Investigating Populations & Succession Flashcards
Define ecosystem
How a community and its abiotic factors interact in a given area
What is a niche?
Describes where an organism lives and its role. (Feeds on, how it interacts with other organisms and the environment)
What is a carrying capacity?
The maximum number of individuals in a species that can be supported indefinitely by its environment.
Define species
A group of closely related organisms that are capable of interbreeding and producing fertile offspring
Define community
All the individuals of all species living together in the same area at the same time
Difference between inter-specific and intra-specific competition?
Inter = Competition for resources between organisms of DIFFERENT species
Intra = Competition for resources between organisms of SAME species
Why do no 2 species have exactly the same niche?
Different niches reduce competition so ensure both species survive (competitive exclusion principle)
What happens when niches overlap?
The better adapted species displaces the second
The mark-release-recapture method can be used to estimate the size of a fish population. Explain how. (4)
- Capture sample of fish and mark then release
- Ensure marking is not harmful to fish
- Allow time for fish to randomly distribute back into POPULATION before collecting second sample.
- Population - No. 1 sample x No. 2 sample / No of marked fish in 2nd sample.
Suggest why the MRR method can produce unreliable results in very large lakes (2)
-Less chance of recapturing fish/unlikely fish distribute randomly
- Fish may remain in one area
Describe how you would determine how many quadrats to use when investigating a habitat (5)
- Calculate running mean
- Running mean levels out when enough quadrats
- Enough samples to carry out a STATISTICAL TEST
- A large number (20 min.) to ensure results RELIABLE and REPRESENTATIVE
- Ensure work can be carried out in time available
Describe how you would determine mean percentage cover of grass on a sand dune (3)
- Method of randomly determining quadrat positions (random no. generator)
- Large number of quadrats (min.20)
- DIVIDE TOTAL % BY NO. OF QUADRATS
What to do when estimating? (3 points)
- Samples collected RANDOMLY to eliminate BIAS
- Ensure data is RELIABLE and REPRESENTATIVE and suitable for STATISTICAL ANALYSIS (large enough sample taken of more than 20)
- Method of sample collection appropriate to species (quadrat = immobile organisms)
Ways of measuring abundance? (3)
- Density
- Percentage cover
- Frequency
Density?1
Count of ALL individuals present.
Time consuming. Most accurate.
Percentage cover?
Area of quadrat covered by 1 species recorded as % of total area (estimated)
Used when too many individuals to count.
Frequency
Proportion of quadrats that contain a particular species (Species found in 40/100 quadrats taken, frequency = 40%). Least accurate.
Method for random quadratting? (4)
- Use a grid to split area into sections
- Method of obtaining random coordinates (random no. generator)
- Count no. of plants in quadrat
- Calculate running mean of plants.
How many quadrats to use in sample? (5)
- Calculate running mean
- Stop sampling when running mean levels out
- Enough samples to carry out STATISTICAL TEST
- Large number to make sure mean is reliable and representative (20 min.)
- Work able to be carried out in time available
What are transects used for?
To know how species abundance varies ACROSS an area rather than what species are present
Define interrupted belt transect
Using one line and placing a quadrat down at equally spaced sampling points and recording species abundance within.
Examples of abiotic factors
- Temperature
- Light Intensity
- Water availability
pH of soil
Biotic Factors
- Competition
- Predation
Define succession
A series of changes within a community. A long process which starts from baron rock to its climax community.
Define and explain pioneer species
The organisms that first colonise an area. (E.g: marram grass in a sand dune ecosystem.)
Typical features include asexual reproduction, photosynthesis, rapid germination, and production of vast quantities of wind-dispersed seeds.
Define Sere
A complete succession from pioneer community to climax community.
Define climax community
The final stage in an ecological succession.
Stable and changes very little. Type of community depends on large extent on abiotic factors.
Define hostility
Where an area’s abiotic factors are unfavourable with few species adapted to survive in such conditions.
Low diversity and abiotic factors dominate distribution of species.
Define abiotic environment
Non-living parts of environment
Define diversity
The relationship between the number of individual organisms and the number of species within a community.
A diverse community will have a wider range of species and a greater number of indivudals present than a less diverse community.
Describe and explain how succession works (5)
- Colonisation by pioneer species.
- Environment altered
- This change enables other species to colonise
- Change in diversity
- Stability increases, less hostile environment.
- Climax community represented by named species.
