Ecological Terms

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Important ecological terms

In terms of ecosystems and their levels of organisation - the following terminology is important.

• The Biosphere is the highest level of organisation and is the sum of all of the Earth’s ecosystems. It is the thin layer of the Earth that all living organisms exist within.
• An ecosystem is all the biotic and abiotic components that interact within an area at once. Biotic factors are living things (eg plants and animals) and abiotic factors are non-living things (eg. soil, water, air, light, nutrients).
• Ecosystem services are services and resources provided by the ecosystem
• A group of organisms of the same species living together in the same area at the same time is known as a population. A community, on the other hand, is defined as all of the populations that live in the same place at the same time.

In communities, we often see something called interdependence. This is when each species depends on the other and the removal of one species affects all the species. An ecotone is the transition zone between two structurally different communities.

The place that an organism lives in is called its habitat.

Glossary of basic ecological terms in alphabetical order

A

• Abundance is the total number of individuals of a species that live in a specific area.
• Allelopathy is the effect of a plant’s metabolic products on the growth of nearby plants.
• Amensalism is when one organism of one species is inhibited/destroyed while the other is unaffected.
• Apparent competition is when a predator feeds on two prey species rather than one. This results in an increased predator density and decreased prey density.
• An autotroph can produce organic material from inorganic chemicals and an energy source eg. plants use the energy from the sun to make organic materials through photosynthesis.

B

• Biodiversity is the variation of species in an ecosystem.
• Biomass is the dry weight of living material per unit area.
• Biota is the total collection of organisms of a geographic region or a time period.

C

• A carnivore eats only meat.
• Carrying capacity is the maximum capacity of an area which can sustain a certain population size.
• A climax community is a biological community that, through the process of ecological succession, has reached a steady state.
• Commensalism is the relationship between species that is only beneficial to one.

• The compensation point is the light intensity in which the rate of photosynthesis is equal to the rate of respiration.
• Competition is a mutually detrimental interaction between species which share limited resources.
• The competitive exclusion principle states that when two or more species coexist using the same resource, one must displace or exclude the other.
• Consumers are unable to make their own energy and have to consume producers or other consumers to survive.

D

• Decomposers break down decaying or dead organisms.
• Density-dependent factors include predation, disease and competition and are related to population size.
• Density-independent factors are limiting factors that do not contribute to the decrease or increase in population size
• Detritivores that consume detritus decomposing plants and animals as well as faeces in order to gain nutrients.
• Dispersal is when organisms leave an area of birth or activity for another area.
• The dominant species is the species that predominate in an ecological community.

E

• An ectotherm is an organism whose body temperature is primarily determined by external thermal conditions.
• An ecotype is a subspecies that is adapted to specific environmental conditions.
• Edaphic means produced by or relating to the soil.
• Emigration is the movement of part of a population permanently out of an area.
• An endemic species is restricted to one geographical region.
• An endotherm is an organism that produces heat internally to maintain body temperature.
• Eutrophic soils are characterised by high nutrient content and high productivity.
• Eutrophication is the process by which a body of water becomes progressively enriched with minerals and nutrients, causing algae to cover its surface. The algae blocks light so plants in the water can’t photosynthesise and due to low oxygen levels aquatic species die.
• Evapotranspiration is the sum of the water vapour loss by evaporation from land and water and by transpiration from plants.

F

• Facilitation is when one species benefits from the presence of another and neither are harmed.
• Fecundity is the natural capability of an organism to produce offspring, measured by the number of gametes or seeds.
• Fertility is the ability to conceive offspring.
• Fitness refers to the ability to survive to a reproductive age, find a mate, and produce offspring.
• The food chain is the movement of energy and nutrients from one group of organisms to another starting with producers and ending with carnivores, detrital feeders and decomposers.
• A foodweb is an interlocking pattern formed by a series of inter-connecting food chains.
• The fundamental niche is the range of environmental conditions in which a species can survive and reproduce.

G

• A generalist species can thrive under many environmental conditions and make use of a variety of different resources.
• The genotype is the genetic constitution of an organism.
• Greenhouse gases are gases that absorb and emit radiant energy within the thermal infrared range, causing the greenhouse effect; e.g. methane, ozone.
• Gross primary production is energy fixed per unit area by the photosynthetic activity of plants before respiration.

H

• Herbivores feed only on plants.
• Heterotrophs are unable to manufacture their own inorganic materials so rely on other organisms as a source of energy and nutrients.
• A host organism provides benefits to other organisms of a different species eg. organisms affected by parasites.

I

• Immigration is when an animal moves to a habitat where there are resources it can use or because the habitat is ideal for them.
• Interspecific competition is between individuals of different species.
• Intraspecific competition is among individuals of the same species.

K

• K-selection occurs when a population nears the carrying capacity of the environment.

L

• A limiting factor is an environmental condition that limits growth, abundance or distribution of an organism/ population in an ecosystem.
• Lotka-Volterra equations are predator-prey equations used to describe the dynamics of a biological system in which two species interact.

M

• Mutualism is when two species both benefit from a relationship.
• Mycorrhizae are fungal associations and symbiotic relationships between plant roots and fungi. These fungi increase the area of roots.

N

• Net primary production refers to the amount of energy available to herbivores in the plant’s biomass after plant respiratory losses
• The niche is the role that an organism plays in an ecosystem including both the environmental conditions it needs and its interactions with other organisms.

O

• An omnivore is an animal that feeds on both animal and plant matter.

P

• Parasitism is the relationship between two species where one lives on or in the other. A Pathogen is a disease-causing organism.
• Phenology is the study of how cyclic and natural phenomena affect plants and animals. Weather, changes in temperature, changes in air pressure, daylight hours etc all affect the behaviour of different species.
• The phenotype is the physical expression of an organism’s characteristics.
• The photoperiod is the relative duration of light and dark experienced by an organism.
• Photosynthetically active radiation (PAR) is the range of the light spectrum (between 400-700nm) that is used by plants in photosynthesis.