Ecological Terms

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Contents
Table of contents

    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.

    It is important to remember that a community involves multiple species whereas a population only refers to one species interacting.

    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.
    • Poikilotherms have variable internal temperatures and can survive in many different heats.
    • Primary succession is the first step of ecological succession after an extreme disturbance, which usually occurs in an environment devoid of vegetation and other organisms.
    • Producers make their own energy through biochemical processes, e.g. plants.
    • Productivity is the rate of production of biomass by an individual, population, or community.

    Q

    • A quadrat is a frame used in ecology, geography and biology to isolate a standard unit of area for the study of the local distribution of plants or animals over a large area.

    R

    • Random sampling - A type of sampling in which each member of the population is equally as likely to be selected.
    • R-selection is a form of selection that occurs in an environment with plentiful resources and it tends to favour individuals that reproduce early, quickly and in large numbers.

    S

    • A saprophyte is a plant that gains food from dead plant and animal matter.
    • Senescence is the condition or process of deterioration with age.
    • Sessile refers to an organism that is immobile; eg. plants
    • Species diversity is a measurement that relates number and relative abundances of species within a community.
    • Species richness is the number of species in a given area.
    • Sublethal effects are physiological or behavioural effects on individuals that survive exposure to a pesticide.
    • Succession is the directional change in structure of a community gradually over time.
    • Symbiosis is an interaction between two different biological organisms.

    T

    • Tannins are secondary metabolites produced by plants as a defence mechanism.
    • We classify organisms in trophic levels according to their feeding relationships.

    Y

    • Yield is the harvestable population growth of an ecosystem. It refers to the individuals, or biomass removed/ harvested from a population per unit time.

    Ecological Terminology - Key takeaways

    • Key terms are important to learn in order to understand a topic.

    • 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 population is a group of organisms of the same species living together in the same area at the same time.

    • A community is defined as all of the populations that live in the same place at the same time.

    Frequently Asked Questions about Ecological Terms

    What is meant by the ecological term community?

    All the populations that live in the same place at the same time.

    What is meant by the ecological term population?

    A group of organisms of the same species living together in the same area at the same time.

    What are the keywords in ecology?

    Keywords are really important as not only do they help you to answer specific 1-2 mark questions but they also help you to further understand the topic and know what questions are referring to in the exam.  

    What are basic ecological terms?

    Biosphere, ecosystem, community, population, habitat, abiotic, biotic.

    What are important ecological terms?

    • 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 population is a group of organisms of the same species living together in the same area at the same time.

    • A community is defined as all of the populations that live in the same place at the same time.

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