Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

What do you understand by parthenocarpy?

All primary productivity is not available for herbivores. Give one reason.

Why is sewage water treated until the BOD is reduced? Give a reason.

Name the mechanism responsible for the formation of seed without fertilization in angiosperms. Give an example of a species of flowering plants with such seed formation.

To use the restriction enzyme to cut the DNA, the DNA must be in a pure form, i.e. free from proteins and RNAs associated with it. How is it achieved?

When was Ramsar Convention developed and adopted and when did it come into force?

In a dihybrid cross carried out by T.H. Morgan in Drosophila, the F, ratio deviated from that of Mendel's dihybrid F, ratio. Give a reason.

Or

Why do certain genes tend to be inherited together in a cell at the time of cell division?

Or

If the frequency of a parental form is higher than 25% in a dihybrid test cross, what does that indicate about the two genes involved?

What is true about Bt toxin?

1. The activated toxin enters the ovaries of the pest to sterilise it and thus prevent its multiplication.
2. The concerned Bacillus has antitoxins.
3. The inactive protoxin gets converted into active form in the insect gut.
4. Bt protein exists as active toxin in the Bacillus.

Write the name of two diseases caused by sexual contact.

Name the largest cell of the embryo sac.