Ecological Techniques Flashcards
What is ecology?
The scientific study of factors which determine the distribution and abundance of organisns
What is meant by distribution?
Areas within a habitat where a specific species is found
What is meant by abundance?
Abundance is the number of individuals of one species in a given area
What is an ecosystem?
The environment and all the organisms that live there (biotic and abiotic)
When measuring abundance, why should large samples be used?
To be representative of the population as a whole
To reduce ethe effect of anomalies
To allow statistical tests to be carried out
Why are RANDOM samples used when investigating an ecosystem?
To remove bias
To be representative of the whole population
To prodice statistically significant results
State three ways to investigate an ecosystem
Randomly placed quadrats
Line/ belt transects
Mark, release, recapture
When sampling, what are rabdomly placed quadrats used for?
To measure the abundance of slow moving animals or plants
Describe the process of randomly sampling with quadrats
• A grid is laid across the sample area using tape measure
• Random numbers are generated to provide coordinates for the grid. A frame quadrant is then placed at these points
• Within each quadrant the community is sampled (each species is identified and the number of each species is counted)
• A large number of randomly placed quadrants are used, as one is unlikely to be representative of an area.
At least 20 quadrants should be used to be able to do any statistical analysis of the results.
What is mark, release and recapture used for?
To measure the abundance of mobile animals
Descirbe how to measure abundance using mark, release, recapture
- A large sample of organisms is collected
- They are marked, counted and released back into the population. (The method of marking must not harm the animal in any way or affect their chance of survival)
- After release, the animals must have enough time to mix with the rest of the population
- Capture a large sample again, using the same sampling technique as before, and count the total that are marked still.
What assumptipns are made during the mark release recapture method?
No births or deaths
No immigration or emigratiom
Marking is not visible so doesnt affect predation
Marking is not toxic so doesnt effect changes of survival
Marking not washed pff so still indentified
Individuals have a change to mix properly with the rest of the population
Describe three ways to record abundance
Measure frequency- record the presence or absense of a species
Measuring species diversity- count number of individuals in each quadrat, and use the mean to calculate population size
Percentage cover- measure the proportion of the ground that is occupied and estimate the percentage of area that is covered by the species
When measuring abundance, what are advantages and disadvantages of measuring frequency
Adv. wuick and easy in a large scale ecosystem
Disadv. Results are not detailed
When measuring abundance, what are advantages and disadvantages of species diversity?
Adv. you can estimate the population size and species diversity
Disadv. Cant always distinguish organisms from others, time consuming
