13: Ecological Techniques

Question 1

Definition of Ecology:
Definition of Ecosystem:

Answer 1

• scientific study of the factors which determine abundance and distribution of organisms in ecosystems
• the environment and all the organisms that live in an area

Question 2

What are the 2 methods of studying ecosystems?

Answer 2

• randomly placing quadrats through line/belt transects, for slow moving or non-motile organisms
• the mark-release-recapture method for motile organisms

Question 3

What type of sampling is used for slow-moving/non-motile organisms and why?
How is this method achieved?

Answer 3

1. Random Sampling:
   - avoid bias
   - be representative
   - produce statistically significant results
2. random co-ordinates are generated through random number calculators, in order for the sample to be big enough (above 20), to represent the whole population

Question 4

What are the 3 methods of measuring abundance in slow-moving/non-motile organisms?
Describe the Pros + Cons:

Answer 4

1. measuring frequency of species: this consists of simply recording if a species is present in each quadrat
   Pro: quick and easy in large scale ecosystems
   Con: not detailed enough as the frequency measured would be the same if there was 1 organism or 200
2. measuring percentage cover: a measure of the proportion of the ground occupied by the species in the quadrat as a percentage
   Pro: quick
   Con: can be quite subjective on how much percentage the species covers
3. measuring species density: simply counting the number of individuals of a species in a quadrat
   Pro: allows you to calculate species diversity, and population size estimate (multiply by total area)
   Con: time consuming, could potentially be difficult to distinguish between different organisms

Question 5

To ________ the total population size, you need to know the ___ number of organisms in a ______ and the ____ of the ecosystem being sampled

Answer 5

1. estimate
2. mean
3. quadrat
4. area

Question 6

What are the 2 methods of investigating distribution in slow-moving/non-motile organisms?

Answer 6

1. Line Transect: a measuring tape is stretched across the habitat, and are sampled at regular intervals (no quadrats)
   - each plant touching the line is identified + recorded
   Pro: quick, useful to investigate if species are present and the zonation of species
   Con: only investigates non-quantitative data
2. Belt Transect: quadrats are placed out at regular intervals along a transect
   - useful due to quadrats: can get detailed values of percentage cover, species density and species frequency.
   Pro: more detailed
   Con: more time-consuming

Question 7

Describe the Method of measuring Abundance in mobile animals:

Answer 7

mark-release-recapture method:
- a large sample of organisms need to be collected via random sampling to avoid bias
- these organisms are marked, counted then released back into the population
- method of marking must not harm, or damage survival chances of the animal
- after release, there must be enough time for the animals to re-integrate and mix with their population
- then once again, capture a large sample (via random sampling), and then count the number which you catch and the number of these that are marked

Then use the equation:

population estimate = number captured, marked on first occasion x total number captured on second occasion / the number recaptured

Question 8

What are 4 assumptions about the organisms in the mark-release-recapture method?

Answer 8

• no immigration/emigration
• no births or deaths
• marking does not affect livelihood of being recaptured or preyed upon
• marked individuals have had chance to fully mix with population