Pressures of Populations

Section 3.2

Population growth

• Population growth is limited for all populations

Population change = (birth + immigration) – (death + emigration)

Population growth

• Immigration – the movement of individuals in to a population

- can increase a population- can stabilize a declining population

Population growth

• Emigration – movement of individuals out of a population

- can occur when resources become scarce

Population growth

• Limiting Factors – prevent the continuation of population growth

Abiotic – non-livingBiotic - living

Population growth

Examples of limiting factors:

Air Locusts Light

Microbes Water Plants

Population growth

• Competition – when organisms try to obtain the same resources as other organisms

Population growth

• Density–dependent – a factor that affects a population when density is high

- competition- disease

Population growth

• Density-independent – factor that have the same effect on a population whether density is high or low

- Temperature- Wildfires

Survival Strategies

• Opportunists – species that reproduce quickly if population falls below carrying capacity

Algae Dandelion Insects

Survival Strategies

• Opportunists– Tend to have short life spans, large amounts of

offspring– Population size changes often, grows quickly– Lives across many areas, can adapt quickly

Survival Strategies

• Competitors – species with adaptations that allow them to live at or near their carrying capacity for long periods of time

Survival Strategies

• Competitors – Live longer with fewer offspring– Offspring take a longer time to develop– Animals take care of young longer– Not distributed across wide areas– Greater number of offspring live to reproduce