1. KEY CONCEPT Populations grow in predictable patterns.

2. Changes in a population’s size are determined by immigration, births, emigration, and deaths.
The size of a population is always changing.
Four factors affect the size of a population.
Immigration – move in
births
Emigration – move out
deaths

3. Population growth is based on available resources.
Exponential growth is a rapid population increase due to an abundance of resources J-shaped curve
Ex. 24 founding rabbits
million in Australia today!
Caused by abundance of food, water, space and no predators

4. Logistic growth is due to a population facing limited resources
Logistic growth is due to a population facing limited resources. S-shaped curve
Initially, abundant resources (exponential growth)
Growth levels off when densely populated - increased
competition
Carrying capacity is the
maximum number of individuals
in a population that the
environment can support.
Can fluctuate depending on
changes within the environment.

5. A population crash is a dramatic decline in the size of a population over a short period of time.
Ex. Reindeer on St. Matthew Island, Alaska
1944 – started with 29 reindeer By 1963 – 6000 reindeer
1964 – only 50 reindeer survived (harsh winter/scarcity of food)
Environmental
changes
Fishkills are
usually caused
by low levels
of oxygen.

6. Ecological factors limit population growth.
A limiting factor is something that keeps the size of a population down.
Density-dependent limiting factors are affected by the number of individuals in a given area.

7. Density-dependent limiting factors are affected by the number of individuals in a given area.
predation
competition
parasitism and disease

8. Density-independent limiting factors limit a population’s growth regardless of the density.
unusual weather
natural disasters
human activities (deforestation, habitat loss, pollution)