2026 Honors Biology: Ecology Unit Study Guide

Vocabulary practice flashcards covering ecosystems, energy flow, trophic levels, ecological pyramids, community interactions, and population dynamics based on the Ecology Unit Study Guide.

Abiotic Factors

The nonliving aspects of the environment, such as sunlight, soil, and tempurture (from the root words $A\text{-}$ meaning without, and biotic meaning life).

Biotic Factors

The living aspects of the environment, including other organisms of the same or different species (from the root word biotic meaning life).

Producers

Autotrophic organisms that produce their own food using solar or chemical energy.

Photoautotrophs

Producers that use photosynthesis driven by sunlight to produce their own food.

Chemoautotrophs

Producers that use chemosynthesis with chemical compounds, such as sulfur, to produce their own food.

Consumers

Heterotrophic organisms that obtain energy from chemical bonds by ingesting other living things or their remains.

Decomposers

Organisms that break down dead organic matter and waste.

Food Chain

A method of describing how energy passes through organisms, in which the diagram arrow points in the direction of matter flow from the organism being eaten to the consumer.

Food Web

An ecological model that illustrates multiple feeding relationships within an ecosystem, rather than a single linear path.

Second Law of Thermodynamics

The principle governing energy transfer between trophic levels stating that no energy transfer is $100\%$ efficient.

Rule of 10

The ecological rule stating that on average, only about $10\%$ of the energy from one trophic level is passed on to the next, while the remaining $90\%$ is lost mainly as heat.

Energy Pyramid

An ecological pyramid that measures the amount of energy at each level; it is always upright and limited by heat loss.

Pyramid of Biomass

An ecological pyramid that measures the total living tissue (dry weight) of living matter; it can rarely be inverted, as seen in aquatic ecosystems where plankton support a larger mass of consumers.

Pyramid of Numbers

An ecological pyramid measuring the total number of individual organisms; it can be inverted or irregular, such as a single large tree supporting thousands of insects.

Symbiosis

A relationship where individuals of two different species live in close association, and at least one species benefits.

Mutualism

A symbiotic relationship in which both species benefit ($+$ / $+$), such as clownfish and sea anemones or gut bacteria.

Commensalism

A symbiotic relationship where one species benefits and the other experiences no effect ($+$ / $0$), such as remoras on a shark or egrets feeding on insects stirred up by ungulates.

Parasitism

A symbiotic interaction where one organism (the parasite) benefits while the other (the host) is harmed ($+$ / $-$), exemplified by ticks, tapeworms, and leeches.

Predation

An interaction in which one organism (predator) eats all or part of another organism (prey), benefiting the predator and harming the prey ($+$ / $-$).

Competition

An interaction in which both parties are negatively impacted ($-$ / $-$), such as two members of the same species fighting over a mate.

Population Growth Formula

$$\text{Population Growth} = (\text{birth} + \text{immigration}) - (\text{death} + \text{emigration})$$

Biotic Potential

The rate at which a species will increase when there are no limits on the population.

Carrying Capacity

The size around which a population stabilizes, representing the maximum population an ecosystem can support.

Exponential Growth Curve

A population growth trajectory represented graphically as a J-shaped curve.

Logistic Growth Curve

A population growth trajectory represented graphically as an S-shaped curve.

Density-Dependent Limiting Factors

Limiting factors that are affected by population density and increase in impact as density rises, including food, water, shelter, and infectious disease.

Density-Independent Limiting Factors

Limiting factors that impact populations regardless of population density, such as weather, climate, natural disasters, drought, and fire.

Intraspecific Competition

Competition that occurs between members of the same species, which intensifies with high population density.

Interspecific Competition

Competition that takes place between members of different species.