7.4 Populations 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
Define biotic factor.
Living feature of an ecosystem
Define abiotic factor.
Non-living feature of an ecosystem
Give examples of biotic factors.
Predators
Disease
Competition
Give examples of abiotic factors.
Light
Temperature
Water
Define habitat.
Where an organism lives within an ecosystem
Define a niche.
The role of a species within its habitat, consisting of both biotic /abiotic interactions
What is meant by carrying capacity?
The maximum population size an ecosystem can support
Name four abiotic factors that can affect population growth.
Temperature
Light
pH
Water/humidity
What is intraspecific competition?
Competition between organisms of the same species
What is interspecific competition?
Competition between organisms of different species
Give examples of resources organisms might compete for.
Food
Water
Shelter
Minerals
Light
Mates
Describe the pattern of a typical predator-prey relationship in terms of population change.
Prey is eaten by predator, predator population increasing & prey population decreasing
Fewer prey means increased competition for food so predator population decreases
Fewer predators means more prey survives and cycle begins again
How are quadrats used to estimate population size?
Can be placed on grid coordinates or intervals along a belt transect
Results reported as either percentage cover or frequency
How is mark-release-recapture used for estimating population size?
A sample of a species is captured, marked and released back into the same area
After a certain period of time another sample is captured and the number of marked organisms are counted
What type of organisms are quadrats used for?
Slow-moving or non-motile organisms
What type of organism is mark-release-recapture used for?
Motile organisms
What is the equation for mark-release-recapture?
Estimated population size = total individuals in first sample x total individuals in 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 population
Few births or deaths
Method of marking does not affect survival
Mark remains
Why are ecosystems described as dynamic?
Populations constantly rise and fall
Any small change can have large effect
Biotic/abiotic factors may alter conditions of ecosystem
What is 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 area
Species change abiotic factors of environment
Over time, allows more complex organisms to survive
What is a climax community?
The final stage of succession
Where ecosystem is balanced & stable
