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Chapter 15. Natural Selection an & The Evidence for Evolution The theory & Supporting Evidence Chapter 15: Learning Objectives Be able to summarize Darwin’s Theory of Evolution Be able to explain how Structural Adaptations relate to natural selection and use examples. How do mimicry and camouflage help species survive? Be able to explain how Physiological Adaptations relate to natural selection and use examples. Distinguish among the types of evidence for evolution; be able to explain how these demonstrate evolutionary relationships. Distinguish between the ways that Natural Selection acts on variations within populations. Fossils, Anatomy, Embryology, Biochemistry Be able to distinguish between Homologous, Analagous and Vestigal Structures How do vertebrate embryos indicate common ancestry? Stabilizing Selection, Directional Selection, Disruptive Selection Be able to define Species and the basis for speciation. How do geographic barriers contribute to speciation? Be able to describe the two theories on the Rate of Speciation, and how they differ; similar. Be able to describe Adaptive radiation and Convergent Evolution Evolution videos Evolution Videos for Students Evolving Ideas.mht (6 evolution video clips) Assignment: Due Monday, April 7th Read Chapter 15, and answer do the following. May (encouraged to) use other sources as well. Be prepared to explain your work in class. Directions: Prepare a booklet ( may use a foldable style such as we used for Biomes) which contains the following: Description of Darwin’s Theory Of Evolution and the process of Natural Selection. List the steps involved in the process of Natural Selection and new species formation (see Fig. 15.2) Define, describe, illustrate the following terms : Homologous Structures Analagous Structures ( 1 plant, 1 animal) Vestigal Structures Geographic Isolation –associated with Speciation ( be sure to include …) *Definition of term *Pictures (2 for each—hand drawn or copied and colored) to illustrate the term. *Explanation of why your pictures demonstrate the terms. EVOLUTION Evolution: Heritable change in a species over time. Theories of Evolutionattempt to explain diversity of life on earth Prior to 1800’s: : Creationism Beginning around 1800:: Scientists attempt to come to terms with growing fossil evidence. 1. De Newer Theories of Evolution Buffon(1707-1788): Life and Earth have a history: Life not fixed since Creation.(very radical). Life evolves. Vestigal structures. 2.George S. Cuvier ( 1769-1832): Theory of Catastrophism: Species were fixed & unchanging. Mass extinctions ; other species migrate to fill in open niche. Jean Lamarck (1744-1829): Life evolves Change through use and disuse. Evolution due to inheritance of acquired characteristics. 3. . 4. Charles Darwin (1809-1882): Life evolves. Species change over time by way of Natural Selection ***Charles Darwin*** Left Med.School; Degree in Theology; Avid interest in nature HMS Beagle to South America & Galapagos Islands- 5 year charting voyage- (1831-1836) Ship’s Naturalist- collect & catalog flora & fauna His observations profoundly change his beliefs Voyage of the H.M.S. Beagle- Charles Darwin 1859 wrote The Origin Of Species by Means of Natural SelectionControversial: He suggested: Apes apes and humans have common ancestry. Species change New Species Presented evidence that evolution occurred Proposed mechanism for evolution—Natural Selection Darwin’s Observations Provided The Evidence and Mechanism for Evolution GALAPAGOS TOTOISES Species unique to the islands, but similar to those observed on the s. American mainland. Marine Iguanas-nowhere else on Earth-swim, cling to rocks eating moss Figure 22.1 Blue-footed boobies-adaptations of other kinds—attract mates Galápagos Finches Insect eaters Insect eaters Berry eater Seed eaters Cactus eaters Beak shape varies with diet His Finch Observations 1.Found on all islands-but slight variances between them. Different beaks. 2. Similar to those on South America mainland. Explaining his observations 1. A few organisms migrated From S. America Populated all 13 islands 2. Variations existed among them. 3.Individuals with useful variations passed these along to the next generation. 4. Over time offspring with certain variations make up most of the population Conditions varied island to island, so finches varied by habitat. 5.Many new species formed from these original ancestors. The process of Natural Selection—Steps Darwin proposes. 1. Organisms produce more ________than can survive 2. Competition/________ for Existence-compete for food, living space; 3. Only some can ______ and reproduce. 4. Those with useful _________ survive in their environment, pass those traits on to _____________. 5. Over time, their traits become more __________ in the population. Evolution video Evolution Videos for Students Evolving Ideas.mht (hummingbird evolution) The Mechanism: How evolution happens… Natural selection : Organisms with _______ (Adaptations) well suited to an _________ are more likely to survive and produce more offspring than organisms without these favorable traits. Only the fittest will survive!!!--- To Summarize Darwin Species change over time and give rise to new species through the process of natural selection (survival of the ___________). ADAPTATIONS-evidence for evolution. . Darwin clearly understood a fundamental principle of evolution—that ____________, not individuals, evolve and become adapted to the environments in which they live. The term “adaptation” has _____ meanings in evolutionary biology. The first meaning refers to the processes by which adaptive traits are acquired. The second meaning refers to the traits that enhance the survival and reproductive success of their bearers. Adaptations: Structural or Physiological Adaptations : any variation that aids an organisms chances for ____________ in its ________________. Arise over time-many ___________. Kinds of Adaptations 1. ________-develop over millions of years 2. ____________-can occur much more rapidly. 1. Structural Adaptations 1. Defense: some defense mechanisms claws, teeth 2. Protective : a) Mimicry-one organism _____________ another b) Camouflage-__________ into the surroundings c) Warning coloration Coloration Conspicuous colors -- warn off predators. poison arrow frogs Mimicry Look alikes Hawk moth larva Snake Mimicry Cuckoo Bee Yellow Jacket mimicry Camouflage A ________ defense where the prey is camouflaged against its environment. peacocks evol video.htm 2. Physiological Adaptations Changes in an organism’s _______________ processes. These can develop rapidly Develop by natural selection Examples: Bacteria-resistance to _______________ Weeds—resistance to herbicides Insects-resistance to ________________ Other evidence for EvolutionMost evidence for evolution is ___________. Fossils Comparative Anatomy Comparative Development Comparative Biochemistry 1. FOSSILS Can help to demonstrate evolutionary path Sinornithosaurus Feathered Dinosaur: Missing Link between Birds and dinosaurs Anatomical Structures Homologous Structures 2. Homologous Structures Structural features that are similar in arrangement, in function or both due to_______ _________ For example: whale forelimb, crockodile forelimb, bird wing; Homologous Structures . VESTIGAL STRUCTURES—A body structure that no longer serves its original purpose; remnants of evolutionary past-whale’s pelvis bone . Vestigial Structures Why do dogs have tiny, functionless toes on their feet (dewclaws)? Ancestral dogs had five toes on each foot As they evolved they became toe-walkers with only four toes on the ground Big toes and thumbs were lost or reduced to their present state Remnants of Toes in Horses Normally a horse’s back foot has only one functional toe, the third Splints are small remnants of toes 2 and 4 that remain as vestiges More vestigal structures Vestigal structures 'Whale Evolution' by PBS RichardDawkins_net.mht Analogous Structures Similar in function, but not structure. Why?? --do not have common ancestor (wings of bats and wings of insects) Analogies: for example, plant adaptations Adapted to similar _________pressures. The Process is called ____________evolution. Analogous Structures example: Embryology Embryo: earliest stages of ________ and ________ of both plants and animals. All vertebrate embryos start out very similarly Pharyngeal ___________ Postanal _________ Organisms evolve by adding stages to their embryonic development, DEVELOPMENTAL PATTERNS , Comparative Biochemistry Compare ______ ______ sequence Closely related species will show more similarities in the _____ ______ sequence that makes up the protein. Example: cytochrome c (table 15.2) Identical amino acids in chimpanzee protein Chicken protein differs by 18 amino acids Yeast protein differs by 56 Despite its diet and its opposable thumb, the Giant . Panda is a bear; and the Lesser Panda is closer to raccoons of N. America The Panda’s Thumb,Is it a bear? Panda web pandafix Other Panda Video.mht RedPandaClipFilm clip - Red panda (subspecies styani) feeding on bamboo, using modified wrist bone as sixth digit Red panda ssp_ - Ailurus fulgens styani ARKive.mht .Giant Panda 15.2 Mechanisms of Evolution Gene Pool: all of the ________ of the population’s genes pooled together. Allelic Frequency: Genetic Equilibrium: Natural Selection acts on Variation: Genetic Variation Occurs in individuals in populations of all species Frequency can change within a population 3 Modes of Selection Directional Selection: Favors _____ phenotypic extreme. Can lead to rapid evolution. Disruptive Selection: Favors _____phenotypic extremes. Stabilizing Selection: Favors the ______phenotype; overall reducing variation. MODES OF SELECTION DIRECTIONAL SELECTION-only one selective force on an allele Unopposed selection. This moves the frequency of one allele in ONE DIRECTION. In the US, these are fewer S.C. mutant alleles than in Africa Where malaria is a problem, having one sickle cell allele does not increase life expectance. 3.Different Types of Natural Selection What can change the frequency? Mutation:_________________ Genetic Drift : ______________ Gene _________ (from immigration or emigration) 3. In Disruptive Selection Individuals at both ________ of the phenotypic range are ____________ over intermediate phenotypes. Fig. 23.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Species Individuals that in nature interbreed and produce _________ ___________. Physical Barriers Geographic Isolation Whenever a ____________barrier divides a population. May cause reproductive isolation Reproductive Isolation Occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring. Due to Different habitats Different behaviors Different mating times The Debate over the Rate of Evolution: Rate of Speciation/Evolution 1.GRADUALISM: Darwin: Evolution occurs at a slow, steady rate. Differences accumulate slowly over a long period of time 2. PUNCTUATED EQUILIBRIUM: Evolution occurs at an irregular rate— long steady periods of little or no change, interrupted by short periods of rapid evolution Convergent Evolution Convergent evolution: unrelated organisms that have similar traits due to adaptation to similar environmental pressures 1. Some organisms appear suddenly in the fossil record. Few transitional forms found. 2. Other show gradual change. The debate is about the rate and regularity of evolution— not about whether evolution occurs.