APES3 AP Environmental Science Unit 3: Populations

Introduced species

Introduced species

Species transferred by humans from native to new habitat

Native species

A species that occurs in an area naturally, without intervention

Cryptogenic

Of obscure or uncertain origin

Invasive species

An introduced species that harms its new environment

K-selected species

Those species present in stable and predictable environments that produce fewer offspring, have longer gestation periods, and provide long-term care after birth, are larger, live longer

r-selected species

Those species that produce a large number of offspring and contribute few resources to each individual offspring, smaller, short-lived

Survivorship curves

Graphs that show the proportion of a population that survives from one age to the next

Cohort

A group of individuals from the same population who are born at the same time

Type I survivorship curves

Represent populations whose organisms tend to survive beyond their young and middle-ages and die when elderly (small # of offspring, lots of parental care ) (ex. whales, humans)

Type II survivorship curves

Represent populations with a constant proportion of individuals dying at each age interval, steadily decreasing chance of surviving (ex. squirrels, birds)

Type III survivorship curves

Represent populations that have a high death rate among the young, but a relatively low death rate for those who survive into middle and old age (lots of offspring, not much parental care) (ex. fish, bugs)

Type I survivorship curve graph

Type II survivorship curve graph

Type III survivorship curve graph

Population growth formula

P(n)= Initial population * growth rate ^n

p= population, n= # of unit of time (ex. 3 of months or years (example, initial pop of 500, growth rate of 10% and 5 years 500×1.1^5)

Logistic growth

The s-shaped curve which contains exponential growth then hitting a carrying capacity

Exponential growth

growth whose rate becomes ever more rapid in proportion to the growing total number or size

Malthusian limit

The human carrying capacity as said by Thomas Malthus

Overshoot

When a population briefly exceeds carrying capacity

Die-off/dieback

Sharp decrease in population size when resource depletion due to overshoot leads to individuals dying

Density-dependent factors

Factors that influence population growth based on size (food, competition for habitat, water, light, disease, food)

Density-independent factors

Factors that influence population growth independent of their size (natural disasters like flood, hurricane, tornado, fire)

Biotic potential

Maximum potential growth rate, with no limiting resources

Population size formula w/ immigration

Population size = (Immigrations + births) - (Emigrations + deaths)

Size (N)

Total # of individuals in a given area at a given time

Density

Number of individuals/ area

Distribution

How individuals in population are spaced out compared to each other (ex. random, uniform, clumped)

Population sex ratio

The ratio of males to females in a population

Population pyramid (age structure diagram)

Shows the distribution of age and sex in a population

Rapid growth

Large proportion of young people and small proportion of older people, high birth, high death

Slow growth

higher proportion of young people as compared to older people, but not as extreme as in rapid growth

Stable population

Relatively similar proportions of young, middle age, and older people (declining birth rates, low death rates)

Declining population

Relatively few younger individuals

Doubling time

The time it would take for a population to double

Rule of 70

Doubling time can be approximated by taking 70 and dividing it by growth rate (% , not decimal)

Demographic transition model

Shows the shift from high birth and death rates to low birth and death rates

Demographic transition model stage 1

Pre-Industrial

Pre-Industrial

High birth rates, high death rates, population stays the same

Demographic transition model stage 2

Transitional/Early Industrial

Transitional/early industrial

Decreasing death rates, industrializing, population increases

Demographic transition model stage 3

Industrial

Industrial

Decreasing birth rates, small population growth

Demographic transition model stage 4

Post-Industrial

Post-Industrial

Birth rates low, death rates low, population stays the same