Populations, biodiversity, ecosystems Flashcards
Describe the process of succession
(6 marks)
- (Colonisation by) pioneer species;
- Pioneers cause change in environmental abiotic / biotic factors (give an example);
- Pioneers make the environment less hostile for new species;
- New species change/make conditions less suitable for previous species;
- Change/increase in diversity/biodiversity;
- Stability increases [population/richness/abiotic factors];
- Climax community
Explain how succession results in a wide variety of fish living on coral reefs
(2 marks)
- Increase in variety and number of species/plants/animals;
- Provides more/different habitats/niches
OR - becomes less hostile;
Describe random sampling
[estimation of population density]
(5 marks)
- Use a grid/ split area into squares;
- Obtain random coordinates using random number generator;
- Count number/frequency of plants in a quadrat;
- Large sample (20+ quadrats) AND Calculate mean/average number (per quadrat/section);
- Calculate total number of ……… e.g. mean number of plants per quadrat multiplied by number of quadrats;
Describe systematic sampling
(3 marks)
- Lay Transect/ tape measure (from one side of the dune to the other);
- Place quadrats at regular intervals along the line;
- Count plants/percentage cover in each quadrat
Describe the mark, release, recapture technique
(4 marks)
- Capture sample, mark and release;
- Appropriate method of marking suggested / method of marking does not harm fish;
- Allow time for marked animals to be redistributed through population
- Take second sample and count marked organisms;
-
No in Population =
(No in sample1 × No in sample2) / Number marked in sample2;
Suggest why the mark-release-recapture method can produce unreliable results in very large lakes
(2 marks)
- Less chance of recapturing fish OR Unlikely fish distribute randomly/evenly;
- Fish may remain in one area OR fish may congregate
Describe how you would determine how many quadrats to use when investigating a habitat.
(4 marks)
- Calculate running mean;
- When enough quadrats, this shows little change/levels out (if plotted as a graph);
- Enough to carry out a statistical test;
- A large number to make sure results are reliable;
- Need to make sure work can be carried out in the time available;
Define ‘carrying capacity’
(1 mark)
Maximum number of individuals of each species an ecosystem can support
Suggest two reasons for conserving rainforests
(2 marks)
- Conserve species for (bio)diversity;
- Conserve/protect habitats/niches for indiginous communities
- Reduces climate change;
- Source of medicines/drugs/wood;
- Reduces erosion/eutrophication;
- Tourism;
Define Biodiversity
The number of species and the number of individuals of each species within any one community
Define Species Richness
The number of different species in a community
Define Community
All the individuals of all the species living together in the same area at the same time
Define Species
- Groups of similar organisms with the same genes
- That reproduce to produce fertile offspring
Define Genetic diversity
Difference in DNA/ base sequence/ genes
Define and describe Niches
- An organims role in the ecosystem/ community
- Describes how a species interacts with other species and how it responds to the environment
- No 2 species occupy the same niche due to interspecific competition
