Ecosystems — BIOLOGY STD 12 Science — Question

1. Given below is the TS of human ovary. Identify the following in the diagram:

• Corpus luteum.
• Secondary oocyte.
• Antrum.
• Primary follicle.
• Primary oocyte.

2. Explain the changes the primary oocyte undergoes while in different follicular stages before ovulation.

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Given below is the diagram of a human ovum surrounded by a few sperms. Observe the diagram and answer the following questions:
Compare the fate of sperms shown in the diagram.

Trace the events taking place in a flower from the time of pollen grain entry up to the completion of fertilisation.

Write the type and location of the gene causing thalassemia in humans. State the cause and symptoms of the disease. How is sickle cell anaemia different from this disease?

Is it true that if the dissolved oxygen level drops to zero, the water will become septic. Give an example which could lower the dissolved oxygen content of an aquatic body.

List 10 modern day animals and using the various resources available link it to a corresponding ancient fossil. Name both of them.

Answer the following questions:
Draw a diagram of a mature human male gamete. Label the following parts: Acrosome, nucleus, middle piece and tail.

Match the sex-chromosome complements in Column I with the male/ female organisms in Column II.

S.No	Column I	S.No	Column II
A.	XO	1.	Human male
B.	XX	2.	Male bird
C.	XY	3.	Male grasshopper
D.	ZZ	4.	Female Drosophila
		5.	Female bird

Draw a diagrammatic sketch of biogas plant, and label its various components given below: Gas Holder, Sludge Chamber, Digester, Dung + water chamber.

For question 1-4, use this key:Key-

1. Ecology.
2. Population.
3. Community.
4. Ecosystem.

1. A community plus its physical environment.
2. Study of the interactions of organisms with each other and with the physical environment.
3. All populations that are found in a particular area.
4. All members of the same species that inhabit a particular area.