Distribution of Organisms Flashcards
Which factors affect the distribution of organisms?
Temperature Availability of water Availability of oxygen and carbon dioxide Availability of nutrients Amount of light
What are quadrats used for?
They are used to study the distribution of small organisms. A quadrat is a square frame enclosing a known area. They are used to compare how common an organism is in two samples areas.
Describe an experiment using quadrats.
1) Place a 1m2 quadrat on the ground at a random point within the first sample area.( randomness can be made by dividing the area into a grid and using a random number generator to pick coordinates).
2) Count all organisms within the quadrat
3) Repeat this as many times as you can, at least 3 or more times.
4) Work out the mean number of organisms per quadrat within the first sample area.
5) Repeat steps 1-4 in the second sample area.
6) Finally compare the two means.
How do you work out the population size?
Work out the mean number of organisms per meter squared and then multiply the mean by the total area of the habitat.
What are transects used for?
They are used to study the distribution of organisms along a line-e.g. more common or less common.
Describe an experiment using a transects line.
Mark out a line in the area you want to study using a tape measure. Then collect data along the line by placing quadrats at regular intervals-e.g.2m along the transect line(tape). Repeat the transect several times again( at least 3 or more times).
How do you improve the reliability of your experiment?
Use a large sample size. Bigger samples are more representative of the whole population
Hoe do you make sure your results are valid?
For your results to be valid, they must be reliable and answer the original question.
You need to control all the variables
Also use random samples, as if samples were in one spot snd everywhere else was different, your results won’t be valid.
What is the distribution of organisms?
Where an organism is found.
