13. Ecological Techniques Flashcards
What is Ecology
the scientific study of the factors which determine the distribution and abundance of organisms
What is an ecosystem
the environment and all the organisms that live in an area.
How do you investigate ecosystems
look at the abundance of organisms in a particular area or their distribution throughout.
How can ecosystems be studied
-Randomly placed quadrats or quadrats along a belt transect for slow moving organims
-Mark-release recapture method
Why is random sampling used
· avoid bias
· be representative
· produce statistically significant results
How are random coordinates generated
Random number table, calculator or computer
How big should a random sample be
Sample 20 quadrats and record the abundance of organisms in each quadrat. Big enough to
· to be representative of the population
· to allow a statistical test to be carried out on the data.
What are the different ways to measure abundance when using a quadrat
-Measuring frequency of a species - record the presence or absence
-Measures of percentage cover - Proportion of the ground occupied
-Measures of species diversity- counting the number of individuals of a species
What is the advantage and disadvanatges of measuring frequency of a species
AD- Quick and easy in large scale ecosystems
DISAD - Results are not detailed as one organism in a species counts the same as 100 in a different quadrat
What are advatnages and disadvanatges of measures of percentage covers
AD - Quick
DISAD - it is a little subjective, so estimates by different workers will vary.
What is the advantage and disadvanatges of measures of species density
AD - Allows you to calculate an estimate of the population size. Can calculate species diversity.
DISAD - Time consuming. Must be able to distinguish one organism from another.
How do you estimate the total population size
need to know the mean number of organisms in a quadrat and the area of the ecosystem being sampled.
How do you investigate distribution
If you are trying to find out how species distribution changes across an area you need to sample systematically
-From lake to shore
-Up rocky shore from sea to land
Can use
-A line transect
-Belt transect
What is a line transect
measuring tape stretched across the habitat and plants are sampled at regular intervals
Each plant touching the line is identified and recorded.
Quick and provides a non-quantitative idea of some of the more typical species present.
Useful in illustrating the main features of a zonation such as a succession from a water community to a land one.
What is a belt tansect
This gives a more detailed record of the changes.
Quadrats placed next to each other along a transect and estimates of the percentage cover or frequency of each species is recorded.
