7.4 Populations in 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
Describe biotic factors, giving examples
Biotic = living features of an ecosystem, e.g. predators, disease
Describe abiotic factors, giving factors
Abiotic = 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 its 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
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 (intraspecifc 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 populations 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 is captured, and the number of marked organisms are counted
What is the equation for mark-release-recapture?
Estimated population size = total no. of individuals in 1st sample x total no. of individuals in 2nd sample / no. 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 and colonise the area
- They change abiotic factors of their environment
- Over time, this allows more complex organisms to survive
What is the climax community?
The final stage of succession, where the ecosystem is balanced and stable
How is the climax community reached?
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
