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BIOL 2600 Midterm Exam 2024/2025 Latest Fall-Spring
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what are the five major developments that preceded darwins "on the origin of species"
- explanations moved from supernatural to methodological naturalism
- from catastrophism to uniformitarianism
- from logic and pure reason to observation, testing, and refutation
- from unchanging world to a world in flux
- away from the idea of spontaneous generation to the idea that species come from other closely related species Darwin's two fundamental insights
- natural selection: nature selects the most successful variants
- ancestry: all species descended from one or a few common ancestors: new species arise from pre-existing species two concepts noted by both charles darwin and alfred wallace
- living species tend to be most similar to other species that geographically nearby
- species in the fossil record tend to be most similar to other species that lived around the same time evolutionary biology the study of the origin, maintenance and diversity of life on earth over approximately the past 3.5 billion years artificial selection human-directed selective breeding neutral mutations genetic changes that have no effect on fitness Catatrophism earths major geological features arose through sudden cataclysmic, large-scale events, rather than through slow gradual change. also posited that these cataclysmic events often involve different forces that those that are currently operating
some individuals leave more offspring in the next generation than others do, often due to advantages in survival or reproduction adaptation a trait that has been shaped by natural selection to serve the same primary function or functions that make it beneficial today exaptation a trait that has a different function today than it did in the past life-history trade-off an increase in one life history is coupled to a decrease in another life history trait what are mendels two laws?
- the law of segregation = each parent has two copies of each gene at each locus, which separate with equal probability into the gametes
- law of independent assortment = alleles from different loci are inherited independently of each other
mendelian traits discrete traits passed onto offspring in the expected mendelian ratios epigenetic inheritance alterations in gene expression without changes in DNA sequence, some epigenetic mechanisms can be heritable, chromosome structured as chromatin; DNA wound around histones, transcription doesnt occur when chromatin is tightly wound around histones DNA methylation addition of a methyl group to a C-G base pair
- affects ability of transcription factors to bind to DNA and methylated regions interact with proteins with determine chromatin structure variation individuals in a population differ from one another
- if you only lost a branch there is less population, and they have already created common ancestors with a part of their DNA in them Redi's experiment 1668
- showed that spontaneous generation (of life) was not how things worked
- early example of empirical hypothesis testing using controls
- experiment where meat was left in jars, some open, some un-opened, the meat that was unopened flies and maggots could not get in Jean-Baptiste Lamarck This man developed the first cohesive theory of evolution after his studies of biology
- thought that shorebirds would want to stretch their legs to stay out of the mud
- thought that these traits would be a result of evolution
- doesn't work like this phaeomelanin producing a light yellow pigment life history
traits include the timing of sexual maturity, the timing of aging or senescence, the number and size of offspring, and whether an organism reproduces repeatedly over the course of its lifetime, or just once during its lifetime gene duplication provides another evolutionary pathway by which a protein can switch functions without loss of the original function. in a gene duplication event, an extra copy of a functional gene is formed. transmission genetics the mechanisms by which genes are passed from parents to offspring and a discussion of genetic variation and mutation evolution the change in allele frequencies over time in a population microevolution small incremental steps (changes in allele frequencies from one generation to the next), leads to macroevolution over long time scales
chi square test equation X^2 = EfiO-E^2/E overdominance heterozygote advantage: leads to a balanced polymorphism for both alleles maintained in a population under dominance heterozygote has lower fitness than either homozygote
- one allele will become fixed reginald punnet 1908, known for creating the punnett squares, was a leading advocate of mendels ideas Brachydactyly
a genetically inherited condition leading to shortened or malformed fingers and toes autosome a chromosome that is not a sex chromosome equilibria a "steady state", what traits will remain the same over a long period of time inbreeding depression when the offspring of genetic relatives have reduced fitnesses what do the results of a chi-square test mean?
- p<0.05 there is a significant difference between the expected and observed numbers of each genotype
- p> 0.05 then either the expected and observed genotypes are similar enough to be attributed to chance - seen in HWE
- Separate populations diverge in their allele frequencies and in terms of which alleles are present population bottle neck a brief period of small population size, increase in the rate of genetic drift, catastrophic event causes a population to decrease
- occurs faster in smaller populations founder effect change in allele frequencies that results from the sampling effects that occur when small number of individuals from a large population initially colonize a new area and "found" a new population phylogeny the branching relationships of populations as they give rise to multiple descent populations over evolutionary time phylogenetic systematics we classify organisms according to their evolutionary histories - and phylogenetic trees are our way of representing these relationships
characters any observable characteristic of organisms; for example, they may be anatomical features, developmental/ embryological processes, behavioural patterns, or genetic sequences taxon a group of related organisms nodes a branching point representing a common ancestor to all taxa that stem from it homologous trait a trait found in two or more species because those species have inherited this trait from an ancestor analogous trait
paraphyletic group is one that does include the common ancestor of all its members but does not contain each and every species that descended from that ancestor rooted trees rooted trees indicate the direction of time
- the base of a rooted tree is called the root
- This is the common lineage from which all species indicated on the tree derived. We can "root" an unrooted tree at different points on the tree, generating different rooted trees in each case. strict consensus tree reflects the monophyletic groups that appear in all of the phylogenies and depicts the uncertain relationships long branch attraction relationship and attraction between the rapidly evolving branches phylogenetic distance method
measure the pairwise "distances" between species then we can use these distances to reconstruct the tree
- The goal is to find a tree with branches arrayed so that the distance along the branches between any two species is as close as possible to the distance that we measured between those two species.
