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Biology/Lower Division
David Holway

Lecture 2 Wednesday January 09 2013 555 PM History of evolutionary thinking and Darwins arguments for descent with modification 1 Origin of the Species 1859 a All organisms evolved from common ancestor descent w modification this was accepted soon after publication i Accepted easily bc it could be reconciled with God ii The thinking at the time organisms didnt change over time Created by God and variationimperfections species were made independently and creation was recent b Mechanism evolution by natural selection This idea was rejected for about 5060 years 2 Observations Darwin Made on Beagle a Tropical diversity in Brazil Organisms there are similar to temperate parts of South America b Discovered bones of extinct giant mammals recognized similarity to extant forms c Found sedimentary rock d Experienced an earthquake i Changes in geography mountain rising several meters perhaps cause of natural selection as changes in geography separated species 3 Colonization and divergence a Observed 3 species of mockingbirds on 4 islands i Each species was different in appearance from each other b Darwin pondered mysteries 20 yrs i Studied barnacles exhaustive taxonomy variations ii Bred pigeons saw how species change artificial selection iii Studied dispersal and colonization processes plants can disperse on their own cross water etc 4 Alfred Russell Wallace a Collected organisms as a living b Admired Darwin c Saw tremendous differences and morphology within a species d Wallace sent a letter to Darwin pushed Darwin to publish and he published in 1 yr 5 Fossils trace of organisms in past often form in sedimentary rock a Fossil sequences reveal timing of evolutionary events b Evidence of organisms that left no living descendants c Episodes of diversification d History of distribution e Succession fossils from one region similar to extant organisms from that same region a Intact fossil intact bone tissue that has not been mineralized i ie teeth b Perminerialized fossils structure looks similar to what it looks like but chemical content has changed i ie petrified wood c Compression cast fossils most common d Trace fossils things like footprints e Resin fossils animals plants trapped in tree sap Tree sap hardened and turned to resin f Living fossil no morphological change over long time periods i Ginkos and horseshoe crabs ii Sand dollars 6 Trilobites thrived in Paleozoic Era abundant and widespread a Lived in shallow seas b Pattern of segmentation like extant arthropods c 4000 species based on morphology d 250mya 7 Transitional forms organisms that have characteristics of both ancestral and modern forms a Useful shows how modern form could have evolved i ie Archaeopteryx 8 Modern birds use feathers for thermoregulation keep eggs warm color attract mates camo 9 Homology similarity due to inheritance from a common ancestor a Similar structure despite diff functions 10 Structural Homology mammalian forelimbs have same basic structure despite different function a Ex stinger in ants bees and wasps is a modified ovipositor organ used for laying eggs 11 Developmental homology similarities during development 12 Molecular homology similarities among organisms at molecular level a Genetic Code in all organisms the same codons specify same proteins 13 Vestigial organs functionless organ in one species that has important function in other species a Ex vestigial eyes in cave organisms b Flightless birds that still have wings c Goose bumps wisdom teeth appendix coccyx humans 14 Convergent Evolution evolution of similar features independently in diff evolutionary lineages usually from different antecedent features or by different developmental pathways Lecture 3 Sunday January 13 2013 124 AM 1 Natural Selection was rejected for 5060 yearsa No sort of central plan for lineages surviving hard to reconcile with religious beliefs b Ideas about age of earth were qualitative at best Geologists knew earth must be older than several thousand years c No clear understanding about inheritance i Idea 1 blending inheritance inherited characteristics are mixed like paint 1 Minimizes inheritance over time Everything is averaged No variation in this process so it contradicted Darwins idea of Natural Selection ii Idea 2 NeoLamarckism SOURCE OF VARIATION inheritance of characteristic acquired in response to environment conditions 1 Acquired characteristics would be inherited to offspringa Buff blacksmith would have buff children d Darwin died few decades after publication 2 1900s Natural Selection influenced by scientific discoveries outside of Natural Selection a How old is the Earth i Radioactivity and radiometric dating 1896 1 Radioactive isotopes decay into other isotopes at particular constant rate 2 Proportions of parentdaughter isotopes provide estimates of age 3 Current estimates of Earths age 46 billion years b Better understanding of genetics i Mendels work on peas published 1865 1 His work was discovered in 1900 2 Parents pass discrete units of info to offspring 3 Concept of gene recessive traits dominant traits 4 Contradicted blending inheritance 5 Mendels work nicely summarized in Chp 14 ii August Weismann German zoologist 1 Showed that you couldnt produce mice without tail 2 Heritable traits pass from generation to generation via material in nuclei of cells 3 Differentiated germ plasm gametes from somatic cells 4 Germ plasm is not altered by use 5 Weismanns work further discredited NeoLamarckism 3 Artificial Selection a Process of selective breeding of plants and animals to produce populations with more desirable traits i Size of fruit amount of fat in animal etc b Individuals with specific traits selected for breeding other individuals do not contribute genes to next generation c Domestic animals crops pets are all products of artificial selection d Useful to study heritability and genetic correlations and genes with large effects on the phenotype 4 Darwins arguments about selection used familiar examples from animal and plant breeding a English carrier used to carry messages b Almond tumbler c Pouter inflatable crop 5 Importance of artificial selection for humans a Nearly all food we eat is product of artificial selection b Most human food comes just six crops corn rice wheat potatoes cassava and sweet potatoes c Todays crops are the products of a campaign of artificial selection that began 12000 years ago d Ancient farmers had insight that offspring resemble parents i Used seed of plant with most crop production e Geographic distribution of plants and animals suitable for domestication left an enormous imprint on human history 6 How did cauliflower come to be a Individuals vary b Individuals with certain traits selected for breeding these individuals have greater survivalreproduction as a consequence c If variation is heritable genetic d Result is evolution i Offspring will look different
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