AP Environmental Science Unit 2

Biodiversity

The variety of life in an ecosystem measured at the genetic, species, and ecosystem levels

Genetic diversity

The variety of genes and genetic differences among individuals within a population of the same species

Species diversity

The variety of species in an ecosystem and the balance of their population sizes

Ecosystem diversity

The variety of habitats and ecosystems within a given area

Species richness

The total number of different species in an ecosystem

Species evenness

How evenly individuals are distributed among the different species in an ecosystem

High biodiversity

A condition that generally increases ecosystem health, resilience, and the ability to withstand disturbances

Genome

The complete set of genetic information in an organism

Mutation

A random change in DNA that can create new genetic variation

Genetic recombination

The rearrangement of genetic material that creates new combinations of genes in offspring

Genetic variation and adaptation

Greater genetic variation increases the likelihood that some individuals possess traits that help them survive environmental changes

Population bottleneck

An event that drastically reduces population size and usually decreases genetic diversity

Bottleneck effect

The loss of genetic variation when a small surviving population no longer represents the original population's genetic diversity

Inbreeding

Reproduction between closely related individuals

Inbreeding depression

Reduced fitness caused by increased expression of harmful genetic mutations in offspring of related individuals

Ecosystem resilience

The ability of an ecosystem to recover its original conditions after a disturbance

Ecosystem services

Natural goods and processes that benefit humans economically or by supporting life

Provisioning services

Ecosystem goods obtained directly from nature, such as food, timber, and medicinal resources

Regulating services

Ecosystem processes that moderate environmental conditions, such as climate regulation and air purification

Supporting services

Natural processes that support human activities and make them easier or less costly, such as pollination

Cultural services

Ecosystem benefits associated with recreation, tourism, and scientific knowledge

Carbon sequestration

The capture and storage of carbon dioxide, including by trees through photosynthesis

Pollination

The transfer of pollen that enables plants to reproduce and can increase agricultural production

Economic consequences of biodiversity loss

Reduced ecosystem services can cause crop failures, lost fishing income, higher healthcare costs, and increased environmental damage

Island biogeography theory

A theory explaining how island size and distance from a mainland influence the number of species present

Island size and species richness

Larger islands generally support more species because they provide more habitats, resources, and ecological niches

Island distance and species richness

Islands closer to the mainland generally support more species because colonization is easier

Colonization

The establishment of a species in a new habitat

Habitat island

An isolated patch of natural habitat surrounded by a different environment, often created by human development

Habitat fragmentation

The division of a large, continuous habitat into smaller, disconnected patches

Wildlife corridor

A strip of habitat that connects isolated habitat patches and allows organisms to move between them

Benefits of wildlife corridors

They support migration, gene flow, recolonization, and movement between habitat patches

Edge effect

Abrupt changes in biotic and abiotic conditions near the boundary between two different habitats

Habitat patch size

Larger habitat patches generally contain more interior habitat and can better support species that require large territories

Habitat fragmentation and biodiversity

Fragmentation often reduces biodiversity by isolating populations, reducing habitat area, and increasing edge effects

Adaptive radiation

The evolution of one ancestral species into multiple species adapted to different ecological niches

Ecological niche

The role of an organism in its ecosystem, including its resource use and environmental requirements

Ecological range of tolerance

The range of environmental conditions an organism can endure before injury or death occurs

Optimal range

Environmental conditions under which an organism can survive, grow, and reproduce successfully

Zone of physiological stress

Environmental conditions under which an organism survives but experiences reduced growth, activity, or reproductive success

Zone of intolerance

Environmental conditions outside an organism's survival limits that result in death

Indicator species

Species that are sensitive to environmental changes and provide evidence about ecosystem health

Characteristics of indicator species

They often have narrow tolerance ranges and respond quickly to pollution or environmental disturbance

Examples of aquatic indicator species

Stonefly nymphs, mayfly nymphs, caddisfly larvae, and trout

Water temperature

A water-quality parameter that affects aquatic organisms and the amount of dissolved oxygen water can hold

Dissolved oxygen

Oxygen present in water that aquatic organisms require for cellular respiration

Low dissolved oxygen

A condition that can cause physiological stress, suffocation, and death in aquatic organisms

Water pH

A measure of acidity or alkalinity that affects aquatic organisms and the toxicity of dissolved metals

Low pH and metal toxicity

More acidic water can make dissolved metals more toxic to aquatic organisms

Eutrophication

Nutrient enrichment of water that can cause algal blooms and oxygen depletion

Algal bloom

Rapid growth of algae that can contribute to low dissolved oxygen when the algae die and decompose

Natural disturbance

A natural event that disrupts the structure or function of an ecosystem

Examples of natural disturbances

Tornadoes, hurricanes, droughts, forest fires, earthquakes, volcanic eruptions, and asteroid impacts

Periodic disturbance

A disturbance that occurs at regular intervals, such as seasonal changes between wet and dry periods

Episodic disturbance

A disturbance that occurs occasionally at irregular intervals, such as a hurricane or drought

Random disturbance

A disturbance without a regular pattern, such as an earthquake or volcanic eruption

Natural climate change

Long-term climate variation caused by natural processes, including changes in Earth's orbit and tilt

Natural disturbances and biodiversity

Major disturbances can reduce biodiversity by destroying habitat and pushing organisms outside their tolerance ranges

Migration

The movement of organisms to a different habitat, sometimes in response to environmental changes

Primary succession

Ecological succession that begins on bare rock or another surface without established soil

Secondary succession

Ecological succession that begins where established soil remains after a disturbance

Primary succession examples

Colonization of newly formed volcanic rock and rock exposed by retreating glaciers

Secondary succession examples

Recovery after a forest fire, flood, or deforestation when soil remains

Pioneer species

Early successional organisms that establish themselves first and tolerate harsh environmental conditions

Primary succession pioneer species

Mosses and lichens that can grow on bare rock and help initiate soil formation

Secondary succession pioneer species

Fast-growing grasses, wildflowers, and other plants that establish in existing soil

Middle successional species

Plants such as shrubs and fast-growing trees that establish after pioneer species improve soil conditions

Late successional species

Long-lived, often shade-tolerant trees that establish after soil becomes deeper and more nutrient-rich

Climax community

A relatively mature community associated with later stages of succession

Why primary succession takes longer

Soil must develop before many plants can establish, whereas secondary succession begins with existing soil

Soil formation during primary succession

Mosses and lichens weather rock, while decaying organic matter contributes to initial soil formation

Natural selection

The process by which individuals with advantageous heritable traits tend to survive and reproduce more successfully

Adaptation

A heritable trait that increases an organism's ability to survive and reproduce in a particular environment

Fitness

An organism's ability to survive and reproduce

Selective pressure

An environmental condition that affects survival and reproductive success

Evolution

Changes in the heritable characteristics of populations across generations

Environmental change and adaptation

Environmental changes can make previously beneficial traits disadvantageous and favor different traits

Finch beak adaptation

Finches with beaks better suited to available food can survive and reproduce more successfully

Genetic diversity and environmental change

Greater genetic diversity increases the probability that a population contains individuals able to survive new environmental conditions

Rate of environmental change

Rapid environmental changes can cause population declines when species cannot adapt or migrate quickly enough

Specialist species

Species with narrow habitat, food, or environmental requirements that are often more vulnerable to disturbance

Generalist species

Species able to use a wider variety of resources and habitats, often making them more adaptable to environmental change

Endangered species

Species facing a high risk of extinction

Overexploitation

Harvesting or killing organisms faster than their populations can replenish themselves

Poaching

Illegal hunting, capture, or killing of wildlife

Invasive species

Non-native species that establish and spread in a new area and cause ecological or other harm

Exotic species

A species introduced outside its native range; not every exotic species becomes invasive

Characteristics of invasive species

They may reproduce rapidly, compete aggressively, adapt easily, and lack effective natural predators

r-selected species

Species that generally reproduce rapidly, produce many offspring, and provide relatively little parental care

Biotic potential

The maximum reproductive capacity of a population under ideal conditions

Invasive species and native species

Invasive species can reduce native populations by competing for food, water, sunlight, and space

Why generalists often become invasive

Their flexible diets and broad habitat requirements help them survive in new environments

Why specialists are often endangered

Their specific habitat and food requirements make them less adaptable to environmental change

Interspecific competition

Competition for resources between members of different species

HIPPCO

Habitat loss, invasive species, population growth, pollution, climate change, and overexploitation as major threats to biodiversity

Habitat loss

The destruction or conversion of natural habitat for activities such as agriculture, roads, and urban development

Pollution and biodiversity

Pollutants such as oil and pesticides can injure or kill organisms and reduce populations

Climate change and biodiversity

Changes in temperature and precipitation can shift habitats faster than some species can adapt or migrate

Population growth and biodiversity

Increasing human populations can increase habitat destruction through urbanization and agricultural expansion

CITES

An international agreement through which countries regulate international trade in endangered species