Module 1 - Ecology & Ecocolumns

AP Environmental Science 2025-26

10% Rule

only about 10 percent of energy stored as biomass in a trophic level is passed from one level to the next. This is known as “the 10 percent rule” and it limits the number of trophic levels an ecosystem can support.

Abiotic

An abiotic factor is a non-living part of an ecosystem that shapes its environment. In a terrestrial ecosystem, examples might include temperature, light, and water.

Adaptation

a modification of an organism or its parts that makes it more fit for existence

Biodiversity

The diversity of life forms in an environment.

Biomass

The total mass of all living matter in a specific area.

Biome

A biome is a large area characterized by its vegetation, soil, climate, and wildlife.

Biotic

A biotic factor is a living organism that shapes its environment. In a freshwater ecosystem, examples might include aquatic plants, fish, amphibians, and algae.

Commensalism

A relationship between species in which one species benefits and the other species is neither harmed nor helped.

Community

In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time

Competition

Competition is an interaction between organisms or species in which both require a resource that is in limited supply.

Constants/Controlled Variables

any variable that's held constant in a research study.

Decomposers

Fungi or bacteria that recycle nutrients from dead tissues and wastes back into an ecosystem.

Detritivores

An organism that specializes in breaking down dead tissues and waste products into smaller particles.

Endangered Species

At serious risk of extinction

Ecology

Ecology is the study of the relationships between living organisms, including humans, and their physical environment.

Ecosystem

An ecosystem consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows.

Ecosystem Services

The process by which natural environments provide life-supporting resources.

Ecological Tolerance

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

Food Chain

The sequence of consumption from producers through tertiary consumers.

Indicator Species

An indicator species is an organism whose presence, absence or abundance reflects a specific environmental condition. Indicator species can signal a change in the biological condition of a particular ecosystem, and thus may be used as a proxy to diagnose the health of an ecosystem

Keystone Species

A species that is far more important in its community than its relative abundance might suggest.

Tragedy of the commons

The tragedy of the commons refers to a situation in which individuals with access to a public resource (also called a common) act in their own interest and, in doing so, ultimately deplete the resource.

Trophic Level

Levels in the feeding structure of organisms. Higher trophic levels consume organisms from lower levels.

Trophic Pyramid

A representation of the distribution of biomass, numbers, or energy among trophic levels.

Food Web

A complex model of how energy and matter move between trophic levels.

Gross Primary Productivity (GPP)

The total amount of solar energy that producers in an ecosystem capture via photosynthesis over a given amount of time.

Invasive Species

An invasive species is an organism that causes ecological or economic harm in a new environment where it is not native.

Independent Variable

a variable (often denoted by x) whose variation does not depend on that of another.

Dependent Variable

a variable (often denoted by y) whose variation does depend on that of another.

Laws of Thermodynamics

“The first law of thermodynamics also known as the law of conservation of energy states that energy can neither be created nor destroyed, but it can be changed from one form to another.” “The second law of thermodynamics states that the entropy in an isolated system always increases.

Mutualism

An interaction between species that increases the chances of survival or reproduction for both species.

Trophic Cascade

trophic cascade, an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling.

Net Primary Productivity (NPP)

The energy captured by producers in an ecosystem minus the energy producers respire.

Parasitism

A predator that lives on or in the organism it consumes.

Pioneer Species

A species that can colonize new areas rapidly.

Population

Population is a group of organisms of one species that interbreed and live in the same place at the same time.

Primary Consumer

An individual incapable of photosynthesis; must obtain energy by consuming other organisms.

Primary Succession

Ecological succession occurring on surfaces that are initially devoid of soil.

Producer

An organism that uses the energy of the Sun to produce usable forms of energy.

Qualitative Data

Qualitative data is information that cannot be counted, measured or easily expressed using numbers

Quantitative Data

Quantitative data is the value of data in the form of counts or numbers where each data set has a unique numerical value.

Resource Partitioning

A situation in which two species divide a resource, based on differences in their behavior or morphology.

Scavengers

A carnivore that consumes dead animals

Secondary Consumer

A carnivore that eats primary consumers.

Secondary Succession

The succession of plant life that occurs in areas that have been disturbed but have not lost their soil.

Species Evenness

The relative proportion of different species in a given area.

Species Richness

The number of species in a given area.

Symbiosis

A relationship of two species that live in close association with each other.

Tertiary Consumer

A carnivore that eats secondary consumers.