Week 1-2: Evolution and Natural Selection

🌱 week 1-2 lecture Course 🌱 biosci 94 Confidence Confident Last Edited @March 19, 2024 2:26 AM evolution and natural selection brief history of evolutionary ideas organisms come in different “types”; “types” are unchanging. varitation among individuals are “trivial deviations” from the “perfect essence” fixed types: organized into a “scale” based on increasing size and complexity (with humans at the “top” as “higher”) week 1-2 lecture 1 species can change through time can form via spontaneous generation, then move “higher” getting larger and more complex. changes passed to offspring caused by acquired changes in a parent life forms better represented by a tree, not a ladder no “higher” and “lower” natural selection, not inheritance of acquired characters, is a mechanism of evolutionary change “scale” or “higher/lower” thinking sometimes persists today even in interpretation of evolutionary trees note that there is NO relevance in the left-right ordering of life forms at the tips of evolutionary trees, we’ll come back to this later week 1-2 lecture 2 why do we identify contributions of specific indivuals? development of ideas involve many people ideas can be best understood in contect (time, culture) contribution of different individuals shaped by their experiences and background Darwin and Wallace’s key insights species change through time (”descent with modification”) (also recognized by Lamarck) species are related by descent from a common ancestor variation among individuals is not “noise” but a crucial substrate for evolution natural selection is an important mechanism for evolutionary change evidence for changes over time fossils rocks and fossils can be dated changes over time extinction most animal and plant spcies that ever lived are now extinct vestigial traits week 1-2 lecture 3 reduced or incompletely developed structure that has no function, but is simialr to functioning structure in other related species ex: human tail bone, previously found in other primates such as spider monkeys evidence for common ancestry similar species are found in the same geographic area Galapagos finches are similar to each other evolution by natural selection — logic 1. individuals in a population vary 2. some of this variation in traits is heritable 3. more offspring are produced than survive; some individuals will produce more offspring than others 4. natural selection occurs when individuals with certain heritable traits produce more offspring than inviduals without these heritable traits (greater “fitness”) natural selection leads to better “match” between traits and environment (adaptations) example: cryptic coloration (camoflague) Darwin’s voyage 1831-1836 around 22 years old (idt this is relevant….) in 1800’s, growing understsanding that Earth was geologically active, changing why the Galapagos islands? week 1-2 lecture 4 formed as a result of volcanic activity (not connected to mainland) when first formed, there were no life forms islands often have species of plants and animals that are “endemic” (not found elsewhere), but are similar to species found on nearby islands or a nearby mainland this suggested to Darwin that islands were colonized by indivuduals that eventually gave rise to new species artificial selection deliberate manipulation by humans, as in animal and plant breeding, of the genetic composition of a population by allowing only individuals with desirible traits to reproduce agriculture varities of vegetables (brassica oleracea) animal breeding >400 described breeds 152 breeds recognized by American Kennel Club most modern breeds < 400 years old closest wild relative of domestic dogs is the grey wolf week 1-2 lecture 5 Charles Darwin bred pigeons evolution = changes in allele freuencies populations and species evolve, meaning that their characteristics change through time, more precisely, evolution is defined as changes in allele frequencies over time allele = particular version of a gene population = a group of individuals of the same species living in the same geographic area at the same time species = a distinct, identifiable group of populations, whose members can interbreed evolution is not progressive evoluton leads to a tree (branching network of relationships), not a linear progression natural selection leads to better “match pesticide, herbicide, and antibiotic resistance are on the rise week 1-2 lecture 6