Populations and ecosystems Flashcards
Define community.
All the different species that live in one area and interact with each other.
Define ecosystem.
All the living organisms found in one area, combined with non-living aspects of their environment. Can vary from very large to very small.
What is meant by the term ‘biotic factor’?
living features of an ecosystem e.g. predators, disease.
What is meant by the term ‘abiotic factor’?
non-living features of an
ecosystem e.g. light, temperature.
Define habitat.
The place where an organism lives within an ecosystem.
Define a niche.
The role of a species within its habitat, consisting of both its biotic interactions
e. g. what it eats, and abiotic interactions
e. g. time of day it is active.
What is meant by carrying capacity?
The maximum size of population an ecosystem can support.
Name four abiotic factors that affect population growth.
- Temperature
- Light
- pH
- Water/humidity
What is meant by intraspecific competition?
competition between
organisms of the same species.
What is meant by interspecific competition?
competition between
organisms of different species.
What resources might organisms compete for?
Food, water, shelter, minerals, light, mates (intraspecific only).
Describe the pattern of a typical predator-prey
relationship in terms of population change.
● Prey is eaten by predator, resulting in predator
population increasing and prey population decreasing.
● Fewer prey means increased competition for food, so predator population decreases.
● Fewer predators means more prey survives, and the cycle begins again.
How are quadrats used for estimating population size?
Can be placed on grid coordinates, or at intervals along a belt transect. Results reported as either percentage cover or
frequency. For slow-moving or non-motile organisms
How is mark-release-recapture used for estimating population size?
● A sample of a species is captured, marked, then
released back into the same area they were caught.
● After a certain period of time another sample of the
is captured, and the number of marked organisms are counted.
For motile organisms
What is the equation for mark-release-recapture?
Estimated population size =
total number of individuals in the first sample X
total number of individuals in the second sample
/number of marked individuals recaptured
What assumptions does the
mark-release-recapture method make?
● Marked individuals distribute evenly.
● No migration in or out of the population.
● Few births or deaths.
● Method of marking does not affect survival.
● Mark does not come off.
Why are ecosystems described as being dynamic?
● Populations constantly rise and fall.
● Any small change can have a large effect.
● Biotic and abiotic factors may alter the conditions of the ecosystem
What is meant by primary succession?
Where an area previously devoid of life is colonised by a community of organisms.
Summarise the process of primary succession.
● Pioneer species can survive harsh conditions &
colonise the area.
● They change abiotic factors of their environment
e.g. decomposition adds nutrients to ground.
● Over time, this allows more complex organisms to
survive.
What is the climax community and how is it reached?
The final stage of succession, where the ecosystem is balanced and stable.
It is reached when the soil is rich enough to support large trees or shrubs, and the environment is no longer changing.
How might a species alter the environment that
develops during succession?
A species may improve the environment to make it more suitable for other species. Alternatively, a species may worsen the
environment by making it less suitable for other species
Define conservation.
The protection and management of species and habitats, in order to maintain biodiversity. Methods need to be adapted to the ecosystem in question.
How might succession be managed in order to aid conservation?
Sometimes succession needs to be prevented in order to preserve an
ecosystem at a certain point, e.g. stopping
moorland from progressing into spruce forest. This is called a plagioclimax
