| A | B |
|---|
| Darwin's definition of evolution | Descent with modification over time |
| New synthesis definition of evolution | Evolution is change in allele frequencies of a population over generations |
| Two themes in The Origin of Species | 1) All organisms descended from a common ancestor with modifications. 2) The mechanism of modification over time is natural selection |
| Definition and three things needed for natural selection to occur | Natural selection is a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. Things needed: 1) Individuals must vary 2) Traits that vary must be heritable 3) Heritable traits must influence fitness |
| Predictions of Darwin's Theory: If species share common ancestry there should be traits shared by all species in a group | Example: homologous traits (traits that are similar due to common ancestor), such as the same bones existing in cat's paws/forelimbs and human's hands/arms |
| Predictions of Darwin's Theory: Natural selection should get rid of costly, unnecessary traits | Example: Emus are large, flightless birds that have vestigial wings that they do not use. Vestigial structures are remnants of features that surved a function on the organism's ancestors |
| Predictions of Darwin's Theory: If natural agents favor certain traits in certain environs, traits should be present in distantly related species who live in similar environs | Example: Convergent evolution, the independent evolution of similar features in different lineages. N.American species (ie. flying squirrels) and Australian species (ie. sugar gliders) occupy similar environs and therefore look similar despite being very distantly related |
| Predictions of Darwin's Theory: We should see sequences of fossils globally that reflect sequential changes across earth | Example: In the fossil record, the deeper the fossil the older the species. Closer to the surface, the species should have evolved. In shale dig sites in California, we can see this in how trilobites changed over time |
| Predictions of Darwin's Theory: Adult forms of species should be more divergent than embryonic forms | Example: Early in development, we resemble distantly related species like cats (comparative embryology) |
| Predictions of Darwin's Theory: Humans should be able to direct evolution by selecting which adults produce offspring | Example: Via artificial selection humans have been able to control the breeds of cats that arose; some for companionship and others for tasks like catching rats |
| Predictions of Darwin's Theory: Species should have limited distribution, only spreading via gradual migration | Example: There are no elephants in North America, but there are species of elephants in Asia and India. This shows that their spread has occurred but been limited |
| Predictions of Darwin's Theory: Because mutations arise regularly and accumulate over time, species related via narrow taxonomic groups (genus, family) should be more similar than those related via broad groups (genus, phylum) | Example: Humans are more closely related to primates than we are to cats |
| Mendel's Law of Segregation | When an individual produces gametes, the two alleles separate so that each gamete receives only one copy |
| Mendel's Law of Independent Assortment | Each pair of alleles segregates independently of each other pair of alleles during gamete formation |
| Mendalian inheritance assumes that: Genotype determines phenotype | Exception: Phenotypic plasticity. In hydrangeas, soil acidity influences the phenotype (flower color) due to phenotypic plasticity |
| Mendalian inheritance assumes that: Alleles are either dominant or recessive | Exception: Partial dominance and co-dominance. In partial dominance, both alleles are present, but one is blank. This can be seen in snapdragons, where red x white = pink. In Co-dominance, both alleles combine to make new colors. In parakeets, blue x yellow can create green |
| Mendalian inheritance assumes that: Each gene/locus affects only one trait | Exception: Pleiotropy. In sickle cell disease, recessive allele at one locus affects both blood oxygen and severity of malarial infection. Alos, in siamese cats, the same protein produces abnormal coloration and crossed eyes |
| Mendalian inheritance assumes that: Each trait is only affected by one gene/locus | Exception: Polygenic inheritance and epistasis. In human skin color, polygenic inheritance occurs because skin pigmentation is controlled by at least 3 separately inherited genes. In epistasis, the expression of a gene at one locus alters that of a gene at another. We see this in mice, because one allele can determine whether or not the mouse's fur has any color at all |
| Mendalian inheritance assumes that: All genes/loci sort independently | Exception: Linkage. Linked genes are two or more genes on the same chromosome that tend to be inherited together |
| Mendalian inheritance assumes that: All traits in diploid organisms are affected by 2 copies of a gene | Exception: Sex-linked traits (which refer to a single gene on a sex chromosome). Tortoiseshell cats can only be female and males can only be one color |
| Hardy-Wienburg equation | p squared + 2pq + q squared = 1, where p represents the homozygous dominant alleles, 2pq represents the heterozygotes, and q represents the homozygous recessives |
| The five Hardy-Wienburg assumptions | 1) large populations 2) no mutations 3) no migration 4) no selection 5) mating is random, not selective |
| Violations of Hardy-Weinburg: Small population | A small population could cause low diversity, and is more susceptible to genetic drift and bottleneck effect |
| Bottleneck effect | When few members of a species remain to mate, resulting in low genetic diversity. Example: Red wolves are facing a bottleneck effect in North Carolina, because the breeding program began with only 14 individuals |
| Genetic drift | A process in which chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations |
| Founder effect | When a few individuals become isolated from larger population, or found a new population whose gene pool differs from the source population. Example: Amish populations founded by a few members resulted in a disproportionately high number of rare recessive traits (polydactly combined with dwarfism ) |
| Violations of Hardy-Weinburg: Mutations occurring | When mutations occur they have the ability to create new alleles, which can throw off the H-W equilibrium |
| Violations of Hardy-Weinburg: Migration occurring | Migration and gene flow involve individuals from other populations moving or mating with individuals from another population. This can throw off the allele frequencies. Example: Migration of new alleles in grass - some more tolerant to mineral concentrations in soil |
| Violations of Hardy-Weinburg: Selection occurring | Selection violates the H-W assumption that mating is random. An assortative mating, individuals are picky about mates and select based on traits that contribute to fittness |
| Positive assortative mating | "I prefer the cat that looks like me!!!" Results in fewer heterozygotes, more homozygotes |
| Negative assortative mating | "I prefer different looking cats!!!" Results in more heterozygotes and fewer homozygotes |
| Evolution of resistance to pesticides | Red scale insects developed a resistance to hydrocyanide because when the insecticide was sprayed, the insects with the resistant allele survived to mate and pass it on to their offspring |
| Sexual selection: Male-male (intrasexual) competition | Males compete with other males to mate with the females. This is the most common form of sexual selection |
| Sexual selection: Intersexual | Females choose mate with the best display (ie. peacock's tail feathers). If a male has an impressive display, it's usually a good sign of his fitness |
| What is the only mechanism that leads directly to adaption? | Selection |
| Darwin vs. Mendel | Darwin focues on population changes and patterns. Mendel focused on tracing traits across pedigrees |
| Mendel's four conclusions | 1) Inheritance is particulate, meaning that parents pass on "heritable factor" or gene 2) Variation is due to different alleles of a single gene 3) Each individual has 2 copies of a gene, one from each parent 4) One allele can be dominant and hide the other, recessive allele |
| Transmutation | Lamarck's (incorrect) theory that acquired traits could be inherited |
| Homozygous vs. heterozygous | An organism with a pair of identical alleles for a character is said to be homozygous (AA, aa). An organism that has two different alleles for a gene is said to be heterozygous (Aa) |
| Crossing over | Crossing over occurs while replicated homologous chromosomes are paired during prophase of meiosis I and results in the end portions of two non-sister chromatids trading places, thus recombining linked genes |
| Catastrophism vs. uniformitarianism | Catastrophism (Cuvier) is the principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present. Uniformitarianism (Lyell) states that mechanisms of change are constant over time. Lyell's idea influenced Darwin's thinking |
