Population Ecology

Population Ecology

Examines the dynamics of species and how they interact with their environment.

Immigration

Join the population

Emigration

Leave the population

Arithmetic growth

growth is constant and non-realistic

exponential growth

Growth accelerates with each generation

Population growth rate

Percentage of population that is new divided by time (percent change per year)

Doubling time

Length required for the population to double in size

carrying capacity

Maximum number of organisms the environment can support

logistic growth

Population growth that is controlled by limited resources

Environmental resistance

All the limiting factors that act together to limit the growth of a population.

Habitat

Environment an organism depends on for survival

What is an ecological niche?

A specific role of a species within an ecosystem.

What does an ecological niche include?

Its use of resources and relationships with other species.

Survivorship

probability of an organism dying during a particular interval

Evolution

Inherited changes in a population over time

Does both Individuals and populations evolve?

No, just populations

Adaptive Evoultion

Species become better suited to their environment over time

Non-adaptive evoultion

Species do not become better suited to their environment

Mutations

changes in the genetic material

Artificial Selection

selective breeding of plants and animals to promote the occurrence of desirable traits in offspring

Differential reproduction

organisms with the best adaptations are most likely to survive and reproduce

Natural Selection

A natural process resulting in the evolution of organisms best adapted to the environment.

Fitness

Ability of an organism to survive and reproduce in its environment

Adaptation

inherited characteristic that increases an organism's chance of survival

Adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

directional selection

occurs when natural selection favors one of the extreme variations of a trait

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Distruptive selection

simiultaneously favors individuals at both extremes of the distribution (aka, diversifying)

Genetic drift

random change in allele frequencies that occurs in small populations

Founder effect

Change in the frequency of an inherited trait that is caused by a small subset of the population

Evolution of species

The gradual change in a species over time

Darwin's Finches

examples of adaption radiation: one species migrates, evolves into many species, and fills many niches.

Species

A group of similar organisms that can breed and produce fertile offspring.

Reproductive isolation

Members of one species doesn't interbreed with member of other species

geographic isolation

isolation between populations due to physical barriers (mountains, barriers)

temporal isolation

When two species breed at different times of day, season, or years.

behavioral isolation

Isolation caused by differences in courtship or mating behaviors

Structural isolation

Differences in reproductive structures effectively isolate many closely related species from one another

Extinction

Dying out or extermination of a species

Mass extinction

A large extinction of species in a relatively short period of time

Background extinction

extinction caused by slow and steady process of natural selection

Pre-agricultural period

The first period of population growth. Was 100,000 years long. 5-10 million people populated the earth.

Agricultural Period

• Began 10,000 years ago

• Domestication of plants and animals

• Doubling time 1,000 years

• 500+ million at end of period

Industrial Period

Technology advance

-Fossil fuels

Sanitation, medicine

-Death rates decline

Our current period

-Population 7 billion

Demographic Transition Model

a model of how the size of a population changes as a country develops its economy

Pretransition

high birthrates and death rates with little population growth (stage 1)

Mortality transition

the shift from deaths at younger ages due to communicable diseases to deaths at older ages due to degenerative diseases (stage 2)

Fertility Transition

a period when the population growth slows because the birth rate decreases, even though the death rate remains low. (stage 3)

stability transition

the fourth stage of the demographic transition that is characterized by low birth, death, and population growth rates

Age structure

Percentage of the population (or number of people of each sex) at each age level in a population.

age-structure pyramids

show the relative number of individuals of each age in a population and can be used to predict and explain many demographic patterns

ecological footprint

the impact of a person or community on the environment, expressed as the amount of land required to sustain their use of natural resources.

Biocapacity

the amount of biologically productive land and sea available to us

ecological debtors

People/companies/countries who consume more than their fair share of the earths resources. Impacts can be reduced by decreasing carbon emissions.

ecological creditors

A country which uses less than their fair share of the earths resources

Community Ecology

The study of how interactions between species affect community structure and organization

Competition

the struggle between organisms to survive in a habitat with limited resources

Exploitative competition

consuming the same resources

interference competition

individuals interact directly with one another by physical force or intimidation

interspecific competition

competition between different species

intraspecific competition

competition between members of the same species

niche differentiation

competing species evolve or adapt to use different resources, occupy different habitats, or behave differently.

ecological niche

Role of an organism fills within it's habitat

Fundamental Niche

The full potential range of the physical, chemical, and biological factors a species can use if there is no competition from other species.

Realized niche

range in which an organism actually exists due to competition

Coevolution

process in which two or more species evolve in response to changes in each other

Herbivory

interaction in which one animal (the herbivore) feeds on producers (such as plants)

Predation

An interaction in which one organism kills another for food.

prey switching

predators focus on most abundant prey species

invasive species

Non-native species disrupting local ecosystems.

Parasitism

A relationship between two organisms of different species where one benefits and the other is harmed

Mutualism

A relationship between two species in which both species benefit

Commensalism

one organism benefits and the other is unaffected