2a.3 - Distribution of Organisms Flashcards
What environmental factors affect where organisms are found? (5)
- Temperature
- Availability of water
- Availability of oxygen and carbon dioxide
- Availability of nutrients
- Amount of light
How can you study the distribution of organisms? (2)
- Measure how common an organism is in two sample areas (using a quadrat) and compare them
- Study how the distribution changes across an area by putting a quadrats along a transect
How do you use a quadrat to study the distribution of small organisms? (6)
- Place a 1m2 (one metre squared) quadrat on the ground at a random point within the first sample area
- Count all the organisms within that quadrat
- Repeat steps 1 and 2 as mant times as possible
- Work out the mean
- Repeat in a second sample area
- Compare means
How do you work out the population size of an area? (2)
- Work out the mean number of organisms per m2 (metres squared)
- Multiply the mean by the total area of the habitat
How do you study how the distribution change across an area by putting a quadrats along a transect? (3)
- Mark out a line in the area you want to study using a tape measure
- Collect data along the line by counting all the organisms your interested in that touch
- Or place quadrats at intervals along the line
What do you need to think about when collecting environmental data?
- Reliability
- Validity
What makes an experiment reliable?
If it is repeatable and reproducable
How do you make collecting environmental data more reliable?
Use a larger sample size
What makes an experiment valid?
Must be reliable and answer the original question
How can you ‘answer the question’ in an experiment?
You control all the other variables
Why is it important to control all the other variables when collecting environmental data?
Because you’ll know whether a difference in distribution is caused by an environmental factor or not
Other than reliability and answering the question, what else improves validity?
Using random samples
