Lecture 2: and Book: Chapter 2

Cuvier: father of modern paleontology Comparative biology: linked morphologies of fossils to living organisms Did not believe in evolution~ species are stable through time BUT- they could go extinct

Lamarkian Evolution Evolution by the inheritance of traits that are ʻemphasizedʼ during an organisms lifetime. If a giraffe stretches itʼs neck, itʼs descendants will have longer necks. Use & Disuse: individuals lose characteristics they donʼt use, and emphasize characteristics that they DO use No

Evolution by Natural Selection : main body of the theory “” Alfred Russel Wallace: codiscovered theory based on biogeographical observations Requires: Inheritance, Variation, and a Selective ʻForceʼ Variants do not have equal reproductive success Fecundity: offspring production Survivorship: not dying These work in parallel. You need both to be ʻfitʼ The fitness of an organism is based on a relative scale. You donʼt need to be ʻabsolutely fit- you just need to be more fit than they other guy/gal Evolution= the change in frequency of genotypes over time.

What defines a ʻsuccessfulʼ organism?

Natural Selection vs. Evolution Natural selection works on the level of individuals Evolution works on the level of populations

Types of Selection Direction, Stabilizing, Disruptive

Speciation

Evidence for Evolution:

Homologous vs. Analogous traits Vestigiality (What are some vestigial traits?) Functionless (or nearly so) structures are remnants of structures that once served a purpose The Fossil Record: Intermediate forms exist Modern examples of evolution by natural selection at work! Darwinʼs Finches: Geographic Radiation: Finches have evolved different-sized beaks to handle different types of food Galapagos Archipelago provides a natural laboratory (geographic barriers -> ) Modern droughts select for finches with large beaks in observable timeframes (because larger seeds survive droughts, and only birds with large beaks are capable of cracking open large seeds)

Coevolution & Arms Race Species that are closely tied to other species often have evolutionary histories that are closely related. This can lead to selective forces that continue to increase the evolutionary ʻbondʼ between the species -> Darwinʼs moth example: An orchid in Madagascar has an extremely large spur. Nectar lies at the base of the spur, and pollen lies near the top. A species of moth has a proboscis that is exactly long enough to reach the nectar, allowing the moth to gain food, and the orchid to dump itʼs pollen on the base of the mothʼs proboscis. The moth then fertilizes the next orchid that it interacts with (via the pollen that has been deposited at the base of the mothʼs proboscis). Over time the mothsʼ proboscis and orchidʼs spur have increasingly become longer. How? If the orchidʼs spur is too short, the moth gets the nectar (yay), but the orchid cannot dump itʼs pollen at the base of the mothʼs proboscis (boo). If the spur is too long, the moth will not be able to get food and will stop visiting the orchids. Therefore, moths that have longer probosces will select for orchids that have equally long spurs (because they will only be fertilizing the longer spur orchids. The orchids with short spurs will not get fertilized, even if the moth drinks the nectar). Over time, the orchids with longer spurs become fertilized, and the orchids with shorter spurs do not!!!

Molecular Evolution

Mendel and pea plants: observed that inheritance is not blending but particulate Statistical patterns in inheritance DNA: Watson, Crick, Franklin in 1953 Molecule that carries genetic info What are genes? What are ? DNA codes for specific amino acids; proteins are made up of lengths of amino acids A section of DNA that codes for a specific protein (i.e. a chain of amino acids) = gene Genotype vs. Phenotype Does natural selection act on the genotype or phenotype? How are explained by evolution by natural selection? Not through design by creator. Not through single . This is infinitely improbable. Most big are bad. Through series of small, intermediate steps. Emphasis on gradual transformation.

If individuals with small morphological or biochemical differences have subtle differences in ability to reproduce or survive, these differences will be preserved through time and build up into ever more complex structures. Just need a large amount of time. Chief evidence for this argument is not perfection of design, but the fact that organisms are designed poorly. Natural selection doesn't make perfect structures. It makes the cheapest possible structures using available designs and materials that fulfill the minimum requirements for functioning. Can lead to highly designed structures if the function is difficult and there is some advantage to having an improved structure.