Population Ecology and Evolutionary Concepts

Population Ecology

Study of how populations interact with their environment. Includes birth, death rates, and immigration and emigration

​

Population

Group of interbreeding organisms in a specific area.

Birth Rate

Number of live births per 1,000 individuals per year.

Death Rate

Number of deaths per 1,000 individuals per year.

Immigration

Arrival of individuals into a population from elsewhere.

Emigration

Departure of individuals from a population to another area.

Arithmetic Growth

Constant addition of individuals over time.

Exponential Growth

Growth rate accelerates with each generation.

J-shaped Growth Curve

Graphical representation of exponential population growth.

Population Growth Rate

Percentage of new individuals divided by time.

Doubling Time

Time required for a population to double in size.

Doubling Time Formula

Quick estimate: 70 divided by growth rate.

Environmental Limitations

Factors like disease and predators affecting population growth.

Net Number

Growth after accounting for losses like deaths.

Growth Rate

(Birth + Immigration) - (Death + Emigration).

Mortality

The incidence of death within a population.

Exponential Growth Formula

Mathematical model for rapid population increase.

Carrying Capacity

Maximum population size an environment can sustain.

Competition

Struggle between organisms for limited resources.

Range of Tolerance

Limits for survival of a species.

Environmental Resistance

Factors limiting population growth and reproduction.

Logistic Growth

Growth pattern with resource limitations, S-shaped curve.

Survivorship

Probability of survival at different life stages.

Type 1 Survivorship

Most individuals die of old age.

Type 2 Survivorship

Equal mortality rates across all ages.

Type 3 Survivorship

Most individuals die young.

Ecological Niche

Role and function of an organism in its ecosystem.

Habitat

Physical environment where an organism lives.

Adaptive Evolution

Species becoming better suited to their environment. Traits make organisms less suited for independent survival.

when several species evolve from a single ancestral species to occupy new niches

Evolution is not always slow and gradual

The trait is only as beneficial as its current environment

​

Non-Adaptive Evolution

Changes in species not improving environmental fit. Evolution not driven by fitness advantages.

Mutation

Source of genetic variation driving evolution. Random changes in DNA sequence.

Artificial selection

Humans breed plants/animals for desired traits.

Differential reproduction

Some individuals produce more offspring due to traits.

Natural selection

Survival of individuals better suited to environment.

Fitness (Biological)

Ability to produce viable offspring in evolution.

Adaptations

Inherited traits enhancing survival and reproduction.

Variation in traits

Differences in characteristics within a population.

Heritable traits

Traits passed down through genetics.

Competition for survival

Struggle among individuals for resources and reproduction.

Directional selection

A type of natural selection favoring one extreme trait in a population.

Stabilizing selection

A type of natural selection favors average traits in a population.

​

Disruptive selection

A type of natural selection favoring extreme traits over average traits.

​

Genetic drift

Random changes in trait frequency due to chance.

Founder effect

Genetic drift from a small population subset.

Adaptive radiation

Multiple species evolve from a single ancestor.

Evolutionary pathways

Different routes species take due to isolation.

Random evolution

Changes in traits not influenced by adaptation.

Survival of the fittest

Individuals best at competition survive and reproduce.

Population change

Alterations in species traits over generations.

Productive isolation

Breeding barriers prevent interbreeding between species.

Geographic isolation

Species separated by physical space.

Temporal isolation

Species mate at different times.

Behavioral isolation

Unique courtship behaviors prevent mating.

Structural isolation

Different anatomical structures prevent reproduction.

Hybrid sterility

Hybrids, like mules, are often sterile.

Mass extinction

Rapid global extinction of species.

Background extinction

Ongoing average extinction rate between mass events.

Artificial selection

Humans selectively breed species for desired traits.

Human impact on evolution

Humans influence species evolution and cause extinctions.

Evolutionary divergence

Species evolve separately due to isolation.

Breeding barriers

Factors preventing species from interbreeding.

Sixth Major Extinction

Current extinction event possibly caused by humans.

Pre-Agricultural Period

Begins approximately 100,000 years ago.

Demographic Transition Model

Framework for understanding population changes over time.

Pretransition Stage

High birth and death rates with limited resources.

Age Structure

Distribution of individuals by age in a population.

Age Structure Pyramid

Graphical representation of age distribution in populations.

Exponential Growth

Population growth rate accelerates over time.

Ecological Footprint

Land area required to support resource consumption.

Biocapacity

Land area available to provide resources sustainably.

Ecological Debtors

Populations with higher ecological footprints than biocapacity.

Ecological Creditors

Populations with biocapacity exceeding their ecological footprint.

Community Ecology

Study of interactions among organisms in a community.

Competition

Interaction where species vie for the same resource.

Exploitative Competition

Species consume shared resources without direct conflict.

Interference Competition

Species actively deny each other access to resources.

Interspecific Competition

Competition between different species for resources. Competition among individuals of the same species.

Competitive Exclusion Principle

Two species competing for the same resource cannot coexist.

Ecological Niche

Role and position of an organism in its habitat.

Fundamental Niche

Potential range of conditions for an organism's existence.

Realized Niche

Actual conditions where an organism exists due to competition.

Think; what you grow up to do. Not everyone can be the president because of competition, so they settle.

​

Niche Differentiation

Division of resources among species to reduce competition.

Coevolution

Mutual evolutionary influence between two or more species.

Arithmetic growth

population growth where population increases by the same amount over each time interval

The growth increases constantly over time; the same # individuals are added at each generation.

​

Intraspecific Competition

Competition among individuals of the same species.