unit 3 (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

age cohort

a group of similarly aged individuals

pre-reproductive cohort

the group of individuals between 0 and 14 years of age

reproductive age cohort

the group of individuals between 15 and 44 years of age

post-reproductive age cohort

the group of individuals 45 years of age and older

total fertility rate (TFR)

the average number of children a woman will have in her lifetime

replacement level fertility

the TFR required to offset deaths in a population and keep the population size stable, typically 2.1 in developed countries but can be higher in less-developed countries as a result of high infant mortality rates

infant mortality rate (IMR)

the number of deaths of children under 1 year of age per 1000 people in a population, and it is typically higher in less-developed countries

causes of a decline in IMR

increased access to clean water, healthcare, and more reliable food supplies

development’s effect on TFR

more developed, or wealthy, nations have a lower TFR than less-developed nations

leads to more educational access for women, more economic opportunity for women, higher access to family planning and contraceptives, a later first-pregnancy, and a less need for children to provide income via agricultural labor

government policy’s effect on TFR

can play a huge role in fertility by coercive (forceful) or noncoercive (encouraging) policies, including forced sterilization and tax incentives to have fewer children

malthusian theory of population

theory that predict that population growth was growing exponentially, while food supply only grows linearly, which will result in the human population reaching a carrying capacity

flaws of malthusian theory

didn’t consider the possibility of humans being able to alter food supply, with technologies such as fertilizers, and thus expand their carrying capacity

growth rate (r)

the percent increase in a population, usually per year

crude birth rate (CBR)

the number of births per 1000 people in a population

crude death rate (CDR)

the number of deaths per 1000 people in a population

rule of 70

a mathematical relationship that determines that the time it takes for a population to double is 70 divided by the growth rate

standard of living

a definition of the quality of life for people of a country

gross domestic product (GDP)

the total value of the goods and services produced, typically a high total value is associated with a higher standard of living

life expectancy

the average age a person will live to in a given country, which increases as access to clean water, healthcare, and stable food sources increases

industrialization

the process of a country’s economic and social transition from an agrarian economy to an industrial one

pre-industrialized countries

countries that have not yet made the agrarian-to-industrial transition, and are typically very poor, with high death rates and infant mortality rates

industrializing countries

countries that are partially through the agrarian-to-industrial transition, and typically have decreasing death rates and IMRs and a rising GDP

industrialized countries

countries that have completed the agrarian-to-industrial transition, and typically have a low death rate and IMR and very high GDP