Topic 7: populations in ecosystems Flashcards
Which abiotic factors would impact the carrying capacity of a plant species population?
Temperature, oxygen and carbon dioxide concentration, light intensity, pH and soil conditions, water availability
Name and describe the two types of competition
1) Interspecific competition is when members of different species are in competition for the same resource that is in limited supply.
2) Intraspecific competition is when members of the same species are in competition for resources and a mate
Describe a method to accurately estimate the percentage cover of grass in a field.
1.To randomly sample an area, place two 20m tape measures at right angles to create a gridded area to sample.
2. Using a random number generator, such as a calculator, two values can be generated to use as coordinates in the gridded area created.
3.The quadrat should be placed on the coordinate and a percentage cover could be estimated.
4.This should be repeated at least 30 times to provide a representative estimate.
5.Calculate a mean
Describe a method of how to estimate the change in species richness along a rocky shore (from the shore line backwards towards the land)
1.Place the tape measure at a right angle to the shore line
2.Place the quadrat every 5 metres / every position
3.Count the number of different species in each quadrat.
4.Repeat by placing another 30 transects along the beach at right angles to the shore line.
5. Calculate a mean for each quadrat position.
What sampling method must be used to estimate the population size of motile organisms?
Mark-release-recapture
How would you ethically sample motile organisms?
Sample/mark organism is a way that causes no permanent harm, does not impact predation or ability to reproduce
What is the formula used to estimate the total population size when using mark-release-recapture?
estimated total population= (no. of organisms initially caught X no. of organisms in second sample) / no. of marked organisms recaptured
Describe a method for how you would estimate the population size of woodlice in a field.
An initial sample of the population in question is captured.
These individuals are then marked and then released back into the wild, and the number caught is recorded.
These marked individuals are released and are left for a period of time to allow them to be randomly dispersed throughout the habitat. Then a second sample is captured.
The total number captured in the second sample and the number recaptured with the marking is recorded.
The size of the population is then estimated using the formula.
The more times this is repeated, the more reliable the results.
Define succession
The change in an ecological community over time.
What is the difference between a primary and secondary succession?
A primary succession starts with a pioneer species colonising bare rock or sand. In a secondary succession, there is disruption and the plants are destroyed. Succession starts again, but the soil is already created.
What is a pioneer species and give an example?
The first organism to colonise e.g. lichen
What is meant by climax community?
The final seral stage where the ecosystem is most stable
What causes the abiotic factors to become less harsh during a succession?
As organisms die and decompose it creates thicker and more nutrient-rich soil (humus).
Why do species become outcompeted during a succession?
The new species are better adapted to the environment
What happens to the biodiversity as succession progresses?
It increases
