Section 7 - Unit 19: Populations in Ecosystems Flashcards
What term is used to describe populations of different species living in the same habitat? (1 mark)
Community
Explain the advantage of species occupying different niches (1 mark)
Less competition for food/resource
Explain the advantage of showing data using standard deviations rather than ranges (2 marks)
- SD is the spread of data around the mean
- SD reduces the effect of anomalies
- SD can be used to determine whether data is significant or not
Suggest one reason for conserving woodlands (1 mark)
- Conserves/protects habitats/niches
- Conserves endangered species
- Reduces global warming
- Source of medicines/chemicals/wood
- Reduces erosion
Explain how a species could evolve (6 marks)
- Geographic(al) isolation
- Separate gene pools/no interbreeding/gene flow (between populations)
- Variation due to mutation
- Different selection pressures/different abiotic/biotic conditions/
- Different(ial) reproductive success
- Leads to change/increase in allele frequency
Describe how you could use the mark-release-recapture method to estimate the number of a specific species (4 marks)
- Capture collect sample, mark and release
- Method of marking does not harm the species/make it more visible to predators
- Leave sufficient time for species to distribute before collecting a second sample
- Population = number in first sample × number in second sample / number of marked species in second sample
Suggest two reasons why a species may become dominant in a habitat (2 marks)
- No/few consumers
- Species outcompetes other species/better competitor for resources
What is a species? (1 mark)
Organisms that can interbreed to produce fertile offspring
What is meant by uniformly distributed? (1 mark)
Same number of organisms in each region/organisms equally spread
How do the assumptions made in proportional sampling differ from those made in mark-release-recapture? (2 marks)
- No assumption that organisms are uniformly distributed
- Size of total area/size of sampled region not required
Give one assumption about the animals caught in the mark-release-recapture method (1 mark)
- Animals are all part of the same population
Suggest why percentage cover is used rather than frequency to record the abundance of a species present (1 mark)
Difficult/too many individual organisms to count
Explain what is meant by the ecological term community (1 mark)
All the groups of species/populations/all the organisms
Describe how you could use quadrats and a transect to measure the number of seeds at different distances from a tree (2 marks)
- Place quadrats at intervals along transect
- Count number of seeds per quadrat to calculate seeds per m^2
Suggest how the shape of mouth is an adaptation to its niche (2 marks)
- Specific mouth shape for specific food
- Competition between species/interspecific competition is reduced
What is meant by an abiotic factor? (1 mark)
Non living factors
Explain why a statistical test is necessary in analysing results (2 marks)
- A statistical test determines the probability of results being due to chance
- Enables null hypothesis/description of null hypothesis to be accepted/rejected
OR - Determines whether correlation/result is significant
Describe how you would use quadrats to determine whether a particular plant species has a clustered or random distribution (3 marks)
- Use of random no.s to place quadrats
- No of individuals counted using a large of quadrats.
- Little variation- random, large variation- clustered
Explain how succession takes place (3 marks)
- Species changes the abiotic conditions/temperature
- Less hostile conditions
- Decline in initial species and increase in the dominant species
- Dominant species are better competitors
Explain why the diversity of animal species is higher towards the end of succession (2 marks)
- Greater variety of food/ more food sources
- Greater variety of habitats/niches
Describe and explain how succession occurs (4 marks)
- Colonisation by pioneer species
- Pioneers/species/organisms change the
environment/habitat/conditions/factors - Environment becomes less hostile for
other/new species - Change/increase in diversity/biodiversity
- To climax community
