Ecosystems and Energy Flow — BIOLOGY STD 12 Science — Question

Explain the causes of global warming. Why is it a warning to mankind?

1. Write the scientific name of the most common species of honeybee reared.
2. Mention the kind of areas that are suitable for beekeeping practices.
3. Mention any two uses of beewax.

Describe pericardium.

A burglar in a huff forgot to wipe off his blood-stains from the place of crime where he was involved in a theft and fight. Name the technique which can help in identifying the burglar from the blood-stains. Describe the technique.

How do kangaroo rats and desert plants adapt themselves to survive in their extreme habitat? Explain.

1.  

Read the graph given above and correlate the uterine events that take place according to that the hormonal levels on.

1. 6-15 days.
2. 16-25 days.
3. 26-28 days (if the ovum is not fertilised).

2. Specify the sources of the hormones mentioned in the graph.

1. Draw a labelled sketch of a mature 7-celled, 8-nucleate embryo-sac.
2. Which one of the cell in an embryo-sac produce endosperm after double fertilisation?

What are the signs and symptoms of filariasis?

1. Expand BOD.
2. At a particular segment of a river near a sugar factory, the BOD is much higher than the normal level. What is it indicative of? What will happen to the living organisms in this part of the river?
3. Under what conditions will the BOD be lowered in the river? How will it affect the aquatic life?

A student was simulating Urey and Millers experiment to prove the origin of life. The set up used by the student is given.

1. Find out the reasons why he could not get desired results.
2. What conclusion was drawn by Urey and Miller through this experiment?
3. Compare the conclusion drawn with the theory of spontaneous generation.