Population Ecology

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

Population Ecology Natural and Human disturbances can lead to a change in a population over time. If the number of species in one community changes it will ultimately lead the changes in the number of species in all other communities in the ecosystem.

Sea Otter Example

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

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

Limiting Factors Limiting factors are factors that cause population growth to slow or stop Ex. food, water, space, sunlight

Growth under ideal conditions Populations can grow exponentially Unlimited food and space What are the limiting factors?

When resources become limited Growth slows Populations stay at the carrying capacity This is good for the environment

Other Growth Curves Too many births “overshoots” the carrying capacity and leads to population crash Predator & prey populations keep populations under the carrying capacity

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

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

Swamp Rats in California

https://www. mysanantonio https://www.mysanantonio.com/bayarea/article/nutria-should-we-eat-invasive-species-swamp-rats-12726054.php#photo-15020981

What Limits the size of a population?

Density dependent limiting factors Depends on population size Operates most strongly on large populations Competition for resources — food, water, space, sunlight Competition within species or with different species

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

Practice Classify each of the following as either density-dependent or density-independent. Intense heat wave Half of the forest trees are cut down 3. Sudden blizzard 4. Overpopulation of an organism