Ecology: Key Concepts in Population and Ecosystem Dynamics

Ecology

Study of how organisms interact with each other and their environment

Individual

Most basic level of study for an ecologist

Population

Group of individuals (same species) living together in a population; interact with each other

Species

Group of individuals that produce offspring

Habitat

Members of a species that live in the same area

Community

All the populations in a particular area

Community ecology

Study of interactions between species

Ecosystem

Includes all living things and their physical environment within a particular area

Ecosystem ecology

Study of living and nonliving components of a system together

Biosphere

All parts of the Earth that host life, with all its organisms and environments

Abiotic

Nonliving

Biotic

Living

Biotic factors

Parts of an ecosystem that are living or used to be living

Abiotic factors

Parts of an ecosystem that have never been living

Resource

Anything an organism needs

Population size

Number of individuals or organisms in a population at a given time

Population density

Number of individuals within a population per unit area

Population distribution

How organisms are spaced within an area (random, uniform, clumped)

Random distribution

Organisms arranged in no pattern

Uniform distribution

Organisms arranged in evenly spaced pattern

Clumped distribution

Organisms arranged evenly in a limited resource

Age structure

Relative number of organisms of each age in the population

Age structure diagram

Visual tool scientists use to show age structure

Sex ratio

Proportion of males to females

Immigration

People coming into country

Emigration

People leaving a country

Natality

Rate of birth

Mortality

Rate of death

Survivorship curves

Likelihood of death

Type 1 survivorship

Higher death rates at old ages

Type 2 survivorship

Equal death rates

Type 3 survivorship

Death is less likely at old age

Migration

Seasonal movement into and out of an area

Exponential growth

Increase at a fixed % each year for a population

Limiting factor

Characteristics of the environment that limit population growth

Carrying capacity

Largest population size a environment can support

Logistic growth

Population with exponential growth is slowed by factors

Density-dependent factor

Higher population density → A comparison

Density-independent factor

Limiting factors whose influence isn't affected by population density

Biotic potential

Maximum ability to produce offspring in ideal conditions

Gestation time

Time it takes for a fetus to develop

Generation time

Time from birth to ability to have its own offspring