Population Ecology

Population Ecology Factors that affect population size: Natural and Human Disturbances play a role in the shaping an ecosystem. Natural Disturbances – fire, tornadoes, hurricanes, etc. Human Disturbances – deforestation, destroying of habitats.

Sea Otter Example

Predict what happens to sea urchin and kelp when sea otters are removed

How Populations Change Over Time Three factors control how a population changes over time: # of births # of deaths # of individuals that migrate

Carrying Capacity Carrying Capacity - The largest number of individuals that the environment can support When an ecosystem reaches its carrying capacity the food web begins to change drastically.

Predict what happens when a population “overshoots” its carrying capacity

Population growth Populations can grow in 2 different ways:

1) Exponential growth Growth under ideal conditions at an ever increasing rate Abundant space, food, protection J-shape curve

2) Logistic growth Growth when resources become less available and growth slows S-shape curve NOTE: even when population growth stops it still rises and falls somewhat AKA Carrying Capacity Graph

Other Growth Curves Boom and Bust Exponential Growth that leads to population crash Predator-Prey Predator & prey populations increase and decrease together

Describe these growth curves

Limiting Factors Limiting factors cause population growth to decrease. Can be dependent on the species in the ecosystem or completely unpredictable like natural disasters.

What Limits the size of a population?

Density dependent limiting factors Depends on population size ( affects large populations) Competition for resources Competition within species or with different species

Density-Independent limiting factors Affects all populations, regardless population size Population crashes Causes: human activity, weather, and natural disasters

Classify as either density-dependent or density-independent. Practice Classify as either density-dependent or density-independent. Intense heat wave Half of the forest trees are cut down 3. Sudden blizzard Overpopulation of an organism Hospital MRSA outbreak

What happens when an invasive species is introduced into an established ecosystem?

How many raccoons can live in this forest?

Not native to ecosystem No natural predators Can outcompete native species for resources Examples: Kudzu vine, Chinaberry trees