Model Paper 4 — BIOLOGY STD 12 Science — Question

Describe diagrammatically the male reproductive organs.

In what way anaerobic sludge diagestion is important in sewage treatments?

A. Explain how advent of biotechnology has helped in preventing infestation by nematodes and thereby increasing crop yield.

Explain the chromosomal theory of inheritance.

Answer the following questions with respect to recombinant DNA technology:
i. Why is plasmid considered to be an important tool in rDNA technology? From where can plasmids be isolated? (Any two sources)
ii. Explain the role of ori and selectable marker in a cloning vector.
iii. r-DNA technology cannot proceed without restriction endonuclease. Justify.

Write about the role of microbes in nitrogen fixation.

1. Write an equation for Verhaulst-Pearl Logistic Growth, where.

N - Population density at a timet E.

r - Intrinsic rate of natural increase.

K - Carrying Capacity.

2. Draw a graph for a population whose population density has reached the carrying capacity.
3. Why is this logistic growth model considered a more realistic one for most animal populations?
4. Draw a growth curve where resources are not limiting to growth of a population.

Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.

What is menstrual cycle. Explain its various events with the help of diagram.###Describe in detail the various stages of menstrual cycle with the help of diagram.###Write a detail note on different stages of menstrual cycle and also sketch out these stages of
menstrual cycle by graphical diagram.###Define sexual reproduction. Explain the process of menstrual cycle.

Write a short note on pyramid of numbers and pyramid of biomass.