If ‘+’ sign is assigned to beneficial interaction, ‘─’ sign to detrimental and ‘0’ sign to neutral interaction, then the
Population interaction represented by ‘+’ ‘─’ refers to
1. amensalism.
2. commensalism.
3. parasitism.
4. mutualism.

Mycorrhiza are the example of
1. Amensalism.
2. Antibiosis.
3. Mutualism.
4. Fungistasis.

Asymptote in a logistic growth curve is obtained when:
1. K = N
2. K > N
3. K < N
4. The value of ‘r’ approaches zero

Natality refers to
1. Number of individuals leaving the habitat
2. Birth rate
3. Death rate
4. Number of individuals entering a habitat

Which one of the following population interactions is widely used in medical science for the production of
antibiotics?
1. Parasitism
2. Mutualism
3. Commensalism
4. Amensalism

In a growing population of a country:

A keystone species is the one which has
1. A small proportion of total biomass but has huge impact on community’s organisation and survival
2.A plenty of biomass but low impacts on community’s organisation
3. A rare species with little impact on biomass and other species in the community
4. A dominant species which has a large proportion of biomass and which affects many other species

A system of rotating crops with legume or grass pastures to improve soil structure and fertility is called:

1. Shifting agriculture
2. Ley farming
3. Contour farming
4. Strip farming

It is much easier for a small animal to run uphill than for a large animal, because:
1. The efficiency of muscles in large animals is less than in the small animals.
2. It is easier to carry a small body weight.
3. Smaller animals have a higher metabolic rate.
4. Small animals have a lower ${\mathrm{O}}_2$ requirement.

Which one of the following characteristics is not shared by birds and mammals? 
1. Warm blooded nature 

2. Ossified endoskeleton

3. Breathing using lungs

4. Viviparity