Biology by Bradford
8.4.APredators and prey in step
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8.4 Effect of Density on Populations: revision map
The subtopic in the middle and five tasks round it: label a diagram, complete a table, put a process in order and fill 7 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Effect of Density on Populations
AP Biology ยท Unit 8 EcologyHover over a box to see it. Untick it to leave it off this sheet and its printout.
Name8.4.ALimiting factors
The carrying capacity K is set by the resource in shortest supply, the , such as food, water, nesting sites or nitrogen. K is not fixed, and rises or falls with the environment. A population that grows beyond K for a time usually crashes, since the resources it has used up take time to recover.
8.4.ADensity-dependent and independent limits
| Density dependent | Density independent | |
|---|---|---|
| Effect depends on | how crowded the population is | |
| Examples | competition for food, predation, disease, waste build-up | fire, flood, drought, a hard freeze |
| Result | slows growth as the population nears K | can remove any fraction of the population |
Topic 8.4Effect of Density on Populations
8.4.AHolding a population in check
In a crowded population each individual has less food and space, parasites and disease spread faster and predators find prey more easily. These effects are negative feedback: they reduce growth more as a population gets denser, so the population settles about its carrying capacity. A storm or fire kills a share of the population whatever its density.
8.4.AA predator-prey cycle
Number the steps in order.
- With less food, the predator population falls.
- The predator population rises.
- Fewer predators means the prey recover, and the cycle repeats.
- More prey are eaten, so the prey population falls.
- Prey are abundant, so predators have plenty to eat.
Word bank density-dependentlimiting factornothing about the densitypeak in prey numberspredator populationprey populationtime
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
LabelPredators and prey in step
- prey population
- predator population
- peak in prey numbers
- time
TableDensity-dependent and independent limits
Density dependent Density independent Effect depends on how crowded the population is nothing about the density Examples competition for food, predation, disease, waste build-up fire, flood, drought, a hard freeze Result slows growth as the population nears K can remove any fraction of the population GapsHolding a population in check
In a crowded population each individual has less food and space, parasites and disease spread faster and predators find prey more easily. These density-dependent effects are negative feedback: they reduce growth more as a population gets denser, so the population settles about its carrying capacity. A storm or fire kills a share of the population whatever its density.
OrderA predator-prey cycle
- Prey are abundant, so predators have plenty to eat.
- The predator population rises.
- More prey are eaten, so the prey population falls.
- With less food, the predator population falls.
- Fewer predators means the prey recover, and the cycle repeats.
GapsLimiting factors
The carrying capacity K is set by the resource in shortest supply, the limiting factor, such as food, water, nesting sites or nitrogen. K is not fixed, and rises or falls with the environment. A population that grows beyond K for a time usually crashes, since the resources it has used up take time to recover.