Distribution of Organisms Flashcards
What is a habitat?
A place where an organism lives
What is the distribution of an organism?
Where an organism is found
What effects where an organism is found? (5)
Temperature Availability of water Availability of oxygen and carbon dioxide Availability of nutrients Amount of light
What are 2 ways to study the distribution of an organism?
1) Measure how common an organism is in 2 sample areas (using quadrats) and compare them
2) Study how the distribution changes across an area eg, by placing quadrats along a transect
use quadrats to study the distribution of …
small organisms
What is a quadrat?
A square frame enclosing a known area. It compares how common an organism is in 2 sample areas
What 3 averages do you use to compare the distribution of organisms?
Mean, Mode and Medium
How do you randomise placing a quadrat?
Divide the area into a grid and use a random number generator to pick coordinates
How do you work out population size from a sample area?
Work out the mean number of organisms per m² then multiply it by the total area
What do transects show?
How organisms are distributed along a line
Describe the method for using a transect
1) Mark out a line in the area you wan to study using a tape measure
2)Collect data along the line
3)You can either count all the organisms you’re interested in that touch the line
OR you can collect data by using quadrats, next to each other or at intervals
What 2 things do you need to think about when collecting data?
Reliability
Validity
What does reliable mean?
Make sure results are repeatable and reproducible
How do you make your results reliable (2)?
1) Take a large sample size (use as many quadrats/transects in your sample area as possible)
2) Use random samples (makes it reproducible)
What to you have to do to ensure validity?
Control all variables but one. When you see a difference in distribution between 2 sample ares you want to know it’s because of 1 environmental factor
