of hepatic caecae in a cockroach. What is their function?