Evolution Exam 1

• Biological evolution: Origin of life, diversification into novel forms (species), change in genetic composition of populations over generation, in the past and into the future.
• Descent with modification -> understanding of the changes in the genetic composition of populations and the processes underlying those changes. Investigation of origins and distribution of species.
• Study evolution -> to clarify the origin and history of populations and species, patterns of diversification and geographic distribution
• Understand genetic changes that occurred in the past and ongoing genetic changes into the future.
• Genetic change of populations result from multiple distinct process: Recombination (mating patterns), Mutation, Selection, Random genetic sampling 'genetic drift', Inter-population movement 'gene flow'.
• Over extended time periods of time, these processes can result in divergence among populations and species.
• Plato, Aristotle -> fixity of organisms (biodiversity)
• Uniformitarianism: change is gradual, with continuity; natural laws are consistent.
• Scientists propose theories based on observations (evidence) from the natural world, and following their reasoning towards logical conclusions.
• Adaptive evolution: evolution that increases the suitability of a population to the habitat it occupies and consequently, its chance to continue persisting there.
• Darwin and Wallace made extensive collections and observations documenting extensive variation within species, as well as among them.
• Variation is, in part, heritable.
• Heritability of differences: for many traits that vary within a population, individuals appear more similar to closer relatives; in particular, offspring resemble their parents.
• Selective breeding takes advantage of heritable variation.
• Descendant species resemble each other because they inherit their characteristic traits from a common ancestor.
• Evidence of common ancestry in nature -> Biogeography - the geographical distribution of biodiversity reflects common ancestry
• Of all juveniles produced, few survive to produce offspring : resources do not suffice for all; many die before reproducing.
• Variation in survival and reproduction, natural selection, could result from resource limitation.
• C&C: Lamarck's hypothesis: Transmission parent to offspring of acquired characteristics --> believed in spontaneous generation as ongoing process
• C&C: Darwin's hypothesis: Transmission parent to offspring of inherent trait differences --> Formulated idea of "descent with modification"
• Disproving spontaneous generation was key to the development of evolutionary theory.
• Life arises from pre-existing life, not spontaneously from non-living materials.
• Obs: Individuals within species vary in phenotype.
• Obs: Offspring look like their parents. Phenotypic differences are, to some extent, heritable, transmitted from parent to offspring.
• Obs: Individuals differ in their survival and reproduction, they differ in fitness.
• If survival and reproduction depend on heritable phenotypic differences then evolution by natural selection (adaptive evolution)
• Species comprise individuals that vary ever so slightly from each other with respect to their many traits.
• Species have a tendency to increase in numbers over generations at a geometric rate.
• Natural selection and artificial selection follow the same principles. Distinction : Natural mediated by Environment, Artificial mediated by human choices.
• Selection: some individuals, because of their traits relative to their environment, are more likely to survive and reproduce than others. They have a higher fitness.
• Higher fitness -> offspring are likely to have inherited values similar to those of their parents. These offspring represent a distinctive subset of their parents. The overall trait dist. of the population and its genetic composition differ from that of the population in the previous generation.
• Natural selection depends on heritable variation of Zinc tolerance in grass.
• Selection: a process occurring within a generation: differential survival and reproduction. Results in change in a population's genetic composition, but the only one that directly promotes increase in average fitness.
• Adaptation: a trait that contributes to fitness and that has been honed by selection. A multigenerational process, mediated by natural selection, by which a population's average fitness in its environment increases.
• Evolution does not progress from "less" to "more" advanced. It is not goal-seeking.
• 'Survival of the fittest': overemphasizes variation in survival, competition/struggle, an extreme simplification of evolution.
• Over larger time scales, Darwin understood that descendant species inherited traits from their ancestral species.
• Particulate inheritance: characteristics of both parents are passed on, but not necessarily visible in phenotypes. (Maintains variation!)
• Law of segregation: each gamete is haploid; carries one allele per genetic locus
• Law of independent assortment: alleles at different loci/chromosomes segregate independently of one another --> new combination of alleles