Evolution — BIOLOGY STD 12 Science — Question

What is called retrovirus? Show the replication of retrovirus with the help of diagram.

How have pest-resistant plants been produced using biotechnology? Explain.

A flower of tomato plant following the process of sexual reproduction produce 240 viable seeds.
Answer the following questions giving reasons:
What would have been the minimum number of ovules present in the ovary?

(i) Write full name of AIDS.
(ii) Write four ways of transmission of HIV infection.
(iii) Write a way to prevent HIV infection.

What does an Ecological Pyramid indicate? Explain the three different types of Upright Pyramids in nature with the help of an example of each.

1. Give reasons for:

1. Both strands of DNA are not copied during transcription.
2. Transcription and translation in bacteria can be coupled.

2. Differentiate between the process of transcription in prokaryotes and eukaryotes.

Following is the sequence of nucleotide in two strands of DNA. Observe the strands and answer the preceding questions.

1. Name the special term used for such an arrangement of nucleotide.
2. Name the special type of enzymes which work/ function at this specific points.
3. Name the enzyme, that cut DNA between GA sequence.
4. Name the single strands produced after the action of the enzyme.

Pragyan takes fruits, vegetables, bread and egg curry in a day's menu. While his teacher was giving a lecture on trophic level, he got fascinated and asked following questions from his teacher.

1. How many trophic levels does he occupy in different food chains?
2. Represent atleast three food chains.
3. Which among them gives him the maximum amount of energy? Give reason.
4. What values are shown by Pragyan?

What is mutualism? Describe any four examples.

Describe the process of decomposition of detritus under the following heads: Fragmentation; leaching; catabolism; humification andmineralisation.