Final Exam: Comprehensive Short Answer Flashcards
(14 cards)
Define evolution.
- Descent with modification
- Changes in allele frequencies over generations
Natural selection postulates (4)
- Individuals in populations vary
- Some variation heritable; passed from parent to offspring
- More offspring produced than survive; differential reproductive success
- Variations favored by environment have greater survival; survival and reproduction of individuals is not random
Explain why evolution by natural selection is not random or progressive.
- Based on environment; changes in environment are random; natural selection is “directed” because it increases adaptation to a particular environment
- Not forward-looking, nothing adapts to the future, adaptation is from past conditions
- Natural selection acts on existing phenotypes/traits
Briefly explain how new genes come into being.
- Gene replication/duplication, new gene product is then acted on in different way by natural selection
- Modification of existing traits by natural selection
Explain the Hardy-Weinberg Equilibrium Principle non-mathematically.
- “Allele frequencies don’t evolve.”
- Null Model: what will have to be true for a population to show no change in allele frequency
- Allele frequencies predict genotype frequencies
- Equilibrium=no change in allele frequency; established in 1 generation
- The 5 Assumptions
5 Assumptions (Hardy-Weinberg Equilibrium Principle)
- No selection - no change in allele frequency
- No mutation - because mutations change allele frequency
- Closed population - because migrations could cause changes in allele frequency and gene flow
- Infinite size - genetic drift violates infinite size
- Panmixia or random mating - doesn’t change allele frequency, but does change genotype frequency; nonrandom mating violates this; inbreeding violates this
Distinguish between vertical and horizontal (lateral) gene transfer and their relevance to evolution.
- Vertical = parent ==> offspring
- Horizontal = species ==> species
- -(1) Endosymbiont to nucleus - mitochondria and chloroplast
- -(2) Plasmids - transfer DNA between bacteria
- -(3) Transposable elements - can effect genome if they cause a frameshift; can be vertically transferred; responsible for large various genome sizes
Briefly explain when altruism is adaptive, non-mathematically.
When the benefit/fitness/survival of the recipient and the actor are closely related outweighs the cost/sacrifice to the actor
List the 3 Main Species Concepts.
- Biological Species Concept
- Phylogenetic Species Concept
- Morphospecies Concept
Explain the biological species concept.
Distinguishing species based on whether or not they interbreed regularly with one another
Explain the phylogenetic species concept.
Distinguishing species by finding smallest monophyletic group on a phylogeny
Explain the morphospecies concept.
Distinguishing species based on the phenotypes
[Distinguish between allopatric and sympatric speciation (with or without ploidy change).]
What is the allopatric distinction?
Allopatric - Populations of species become geographically isolated; gene flow between them ceases
- -Dispersal (small population = founder effect)
- -Vicariance
The vicariant populations then undergo genotypic/phenotypic divergence as they become subject to different selective pressures, undergo genetic drift, and different mutations arise in the population’s gene pool.
[Distinguish between allopatric and sympatric speciation (with or without ploidy change).]
What is the sympatric distinction?
Sympatric - New species forms within existing range or at edge, never a barrier
WIthout ploidy change: Different preference of novel resource
- –Fruit fly with hammerhead, combat
- —-Big head alleles introduced, mutation became fixed in population because of success, new species made
With ploidy change: Plants
—Parents have tetraploid, mate with other tetraploids, new species made overnight
