Topic 13 Population Growth

populations changing across time

How do populations increase in size?

1. births

2. immingration

(B= total number of births, b= per capital birth rate)

How do populations decrease in size?

1. deaths

2. emigration

(D= total number of deaths, d= per capital death rate)

Population Size Regulation

interactions with environmental factors affect population size

i.e weather, resources, competition, predation, parasitism

(density-dependent factors, density-independent factors)

Density-dependent factors

the factor’s influence on the population changes with the density of the population.

ex: disease, intraspecific competition, territoriality, waste, predator- prey interactions.

Density Independent Factors

The factor’s influence on the population is not affected by population density.

ex. temperature, precipitation, forest fire, natural disaster. human impacts: pollutants, deforestation.

Change in population size

Population growth models

Can be used to visualize and predict growth of a population

1. exponential

2. logistic

Exponential Growth

J shaped curve

r is not limited by environment/pop density

seen in, colonization of population, recovery following population crash, invasive species.

Logistic Growth

incorporates density dependence through carrying capacity (K): maximum population size the environment can support