7.4 Populations in Ecosystems Flashcards
Define an Ecosystem
A dynamic system consisting of a community and the abiotic factors
Define a population
The number of organisms of one species in an ecosystem
Define a community
Organisms of all populations in an ecosystem
Define a habitat
The place where an organism lives
Define a niche
How an organism fits into it’s enviroment
Define carrying capacity
Maximum population size a habitat can support, over an extended period of time
What abiotic limiting factors affect carrying capacity
- Temperature
- Light intensity
- Soil pH
- Water avaliability
What biotic limiting factors affect carrying capcity
- Interspecific competition for food
- Intraspecific competition for food
- Predation
What are the 3 ways to estimate a population size
- Random sampling
- Systematic sampling
- Mark-Release-Recapture
Describe how to use random sampling to estimate a population size
- Divide area into grid with co-ordinates
- Obtain random co-ordinates from a random number generator, and use this to place quadrats
- Count the number of individuals/percentage cover in each quadrat
- Take a large sample, and find the mean number/percentage cover
- Total individuals for area = mean x number of qudrats that fit into area
Describe how systematic sampling is used to estimate a population size
- Lay tape measure perpendicualar to starting point
- Take samples at random intervals (e.g 1m) with a quadrat
- Count number of individuals/percentage cover in each quadrat
- Repeat with a large number of quadrats
When estimating population size, howe are samples representative with bias eliminated
- Large sample
- Random number generator used to select individuals
Describe how to estimate a population size using the Mark-Release-Recapture Method
- Capture sample, mark each individual and release
- Ensure marking doesn’t harm or affect survivial of organism
- Allow time period for organism to randomly and evenly distribute
- Collect second sample
- Population = no. marked in 1st x no. marked in 2nd / number recaptured
What assumptions are made during the Mark-Release-Recapture Method
- No migration
- Constant population (no reproduction or deaths)
- Marking doesn’t influence behaviour or increase vulnarability to predators
What is important about the marking for the Mark-Release-Recapture method
Must not harm or affect the survival of an organism
W
Equation used when estimating population size using the Mark-Release-Recapture method
Describe the process of succession
- Colonisation from pioneer species
- Pioneer species change the enviroment and conditions, by providing food for other species
- Enviroment becomes less hostile for new species, and less suitable for previous species
- Pioneer species outcompeted as succession continues
- Biodiversity increases
- Climax community reached
What is the difference between primary and secondary succession
- Primary occurs from an inorganic starting point (sand dunes)
- Secondary occurs from an area cleared of organisms, but with soil present
What is deflected succession part of, and why is it used
- Part of conservation
- Prevent climax community being achieved
What are the features of a climax community
- Population stable over a long period of time
- Community stable over a long period of time
- Abiotic factors constant over a long period of time
