AP BiologyChapters 53.1-3, 53.5

54.1-2

Population: group of individuals of a single species living in the same general area who interact and interbreed

density: number of individuals per unit area

not a static number...constantly changing (births, deaths, immigration, emigration)

dispersion: pattern of spacing among individuals, indicates social interactions in a population

clumped, uniform, or random

territoriality also influences dispersion

Not easy to count all individuals in a population...use mark-recapture method to estimate population sizes

Survivorship Curves

graphical representation of number of organisms alive in a population over time in age ranges (death rate)

Type I: low death rates early in life, increases in older age-groups

humans, elephants, primates and other organisms with lots of parental care

Type II: constant death rate over life span

squirrels, rodents, plants

Type III: high death rate in younger ages, death rate declines (levels off) in older age groups

organisms with large numbers of offspring and little parental care (invertebrates and fishes)

Exponential Growthrapid growth, occurs in

times of unlimited resources (no carrying capacity)

produces a J-shaped curve

Formula:population growth= rmax (N)

(births-deaths)

rmax = maximum per capita growth rate of a population

N= population size

Logistic Growth

growth limited by a carrying capacity (number of individuals an ecosystem can support)varies with

changing resources

growth rate approaches zero as the carrying capacity is reached

r= rmax = maximum per capita growth rateN= population sizeK= carrying capacity

Factors regulating population size

density-independent: does not influence the birth or death rate

natural disasters, weather, sunlight, temperature

density-dependent: increases death rate, decreases birth rate

competition, predation, intrinsic physiologic factors, waste buildup, territoriality, disease

negative feedback!

Species Interactions

two or more species interacting in a positive, negative, or neutral relationship

competitive exclusion: two species competing for the same resource cannot coexist permanently; one species will use the resource more effectively and outcompete the other species

symbiosis: individuals of two or more species live in direct close contact with one another

cooperative behavior: organisms work together for mutual benefits (social animals, insects)

Species Interaction

+/- Description Example

interspecific competition

-/-

individuals of a different species compete for a

resource that limits their growth and survival

Bison and grasshoppers both compete to eat grass

Predation +/-one species (predator) kills and eats the other

(prey)

lion attacking and eating an antelope

Herbivory +/-an organism eats all or

part of a plant/algaecows and sheep eat grass; manatee eating sea grass

Parasitism +/-an organism (parasite)

eats and lives on or inside another (host)

tapeworms in small intestine; fleas on outside

of dog

Mutualism +/+ benefits both speciesnitrogen fixing bacteria and legumes, bacteria in

digestive system

Commensalism

+/0one species benefits, the

other is neither hurt/benefited

birds and grazing animals, barnacles and

whales