Lab 3 Review: Histograms and Fitness Functions

Question 1

variance

Answer 1

-a measure of the amount of variation

Question 2

what trait is necessary for natural selection?

Answer 2

-variation

Question 3

fitness

Answer 3

• how good a particular type of individual is at producing offspring
• only relevant in the context where it was measured
• can vary overtime

Question 4

what are the three forms of selection

Answer 4

• directional
• stabilizing
• disruptive

Question 5

directional selection

Answer 5

• one extreme is the best trait to have
• looks like a linear graph
• mean is always changing
• i.e. bacterial resistance to drugs

Question 6

stabilizing selection

Answer 6

• the avg trait is best to have
• favors the mean phenotype
• keeps populations the same
• bell shape curve
• i.e. height in humans

Question 7

disruptive selection

Answer 7

• both extremes are favorable traits to have

- upside down bell shape curve

Question 8

fitness function

Answer 8

• allows us to view the overall pattern of selection after a selective event
• doesn’t show the evolutionary outcome of the event bc it only shows 1 generation

Question 9

what is the x-axis of a fitness function and a histogram supposed to represent?

Answer 9

-always a specific phenotypic state

Question 10

what is the y-axis of a fitness function and a histogram supposed to represent?

Answer 10

• % survival

- (fitness is calculated from histogram that shows the number of individuals before and after an event)

Question 11

selection differential

Answer 11

-the difference btwn the mean phenotypic state after and before selection (mean survivors - mean total)

Question 12

when is selection differential zero?

Answer 12

-in pure stabilizing and disruptive selection

Question 13

histograms

Answer 13

• used to show the effects of selection
• it’s a way to diagram the frequency of a set of items
• a larger spread away from the man value signifies a higher level of variation

Question 14

three conditions of natural selection

Answer 14

• the trait under selection must vary btwn individuals
• certain phenotypes must have higher survival or reproduction (variation in fitness)
• traits must be heritable

Question 15

if you know what trait you’re testing for, what should you label the axis: the phenotypic state or the trait)

Answer 15

-the trait (w units if applicable)