Quantitative investigations of variation Flashcards
(17 cards)
What is interspecific variation?
Interspecific variation is the difference between members of different species
What intraspecific variation?
Intraspecific variation is the difference between individuals of the same species
Why do even genetically identical organisms differ?
This is because of the different environments and experiences they are exposed to during their lives
Why is measurement particularly challenging for biologists?
This is because living organisms are all different, making it harder to get consistent measurements
Why do biologists take many measurements of the same thing?
To get more reliable and representative understanding of variation within a species
Why don’t biologists measure every individual in a population?
It is impractical or impossible to measure every organism, especially in large populations
What method do biologists use to deal with variation in populations?
They take samples to estimate characteristics of the whole population
What is sampling in biology?
Sampling involves taking measurements of individuals selected from a population to estimate characteristics of the whole population
What are the two main reasons why a sample might not be representative?
Sampling bias and chance
What is sampling bias?
When the selection process is not random and leads to unrepresentative samples, either intentionally/unintentionally
What is one method to avoid sampling bias, then describe it
Random sampling
Divide the study area into a grid using tape measures, then use random numbers to select coordinates for sampling
Can chance be completely removed from sampling, how can the effect of chance in sampling be minimised?
No, but its effect can be minimised by using a large sample size and analysing the data using statistical tests
Why does a larger sample size reduce the influence of chance?
This is because anomalies have less impact and its less likely all samples will be unrepresentative
Why is the mean sometimes misleading?
Because it does not show how the values are distributed around
What is standard deviation?
A measure of how spread out the data is around the mean; it reflects the width of the normal distribution curve
What is the formula for standard deviation?
S = √( ∑(x- x̄)² / (n-1) )
What does each symbol in the standard deviation formula represent?
x: individual measured value
n: total number of values
x with line n top: mean value
