Initiation

Assume that a pair of rabbits produces 6 offspring, and half the offspring are male and half are female. Assume no offspring die. If each pair of rabbits breeds only once, how many offspring

would be produced each year for 5 years?

Unit 7EcologyDiscussion 7.3

Objectives

SWBAT...identify factors that affect population size.

Key Questions

What factors affect population size?

Words To Live By...

Population density

Carrying capacity

Limiting factor

Key Points

Three important factors can affect population size: the number of births, the number of deaths, and

the number of individuals that enter and leave the population.

The limiting factors of population growth can exist in two forms: density-dependent and density

independent.

Population DensityPopulation Density =

Number of Individuals ---------------------------

Unit areaSuppose there are 150 bullfrogs living

in a pond that covers an area of 3 square kilometers. What is the

population density of the bull frog population?

Population GrowthHow are these graphs alike? How are these graphs different?

Exponential Growth Vs. Logarithmic Growth

Under ideal conditions with unlimited resources, a

population will grow Exponentially.As resources become less available, the growth of

a population slows or stops. This is called Logistic growth.

Carrying capacity represents the

maximum amount of individuals an

environment can take.

Limiting Factors

What are some things that might cause a population of organisms to decrease?

A limiting factor is a factor that population growth to decrease. There are two major types of limiting factors: Density-Dependent Factors and Density-

Independent Factors.

Density Dependent vs. Density Independent

Population Size

Competition

Predation Parasitism/DiseaseClimate Change

Human Disturbances

Which limiting factors do you feel depend on the size of the population to have any

effect?

Which limiting factors do you feel do not depend on the size of the population to have

any effect?Dependent

Independent

Termination

What is the difference between exponential and logistic growth? Which type graph represents

growth under ideal conditions?