Evolution — BIOLOGY STD 12 Science — Question

Explain how xerarch succession progresses from serie to mesic condition and forms a stable climax community. You may use a flow chart.

Study the graph given below and answer the questions that follow:
Identify the ovarian phases during a menstrual cycle:

1. 5th day to 12th day of the cycle.
2. 14th day of the cycle.
3. 16th day to 25th day of the cycle.

(i) Define translation.
(ii) Explain the translation process.
(iii) Draw a labelled diagram of the translation.

1. Explain the process of spermatogenesis in humans.
2. Draw a human sperm and label acrosome and middle piece. Mention their functions.

i. How and why is charging of tRNA essential in the process of translation?
ii. State the function of ribosome as a catalyst in bacteria during the process of translation.
iii. Explain the process of binding of ribosomal units to mRNA during protein synthesis.

i. What is the chemical name of smack? Why is the consumption of smack considered as an abuse?
ii. Name the source plant and one effect of the following drugs on the human body:
1. Marijuana
2. Cocaine
3. Morphine

Name the type of cells attacked by AIDS virus in the human body. Also, explain the events in sequence undertaken by virus to increase its progeny.

Angiosperm flowers may be monoecious, cleistogamous or show self-incompatibility. Describe the characteristic features of each one of them and state which one of these flowers promotes inbreeding and outbreeding respectively.

(a) Draw the diagram of human sperm and label the cellular component. Also mention the functions of three components.
(b) Where does the head of sperm remain embedded in spermatogenesis.

Show that Darwin’s natural selection is based on natural observation, with an example for each.