Population BiologyPopulation Biology

Unit 2Unit 2

Chapter 4Chapter 4

PopulationPopulation: : group of same species group of same species living in a specific arealiving in a specific area

This is a population of This is a population of bacteria that can be bacteria that can be studied easily in a studied easily in a laboratory setting.laboratory setting.

Exponential growthExponential growth: as population : as population gets larger, the growth rate gets larger, the growth rate becomes fasterbecomes faster

Populations will Populations will continue to grow continue to grow exponentially until exponentially until they run out of food or they run out of food or space.space.Growth starts off Growth starts off slowly because there slowly because there are few in the are few in the population that can population that can reproduce.reproduce.

Population Growth of Houseflies

Carrying capacityCarrying capacity

The total The total number of number of organisms of organisms of one species one species that an that an environment environment can support can support indefinitelyindefinitely

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Stopping population growthStopping population growth

When a population becomes larger than When a population becomes larger than the carrying capacity, the carrying capacity, limiting factorslimiting factors can can stop population growth.stop population growth.

What can limit the growth of a What can limit the growth of a population?population?

Characteristics of Population Growth

Exponential growth

Carrying capacity

J curve S curve

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PredationPredation can affect populations. can affect populations. What else can affect populations?What else can affect populations?

What is the relationship between What is the relationship between predator and prey populations?predator and prey populations?

Lynx and Hare Pelts Sold to the Hudson’s Bay Company

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Different growth ratesDifferent growth rates

Some populations grow very rapidly. Some populations grow very rapidly. Why?Why?– Ex: bacteriaEx: bacteria

Different growth ratesDifferent growth rates

Some populations Some populations grow slowly. Why?grow slowly. Why?– Ex: elephants, Ex: elephants,

bearsbears

Demography Demography

study of human population size, density study of human population size, density and distribution, movement, and its birth and distribution, movement, and its birth and death ratesand death rates

Birth rateBirth rate is the number of live births per is the number of live births per 1000 population in a given year.1000 population in a given year.

Death rateDeath rate is the number of deaths per is the number of deaths per 1000 population in a given year.1000 population in a given year.

Calculating how fast populations Calculating how fast populations growgrow

Birthrate – Death rate = Population Growth Birthrate – Death rate = Population Growth Rate (PGR)Rate (PGR)

If PGR > 0, then the population is growing.If PGR > 0, then the population is growing.

If PGR < 0, then the population is If PGR < 0, then the population is declining.declining.