13.1 Investigating population Flashcards
Species
Group of closely related individuals that have the ability to interbreed and produce fertile offspring
Population
All the individuals of a given species living together in the same area at the same time
Carrying capacity
The maximum equilibrium number of organisms of a particular species that can be supported indefinitely in each stable environment
Community
All the individuals of all the species living together in the same area at the same time
Habitat
The place where all the organisms live within an ecosystem
Niche
Where an organisms lives and what it does, how it feeds and interacts with other organisms and the environment
What is the advantage of organisms occupying different niches?
Less overlap, therefore less competition between species and are more likely to coexist
Interspecific competition
Competition for resources between organisms of different species
Intraspecific competition
Competition for resources between individuals of the same species
When should you use percentage cover?
- When the organisms are too small to count
- Too many individuals to count
- Hard to identify
- Overlap with another species
Reliability definition
When an investigation can be repeated and other people get the same results
How do you ensure reliability when sampling?
- Sample sites must be selected at random to avoid bias
- Large enough sample sizes and suitable for statistical analysis so the data is reliable and representative
- Method of collection must be appropriate to species
How do you calculate species density?
Count all species present in quadrant
How do you calculate percentage cover?
The area of the quadratic covered by the species recorded as a percentage of the total area
How do you calculate frequency of species?
The proportion of quadrants that contain a particular species
Why do you use random quadrating?
- To find out what species are present and their relative abundance a specific area
- Compare the species between two areas
- Compare the species abundance at one site at different seasons
Random quadrating method
- Place two tape measures perpendicular to each other
- Use a random number generator to generate a series of coordinates
- Place a quadratic down at the intersection of one of these quadrants
- Abundance can then be estimated
- Continue until running mean has stabilised
Equation for percentage cover
Total area covered by species / total area covered by quadrants x 100
What is systematic sampling?
Transects, used for very slow moving animals or plants
What are the different types of systematic sampling?
Transect - what species are touching the line at each sampling point
Belt transect - Placing two parallel lines across a meter apart and recording what species are found between the lines
Interrupted belt transect - Using one line and placing a quadratic every 5m and recoding abundance within the quadratic
Describe how you would investigate the distribution of marram grass from one side of the dune to the other
- Transect from one side of the dune to the other
- Place quadrants every 5m
- Count plants in quadratic and calculate abundance
Mark - release - recapture method
- Animals of a particular species are ethically collected (traps, netting or tranquilliser)
- The animals are marked in a way that doesn’t affect their ability to feed or make them more susceptible to predation
- Release the animals to disperse back into their population
- After a reasonable length of time, recapture the same sample size and note how many have already been marked
Population size equation
N1 x N2/ Nm
N1 = number caught in first
N2 = number caught the second time
Nm = Number caught second time that were marked
Consideration for mark release recapture
No immigration or emigration
No births or deaths
