Glossary
Apex predators
Organisms at the very top of a food chain, having no natural predators in their ecosystem.
Example:
Polar bears are considered apex predators in the Arctic, hunting seals and fish without being hunted themselves.
Bioaccumulation
The buildup of substances, such as pollutants, in an individual organism's tissues over its lifetime.
Example:
A single oyster living in slightly contaminated water might bioaccumulate trace amounts of heavy metals in its body over several years.
Biomagnification
The increase in concentration of toxins as they move up through successive trophic levels in a food chain.
Example:
If small fish consume contaminated algae, and then larger fish eat many small fish, a top predator like a bald eagle eating many large fish will experience significant biomagnification of the toxin.
DDT
A persistent organic pollutant (POP) formerly used as a pesticide, known for its bioaccumulation and biomagnification effects, particularly on bird eggshells.
Example:
The widespread use of DDT in the mid-20th century caused severe reproductive issues in birds of prey, leading to thin eggshells that broke during incubation.
Food chain
A hierarchical series of organisms in an ecosystem, each dependent on the next as a source of food and energy.
Example:
A simple food chain in a forest might start with acorns, which are eaten by squirrels, which are then eaten by hawks.
Keystone species
A species that has a disproportionately large impact on its environment relative to its abundance, often maintaining ecosystem structure.
Example:
Wolves are a keystone species in Yellowstone National Park because their presence helps regulate elk populations, which in turn affects vegetation growth and river ecosystems.
Methylmercury
An organic form of mercury, highly toxic, that readily bioaccumulates and biomagnifies in aquatic food chains.
Example:
Concerns about methylmercury levels lead to advisories for pregnant women to limit consumption of certain large, long-lived fish like swordfish and shark.
Trophic level
The position an organism occupies in a food chain, indicating its primary source of energy.
Example:
Herbivores like deer occupy the primary consumer trophic level, feeding directly on producers.