Explain how intraspecific competition leads to variation in population size
Population of species increases when resources plentiful Population ↑ = more organisms competing for same amount of space + food Resources become limiting (not enough for all organisms) Population ↓ Smaller population = less competition = better for growth and reproduction Population ↑
Key Terms
Explain how intraspecific competition leads to variation in population size
Population of species increases when resources plentiful Population ↑ = more organisms competing for same amount of space + food Resources become l...
Explain how predation leads to variation in population size
Predator population peaks after prey population Prey population ↑ (due to less preadators/more food available) More food available = predator popul...
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| Term | Definition |
|---|---|
Explain how intraspecific competition leads to variation in population size | Population of species increases when resources plentiful Population ↑ = more organisms competing for same amount of space + food Resources become limiting (not enough for all organisms) Population ↓ Smaller population = less competition = better for growth and reproduction Population ↑ |
Explain how predation leads to variation in population size | Predator population peaks after prey population Prey population ↑ (due to less preadators/more food available) More food available = predator population ↑ As predator population ↑, ↑ predation ∴ prey population ↓ Less food for predators = predator population ↓ |
Predator and Prey Population Cycle Why does the prey population initially decline? | ∵ there’s too many of them for amount of food available (This is then accelerated by predation) |
Describe how to take a random sample from an area you’re investigating | Choose an area to sample Samples should be random to avoid bias e.g. divide field into grid and use random number generator to select coordinates Use appropriate technique to take sample Repeat processes many times to reduce likelihood that results are due to chance No. of individuals for whole area can be estimated by taking mean of data collected in each sample & multiplying it by size of whole area |
Name 2 methods of investigating non-motile organisms | Transects Quadrats |
What is recorded in each quadrat? | Species frequency or no. of individuals of each species |
How can the percentage cover of a species be measured? | By counting how much of quadrat is covered by species Count a square if it's more than half-covered |
What is the benefit of measuring percentage cover? | Quick way of investigating populations & don't have to count all individual organisms |
What are transects used for? | Used to find out how organisms (e.g. plants) are distributed across an area |
Describe how you would conduct a belt transect | Place quadrats are next to each other along a transect to work out the species frequency & percentage cover along transect |
What's an interrupted belt transect? | (It's for larger distances) quadrates placed at intervals along the line |
Name the method you would use for investigating motile species | Mark-Release-Recapture |
What is the mark-release-recapture method used for? | To measure abundance of motile species |
Describe how you would conduct a Mark-Release-Recapture | Capture a sample of a species using appropriate technique & count them Mark them in harmless way Release them back into habitat and allow time to re-integrate with rest of population (Wait a week) Take 2nd sample from same population Count how many of the second sample are marked Use an equation to estimate total population size |
Mark-Release-Recapture State the equation you use to estimate the total population size | |
Name 3 assumptions made when using the Mark-Release-Recapture method | Marked sample has had enough time and opportunity to mix back in with population Marking hasn't affected individuals' chances of survival & marking is still visible No changes in population size due to births, deaths and migration during period of study |
What is succession? | The process by which an ecosystem changes over time (Biotic + abiotic conditions change) |
Where does primary succession happen? | Happens on newly formed/exposed land There's no soil or organic material to start with e.g. just bare rock |
Give an example where primary succession may occur | Where volcano has erupted to form new rock surface or where sea level dropped and exposed new land |
Where does secondary succession happen? | Happens on land that's been cleared of all plants but soil remains |