CH44: population ecology

population

population

a group of organisms of the same species that live in the same area and interbreed

population ecology

the study of living organisms' population dynamics and interactions with the environment. It focuses on factors like size, density, distribution, growth rate, and species interactions.

ecology

Branch of biology dealing with how populations interact with eachother and the nonliving environment

demographics

statistics that describe a population’s traits

population size

number of individuals in a population

plot sampling

estimates total number of individuals in an area; most accurate for non-mobile organisms with uniform conditions

mark-recapture sampling

technique for sampling mobile animal population size

population density

number of individuals per unit area or volume; i.e number of dandelions per square meter of lawn

population distribution

describes the location of individuals relative to one another

clumped distribution

Members of a population are closer to one another than would be predicted by chance alone; most animals. due to uneven distribution of resources, limited dispersal ability, asexual reproduction, some animals just live in groups.

near-uniform distribution

equal distance apart. can be created by competition for limited resources.

random distribution

occurs when resources are uniformly available, no benefit or harm from proximity to others.

age structure

refers to the number of individuals in various age categories

reproductive base

all individuals who are of reproduction age or younger (pre-reproductive and reproductive). the greater size of this gives a population a greater capacity to grow.

immigration

Arrival of new residents that previously belonged to another population

emigration

Departure of individuals who take up residence elsewhere

zero population growth

time period in which the number of deaths and births is equal. no net increase or decrease in a population’s number of individuals.

per capita growth rate, r

per capita growth rate - per capita birth rate

exponential growth model

predicts growth of an idealized population that has no limits on population growth

biotic potential

growth rate for a population under ideal conditions

density-dependent limiting factors

as density increases, causes birth rates to slow and/or death rates to rise, so the rate of population growth decreases

intraspecific competition

competition among members of the same species

logistic growth

occurs when density-dependent factors affect population size over time; graph results in a S-shaped curve

carrying capacity, K

maximum number of individuals a population’s environment can support indefinitely

density-independent limiting factors

crowding does not influence the likelihood of the occurrence of or magnitude of the effect of natural disasters and weather events

life history

the manner in which individuals allocate resources to growth, survival, and reproduction over the course of their lifetimes

cohort

a group of individuals born during the same interval

survivorship curve

plot showing how many members of a cohort remain alive over time

opportunistic species

live where conditions vary in an unpredictable manner, and thus seldom reach carrying capacity. little competition for resources

r-selection

per capita growth rate under optimal conditions. opportunistic species are subject to this.

equilibrial species

live in a stable environment and thus may reach carrying capacity, ability to successfully compete for resources affects reproductive success.

K-selection

adaptive traits provide a competitive advantage when population size is near carrying capacity (K)

demographic transition model

describes how changes in population growth often unfold in four stages of economic development

ecological footprint

the amount of Earth’s surface to support a particular level of development and consumption in a sustainable fashion