CHAPTER 5.3: POPULATION ECOLOGY, COMMUNITY ECOLOGY, HUMAN POPULATION, AND ENVIRONMENTAL HISTORY

Population biologists

Scientists who study the interactions that occur between living things and how populations change over time.

Individual

The simplest level of biological organization; each individual is a member of a population.

Population

A group of individuals of the same species that occupy the same environment and interact with each other.

Community

Many different populations living and interacting together.

Ecosystem

A community of organisms interacting with each other and with the nonliving environment.

Biome

A group of ecosystems that share similar temperature and moisture conditions.

Biosphere

All the biomes on Earth combined; the largest level of ecological organization.

Levels of complexity of living organisms on Earth

1. Individual 2. Population 3. Community 4. Ecosystem 5. Biome 6. Biosphere.

Population size

The number of individuals that make up a population.

Population density

The number of individuals in a population relative to the area they inhabit.

Population distribution

Indicates where individuals are located across the environment they occupy.

Sex ratio

The number of males versus females in a population.

Age structure

Describes how many individuals fall into different age groups within a population.

Density-dependent factors

Factors whose influence on a population changes as population size changes.

Density-independent factors

Factors that affect populations regardless of population size.

Exponential growth model

A population growth model where population size increases rapidly without environmental limitations.

J-curve

A graph showing exponential growth because the population increases quickly over time.

Exponential growth equation

dN/dt = rN

Exponential growth equation in words

The change in the number of individuals over time equals the rate of increase multiplied by the number of individuals.

Logistic growth model

A population growth model where growth slows as the population approaches carrying capacity.

S-curve

The graph shape produced by logistic growth.

Logistic growth equation

dN/dt = rN(1-N/K)

Logistic growth equation in words

The change in population size over time depends on the rate of increase, population size, and proportion of carrying capacity remaining.

Carrying capacity

The maximum number of individuals an environment can successfully support with available resources.

Overshoot and collapse

A pattern where a population exceeds carrying capacity and later declines because resources become insufficient.

Reproductive strategies

The ways species reproduce to increase or maintain population size.

K-selected species

Species that maintain populations near carrying capacity; they usually have long lifetimes and few offspring.

r-selected species

Species that reproduce quickly, produce many offspring, and experience rapid population growth and decline.

Intraspecific competition

Competition among individuals of the same species for resources.

Community ecologists

Scientists who study interactions among species in communities.

Competitive exclusion principle

The principle stating that two species competing for the same limiting resource cannot coexist permanently.

Resource partitioning

The division of resources among species based on differences in behavior, lifestyle, or physical characteristics.

Temporal resource partitioning

When species use the same resource at different times.

Spatial resource partitioning

When species use different spaces or locations to access resources.

Morphological resource partitioning

When species use similar but not identical resources because of differences in physical characteristics.

Predation

An interaction where one organism uses another organism as a food resource.

True predators

Animals that kill and consume another animal as food.

Herbivores

Animals that consume plants.

Scavengers

Organisms that eat animals already killed by predators or that died naturally.

Predator-prey interaction

An interaction affecting population size and distribution in ecosystems.

Keystone predator

A predator that plays an important role in maintaining ecosystem stability.

Keystone species

A species with a major effect on ecosystem structure despite its population size.

Predation pressure

The effect or risk of being hunted by predators.

Chemical defense

A defense mechanism where organisms produce chemicals that make them harmful or unpleasant to predators.

Mimicry

An adaptation where a species resembles another species with strong defenses.

Camouflage

An adaptation where organisms blend into their surroundings to avoid detection.

Coevolution

The change in physical or behavioral characteristics of species due to long-term interactions with another species.

Symbiosis

A close relationship between two species where at least one species depends on the other.

Mutualism

A symbiotic relationship where both species benefit.

Commensalism

A symbiotic relationship where one species benefits and the other is neither helped nor harmed.

Parasitism

A symbiotic relationship where a parasite benefits while the host is harmed.

Difference between predation and parasitism

In predation, the predator kills the prey; in parasitism, the parasite keeps the host alive while taking nutrients.

Fundamental niche

All possible environments a species could successfully inhabit without competition.

Realized niche

The smaller portion of the environment a species actually occupies because of competition and other interactions.

Indicator species

Species sensitive to environmental changes and used to monitor ecosystem health.

Niche generalists

Species that can survive in many different habitats.

Niche specialists

Species that survive only under very specific environmental conditions.

Niche

The role and lifestyle of an organism within its community.

Pioneer species

Species that can survive in harsh environments with low nutrients and begin ecological succession.

Ecosystem engineers

Species that modify their environment in ways that create or improve habitats for other species.

Beavers

Ecosystem engineers that build dams, changing water flow and creating habitats.

Alligators

Ecosystem engineers that create nesting mounds and influence habitats.

Earthworms

Detritivores that recycle nutrients by breaking down organic matter in soil.

Corals

Ecosystem engineers that build reefs providing habitats for marine organisms.

Abundance

The total number of organisms in a community.

Richness

The number of different species in a community.

Ecological structure

The physical arrangement and location of organisms within an environment.

Succession

The process where communities change and develop over time.

Primary succession

The development of a community in an area where no soil exists.

Secondary succession

The recovery of a community after a disturbance where soil remains.

Climax community

The final stable stage of succession.

Disturbances

Events that disrupt community structure.

Disturbance-adapted species

Species that evolved to depend on occasional disturbances for survival.

Resilience

The ability of an ecosystem to recover quickly after disturbance.

Demography

The study of human populations.

Demographers

Scientists who study human populations.

Industrial age

The period when human population began increasing rapidly due to advances in technology and resources.

Crude birth rate

The number of births per 1,000 people in one year.

Crude death rate

The number of deaths per 1,000 people in one year.

Total fertility rate

The estimated average number of children born to a woman during her lifetime.

Doubling time

The estimated time required for a population to double.

Natural increase rate

Crude birth rate minus crude death rate.

Emigration

Movement of people out of a country.

Immigration

Movement of people into a country.

Total growth rate formula

(Crude births + Immigration) - (Crude deaths + Emigration).

Zero population growth

When births and immigrants equal deaths and emigrants.

Replacement level fertility

The fertility level needed to maintain a stable population, usually about two children per woman.

Demographic transition theory

The theory explaining how populations change as countries develop from agricultural to industrial societies.

Stage 1 (Pre-modern)

High birth rate and high death rate with slow population growth.

Stage 2 (Industrializing)

Population grows rapidly because birth rates remain high while death rates decline.

Stage 3 (Industrial)

Population growth slows as birth rates decrease.

Stage 4 (Post-industrial)

Low birth rates and low death rates with stable population size.

Demographic trap

A situation where developing countries remain stuck in early stages of demographic transition.

IPAT formula

A formula used to estimate human impact on the environment.

IPAT equation

Impact (I) = Population (P) + Affluence (A) + Technology (T).

Population size

The number of people in a population; one component of IPAT.

Affluence

The level of consumption of goods and services.

Technology

The resources and methods humans use to create goods and their environmental effects.