AP Environmental Science Unit 9 Notes: Biodiversity Loss and Conservation

Invasive species

A non-native (introduced) species whose spread causes harm to the environment, the economy, and/or human health.

Non-native (introduced) species

A species living outside its historical range, often due to human activity; being non-native does not automatically mean it is invasive.

Biodiversity

The variety of life at three levels: genetic diversity (within species), species diversity (between species), and ecosystem diversity (among ecosystems).

HIPPCO

Mnemonic for major drivers of biodiversity loss: Habitat loss/fragmentation, Invasive species, Population growth (resource use), Pollution, Climate change, Overexploitation.

Vector (in species introductions)

The transport mechanism that moves a species to a new area (e.g., trade pathways, vehicles/gear, pet or aquarium releases).

Introduction (arrival)

The first invasion stage where a non-native species is transported into a new ecosystem, often through human travel and trade.

Establishment (survival and reproduction)

Invasion stage where the introduced species survives local conditions and reproduces enough to maintain a population.

Spread (expansion)

Invasion stage where an established non-native population expands across the landscape or ecosystem, sometimes rapidly.

Disturbed habitat

An ecosystem altered by impacts like construction, land clearing, or pollution; often easier for invasives to establish because normal ecological controls are weakened.

Enemy release hypothesis

Idea that invasive species may spread quickly in a new range because their natural predators, parasites, and competitors are absent or reduced.

Competition (invasive impact pathway)

When an invasive outcompetes native species for resources such as food, light, nesting sites, or space, reducing native populations and diversity.

Predation (invasive impact pathway)

When an introduced predator reduces native prey populations, especially if the prey lack evolved defenses, potentially causing rapid declines.

Disease and parasite introduction

Ecological harm pathway where introduced pathogens or parasites spread through native species that may lack immunity, lowering survival and reproduction.

Ecosystem engineering (habitat modification)

When an invasive alters the physical environment (e.g., fire regimes, water flow, nutrient cycling, soil chemistry), causing native species declines even without direct interaction.

Prevention (invasive species management)

Strategies to stop introductions before they occur or spread widely (e.g., regulating pathways, public education, early detection); usually most effective and least costly.

Biological control

Managing an invasive by introducing a natural predator/parasite from its native range; can provide long-term control but risks harming non-target species or becoming invasive itself.

Endangered species

A species at very high risk of extinction in the near future.

Threatened species

A species likely to become endangered if conditions do not improve.

Keystone species

A species with a disproportionately large effect on ecosystem structure and function relative to its abundance.

Umbrella species

A species with large habitat needs; protecting it can indirectly protect many other species that share the same habitat.

Indicator species

A species sensitive to environmental changes that can signal ecosystem health or degradation.

Habitat fragmentation

Breaking continuous habitat into smaller, isolated patches, which reduces gene flow and increases extinction risk through smaller, more vulnerable populations.

Edge effects

Changes in environmental conditions at habitat boundaries (e.g., more light, wind, temperature variation) that can increase predation, invasives, and disturbance compared with habitat interiors.

Minimum viable population (MVP)

The smallest population size that has a reasonable chance of long-term survival; used in conservation to reduce extinction risk from randomness and low genetic diversity.

Bioaccumulation

The buildup of a persistent pollutant in an organism over time; related concept: biomagnification is increasing pollutant concentration at higher trophic levels, often harming top predators.