Trophic Positions

Autotrophs

Organisms that can capture energy from sunlight or chemicals and use it to produce their own food from inorganic compounds.

Photosynthetic Autotrophs

Organisms that convert carbon dioxide and water into glucose and oxygen using sunlight energy captured by chlorophyll.

Chemosynthetic Autotrophs

Organisms, such as certain aquatic bacteria near hydrothermal vents, that use energy from chemical reactions to produce nutrients.

Heterotrophs

Organisms that must obtain energy and nutrients by consuming other organisms.

Food Webs

Models that summarize the complex feeding relationships and flow of energy within an entire community.

Energetic Hypothesis

The theory that food chain length is limited by the inefficiency of energy transfer, as only about 10% of energy is typically passed to the next level.

Primary Production

The amount of light energy converted to chemical energy by autotrophs during a given time period.

Photosynthetic Efficiency (PE)

The efficiency with which plants convert photosynthetically active radiation (PAR) into net production (NP).

Secondary Production

The amount of chemical energy in consumers' food that is converted to their own new biomass during a given period.

Consumption Efficiency

The proportion of available biomass at one trophic level that is actually ingested by the next higher level.

Assimilation Efficiency (EA)

The fraction of energy stored in ingested food that is actually absorbed by the organism and not lost as waste (feces).

Growth Efficiency (EG)

The ratio of a consumer’s production (new biomass) to the total amount of food material they successfully assimilated.

Ecological Efficiency

The total percentage of energy transferred from one trophic level to the next, generally estimated to be around 10%.

Trophic Cascade

A process where predators at high trophic levels indirectly affect organisms at much lower levels, often altering community structure.

Direct Effect

A physical or biological interaction between two species without an intermediate (e.g., a predator eating prey).

Indirect Effect

An interaction between two species where one affects the other through a third "middle-man" species.

Keystone Species

Species that exert strong control on community structure not by their size or abundance, but by their pivotal ecological roles.

Dominant Species

Species in a community that are the most abundant or have the highest collective biomass, exerting significant influence over the environment.

Robert Paine’s Experiment

A famous study in the rocky intertidal zone showing that removing a keystone predator (Pisaster seastar) drastically reduced species diversity.

Competitive Exclusion

The process where one species outcompetes others for resources, potentially leading to lower local diversity if a keystone predator is not present to manage the population.

Biomass

The total mass of all living organisms within a specific area or community.

Community Stability

The ability of a community to maintain its productivity and recover from environmental stresses

Invasive Species

Organisms that become established outside of their native range, often thriving better in communities with low species diversity.