Ecosystems and Energy Flow — BIOLOGY STD 12 Science — Question

What is meant by emasculation? When and why does a plant breeder employ this technique?

What is a recombinant DNA? List its features. How do enzymes restriction endonuclease and DNA Ligase help its formation?

Medically it is advised to all young mothers that breastfeeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer.

Differentiate between somaclones and somatic hybrids. Give one example of each.

1. State how the constant internal environment is beneficial to organisms
2. Explain any two alternatives by which organisms can overcome stressful external conditions.

Sapna's younger brother saw a banana tree in backyard of a house. He could see the fruits but no seeds.
He wanted to know how a new plant will be produced without seed and asked Sapna (a class XII biology student) about it. She explained that some plants can grow without seeds and the phenomenon is called vegetative propagation. Her brother was amazed to know the new concept about plants.

1. How does banana produce a new plant? Is this reproduction, sexual or asexual?
2. Give examples of some other fruits and vegetables that can reproduce by this method.
3. Identify the values shown by Sapna's brother.

Give three reasons as to why the prokaryotes are not given any figures for their diversity by the ecologists.

1. Explain adaptive radiation with the help of a suitable example.
2. Cite an example where more than one adaptive radiation have occurred in an isolated geographical area. Name the type of evolution your example depicts and state why it is so named.

What are the major causes of species losses in a geographical region?

What is the difference between a primary oöcyte and a secondary oöcyte?