APES Unit 3

Generalists

Thrive in diverse environments with broad ecological tolerance. Resilient to environmental changes.

Examples: gray kangaroos and stickleback fish.

Specialists

Require specific habitats and diets. Thrive in stable conditions but are vulnerable to changes.

Examples: koalas or leaf beetles

K-selected

Slow growth, large size, delayed reproduction, few offspring, high parental care. Populations are stable but vulnerable to extinction.

Examples: elephants and humans.

r-selected

Rapid growth, small size, early reproduction, many offspring, little/no parental care. Populations fluctuate and adapt quickly.

Examples: mice and cockroaches

Type I

A Type

High survival early/midlife, decline with age

Example: K-selected species like humans and elephants.

Type II

Constant mortality rate

Example: Chipmunks, birds

Type III

High mortality early, survivors live longer

Example: r-selected like Frogs, birds, and spiders.

Carrying Capacity

Maximum population size an environment can sustain with available resources.

- Population Impact: Exceeding capacity leads to “dieback” and eventual stabilization around the limit.

- Examples: Reindeer on St. Paul Island grew rapidly, crashed due to resource exhaustion, and stabilized under management.

Exponential Growth Model

“J-shaped” curve of rapid growth under ideal conditions, rarely sustained.Characterized by unlimited resources and no environmental resistance.

Logistic Growth Model

“S-shaped” curve; growth slows as resources limit population near carrying capacity.It describes how populations grow more slowly as they approach the environment's carrying capacity, reflecting the influence of resource availability and competition.

Density-Dependent Factors

Size- dependant factors that impact population growth

Examples: Competition, predation, and disease

Density-Independent Factors

Affect all equally

Examples: Natural disasters and climate.

Limiting Resources

Essential resources cap population size; depletion reduces carrying capacity. Examples: food, water, shelter, and space.

Impact: Overpopulation, depletes resources, altering ecosystems temporarily (e.g., regrowth) or permanently (e.g., soil erosion).

Examples: Overgrazing in China degraded land; sub-Saharan Africa faces resource scarcity due to population growth

Reindeer case study

Rapid growth and crash due to resource exhaustion.

Lynx & Hares

Predator-prey cycles regulate populations.

Moose and Wolves

Wolf reintroduction stabilized both populations.

Goldeneye Ducks

Habitat loss limits growth despite food availability.

Age Structures

Pyramid (rapid growth, e.g., Nigeria), Column (stable, e.g., U.S.), Inverted Pyramid (decline, e.g., Italy).

Population Momentum

Young populations sustain growth despite policy changes.

Total Fertility Rate

Influenced by education and income (e.g., Ethiopia: 1.5 with education vs. 5.8 without).

Family Planning

Campaigns (e.g., Kenya) lower TFR via contraceptive use (drugs to prevent pregnancy)

Aggregate Demand

Total demand influenced by consumer confidence, interest rates, and exchange rates

Aggregate Supply

Represents the total quantity of goods and services that producers in an economy are willing and able to supply at various price levels

Fiscal and Monetary Policies

Governments influence economies through spending/taxes (fiscal) and money supply/interest rates (monetary)

Fiscal → Government

Monetary → Central banks, etc

CBR, CDR, IMR, TFR

influence growth, decline, and distribution

Demographic Transition Model

outlines population changes during economic development

Causes for Growth

High CBR/TFR, low IMR, early marriage, limited family planning (e.g., developing nations).

Causes for Decline

Low CBR/TFR, delayed marriage, access to family planning (e.g., developed nations) all are…

Case Study: China

TFR dropped from 6.3 (1970) to 1.5 due to One Child policy.

Stages of Demographic Transition

Pre-Industrial: High birth/death rates, stable population (e.g., pre-Industrial Revolution).

Industrializing: Death rates fall; rapid growth due to cultural lag (e.g., early 20th-century U.S.).

Industrialized: Birth rates decline, growth slows (e.g., Uruguay).

Post-Industrial: Birth rates drop below death rates; aging population (e.g., Japan).

The IPAT Equation

Impact = Population × Affluence × Technology

Population: More people = greater strain.

Affluence: Wealth drives consumption.

Technology: Can harm (pollution) or aid (efficiency).