Ecological Niches, Population Dynamics, and Human Impact in Ecology

Specialist

Smaller range of tolerance, or narrower ecological niche makes them more prone to extinction.

Generalists

Larger range of tolerance, broader niche makes them less prone to extinction and more likely to be invasive.

K-selected species

Few offspring, heavy parental care to protect them; generally have fewer reproductive events than r-strategists. Example: most mammals, birds.

R-selected species

Many offspring to no parental care; generally have fewer reproductive events than r-strategists. Example: insects, fish, plants.

K-selected habitats

Usually live in habitats with higher competition for resources.

R-selected habitats

Usually live in habitats with lower competition for resources.

Survivorship curves

Line that shows survival rate of cohort (group of same aged individuals in a population) from birth to death.

Type I survivorship

High survivorship early in life due to high parental care. Example: most mammals.

Type II survivorship

Steadily decreasing survivorship throughout life.

Type III survivorship

High mortality (low survivorship) early in life due to little to no parental care. Example: insects, fish, plants.

Carrying capacity

The max # of individuals in a population that an ecosystem can support (based on limiting resources).

Overshoot

When a population briefly exceeds carrying capacity. Example: deer breed in fall, give birth all at once in spring, sudden spike in population = overshoot.

Die-off

Sharp decrease in population size when resource depletion (overshoot) leads to many individuals dying. Example: many deer starve with too many new fawns feeding in the spring.

Size (n)

Total number of individuals in a given area at a given time; larger = safer from population decline.

Density

Number of individuals/area. Example: 12 panthers km^2; high density = high competition, possibility for disease outbreak, possibility of depleting food source.

Distribution

How individuals in population are spaced out compared to each other.

Sex ratio

Ratio of males to females; die off or bottleneck effect can lead to skewed sex ratio (not enough females) limiting population growth.

Density dependent factors

Factors that influence population growth based on size. Example: food competition for habitat, water, light, even disease.

Density independent factors

Factors that influence population growth independent of their size. Example: natural disasters.

Biotic potential

Exponential growth.

Logistic growth

Initial rapid growth, then limiting factors limit population to K.

Population size equation

Population size = (immigration + births) - (emigration + deaths).

Percent change in population equation

New-old/old x 100.

Total fertility rate

Average number of children a woman in a population will bear throughout her lifetime; higher TFR = higher birth rate, higher population growth rate.

Replacement level fertility

The TFR required to offset deaths in a population and keep population size stable.

Infant mortality rate (IMR)

Number of deaths of children under 1 year per 1,000 people in a population; higher IMR: higher TFR, due to families having replacement children.

Development (affluence)

More developed, or wealthy nations have a lower TFR than less developed nations; educational access for women.

Opportunity for women

High access to family planning education and contraceptives

Later age of first pregnancy

A factor that can influence population growth.

Government policy

Can play a huge role in fertility by coercive (forceful) or non-coercive (encouraging) policies.

Malthusian theory

Earth has a human carrying capacity, probably limited by food production.

Human population growth

Happening faster than growth in food production.

Growth rate

% increase in a population (usually per year).

Rule of 70

The time it takes (in years) for a population to double is equal to 70 divided by the growth rate.

Factors that increase population growth

Higher TFR -> higher birth rate, high infant mortality rate can drive up TFR, high immigration level, increased access to clean water and health care (decrease death rate).

Factors that decrease population growth rate

High death rate, high infant mortality rate, increased development (education and affluence), increased education for women, delayed age of first child, postponement of marriage age.

Standard of living

What the quality of life is like for people of a country.

Industrialization

The process of economic and social transition from an agrarian (farming) economy to an industrial one (manufacturing based).

Preindustrialized

A country that has not yet made the agrarian to industrial transition, typically very poor (low GDP), high death rate, and high infant mortality.

Industrializing

Part way through this transition, decreasing death rate and infant mortality rate (IMR), rising GDP.

Industrialized

Completed the transition, very low crude death rate (CDR) and IMR, very high GDP, low total fertility rate (TFR).