Ch. 20.2 Population Ecologypp.383-387

Growth rate = birth rate – death rate

ADD:• Immigration = individuals

move into the pop.• Birth rate = SUBTRACT:• Emigration = individuals

move out of pop.• Death rate =

Ch. 20.2 Population Ecologypp.383-387

Exponential growth = population is growing without limits• Common for bacteria, and

in early growth• Sometimes called

“doubling”• Cannot continue forever

because soon goes to infinity

• Resources always become limited

Ch. 20.2 Population Ecologypp.383-387

Limiting factor = a resource that runs out and limits growth• Food, habitat,…

Logistic growth = when a population grows to a maximum that the environment can support• Often starts exponentially

but eventually reaches the limit

Ch. 20.2 Population Ecologypp.383-387

Carrying capacity = number of individuals (capacity) that the environment can carry for a long period of time• Abbreviated K• Birth rate = death rate;

or balanced

How many days are the Paramecia below in exponential growth?The daphnia…?

Ch. 20.2 Population Ecologypp.383-387

Density- independent limiting factors = limit growth but NOT related to population density• Weather, fire, pollution…• The limiting factor is

independent of the size of the population

Ch. 20.2 Population Ecologypp.383-387

density-dependent limiting factor = does depend on the size of the population in the area • Food, nesting sites, finding

mates, diseases

Inbreeding = loss of genetic diversity because of few individuals• Close relatives mating• Increase in genetic disease

Ch. 20.2 Population Ecologypp.383-387

flux = populations fluctuate, or constantly increase or decrease• Common in predator- prey

interactions• Lynx and Snowshoe hare