Respiration and Circulation — BIOLOGY STD 12 Science — Question

The scientists believe that evolution is gradual. But extinction, part of evolutionary story, are 'sudden' and 'abrupt' and also group-specific. Comment whether a natural disaster can be the cause for extinction of species.

What must have provided energy for the warmth for life to originate on primitive earth? Name the first organism to release oxygen into the atmosphere.

DNA being hydrophilic cannot pass through the cell membrane of a host cell. Explain how does recombinant DNA get introduced into the host cell to transform the latter.

Name the following : Therapies used for treatment of cancer.

1. Why are the plants raised through micropropagation termed as somaclones?
2. Mention two advantages of this technique.

Name the first transgenic cow. Which gene was introduced in this cow?

Name the enzyme responsible for delay in ripening of tomato fruit.

What are untranslated regions (UTRs)?

Draw the microscopic structure of a human sperm and relate its different parts with their functions.
OR
Draw a labelled diagram of the microscopic structure of a human sperm. Explain the functions of each part.

Differentiate between population size and population density.