Biodiversity, Conservation and Environmental Issues — BIOLOGY STD 12 Science — Question

Describe mechanism of absorption of water.

Draw a diagram of L. S. of an anatropous ovule of an angiosperm and label the following parts.

1. Nucellus.
2. Integument.
3. Antipodal cells.
4. Secondary nucleus.

Name two hormones that are constituents of contraceptive pills. Why do they have high and effective contraceptive value? Name a commonly prescribed non – steroidal oral pill.

Explain the pattern of inheritance of haemophilia in humans. Why is the possibility of a human female becoming a haemophilic extremely rare? Explain.

Two types of aquatic organisms in a lake show specific growth patterns as shown below, in a brief period of time. The lake is adjacent to an agricultural land extensively supplied with fertilisers.

Answer the questions based on the facts given above:

1. Name the organisms depicting the patterns A and B.
2. State the reason for the growth pattern seen in A.
3. Write the effects of the growth patterns seen above.

During his studies on genes in Drosophila that were sex-linked. T.H. Morgan found population phenotypic ratios deviated from expected 9 : 3 : 3 : 1. Explain the conclusion he arrived at.

Common cold is the most frequent ! infectious disease in humans.

1. Why did Hershey and Chase use radioactive sulphur and radioactive phosphorus in their experiment?
2. Write the conclusion they arrived at and how.

Name two types of particulate pollutants found in air. Add a note on ill effects of the same on human health. ### Describe any 2 particulate and gaseous pollutants.

Write a short note on
Adaptations of plants to water scarcity: