Populations

generalist species

species that have a larger range of tolerance, or broader ecological niche, and makers them less prone to extinction, but more likely to be invasive

example: racoon

specialist species

species that have a smaller range of tolerance, or narrower ecological niche, and makes them more prone to extinction

example: pandas

k-selected species

species that typically reproduce by having few offspring, with large amounts of parental care to protect their offspring

have a longer time until sexual maturity is reached, and thus have a lower biotic potential with a slow population growth rate, and are more likely to be disrupted by environmental change

r-selected species

species that typically reproduce by having many offspring at once, with minimal amounts of parental care

reach sexual maturity quickly, and thus have a high biotic potential with a high population growth rate, and are more likely to be invasive

biotic potential

the maximum rate at which a species can reproduce, when there are no limitations placed on an organism’s rate of growth

survivorship curve

a line that shows the survival rate of a cohort in a population from birth to death

cohort

a group of same-ged individuals

type 1 survivorship curve

typically K-selected species, with high survivorship in early- and mid-life, but have a rapid decrease in survivor ship in late-life

examples: whales, humans

type 2 survivorship curve

steadily decreasing survivorship throughout life

examples: birds, rodents

type 3 survivorship curve

typically r-selected species, with a low survivorship in early-life, making it so that few make it to mid-life and beyond

examples: insects, fish, plants

carrying capacity (K)

the maximum number of individuals in a population that an ecosystem can support, based on limiting resources

overshoot

when a population briefly exceeds carrying capacity

example: deer breeding in the fall, giving birth in the spring, leading to an overshoot in population in the spring

limiting resources

food, water, and habitat (nesting sits, space, etc.)

consequence of overshoot

resource depletion

example: overgrazing in deer

die-off

a sharp decrease in population size when resource depletion leads to many individuals dying

example: many deer die in the spring due to many new fawns feeding in the spring

size (N)

the total number of individuals in a given area at a given time

density

the number of individuals in a given area

consequences of high density populations

higher competition, higher possibility for disease outbreak, and higher possibility of depleting food sources

distribution

how individuals in a population are spaced out compared to each other

random distribution

an unorganized distribution of a population

uniform distribution

a distribution where organisms are evenly spaced apart from each other

clumped distribution

the distribution where large numbers of a populations are located close to each

sex ratio

the ratio of males to females

a closer to 50:50 ratio is ideal for breeding, usually

density-dependent factos

factors that influence population growth based on size, and effect larger populations more than smaller ones

examples: food, competition for habitat, water, light, even disease

density-independent factors

factors that influence population growth independent of their size and effect populations no matter their size

examples: floods, hurricanes, tornadoes, fires