Reproduction in Lower and Higher Plants — BIOLOGY STD 12 Science — Question

Write chemical reactions to represent Methanogenesis.

Give scientific reasons: Nucellar polyembryony is significant in horticulture.

Explain Homologous and Analogous organs with example.

The cytological observations made in a number of insects led to the development of the concept of genetic/ chromosomal basis of sex-determination mechanism. Honey bee is an interesting example to study the mechanism of sex-determination. Study the schematic cross between the male and the female honey bees given below and answer the questions that follow:

1. Identify the cell divisions ‘A’ and ‘B’ that lead to gamete formation in female and male honey bees respectively.
2. Name the process ‘C’ that leads to the development of male honey bee (drone).

What is ecological succession? Where and why would the rate of succession be faster, in a newly created pond or a forest destroyed by a forest fire?

On a visit to a Hill station, one of your friend suddenly became unwell and felt uneasy.

1. List two symptoms you would look for to term it to be due to allergy.
2. Explain the response of the body to an allergen.
3. Name two drugs that can be recommended for immediate relief.

Draw a labelled diagrammatic sectional view of a human seminiferous tubule.

Give reasons : Lake can literally get choked to death due to eutrophication.

Draw a labelled diagram of the reproductive system in a human female.

Kanchan went to a garden and saw some flowers which were closed. She assumed that those flowers must be buds. But she was astonished to see that all the flowers of that plant were closed and none of them was open. She was confused and asked her queries to her teacher.

1. What do you think, are there any plants with closed flowers? Give an example.
2. Are such plants get pollinated? Explain.
3. What are such flowers/ plants called?
4. What values are shown by Kanchan?