IB Biology Topic 4 Definitions

This page contains our IB Biology definitions for topic 4. By learning each one of these definitions, you will fully cover the content for IB Biology 'Ecosystems'.
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abiotic

The component of an environment that is not alive

adaptation

Characteristics that make an individual suited to its environment and way of life

adaptive radiation

The divergence in function of homologous structures over time

afforestation

The process of establishing a forest in an area where there was no forest before, or not for a long time.

analogous structure

A different structure found in different organisms for the same function

anthropogenic

Something that originates from human activity

autotroph

Species that obtain their food by producing organic compounds from inorganic compounds

Autotrophic nutrition

A form of nutrition reliant on chemical/light energy

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behavioural isolation

Reproductive isolation due to populations of the same species behaving differently in a way that prevents interbeeding, such as having different mating calls or rituals

bioaccumulate

The process by which toxins are passed up the trophic levels of an ecosystem, concentrating within the organisms they are passed to.

Biodiversity

The variety of life on Earth

Biomagnification

The process by which toxins are passed up the trophic levels of an ecosystem, concentrating within the organisms they are passed to.

biotic

The component of an environment that is alive

carbon sequestration

The removal of CO2 from the atmosphere.

climate change

The extreme change in climate conditions due to changing global conditions/factors

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climax community

A community which through ecological succession over time has reached a steady state.

community

The population of different species living together and interacting in a single area

consumer

A heterotroph that obtains nutrients by digesting other organisms

detritivore

A heterotroph that obtains nutrients from detritus via internal digestion

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Ecological succession

The process of sequential change over time within an ecosystem.

ecosystem

The interaction of a community with its abiotic environment

eutrophication

The dense plant and algal growth due to nitrates that uses up all oxygen and suffocates other life

evolution

A change in heritable characteristics of a species over time

food web

A diagram that describes the complex feeding networks within a community

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gene pool

All the genes and their different alleles present in an interbreeding population

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geographical isolation

Reproductive isolation due to populations of the same species living in different areas. This can be as extreme as different continents to as close as different parts of a tree

Global warming

It is the increase in Earth's mean temperature

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gradualism

The gradual separation with changes over time building up to form a new species

greenhouse effect

The process by which gases in the atmosphere absorb and re-emit radiation to keep the Earth's surface warm

Greenhouse effect

It is the process by which atmospheric gases absorb infrared radiation emitted from Earth and re-emit them back down to warm the atmosphere and Earth's surface

Greenhouse gases

They are the atmospheric gases that contribute to the greenhouse effect

Heterotrophic nutrition

A form of nutrition reliant on ingestion of other organic matter.

hetertroph

Species that obtain their food by consuming other organisms

homologous structure

A similar structure found in different organisms for different functions, suggesting a common ancestor from which it originated

keystone species

Species within an ecosystem which play an integral role, without which the ecosystem would fail to exist.

melanism

The dark variation of light insects

mesocosm

An artificial mini-ecosystem

Mixotrophic nutrition

A form of nutrition where nutrients are obtained by Autotrophic or Heterotrophic methods.

natural selection

The favoritism of an organism's adaptations leading to better and prolonged survival over other organisms

open ecosystem

An ecosystem that allows energy to enter and exit

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Phenology

The study of the timing and cyclical patterns of events in the natural world.

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polyploidy

An error in meiosis leading to a doubling of chromosomes

quadrat sampling

A data sampling method that is used to view the relationship between organisms by sampling random square areas and recording the presence or absence of organisms or the number of individuals

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reproductive isolation

When populations of the same species stop interbreeding, a requirement for speciation

saprotroph

A heterotroph that obtains nutrients from dead organisms via external digestion

selective breeding

The artificial selection and mating of organisms such as horses and cows to express desired characteristics

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speciation

The formation of a new species as a result of evolution

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temporal isolation

Reproductive isolation due to populations of the same species breeding at different times, and so they do not interbreed at all

trophic level

An organism's position in the food chain

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