4B - Investigating variation Flashcards
What is interspecific variation?
Refers to differences between different species.
What is intraspecific variation?
Refers to differences within members of the same species.
What can variation be caused by?
Genes or the environment or both.
What is variation?
The differences that exist between individuals.
What do you need to do to study variation?
Sample a population.
Why are samples used to investigate variation rather than the whole population?
Otherwise it would be time-consuming or impossible to catch all the individuals in the group.
Why might samples not be representative of the whole population?
Due to:
- sampling bias
- chance
How can sampling bias be reduced?
By using random sampling with a large sample size and when data analysis is performed.
When is random sampling most effective?
When a large sample size is used and when data analysis is performed.
How can chance be reduced in sampling?
When a large sample size is used and when data analysis is performed.
How can random sampling be done?
Dividing the field into a grid and using a random number generator to select coordinates.
What is the mean?
The average of the values collected in a sample.
What is a normal distribution?
A bell shaped curve typical of features that show continuous variation, for example, height and weight.
Where is the mean on a normal distribution curve?
The max height of a normal distribution curve.
What is standard deviation?
The distance from the mean to the point where the curve changes from being convex to concave (the point of inflection).
What does standard deviation give a measure of?
The range of values either side of the mean.
What are the % for the deviations?
68% within first SD.
95% within second SD
What does a large standard deviation mean?
The values in the sample vary a lot.
What does a small standard deviation mean?
Most of the sample data is around the mean value, so varies little.
What can you draw using standard deviation?
Error bars.
How do you draw error bars using standard deviation?
Error bars extend 1 SD above and 1 SD below the mean (so the total length of an error bar is twice the SD).
The longer the error bar…
…the larger the standard deviation and the more spread out the sample data is from the mean.
