Biodiversity and Conservation — BIOLOGY STD 12 Science — Question

What are the advantages of tissue culture methods over conventional method of plant breeding in crop improvement programmes?

1. State the objectives of animal breeding.
2. List the importance and limitations of inbreeding. How can the limitations be overcome?
3. Give an example of a new breed each of cattle and poultry.

Read the following and answer any four questions from (i) to (v) given below:
Apomixis is a mode of reproduction which does not involve formation of zygote through gametic fusion. In plants, apomixis commonly mimics sexual reproduction but produces seeds without fertilization. There are several methods of atomistic development in seeds. Thee two common ones are recurrent agamospermy and advective embryony.

1. Apomixis is a type of reproduction in plants, in which?

1. Fertilization does not take place.
2. Male nucleus takes part in fertilization.
3. Pollen fusion takes place.
4. Generative nucleus takes part in fertilization.

2. Which of the following statements is incorrect regarding recurrent agamospermy?

1. It is the formation of seed that has an embryo formed without meiosis and syngamy.
2. All the cells of embryo sac are diploid.
3. An embryo develops directly from a diploid cell other than egg like that of nucleus and integument.
4. None of these.

3. Adventive embryony is found in:

1. Citrus.
2. Opuntia.
3. Apple.
4. Both (a) and (b).

4. Formation of embryo directly from diploid egg without fertilization is called:

1. Apospory.
2. Diplospory.
3. Polyembryony.
4. Diploid parthenogenesis.

5. If any somatic cell of sporophyte produces gametophyte without reduction division, it is called:

1. Parthenogenesis.
2. Apogamy.
3. Apospory.
4. Amphimixis.

Gene expression can be controlled with the help of RNA. Explain the method with an example.

The following is the illustration of the sequence of ovarian events (a – i) in a human female.
Write the difference between ‘c’ and ‘h’.

1. Distinguish between parasitism and predation, with an example of each.
2. Name two groups of animals, that are regulaters.
3. When does the growth curve assume of J shape?

During her tour to a renowned forest, Sakshi saw a highway being constructed, which passes through the middle of the forest. She was unhappy seeing that and on return, she contacted the local eco-club and approached the concerned department to stop the work.

1. What would be the effect on biodiversity, if the highway is constructed?
2. How forests are useful to mankind?
3. What values of Sakshi reflect here?

Describe various methods of asexual reproduction in animals.

Can you think of a scientific explanation, besides analogy used by Paul Ehrlich, for the direct relationship between diversity and stability of an ecosystem?

(i) Write the causes of cancer.
(ii) Explain cancer detection.
(iii) Draw a schematic diagram of the lymphatic system.