Biol 100 Lecture 29 Evol III-1 PDF

When Darwin proposed the idea of Natural Selection he was thinking primarily of simple survival: You can’t have kids if your dead! Professor Farnsworth “Sexual selection and summary” But there is more to Natural Selection than just survival. Overall FITNESS (e.g., survival, feeding, finding a ma...

When Darwin proposed the idea of Natural Selection he was thinking primarily of simple survival: You can’t have kids if your dead! Professor Farnsworth “Sexual selection and summary” But there is more to Natural Selection than just survival. Overall FITNESS (e.g., survival, feeding, finding a mate, parental care etc.) Thus SURVIVAL OF THE FITTEST. Natural Selection does not favour the fittest, it determines the fittest. Survival is determined in part by chance (an idea Darwin really didn’t deal with) but he did pick up on “sexual selection” or the attractiveness idea. That is “Is the likelihood of survival the only factor which determines who you get a date with this Friday” - NO! Characteristics important for survival are not necessarily good for securing a mate Causes of Micro-evolutionary change 1. Chance events (= genetic drift). Often called neutral selection a) Founder effect – a few individuals begin a new population b) bottleneck effect - occurs when a population size is radically reduced Founder Effect Bottleneck effect Other causes of Micro-evolutionary change 2. Gene flow - due to immigration or emigration new ind coming into pop w/ new genes , introduces new genes 3. Mutation - change due to this is a fact variation most meltations -> generates of life by neutral neg a new gelt of origin material moreLack be pos 4. Natural Selection are , - - - => individuals wh alleles that some aren't allels are favourited favorited don't survive or Modes of Natural Selection Stabilizing - discriminates against the extremes Directional - discriminates against one extreme Disruptive - discriminates against the mean (opposite of stabilizing) Neutralist - Selectionist arguments There is healthy debate about which and when it is more important. That is we still have things to learn about the mechanism of evolution - not whether it occurs or not. Prestigious Biological Journal: “Evolution” Micro- versus Macro-evolution Until now I have been discussing Micro-evolution or changes in allele frequencies in a population. Macro-evolution concerns the evolution of new species. What is a species? A SPECIES is a population (group of individuals) which actually or at least potentially can interbreed with each other but are not members of other populations Problems with the SPECIES concept: 1. Presumed reproductive capability 2. What about asexual organisms? 3. Fossil organisms? 4. Geographic isolation? 5. Clines Clinal Variation Mummichog fish vary in a cold-adaptive allele along a temperature gradient Species concept: Horse x Donkey = Mule Professor Farnsworth “Grelbers and Ruffers” Phyletic evolution = Sympatric speciation Gradual evolution of one species into another – Waxy Grelbers Allopatric speciation Geographic isolation – thin-furred vs thickfurred Ruffers Adaptive Radiation Darwin’s Finches In sympatric speciation, a reproductive barrier isolates a subset of a population without geographic separation from the parent species Sympatric speciation can result from the appearance of new ecological niches For example, the North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees Soapberry bugs Sympatric speciation can result from the appearance of new ecological niches For example, the North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees Soapberry bugs Sympatric speciation can result from the appearance of new ecological niches For example, the North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees Soapberry bugs Sympatric speciation can result from the appearance of new ecological niches For example, the North American maggot fly can live on native hawthorn trees as well as more recently introduced apple trees Soapberry bugs