Bellringer• List 3 reasons why a population

might decrease in size

Population• Limiting Factor: A factor that causes population growth

to decrease• 2 Types:

o 1. Density-dependent: Factors that depend on the size of the population• Only become limiting when the population density

becomes very high• Effects are intensified as the pop. Density increases

o 2. Density-independent: Factors that do not depend, or are independent, of the size of the population• Are limiting regardless of the size of the population• Affect all populations in similar ways

Limiting Factors

Deforestation• Density-Independent• Human activities

o Deforestation; over-hunting/fishingo Effects are harmful on population regardless of size

Predation• Density-Dependent• Predation

o The effect of predation intensifies as the population density of predators increases.

Disease• Density-Dependent• Disease

o High population densities make the spread of disease easier to transmit

Natural Disasters• Density-Independent• Natural Disasters

o Hurricane, tornado, flood, severe droughto Equally devastating to populations regardless of size

Competition• Competition:

o More members of a population = Less Available resources = More competition

o Less members of a population = More available resources = Less competition

Parasitism• Density-Dependent• Parasitism

o High densities make it easier for parasites to find hosts, and spread diseases

Severe frost• Density-Independent• Weather

o Extremely hot/cold temperatures; frosto Adversely effects all populations regardless of their size.

Creative Writing1. Each group will work together to develop the

beginning of a story.o Introduce your characters, setting, problem (limiting factor), and size of

population in that characters communityo Pass your story to the next group

2. Each group will read the introduction of the their new story, and:

o Explain how the characters are being affected by the problem introduced in Part 1 (what fears/concerns does this organism have for his/herself and his population

o Pass your story to the next group

3. Each group will read their new story, and write its ending:

o Explain what happened to the character and his/her population as a result of the problem; will they be doing anything to re-build their population?

o Explain the impact this problem had on the overall population size?