Transcript CHAPTER 22
Descent With Modification Chapter 22 Historical Context • Darwin 1st to propose idea of natural selection. • Wrote The Origin of Species. • After natural theology (Creationism), creation of taxonomy (system of naming organisms) http://images-eu.amazon.com/images/P/0517123207.01.LZZZZZZZ.gif • Darwin’s views influenced by fossils, impressions of organisms from past and other researchers. • Strata (layers) of rock held fossils dated from youngest (towards top layer) to oldest. • Study of fossils (paleontology) supported idea that change had happened. • Cuvier – catastrophism - large floods occurred between layers of rock - new species repopulate devastated area. http://www.grisda.org/origins/images/05n1-cvr.jpg • Lyell – uniformitarianism -geological processes not changed throughout history. • 1809 - Lamarck - theory of evolution based on observations of fossil invertebrates. • Use and disuse of parts and inheritance of acquired characteristics important in theory. • No evidence that acquired characteristics inherited. http://www.africanfauna.com/images/giraffe.jpg Darwinian Revolution • Darwin set sail on The Beagle discover coastlines of South America and to chart out South American coastlines. • Collected specimens - noticed they differed between various parts of the world. • Origin of new species and adaptation of species to environment closely related processes. • Finches on Galapagos Islands differed in beak sizes according to what they ate. • Darwin wrote The Origin of Species. • Outlined ideas on evolution and natural selection (Darwinism) • 1st major point of ideas - descent with modification - all creatures share common ancestor. http://www.blackwellpublishing.com/ridley/images/evolution.jpg • Organisms developed characteristics to adapt to surroundings. • Closer related species are, more recent their common ancestor. • This evolutionary tree of the elephant family is based on evidence from fossils. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 22.7 • Developed theory of natural selection. • Observations based on ideas: • 1All organisms have potential to have many offspring; something must limit number. http://www.mms.mcn.org/~sneri/computer/baby_animals15.jpg • 2Populations of organisms tend to remain steady in size over time. • 3Environmental resources limited. • Inference #1 - too many offspring produced - struggle to survive occurs - certain number of offspring will survive. http://savinganimals.smugmug.com/keyword/dogs#36007645 • 4No 2 individuals in population alike. • 5Differences are inherited. • Inference #2 – Survival depends on heritable differences. • Inference #3 – Favorable characteristics – survive - more offspring with favorable characteristics. http://evolution.berkeley.edu/evosite/evo101/images/vert_tree.gif • Main points: • 1Natural selection - unequal ability of species to survive and reproduce. • 2Based on ability to interact, adapt to environment. • 3Based on ability for characteristics to be passed. • For example, these related species of insects called mantids have diverse shapes and colors that evolved in different environments. Fig. 22.10 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Thomas Malthus noticed humans produce quicker than resources. • Certain inherited characteristics allow certain members of population to survive such conditions. • Differential reproduction - passing on of favorable traits to offspring. • Traits become more dominant in population over time - evolution. http://static.howstuffworks.com/gif/evolution-skull.jpg • Artificial selection - organisms with favorable traits selected to mate with others like them - increases frequency of traits in population (breeding). http://www.bbc.co.uk/schools/gcsebitesize/img/bidogtree.gif • Darwinian view on life: • 1Diversity comes from descent with modification from ancestral species. • 2Modification - result of natural selection over long period of time. http://www.emc.maricopa.edu/faculty/farabee/biobk/jawevol_3.gif • Population, not individual, evolves. • Natural selection involves changes between individual and environment - ultimately population that evolves. http://evolution.berkeley.edu/evosite/misconceps/images/misconceptions_beavers.gif • Population - group of interbreeding individuals of single species that share common geographic area. • Evolution measures change in relative proportions of heritable variation in population over succession of generations. http://islandfox.org/uploaded_images/babyKrisWillis-730268.jpg • Evolution increase or decrease inherited traits, not individual traits that person may have acquired over lifetime. • Natural selection situational. • Some traits are helpful in one environment; not helpful in other. http://www.biologyreference.com/images/biol_01_img0111.jpg Examples of natural selection • Insects - resistant to insecticides. • Those survived insecticide survived to pass gene on. • Result - immunity to certain pesticides. Fig. 22.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Natural selection favors characteristics in variable population that fit current, local environment. • Drug resistance - evolution has occurred. • Drug-resistant strains evolve rapidly in HIV population, making drug treatment difficult. Other evidence • Evidence of gradual change throughout fossil history. • New species evolve by modifications as populations adapt to new environments. • Similarity in characteristics resulting from common ancestry homology. http://www.plyojump.com/courses/biology/images/homologous.jpg • Anatomical similarities among species - wing of bird, arm of human - different functions, similar anatomy. • Forelimbs of human, cats, whales, bats share same skeletal elements homologous structures. • Study of comparing similar structures - comparative anatomy. • Vestigial organs do not have any importance to current organism, had important functions in ancestors. • Some snakes - have pelvic, leg bones. http://www.answersingenesis.org/home/area/magazines/tj/images/v14n2_vestigial_structures.gif • Darwin studied biogeography - led to evolution. • Species that lived close tended to be more similar than species that lived further away. • Sugar glider, flying squirrel adapted to same mode of life - not closely related. Like a marsupial mammal Like a placental mammal • Islands show strong evidence for evolution - many species of plants and animals that are endemic (found nowhere else in world) Why is it a theory? • Those who dismiss Darwin’s theory unable to separate main parts of theory. • Natural selection well accepted can be tested and proved.