Population dynamics and role of biotic factors

Lecture 9 : Population dynamics and role of biotic factors


Attributes of a population

i. Density : Population size per unit area
ii. Birth rate (Natality) : Rate at which new individuals are added to the
population by reproduction
iii. Death rate (Mortality) : The rate at which individuals are lost by death.
iv. Dispersal : The rate at which individuals immigrate into and emigrate out of
the population.
v. Dispersion: the way in which individuals are distributed in space. It may be of
3 types.
a) Random distribution
b) Uniform distribution
c) Clumped distribution

vi. Age distribution: the population of individuals of different ages in the group.
vii. Genetic characteristics : adaptiveness, reproductive fitness, persistence.
viii. Population growth form: the way in which population changes / grows as a
result of natality, mortality, and dispersal.

Population dynamics.

Populations grow in two contrasting ways. They are

i. J- shaped growth form (Fig 1a)
ii. S- Shaped or sigmoid growth form (Fig 1b)



N K

Density Density




Time Time

Fig. 1a. J- shaped growth form Fig. 1b. S - shaped growth form.