Lecture 9, Natural Selection 2_NOTES

Lecture 9, Natural Selection 2_NOTES - Lecture 9: Natural...

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Unformatted text preview: Lecture 9: Natural Selection II: Darwin and Wallace’s solution to the problem of adaptation Wallace’s III. The Theory of Evolution by Natural Selection E. Questions Answered by Natural Selection The Theory of Natural Selection answered several The nagging questions present during Darwin’s time: nagging 1. Why do organisms appear to be designed? 1. Why 1. Where do new species come from? 2. Why do organisms resemble each other, even in their Why underlying features? 3. Why do organisms have vestigial structures? Evolutionary 3. Why relicts (organisms are built on their ancestor’s body plans) OR an undiscovered function? OR 4. Why do organisms sometimes seem to be so badly designed? Why Evolutionary legacy OR a cruel / inept designer or creator? OR III. The Theory of Evolution by Natural Selection III. E. Questions answered by Natural Selection 1. Why do organisms appear to be designed? Why We now know the We Answer: Answer Natural selection Natural creates “adaptations” “adaptations” III. The Theory of Evolution by Natural Selection III. E. Questions answered by Natural Selection 1. Why do organisms appear to be designed? Why Mimicry in freshwater mussels Mimicry Ptychobranchus occidentalis (Ouachita kidneyshell) ovisacs -- look ovisacs (and even move) like larval fish like mussel larvae mussel Fish (darter) attacking: Fish Ovisac ruptures; larvae escape into darter’s mouth darter mouth & gills gills III. The Theory of Evolution by Natural Selection III. E. Questions answered by Natural Selection 2. Where do new species come from? 2. Answer: New species evolve New from other species through the process of speciation speciation III. The Theory of Evolution by Natural Selection III. E. Questions answered by Natural Selection 3. Why the resemblances among organisms? 3. Answer: inheritance from common ancestor=HOMOLOGY Answer inheritance III. The Theory of Evolution by Natural Selection E. Questions answered by Natural Selection 4. Vestigial organs: why do organisms have them? Ear Ear muscles muscles Vermiform appendix Vermiform Answer: historical baggage/evolutionary legacy historical III. The Theory of Evolution by Natural Selection III. E. Questions answered by Natural Selection 4. Vestigial organs: why do organisms have them? Vestigial hindlimbs in boas and pythons Vestigial III. The Theory of Evolution by Natural Selection III. E. Questions answered by Natural Selection 4. Vestigial organs: why do organisms have them? Vestigial hindlimbs in whales whales III. The Theory of Evolution by Natural Selection E. Questions answered by Natural Selection 5. Why do some things appear to be designed poorly? some Answer: selection works on historical Answer: contingency/pre-existing traits; and sometimes tradeoffs lead to imperfect solutions. III. The Theory of Evolution by Natural Selection F. Important terminology Natural Selection is: The differential contribution of offspring to the Natural next generation by various genetic types belonging to a population next Natural Selection leads to EVOLUTION: Natural EVOLUTION Evolution = changes in the heritable properties of populations over Evolution the course of generations, changes in allele frequency over a generation (evolution can happen relatively quickly) generation We measure increased survival / reproduction as _FITNESS__: We _FITNESS__: • Fitness in bio means the amount of offspring in BIO • The number of offspring that survive and reproduce (i.e. the The contribution of genes to the next generation); often measured by proxies; relative fitness is key by III. The Theory of Evolution by Natural Selection F. Important terminology Natural Selection leads to _ADAPTATION_ : _ADAPTATION_ • An adaptation is a trait that increases an organism’s survival or reproductive success (a __noun________) __noun________ • Adaptation also refers to the process by which a beneficial trait (i.e. an adaptation) spreads in a population (i.e. trait evolves by natural selection) evolves III. The Theory of Evolution by Natural Selection III. F. Important terminology Natural selection ... Natural ... is a process by which “design” (i.e. adaptations) can emerge ... without requiring a conscious designer. It Is a materialistic explanation for the complexity of life on earth – a radical idea! radical ... acts on phenotypes, and thus indirectly on genotypes. What ... phenotypes, does this mean? Selection is acting on outward expression of traits of the genes, but in turn can cause an impact on gene frequency in population. (Acts directly on phenotype, indirectly on genotype.) on ...Selection (i.e. selective forces) act on the individual, but natural ...Selection individual but selection leads to evolution in _populations, not individuals. _populations, Individuals don’t evolve, got genes from parents, and cannot swap out genes, Individuals populations evolve, selection on gene frequency on populations. What happened to the population phenotypes? population ...genotypes? What did selection act on? What evolved? What III. The Theory of Evolution by Natural Selection F. Important terminology Natural selection ... Natural ... Is a scientific “theory”, not just a “hypothesis” ... not Theory= A testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise verified through _empirical observation _empirical Hypothesis= a suggested explanation for a phenomenon III. The Theory of Evolution by Natural Selection G. Things that were hard for Darwin to explain... In Darwin’s day, they believed in _blending inheritance In Problem: Eventually, the population should become Eventually, phenotypically uniform. So much for selection... phenotypically P1 Father x Mother Offspring Offspring Offspring F1 Mendel to the rescue! III. The Theory of Evolution by Natural Selection G. Things that were hard for Darwin to explain... Other things that Darwin had a hard time explaining at first at (but which he or others later explained)... We’ll discuss these later these Gaudy Animals... Cooperation... ...
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