population ecology and growth

population

a collection of individuals of the same species living in the same geographic area

community

a collection of populations of species in a geographic area

ecosystem

individuals of the community & the environment in which it exists

ecosystem — biotic components

living organisms of the ecosystem

ecosystem — abiotic components

nonliving players in an ecosystem

eg. weather & nutrients

biosphere

entire life-containing area of a planet — all communities and ecosystems

niche

all the biotic and abiotic resources used by the organism

population density

describes how ,amy individuals are in a certain area

distribution

describes how populations are dispersed over that area

dispersion pattern — clumped

individuals live in packs that are spaced out from each other like schools of fish or herd of cattle

dispersion pattern — uniform

individuals are evenly spaced out across a geographic area, like birds on a wire

dispersion pattern — random

species are randomly distributed across a geographic area, like tree distribution in a forest

population ecology

study of the size, distribution, and density of populations and how these populations change with time

Size of the population, N, indicates how many individuals of that species are in a given area

demographers

study the theory & statistics behind population growth and decline

birth rate — make sure yk how to analyze/read the graph

offspring produced per time period. Highest among those in the middle of the age spectrum

death rate — make sure yk how to analyze/read the graph

number of deaths per time period. Highest among those at 2 extremes of the age spectrum

sex ratio — make sure yk how to analyze/read the graph

proportion of males & females in a population

generation time — make sure yk how to analyze/read the graph

time needed for individuals to reach reproductive maturity

age structure — make sure yk how to analyze/read the graph

statistic that compares the relative numbers of individuals in the population from each age group

immigration rate — make sure yk how to analyze/read the graph

rate which individuals relocate into a given population

emigration rate — make sure yk how to analyze/read the graph

rate at which individuals relocate out of a given population

biotic potential

maxmimum growth rate of a population given unlimited resources, space, and lack of competition/predators. Rate varies by species

carrying capacity

maximum number of individuals that a population can sustain in a given environment

limiting factor — density-dependent factors

population's per capita growth rate to change—typically, to drop—with increasing population density

eg. competiiton w/ limited food

limiting factor — density-independent factors

affect per capita growth rate independent of population density. Examples include natural disasters like forest fires

population growth — exponential growth

population grows at a rate that makes a J-shaped curve. Population grows as if there are no limitations as to how large it can get (biotic potential)

population growth — logistic growth

the population grows at a rate that creates an S-shaped curve. Limiting factors are responsible for S shape, putting a cap on the size to which the population can grow

population cycle

when a population size dips below carrying capacity, it will later come back to the capacity and even surpass it. However, the population could dip below the carrying capacity as a result of some major change in the environment and equilibrate at a new, lower carrying capacity

when population is over carrying capacity…

overpopulation due to resource availability. Resources will eventually decline, buildup of waste & disease occurs that drive population back down

when population is below carrying capacity…

resources replenish, allowing for increase in the birth rate & decline in death rate

population growth equation

(dN) / (dt) = B - D

• dt = change in time

• B = birth rate

• D = death rate

exponential growth equation

(dN) / (dt) = r_maxN

• N = population size

• r_max = maximum per capita growth rate of population

logistic growth equation

(dN) / (dt) = r_maxN ((K - N) / K)

• N = population size

• r_max = maximum per capita growth rate of population

• K = carrying capacity