AP Environmental Science: Populations, Growth, and Demographic Transition

Specialist Species

Species with a smaller range of tolerance or narrower ecological niche, making them more prone to extinction.

Generalist Species

Species with a larger range of tolerance and broader niche, making them less prone to extinction and more likely to be invasive.

R-selected Species

Species characterized by high biotic potential, many offspring, little to no parental care, and a short lifespan.

K-selected Species

Species characterized by low biotic potential, few offspring, heavy parental care, and a long lifespan.

Biotic Potential

The maximum reproductive capacity of an organism under optimal environmental conditions.

Parental Care Spectrum

The range of parental investment in offspring, from high care in K-selected species to low care in r-selected species.

Survivorship Curve

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

Type I Survivorship Curve

Characterized by high survivorship early in life due to high parental care, with a rapid decrease in survivorship in late life.

Type II Survivorship Curve

Characterized by steadily decreasing survivorship throughout life.

Type III Survivorship Curve

Characterized by high mortality early in life due to little to no parental care, with few making it to adulthood.

Invasiveness

The ability of a species to spread rapidly and outcompete native species for resources.

Population Density

The number of individuals of a species per unit area or volume.

Hudson River

A river in New York where the relationship between Zebra Mussel and Unionid Mussel population density is studied.

Extinction Risk

The likelihood of a species becoming extinct due to various factors, including ecological niche and adaptability.

Adaptability

The ability of a species to adjust to changes in environmental conditions.

Ecological Niche

The role and position a species has in its environment, including all interactions with biotic and abiotic factors.

Rapid Population Growth

A characteristic of r-selected species, often resulting in a higher chance of adaptation and lower chance of extinction.

Disturbance

An event that disrupts ecosystem structure and function, impacting species survival and population dynamics.

Invasive Species

Non-native species that spread widely in a new habitat, often causing harm to native species and ecosystems.

Reproductive Events

Instances of reproduction that can vary in frequency between r-selected and K-selected species.

Mortality Rate

The rate at which individuals in a population die, which can influence survivorship curves.

Cohort

A group of individuals of the same age within a population.

Environmental Change

Alterations in the environment that can affect species survival and population dynamics.

Carrying Capacity (k)

the max. number of individuals in a pop. that an ecosystem can support (based on limiting resources)

Die-off

sharp decrease in pop. size when resource depletion (overshoot) leads to many individuals dying

Overshoot

when a population briefly exceeds carrying capacity

Consequence of overshoot

resource depletion, e.g., overgrazing in deer

Example of Die-off

Reindeer of St. Paul Island: 25 introduced in 1910, growth was gradual (10'-30'), then exponential (30'-37'), carrying capacity was overshot, sharp die-off led to pop. crash as food resource (lichen) was severely depleted

Population Characteristics

Size (N): total # of individuals in a given area at a given time

Density

# of individuals/area, e.g., (12 panthers/km2)

Distribution

how individuals in pop. are spaced out compared to each other: Random (trees), Uniform (territorial animals), Clumped (herd/group animals)

Sex Ratio

ratio of males to females; closer to 50:50, the more ideal for breeding (usually)

Density-Independent Factors

factors that influence pop. growth independent of their size

Density-Dependent Factors

factors that influence pop. growth based on size, e.g., natural disasters (flood, hurricane, tornado, fire)

Example of Density-Dependent Factor

Food is a density dependent factor (also a limiting resource); when twice as much food was added to the dish, both species increased carrying capacity by about 2x

Logistic Growth

initial rapid growth, then limiting factors limit pop. to K

Calculating Population Change

Population Size = (Immigrations + births) - (immigrations + deaths)

Example of Population Change Calculation

An elk pop. of 52 elk has 19 births and 6 deaths in a season, and 5 new elk immigrate to the herd and 0 elk emigrate from the herd: (19+5) - (6+0) = + 18 elk; 52 + 18 = 70 elk

Percent Change in Population Size

Calculate the percent change in the population size of a 14 wolf pack that experiences 5 deaths, 3 births, and 4 new wolves released into the pack from a nearby wildlife sanctuary.

Age Cohorts

Groups of similarly aged individuals.

Prerproductive Age

Individuals aged 0-14.

Reproductive Age

Individuals aged 15-44.

Post Reproductive Age

Individuals aged 45 and older.

Growth Rate

Indicated by the size difference between age cohorts 0-14 and 15-44.

Extreme Pyramid Shape

Indicates rapid population growth.

Less Extreme Pyramid

Indicates slow, stable population growth.

House Shape

Indicates stable population with little to no growth.

Narrowest at Base

Indicates a declining population.

Infant Mortality Rate (IMR)

Number of deaths of children under 1 year per 1,000 people in a population.

Total Fertility Rate (TFR)

Average number of children a woman in a population will bear throughout her lifetime.

Replacement Level Fertility

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

Factors in IMR Decline

More reliable food supply, access to clean water, and access to healthcare.

Government Policy

Can play a huge role in fertility through coercive or noncoercive policies.

Affluence

More developed or wealthy nations have a lower TFR than less developed nations.

Female Education

More education leads to fewer unplanned pregnancies and more job opportunities for women.

Malthusian Theory

The theory that Earth has a human carrying capacity, probably based on food production.

Technological Advancement

Humans can alter earth's carrying capacity with technological innovation.

Exponential Increase in Food Supply

Dramatic increase in food supply due to innovations like synthetic fertilizers.

Growth Rate (r)

Percentage increase in a population, usually per year.

Crude Birth Rate (CBR)

Births per 1,000 people in a population.

Crude Death Rate (CDR)

Deaths per 1,000 people in a population.

Global CBR

20

Global CDR

8

Doubling Time (Rule of 70)

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

Example of Doubling Time Calculation

For a global growth rate of 1.2%, doubling time is 70/1.2 = 58.3 years.

Annual Growth Rate Calculation

For a country with a CDR of 9 and a CBR of 18, the growth rate is (18-9)/10 = 0.9%.

Doubling Time from Growth Rate

For a growth rate of 0.9%, doubling time is 70/0.9 = 77.77 years.

Factors Increasing Population Growth

Higher Total Fertility Rate (TFR), high immigration levels, and increased access to clean water and healthcare.

Factors Decreasing Population Growth

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

Standard of Living

Quality of life indicators for people in a country.

Life Expectancy

Average age a person will live to in a given country; a key health indicator of standard of living.

Gross Domestic Product (GDP)

Total value of goods and services produced; a key economic indicator of standard of living.

Per Capita GDP

Total GDP divided by total population.

Stage 1 - Preindustrial

Characterized by high infant mortality rate (IMR) and high death rate due to lack of access to clean water, stable food supply, and healthcare.

Stage 2 - Industrializing/Developing

Marked by declining IMR and CDR, low per capita GDP, and high TFR due to factors like high infant mortality and lack of education for women.

Stage 3 - Developed/Industrialized

Features high per capita GDP, low infant mortality, and delayed marriage and first child, with TFR near replacement level (2.1).

Stage 4 - Post-Industrialized/Highly Developed

Characterized by very high per capita GDP, longest life expectancy, TFR below replacement level (2.1), and negative population growth.

Demographic Transition

The process of economic and social transition from an agrarian economy to an industrial one.

Generational Lag

The time it takes for education and societal change to spread.

High TFR

Indicates a higher birth rate, often driven by high infant mortality and the need for child agricultural labor.

High Infant Mortality Rate

Can drive up TFR as families have more children to ensure some survive.

Access to Family Planning

Involves availability of contraceptives and education to help manage birth rates.

Economic Indicators of Development

High GDP and life expectancy are both indicators of development and low population growth.

Population Growth Rate

The rate at which the number of individuals in a population increases in a given time period.