B4.7. Ecology

What is an ecosystem?

The interaction between a community of living organisms and the non-living parts of their environment.

What is a habitat?

The place where an organism lives.

What is a population?

A group of organisms of the same species living in the same area.

What is a community?

All the populations of different species living and interacting in an area.

What is an organism?

An individual living thing.

What is the order of organisation from smallest to largest?

Individual organism → population → community → ecosystem.

What are biotic factors?

Living factors that affect organisms in an ecosystem.

What are abiotic factors?

Non-living factors that affect organisms in an ecosystem.

What is interdependence?

The dependence of organisms on other organisms for things such as food, shelter, pollination and seed dispersal.

Why is interdependence important?

A change in one species can affect other species in the community because organisms depend on each other.

What is a stable community?

A community where all the species and environmental factors are in balance, so population sizes remain fairly constant.

What do plants compete for?

Light, space, water and mineral ions from the soil.

What do animals compete for?

Food, mates and territory.

What is competition?

When organisms require the same limited resources.

What is an abiotic factor?

A non-living factor in an ecosystem that can affect organisms.

What abiotic factors can affect a community?

Light intensity, temperature, moisture levels, soil pH, mineral content, wind intensity and direction, carbon dioxide levels for plants and oxygen levels for aquatic animals.

How can light intensity affect plants?

It can affect the rate of photosynthesis and therefore plant growth.

How can temperature affect organisms?

It affects enzyme activity and metabolic reactions, so changes can affect survival and growth.

How can moisture levels affect organisms?

Organisms need water for biological processes, so changes in moisture can affect their survival and distribution.

How can soil pH affect plants?

Plants may be adapted to particular soil pH levels, so unsuitable pH can reduce growth.

How can mineral content affect plants?

Plants need mineral ions for healthy growth, so a lack of them can limit growth.

How can wind intensity affect organisms?

Wind can increase water loss from plants and affect temperature and movement of organisms.

How can carbon dioxide levels affect plants?

Carbon dioxide is needed for photosynthesis, so changes can affect the rate of photosynthesis.

How can oxygen levels affect aquatic animals?

Aquatic animals need dissolved oxygen for aerobic respiration, so low oxygen levels can limit survival.

What are biotic factors that can affect a community?

Availability of food, new predators arriving, new pathogens and competition from other species.

How can availability of food affect a population?

More food can increase survival and reproduction, while less food can reduce population size.

How can a new predator affect a population?

It can reduce the population of its prey.

How can a new pathogen affect a population?

It can cause disease and reduce population size.

How can one species outcompeting another affect its population?

The less competitive species may have fewer resources available and its population may decrease.

What is an adaptation?

A feature that enables an organism to survive in the conditions where it normally lives.

What are the three types of adaptation?

Structural, behavioural and functional adaptations.

What is a structural adaptation?

A physical feature of an organism that helps it survive.

What is a behavioural adaptation?

A way an organism behaves that helps it survive.

What is a functional adaptation?

A process or mechanism inside an organism that helps it survive.

What is an extremophile?

An organism adapted to live in an extreme environment, such as one with high temperature, pressure or salt concentration.

What is an example of an extremophile?

Bacteria living in deep-sea vents.

What is a producer?

An organism that makes its own food, usually by photosynthesis.

Why are producers important?

They make the biomass that provides the energy and materials for other organisms in food chains.

What is a food chain?

A diagram showing feeding relationships and the transfer of biomass and energy between organisms.

What does a food chain usually begin with?

A producer.

What is a primary consumer?

An organism that eats a producer.

What is a secondary consumer?

An organism that eats a primary consumer.

What is a tertiary consumer?

An organism that eats a secondary consumer.

What is a predator?

An animal that kills and eats another animal.

What is prey?

An animal that is eaten by a predator.

What happens to predator and prey populations in a stable community?

Their numbers rise and fall in cycles.

Why do predator and prey populations cycle?

An increase in prey provides more food for predators, causing predator numbers to rise. More predators then reduce prey numbers, causing predator numbers to fall. Fewer predators allow prey numbers to recover.

What is a trophic level?

The position of an organism in a food chain.

What is biomass?

The total mass of living material in a particular organism or group of organisms.

Why is biomass transferred between trophic levels?

Organisms consume other organisms and use the nutrients and energy stored in their biomass.

Why is not all biomass transferred to the next trophic level?

Some material is lost through waste, respiration and uneaten parts.

What happens to energy transferred through a food chain?

Some energy is transferred to the next trophic level, but much is lost through respiration and other processes.

What are quadrats used for?

To estimate the abundance or distribution of organisms in an area.

What is a quadrat?

A square frame used to sample organisms in a habitat.

How can quadrats be used to estimate population size?

Place quadrats randomly, count the organisms inside them, calculate the mean number per quadrat and use this to estimate the population in the whole area.

Why should quadrats be placed randomly?

To avoid bias and make the sample more representative of the habitat.

What is a transect?

A line across a habitat along which samples are taken to investigate how organisms are distributed.

What is a line transect?

A line along which organisms touching the line are recorded at set intervals.

What is a belt transect?

A strip along a transect where organisms are recorded within quadrats placed at intervals.

Why are transects useful?

They show how the distribution and abundance of organisms changes across an environmental gradient.

What should be considered when sampling a population?

Sampling should be representative and large enough to produce reliable results.

What does abundance mean?

The number of organisms of a particular species in an area.

What is frequency?

How often a particular species occurs in a sample.

What is a mean?

The total of all values divided by the number of values.

What is the median?

The middle value when data are arranged in order.

What is the mode?

The value that occurs most frequently.

What should you be able to do with ecological data?

Calculate means, identify medians and modes, and interpret charts, graphs and tables.

What is the carbon cycle?

The continuous movement of carbon between organisms and the environment.

How does carbon enter living organisms?

Plants and algae take in carbon dioxide during photosynthesis and use it to make organic compounds.

How is carbon returned to the atmosphere?

Through respiration by animals, plants and decomposing microorganisms.

How do microorganisms contribute to the carbon cycle?

They decompose dead organisms and waste, releasing carbon dioxide through respiration.

How does combustion affect the carbon cycle?

Burning fuels and biomass releases carbon dioxide into the atmosphere.

What is the water cycle?

The continuous movement of water between the atmosphere, land and living organisms.

What is evaporation?

The change of liquid water into water vapour.

What is precipitation?

Water falling from the atmosphere to Earth's surface, such as rain or snow.

Why is the water cycle important?

It provides fresh water for plants and animals on land.

How do microorganisms help cycle materials?

They decompose dead organisms and waste, returning carbon dioxide to the atmosphere and mineral ions to the soil.

What is biodiversity?

The variety of all the different species of organisms on Earth or within an ecosystem.

Why is biodiversity important?

High biodiversity helps maintain stable ecosystems and reduces dependence on a single species for food, shelter and maintenance of the physical environment.

Why is maintaining biodiversity important to humans?

Human survival and development depend on functioning ecosystems and the services they provide.

How can human activities reduce biodiversity?

Through pollution, land use, deforestation and global warming.

How can pollution reduce biodiversity?

Pollution can kill plants and animals, reducing the number and variety of species.

What types of pollution are included in the specification?

Water pollution from sewage, fertiliser and toxic chemicals; air pollution from smoke and acidic gases; and land pollution from landfill and toxic chemicals.

How can water pollution affect ecosystems?

Sewage, fertilisers and toxic chemicals can harm or kill organisms and reduce biodiversity.

How can air pollution affect ecosystems?

Smoke and acidic gases can damage organisms and habitats.

How can land pollution affect ecosystems?

Landfill and toxic chemicals can damage habitats and harm organisms.

Why is waste production increasing?

Rapid population growth and increased standards of living mean more resources are used and more waste is produced.

How does land use reduce biodiversity?

Humans use land for building, quarrying, farming and dumping waste, reducing the land available for other organisms.

Why is peat important?

Peat bogs provide habitats for many species and store carbon.

Why does destroying peat reduce biodiversity?

It destroys the habitat of plants, animals and microorganisms living in peatlands.

Why does destroying or burning peat contribute to global warming?

The decay or burning of peat releases carbon dioxide into the atmosphere.

Why is there a conflict over using peat for garden compost?

Peat can be used to produce cheap compost, but extracting it damages habitats and releases carbon dioxide.

What is deforestation?

The large-scale removal of forests.

Why does deforestation occur in tropical areas?

To provide land for cattle and rice fields and to grow crops for biofuels.

How does deforestation reduce biodiversity?

It destroys habitats, reducing the number and variety of species that can live there.

How does deforestation contribute to global warming?

Fewer trees means less carbon dioxide is removed from the atmosphere by photosynthesis, while burning and decay release carbon dioxide.

What is global warming?

The increase in average global temperature associated with increasing concentrations of greenhouse gases.

Which gases are specifically linked to global warming in the specification?

Carbon dioxide and methane.

Why are carbon dioxide and methane important in global warming?

Their increasing concentrations contribute to the enhanced greenhouse effect and rising global temperatures.

What are some biological consequences of global warming?

Changes in distribution of species, changes in migration patterns, changes in flowering or breeding times and loss of habitats or species.