Population Growth & Resource Availability

Limiting Factors

limit population size

determines carrying capacity

when factors abundant —> population growth accelerates

when factors limited —> inc. mortality, dec fecundity (pop growth slows / becomes zero / declines)

Density Dependent Limited Factors

factors that influence population growth based on size, usually biotic

ex: pathogens, predation, parasites, competition, disease

small pop. don’t experience these, large do

Density Independent Limited Factors

factors that influence population growth independ of their size, usually abiotic

ex: humans, volcanic eruptions, earthquakes, pollution, weather, storms, floods

doesn’t matter how big or small a pop. is, natural disasters limit them both

Doubling Time Equation

70/growth rate %

Size (N)

total # of individuals in a given area at a given time

larger = safer from population decline

Density

# of individuals/area

ex: 12 panthers/km²

high density = higher competition, possibilty for disease outbreak, possibility of depelting food source

Distribution

how individuals in population are spaced out compared to each other

random (trees)

uniform (territorial animals)

clumped (herd/group animals)

Sex Ratio

ratio of males to females. closer to 50:50, the more ideal for breeding (usually)

die-off or bottleneck effect can lead to skewed sex ratio (not enough females) limiting pop. growth

Population Change

(Immigrations + births) - (emmigrations + deaths)