Topic 1.1 Biodiversity Flashcards
Species Richness
The number of different species in a ecosystem
Species Evenness
- Aka relative species abundance
- Compares the population size of each species
- More similar each population size is, the higher the species evenness
Simpson’s Diversity Index
- Value 0-1 with 1 being infinite diversity
- Affected by species evenness and richness
- Probability of two randomly selected organisms being different species
Comparing Ecosystem Across Temporal Scale
Comparing ecosystem and species diversity at different times
e.g. throughout the year (seasons), day vs night
Species Interactions
- Interspecific or intraspecific competition
- Symbiosis (parasitism, commensalism, mutualism)
- Predation
- Disease
Biodiversity
- Measure of the variation of diversity in:
- Genetics (change in allele frequencies or gene pool)
- Species (species richness)
- Ecosystems (number of different habitats)
Population Density
Measure of the number of organisms that make up a population in a defined area
Distribution or Dispersion Patterns
- Way in which organisms of a species are spread over a defined area
- Three types:
- Random: abundant resources/wind or sea current dispersed organisms/ little competition
- Uniform: scarcity of resources/ organisms that are highly territorial/ solitary/ plants produce alleopathic chemicals to inhibit growth of other plants nearby/ high competition
- Clumped: patchy resources/organism in groups around resource/protection in groups/ more successful hunting or evasion of predators/
Minimising Bias in Sampling Ecosystems
- Counting Criteria (when using quadrats)
- Random number generators
- Calibrating equipment
- Consider equipment precision
- Size of area and number of samples
Sampling Methods
- Considered to ensure representative sample taken
- Three types:
- Stratified
- Random
- Systematic
Ecological Survey Techniques
- Methods of collecting data
- Quadrats (point or frame)
- Transects (line or belt)
Purpose of Sampling Ecosystems
- Estimate population size
- Population density
- Environmental gradient
- Zonation or stratification
- Profile
- Distribution
Stratified Sampling
- Partitioning area into zones or strata taking into account different regions of the area
- Each stratum should be homogenous
- e.g. vertical zonation (stratification) of rainforest
- e.g. Rocky shore
- Advantages: species in each stratum should be fairly represented therefore more accurate measures of population taken/ flexible can be used with random or systematic/ good for comparing sub-sets of ecosystems e.g. splash zone vs intertidal region of rocky shore
- Disadvantage is you must know size of strata for accurate representation
Systematic Sampling
-Useful for areas where there is an environmental gradient
-Samples taken at fixed intervals throughout area
-Disadvantage: area in between intervals species may be missed or in lower/higher numbers therefore impacting accurate estimates of those species/may be biased as different places have different chance of selection
Advantage: taking samples at fixed intervals saves time/ easier to apply than random as no grid required
Random Sampling
- Advantage: Suitable for large areas/ Unbiased as random number generator used to select regions of site to sample
- Disadvantage: some areas may be missed in a large site/possible some areas of site not accessible
