Practical Skills Flashcards
Define: Independent Variable
The factor that is deliberately altered or measured to see if it affects the dependent factor.
Define: Hypothesis
The theory or explanation that is being investigated.
Define: Dependent Variable
The factor that may be controlled by the independent variable.
Define: Null Hypothesis
The no-link theory against which the hypothesis is being tested.
Define: Homogenous
Evenly mixed.
Define: Quadrat
An area, usually square or circular, in which samples are taken.
Define: Pitfall Trap
A method of sampling animal populations by collecting individuals that fall into traps set into the ground.
Define: Transect
A line or belt of sampling across an area.
Define: DAFOR Abundance Scale
A qualitative scale that judges the abundance of organisms.
Define: Lincoln Index
A catch, mark, release, recapture method of estimating animal populations.
Define: Surber Sampler
An aquatic invertebrate sampling frame and net that provides more quantitative data than kick sampling.
Define: Pooter
A mouth-suction device to pick up invertebrates in soil or leaf litter.
Define: Tullgren Funnel
A piece of equipment used to extract invertebrates from soil or leaf litter.
Define: Secchi Disc
A circular disc divided into four black and white segments that is used to estimate water turbidity.
What are the different methods of sampling?
- Random Sampling (areas chosen from random numbers)
- Systematic Sampling (areas chosen from patterns/spacing)
- Stratified Sampling (areas with sub-areas that influence results must be studied individually and then combine the results)
What is ‘first-hand experience’?
- Personally performing/witnessing an experiment/activity
- Working in a group is advantageous (discuss, criticise and justify options)
What does the DAFOR abundance scale represent?
D = Dominant A = Abundant F = Frequent O = Occasional R = Rare
What are the limitations of abundance scales?
- Subjective (different judgements)
- No distinction between species in same category
- Lack of quantitative data makes statistical analysis difficult
How is a sample population estimated?
Total population = (Number in 1st sample x Number in 2nd sample) \ (Number in 2nd sample that have marks)
What are the features of a population whose size can be estimated using the Lincoln Index?
- Mobile individuals can be caught
- Births/Natural mortality do not affect population
- Caught and marked does not affect mortality
- Population not affected by immigration or emigration
- Population members mix freely and not territorial
- All members equally likely to be caught
What are the limitations of kick sampling?
- Disturbance by kicking cannot be standardised
- Rock attached organisms not collected
- Organisms that swim may escape
What are the limitations of pitfall traps?
- Underground organisms cannot be collected
- Killing fluid may attract/repel organisms
- No killing fluid will allow predators to eat animals that fall in
- Active animals more likely to be trapped
What are examples of suction samplers?
- Pooter (collects small visible invertebrates)
- Backpack suction samplers (motorised sampler collects grassland invertebrates)
What are the limitations of Tullgren funnels?
- Immobile organisms not collected
- Large organisms cannot pass through mesh
