Population Dynamics and Growth Patterns

Logistical versus exponential growth curves

Exponential growth is rapid and unchecked, forming a J-shaped curve. Logistical growth considers limiting factors and carrying capacity, forming an S-shaped curve.

What is ecological carrying capacity?

The maximum population size of a species that an environment can sustain indefinitely without degrading the ecosystem.

What is minimum viable population size?

The smallest number of individuals needed for a population to survive and maintain genetic diversity.

Population survivorship curves — type I, II, and III populations and examples of organisms that exhibit each growth type

Type I: High survival early and mid-life, steep decline later (e.g., humans, large mammals). Type II: Constant death rate at all ages (e.g., birds, squirrels). Type III: High early mortality, few survive to adulthood (e.g., insects, frogs, oysters).

Density dependent versus independent limiting factors

Density-dependent: Affected by population size (e.g., disease, competition, predation). Density-independent: Not related to population size (e.g., weather events, natural disasters).

Biotic versus abiotic factors and population controls

Biotic factors: Living components like predators, parasites, food. Abiotic factors: Non-living elements like temperature, water, pH. Both control population size through availability of resources or survival conditions.

K versus r-selected species and what types of growth survivorship curves do they have?

K-selected: Fewer offspring, more parental care, stable environment, Type I or II curves (e.g., elephants). r-selected: Many offspring, little parental care, unstable environment, Type III curves (e.g., insects).

Island biogeography; how related/compared to habitat fragmentation

Island biogeography explains species richness based on island size and distance from the mainland. Habitat fragmentation mimics this, creating "islands" of habitat that reduce biodiversity similarly.

Annual world population growth and where is that growth mostly happening?

Current global population growth is around 1% per year. Most growth is occurring in developing countries, especially in Sub-Saharan Africa and parts of Asia.

What factors led to rapid population growth in the 1600s?

Improvements in agriculture, sanitation, medicine, and industrialization led to lower death rates and longer lifespans.

What did Thomas Malthus predict about a growing human population? Was he right? Why?/Why not?

Malthus predicted population would grow faster than food supply, causing famine. He was partially wrong—he didn't account for technological advances that increased food production.

Know age structure diagrams, how to read them, what do they show and how is future projected growth measured based on shape of diagram?

Wide base = growing population. Narrow base = declining growth. Rectangular shape = stable population. Shape predicts future population trends (rapid, slow, or no growth).

Which countries have the highest fertility rates?

Mostly in Sub-Saharan Africa (e.g., Niger, Somalia), with fertility rates above 5 children per woman.

What is I=PAT formula?

I = Impact, P = Population, A = Affluence, T = Technology. Describes how human population and behaviors affect the environment.

Crude birth/death rate: definition and factors that affect it

Number of births/deaths per 1,000 people per year. Affected by health care, nutrition, access to contraception.

Replacement level fertility rate: definition and factors that affect it

Average number of children a couple must have to replace themselves (≈2.1 in developed countries).

Total fertility rate: definition and factors that affect it

Average number of children born per woman in her lifetime.

Life expectancy: definition and factors that affect it

Average age a newborn is expected to live. Affected by healthcare, sanitation, lifestyle.

Dependency ratio: definition and factors that affect it

Ratio of non-working (young and elderly) to working-age people.

"Birth dearth": definition and factors that affect it

Declining birth rates leading to population aging and shrinking.

Demographic transitions: definition and factors that affect it

Model showing shifts in population growth as countries develop (4 stages: pre-industrial, transitional, industrial, post-industrial).

Family planning: definition and factors that affect it

Providing education and access to contraception to control fertility.

Doubling time calculations Dt = 70/r

Dt = Doubling time in years; r = growth rate (%). Example: If r = 2%, then Dt = 70 / 2 = 35 years.