a.

physical variation

b.

physiological variation

c.

morphological variation

d.

discontinuous variation

a.

circulatory system

b.

respiratory system

c.

transport system

d.

digestive system

a.

angiosperm

b.

bryophytes

c.

pteridophytes

d.

algae

a.

Drought

b.

Low rate of reproduction

c.

Emigration

d.

Topography