Evolution — BIOLOGY STD 12 Science — Question

Answer the following questions:
Draw a diagrammatic sectional view of a human seminiferous tubule, and label Sertoli cells, primary spermatocyte, spermatogonium and spermatozoa in it.

Discuss the role of fishery in enhancement of food production.

Write the causes, symptoms and prevention measures of diphtheria.

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.

What does an Ecological Pyramid indicate? Explain the three different types of Upright Pyramids in nature with the help of an example of each.

Discuss in detail the contributions of Morgan and Sturvant in the area of genetics.

Define totipotency of a cell. List the requirements, if the objective is to produce somaclones of a tomato plant on commercial scale.

There is greater biodiversity in tropical /subtropical regions than in temperate region. Explain.

1. Write the scientific names (binomials) of the causative organisms of pneumonia.
2. How does a healthy person acquire infection of this disease?
3. Mention the characteristic symptoms of the disease.

The relation between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola. Give a brief explanation.