MODEL PAPER 7 — BIOLOGY STD 12 Science — Question

1. Write the importance of measuring the size of a population in a habitat or an ecosystem.
2. Explain with the help of an example how the percentage cover is a more meaningful measure of population size than more numbers.

A pea plant with purple flowers was crossed with white flowers producing 50 plants with only purple flowers. On selfing, these plants produced 482 plants with purple flowers and 162 with white flowers. What genetic mechanism accounts for these results? Explain.

During a school trip to ‘Rohtang Pass’, one of your classmate suddenly developed ‘altitude sickness’. But, she recovered after some time.

1. Mention one symptom to diagnose the sickness.
2. What caused the sickness?
3. How could she recover by herself after some time?

(i) What is shown in the attached diagram?
(ii) Write the names of the parts named 'a' and ‘b’.
(iii) Name of the cell type that produces this molecule.

Fertilisation is essential for production of seed, but in some angiosperms, seeds develop without fertilisation.
Explain the two ways by which seeds develop without fertilisation.

1. Describe the endosperm development in coconut.
2. Why is tender coconut considered a healthy source of nutrition?
3. How are pea seeds different from castor seeds with respect to endosperm?

Describe a biogas plant.

1. Draw the figure of vector pBR322 and label the following:

1. Origin of replication.
2. Ampicillin resistance site.
3. Tetracycline resistance site.
4. BamH1 restriction site.

2. Identify the significance of origin of replication.

Why are adolescents especially advised not to smoke? How does smoking affect the functioning of the body?

What characteristics make a community stable?