Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20 mg/L, 8 mg/L and 400 mg/L respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?

Study the graph given below and answer the question that follow:

1. Write the status of food and space in the curves (a) and (b).
2. In the absence of predators, which one of the two curves would appropriately depict the prey population?
3. Time has been shown on X-axis and there is a parallel dotted line above it. Give the significance of this dotted line.

Why do you think the exine should be hard? What is the function of germ pore?

Name the place in human ovary where the first meiotic division is completed during oogenesis. What are the products of this division? Give the chromosome number of each type of cells involved in the process.

Name the type of curve that characterizes most populations growing in favourable environment. Define carrying capacity.

Explain any three inbreeding devices in flowering plants.

What are viruses parasitising bacteria called? Draw a well labelled diagram of the same.

Observe the diagram for genetic mapping of human DNA and answer the following questions:

i. Explain DNA polymorphism as the basis of genetic mapping of the human genome.
ii. State the role of VNTR in DNA fingerprinting.

There are many animals that have become extinct in the wild but continue to be maintained in zoological parks.
Which type of biodiversity conservation is observed in this case?

Give the name of the hormone which is secreted by corpus luteum.