| A | B |
|---|
| Directional Selection | One trait is favored, moves graph to reflect one extreme |
| Stabilizing Selection | Favors the phenotype in the middle, against two extremes |
| Disruptive Selection | Selects against traits in the middle, favors extremes on either side. Example: in fish, some males stay small and dull like females so they can sneak in and fertilize eggs, while other males are brightly colored to attract females and gain access to eggs that way - both strategies work |
| Relative fitness | The contribution of an individual to the gene pool relative to the contributions of other individuals. |
| If the most fit phenotype is given a value of 1, then the less successful phenotype is given a value of what? | less successful phenotype would be 1-s, with -s- being the reduction of fitness relative to the most successful phenotype |
| 2 reasons that organisms cant be "perfectly adapted" | 1) Selection can only act on existing variables. New advantageous alleles don't arise on demand, but organisms can adapt pre-existing variations. Ex. flying fish have "wings" that are actually just adapted pectoral fins. 2) Evolutionary tradeoffs. Ex. Beetles with larger horns are better at fighting while those with larger testes are more fertile, but there are energy constraints that prevent a beetle from having a very large horns and very large testes simultaneously |
| Three sources of genetic variation: | 1) Mutation, the only source of completely new alleles. 2) Migration/geographic variation cause alleles to be spread between populations, and these alleles may differ as a result of adaptation to different environs. Ex. Beach mice have different coat colors favored in different geog. locations, but breeding between pops maintains variation. 3) Dominance and Co-dominance ensure that rare deleterious alleles remain hidden when dominant phenotype is favored. Ex. The sickle cell disease is co-dominant on a cellular level because even when an individual doesn't show the full blown disease they still have some sickle shaped cells |
| Cline | gradual geographic variation correlated with ecological variants. Ex. Variation in yarrow plant heights at differing altitudes - low altitude, tall plant; high altitude, short plant |
| Morphological species concept | Species are distinct, unchanging entities defined by unique morphological features (body shape, structural features, etc) |
| Issues with the morphological species concept | 1) Does not account for species with sexual dimorphism, where males and females differ. Ex. mallard ducks. 2) Does not account for metamorphosis. Ex. Caterpillars becoming butterflies. 3) Does not account for phenotypic plasticity. Ex. Yarrow plants in different altitudes. 4) Does not account for cryptic species, which look the same but dont mate. Ex. male field crickets look the same but each species has a different call |
| Biological species concept | Defines a species as a group of populations whose members have the potential to interbreed and produce viable ofspring |
| Issues with biological species concept | 1) It can be hard to breed some organisms to test if they are or arent of the same species by these conditions. Ex. We can't really breed whales. 2) Does not account for hybrids that are fit and viable, also does not provide an answer for species that we only know from fossils, or those that reproduce asexually |
| Autopolyploid | An individual that has more than 2 chromosome sets that are all derived from a single species |
| Allopolyploid | An infertile hybrid propagates itself and makes a fertile polyploid that can breed with itself but not the parent species |
