Exam 2 Flashcards
Are discrete or continuous traits quantitative or qualitative?
- Continuous: quantitative
- Discrete: qualitative
Number of legs is an example of a ________ trait
discrete
Height is an example of a ________ trait
continuous
What are quantitative traits usually determined by?
Genotype at many loci and the environment
Do traits that have many genes involved in them (quantitative traits) follow the Mendelian model?
Yes, they can!
Define/describe broad sense heritability
The percent of the total phenotypic variation that is due to genetic variation
Define/describe narrow-sense heritability
Only considers additive genetic variation (not dominant genetic variation)
How do we estimate/measure heritable variation?
Cross fostering experiments
What does measuring heritable variation allow us to do?
Predict how a population will respond to selection
Any estimates of heritability are specific to…
A particular environment
Heritability includes both ______ and ______
V(G) and V(E)
What do heritability scores NOT tell us?
- Tell us nothing about how much the environment would contribute to variation in a different environment
- High heritability tells us nothing about the origin of differences between groups
- Heritability tell us nothing about the role of genes in determining traits that are shared by most members of a population
What would be the heritability score of number of eyes in humans? Why?
- Very low!
- Little to no phenotypic variation –> low score/low heritability
Why is it important to measure heritability?
Allows us to predict whether selection on the trait will cause a population to evolve and how quickly these changes will happen
Can influence of the environment be inherited?
Yes!
What is epigenetics?
The study of heritable changes in phenotype (appearance) or gene expression caused by mechanisms other than changes in the underlying DNA sequence
Are epigenetic changes heritable?
Yes!
What are selection differentials?
Difference in mean for selected and mean for entire population
What is the relationship between selection differentials and selection gradients?
The selection gradient (B) for trait t is equal to the selection differential (S) divided by the variance in the population
If the selection gradient tell us about the strength of selection, why do we need to know the selection differential?
Selection differential (S) is what we use to predict the strength of the response to selection
How/why is the selection gradient useful?
Often the easiest measure in the field
For predicting evolutionary response (R ) to selection, do you need to know heritability or selection differential?
Both!
What “defines” male and female across all animals?
A. Males are larger
B. Females provide more parental care
C. Males fight and females choose
D. Males produce smaller sex cells
E. You need all of the above to define males and females
D. Males produce smaller sex cells
What limits reproductive success?
- Resources
- Access to mates