Do Now

1. What is the carrying capacity of a population?

One way humans manage elk populations is to allow hunting seasons. Each person is given a permit to hunt a certain number of elk. Some years there is a limit as to what gender or size they are allowed to hunt.

2. Do you agree or disagree that hunting is a responsible way to manage a population of elk? Explain.

3. What about other species like deer, fishes,

bears, coyotes, rabbits?

Homework and Announcements

▪ Endangered Species?... Maybe not

▪ Due: Worksheet pages 51-53

▪ Homework▪ Wks pages 54-55▪ Project research▪ USA TestPrep

Limits to Growth

SWBAT IDENTIFY LIMITING FACTORS AND OTHER POPULATION DYNAMICS.

Brain Pop – Populations and Quiz

5.2 Limits to Growth

Limiting factor: a factor that controls the growth of a population.▪Competition▪ Predation▪ Parasitism and disease▪Natural disasters▪Unusual weatherThe first three depend on population density… the last two do not.

Limits to Growth

▪Acting separately or together, limiting factors determine the carrying capacity of an environment for a species.

▪They keep populations from becoming extinct or overrunning the planet.

Density-Dependent Limiting Factors

Affect large, clumped populations – too many individuals

▪These factors include▪Competition▪Predation▪Herbivory▪Parasitism▪Disease▪Stress from overcrowding

Density-Dependent Interactions

Competition: Too much crowding leads to competition for food, water, space, sunlight, and other essentials▪ Can lower birthrates, increase death rates, or both.▪ Is density-dependent because the more individuals in an

area, the sooner they use up all the resources.▪ Can be between the same species or different species

Density-Dependent Interactions

Predation and Herbivory: Too many predators can affect the prey population, which can in turn affect the plant population. ▪ Continuous cycle of up and

down: Wolf population will increase when Moose population increases, but eventually the wolf will eat more Moose than are being produced and the Moose population will drop, and so will the Wolf population. ▪ Same with Moose and their

plant food – cycle of up and down▪ Can happen with Humans as

predators – our fishing cycles

Density-Dependent Interactions

Parasitism and Disease: Density dependent because the more host population there is, the easier the parasites and infection can spread.

Density-Dependent Interactions

▪ Stress from Overcrowding: Too many species causes fighting.▪ Some females will be so stressed that they neglect, kill or even eat their own offspring▪Causes lower birthrates, higher death rates, and can increase the rate of emigration (leaving of individuals).

Density-Independent Interactions

▪Affects all populations in similar ways, regardless of population size and density▪Examples: hurricanes, droughts, floods, wildfires, tornadoes, etc. ▪Populations may or may not bounce back