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Transcript
NOTES: CH 16 – Darwin’s Theory of Evolution by Natural Selection / Evidence for Evolution • Vocabulary – Artificial Selection – Natural Selection – Homologous Structures – Analogous Structures – Vestigial Structures How many scientists are involved in developing the theory of evolution? William Bateson Carolus Linneaus George Buffon Charles Lyell Watson and Crick Thomas Robert Malthus Hugo de Vries Ernst Mayr Theodosius Dobzhanky Gregor Mendel Eldredge and Gould John Ray J.B.S. Haldane George Simpson Hardy and Weinberg G. Ledyard Stebbins James Hutton Alfred Russel Wallace` Thomas Huxley Alfred Wagner Jean Baptiste Lamarck What kinds of sciences did these scientists study? • • • • • • • • • • • Biology Paleontology Geology Genetics Botany Naturalists Microbiology Biochemistry Molecular chemistry Ecology Chemistry When did the theory of evolution begin to develop? • Late 1600’s with John Ray – Major contribution was his writings called Historia Plantarum • Rejected the system of dichotomous division where species were classified by a preconceived type of system • Instead, plants were classified by similarities and differences from observation • Coined the term “species” • When did Darwin write Origin of the Species? – 1859 – So, about 200 years after John Ray NOTES: CH 16 – Darwin’s Theory of Evolution by Natural Selection / Evidence for Evolution DEFINITION OF EVOLUTION: ● change over time: the process by which modern organisms have descended from ancient organisms. The Life of Charles Darwin Portrait of Darwin in 1840 (31 years old) (Darwin 65 years old) The Life of Charles Darwin • Born 1809 (England) • Completed college after studying to become a doctor but could not stand sight of blood … • Set sail on 5 year voyage on H.M.S., Beagle in 1831 as the natural historian for expedition. The Life of Charles Darwin • Made extensive drawings and notes on the trip but also collected many species of plants and animals. • Began to OBSERVE that animals were well adapted to their environments, (wondered why were different animals found in areas that appeared to be similar in climate? and some survived while others did not?) • Argentina • Australia • Europe All had grasslands but very different animals The Life of Charles Darwin • He collected fossils. – noticed some looked like living organisms – others looked like nothing he had ever seen before • Were these related to the living (present day) organisms? • Why did some organisms disappear altogether? The Life of Charles Darwin Galapagos Islands Organisms Darwin Observed on the Galapagos • Land Tortoise = different shaped carapace (shell) depending what island they inhabited. • Finches = different shaped beaks depending on environment in which they lived. • he realized that characteristics of many animals and plants varied noticeably among the different islands of the Galapagos. • On the journey home he began to pose the question… – Could animals on the different islands once have been members of the same species? Those Who Influenced Darwin Hutton (Geologist) – Geologic processes operate extremely slowly (take millions of years!) – therefore, the earth is very old Lyell (Geologist) – Scientists must explain past events in terms of processes that they can actually observe • processes that shaped the Earth millions of years ago continue to shape present day Earth • this explained how geological features can be built or torn down over long periods of time. Darwin wondered… • If the earth could change over time, could life change as well? • Also: it must have taken many, many years for life to change the way Darwin had in mind – This would only be possible if the earth was very old… Those Who Influenced Darwin Malthus (Economist) • proposed that war, famine, disease, limits the growth of human populations • if populations continue to grow unchecked, they will run out of resources (food/shelter) 2 IMPORTANT CONCEPTS TO HELP US UNDERSTAND THE PROCESS OF EVOLUTION: Variation & Adaptation VARIATION: differences between individuals in a population Give me an example, PLEASE!! ADAPTATION: inherited characteristic that increases an organism's chances of survival EXAMPLES OF ADAPTATIONS! What are some adaptations this polar bear has? How do they help polar bear’s survive? How are the adaptations of this bear different than those of the polar bear? What are some adaptations of a cactus? What about this desert plant? What helps this kelp crab survive? (It lives on the kelp in the ocean.) What the heck are these? EVIDENCE FOR EVOLUTION 1) Fossils: ● evidence of once-living things (shells, casts, bones, teeth, imprints) ● show a succession of forms through a vast span of time ● progressive changes based on the order they were buried in sedimentary rock few fossils / species many fossils/ species simple organisms complex organisms EVIDENCE FOR EVOLUTION 2) Biogeography and age of the earth: ● distribution of plants & animals 13 species of finches on the 13 Galapagos Islands 57 species of kangaroos… all in Australia! 2) Biogeography and age of the earth: ● Radioactive dating tells us the earth is about 4.6 billion years old ● Rate of motion of tectonic plates 3) Adaptations: Evidence for Evolution ● MIMICRY: one species resembles another ● CAMOUFLAGE: enables species to blend with their surroundings ● PHYSIOLOGICAL: ability to resist disease or drought 4) “Artificial Selection” 4) Applied Genetics ("artificial selection"): ● Darwin noticed that farmers “selected” the best crops, animals – he wondered if there could be a “selective” force in nature ● today we see DDT-resistant insects; antibiotic-resistant bacteria 5) Anatomical Structures: Evidence for Evolution 5) Homologous and Vestigial Structures 5) Homologous Structures = shared common anatomical or biochemical traits ex: " forearm bones” • structures that develop from the same clumps of cells – later develop into structures that have different forms and functions • arms, flippers, & wings look very similar at the beginning of development, but differ as the animal matures – The function differs as well! 5) Vestigial Structures: structures that no longer serve a purpose in an organism ex: wisdom teeth, tailbone, appendix, nictitating membrane, some pythons & boa constrictors have tiny leftover leg bones (and whales!) koala's have a large functioning appendix (eat primarily plant materials) 6) Embryological Development • Similarities of vertebrate organisms in early stages of development • All animal development begins in the same way (from the same ball of cells) – BUT recognizable features for that species develop as the organism grows • 7) Cellular and Molecular Evidence: Cellular Evidence • All organisms are made of cells – consist of membranes filled with water containing genetic material, proteins, lipids, carbohydrates, salts and other substances 7) Cellular and Molecular Evidence Molecular Evidence • the DNA code links all life on Earth to a common ancestor – DNA and RNA = simple four-base code that provides the recipe for all living things • Transfer genetic material from the cell of one living thing to the cell of another – the recipient would follow the new instructions as if they were its own • EX: Roundworms share 25% of their genes with humans. Protein Sequence Similarities! Review—major evidence for evolution • Fossil record • Biogeography and age of the earth (using radioactive dating) • Adaptations • Artificial Selection • Homologous structures and vestigial organs • Embryology • Cellular and Molecular Evidence EVOLUTION: DARWIN vs. LAMARCK LAMARCK’s explanation on evolution ASSUMPTION #1 Law of Use and Disuse: an organism can change certain body parts during its lifetime and pass these changes on. CRITICISM OF THIS ASSUMPTION Implies that an organism can sense its needs and change to meet them. LAMARCK continued… ASSUMPTION #2 CRITICISM OF THIS ASSUMPTION Inheritance of Acquired Characteristics: acquired traits can be passed on to offspring over time the population changes. Suggests that changes in body cells can be inherited / passed down. 2 factors that helped DARWIN formulate his explanation 1) Overproduction of offspring occurs in nature; competition for food, space, mates 2) Artificial selection (selective breeding) Darwin wondered if a similar force existed in nature. Charles Darwin’s Explanation on Evolution (six major ideas of Darwin) Overproduction occurs in nature Not all organisms can survive Variation occurs in all populations Variations are inherited Organisms with favorable variations survive and reproduce Populations as a whole become FIT = evolved! LAMARCK: Individuals can change DARWIN: Evolution acts on populations DARWIN’S THEORY OF NATURAL SELECTION 1. ORGANISMS HAVE MORE OFFSPRING THAN CAN SURVIVE AND… …a herd of giraffes would produce hundreds of descendents over several generations. 2. RANDOM, HERITABLE VARIATION EXISTS AMONG THESE ORGANISMS (EX. MUTATIONS), SO… …by genetic “chance”, some giraffes were born with longer necks. 3. BECAUSE THERE IS A STRUGGLE FOR EXISTENCE (COMPETITION), THEN… …giraffes were competing for food source (vegetation). 4. THE ORGANISMS WITH FAVORABLE VARIATIONS (THE “FITTEST”) SURVIVE AND… …a long neck enabled giraffes to reach an “untapped” food source…tree tops! (short-necked giraffes ran out of food and starved) 5. GENES FOR FAVORABLE FEATURES ARE PASSED TO OFFSPRING THROUGH REPRODUCTION, AND THEREFORE, THE POPULATION EVOLVES!!! The giraffes with longer necks survive and pass their genes (for longer necks) on to their offspring…the process continues, and whole population EVOLVES. AND, if populations are geographically isolated, changes will accumulate to the point of reproductive isolation ( NEW SPECIES!!) EVOLUTIONARY CONCEPTS • Mutations, genetic recombination, crossing over, etc. are “accidents” in the genes of organisms. They do not appear according to any purpose; they just happen. • Mutations cause a large amount of variation among organisms in a population. • There is room on Earth for only a fraction of organisms that are born or hatched. The individuals which happen to have the mutations giving them the best adaptations to the environment will be the ones that survive. EVOLUTIONARY CONCEPTS • The survivors will have their own offspring. The offspring will be subject to their own random mutations. Again, only the most advantageous mutations will result in the survival of the next generation of offspring, and hence be “passed down” to the next generation. • Countless generations of mutations and natural selection result in organisms that have very different structures.