Traits
Describe an example of a polygenic trait
Height, kernel color, skin color
Define heterozygote advantage AND provide an example
When heterozygous individuals have a HIGHER fitness than BOTH homozygous genotypes
ex: sickle-cell anemia
Define heritability
Heritability: "proportion of phenotypic variation IN A POPULATION attributable to genetic variation"
What are single-nucleotide polymorphisms?
SNPs: "variation in a SINGLE base (A, T, C, or G) within a sequence of DNA"
Name the 3 types of selection that have effects on the PHENOTYPIC distribution of traits
1) directional selection
2) disruptive selection
3) stabilizing selection
What is the difference between ancestral and derived traits?
Derived-- "account for DIFFERENCES among organisms"
What is the difference between a discrete trait and a polygenic trait?
Discrete: phenotypes fall into few DISTINCT classes
Polygenic: Display a (bell-shaped) normal distribution
Explain the difference between positive and negative selection
Positive: "PROMOTES the spread of ADVANTAGEOUS alleles"
Negative: "STOPS the spread of DELETERIOUS alleles"
What is the midparent?
Midparent: "average of mother and father"
Homology-- "similarities due to COMMON descent from a shared ancestor"
Analogy-- "similarities that evolved INDEPENDENTLY in different organisms as a result of adaptation to similar environments"
--ex: bat, bird, & butterfly wings
Name & describe Darwin and Wallaces's 2 big ideas.
1) Descent with Modification
-life on earth had SINGLE Origin and all diverse organisms today are descendants (via evolutionary processes) of this COMMON ancestor
2) Natural Selection
-process by which individuals w/ heritable traits that give them an advantage in a given environment produce MORE OFFSPRING than individuals lacking those traits; alleles associated w/ favored traits increase in frequency in subsequent generations
What influences the frequency of an allele in a population?
Their influence on an individual's fitness
What is selective pressure? Provide an example.
Selective Pressure: "any phenomena which alters the behavior and fitness of living organisms within a given environment. It is the driving force of evolution and natural selection"
EX: environmental conditions, disease
How do you measure heritability?
Plot graph of mid parent vs. child
What are the 3 conditions necessary for natural selection?
1) Variation in traits
2) Inheritance (reproductive capacity)
3) Competition
TRUE OR FALSE:
Directional selection applies to polygenic traits only.
FALSE! Directional selection applies to BOTH discrete & polygenic traits.
*Stabilizing selection applies to polygenic traits ONLY*
What are antibiotic, pesticide, & herbicide resistance examples of?
Directional Natural Selection caused by HUMANS
***NOT artificial selection***
-allele frequencies change in one direction (one allele OR one tail of phenotypic distribution is favored)
How do environmental factors influence phenotypic distributions in a population?
Certain environments will make some phenotypic traits more favorable than others
Label the following points on a phylogeny:
node, branch, polygamy, root, taxon, sister taxon, outgrip, monophyletic group, non-monophyletic group
(Lecture 7, page 21)