AP Biology – Chapter 22 Evolution – Descent with Modification AP Biology Campbell Chapters 22-24 Science happens within a culture AP Biology Evolution Descent with modification Change in genetic composition of a population from generation to generation Pattern and process AP Biology 1 AP Biology – Chapter 22 The Pattern of Evolution Revealed by data from a range of scientific disciplines Ex: biology, geology, physics, chemistry Data are facts – observations of the natural world The Process of Evolution Consist of the mechanisms that produce the observed pattern of change Natural causes of the natural phenomena we observe AP Biology Before Darwin….. Plato – idealism or essentialism Viewed as 2 coexisting worlds: Ideal, eternal, real world Illusionary, imperfect world perceived by our senses (the world we live in) Allows for NO evolution Aristotle (384-322 BC) – viewed species as fixed Scala Naturae – “Scale of Nature” - Classification of Species Thought species could be arranged on a scale of increasing complexity simple to complex Allows for no evolution since all organisms are fixed AP Biology in their position Before Darwin….. Linnaeus (1707-1778) – founder of taxonomy classified life’s diversity “for the greater glory of God.” Developed a binomial nomenclature (Homo sapiens) Grouped similar species together into general categories (species, genus, family, etc.) figure 1.14 Allows for NO evolution since clustering of species did NOT imply evolutionary relationships AP Biology 2 AP Biology – Chapter 22 Before Darwin….. Cuvier (1769-1832) Studied fossils (paleontology) – remains or traces of organisms from the past Noticed fossil differences in each layer (strata) of rock as he dug deeper Catastrophism – his view of the earth – changes in species found in each strata were due to major catastrophes or extinctions Allows for NO evolution AP Biology Before Darwin…. Hutton and Lyell Uniformitatianism – geological processes are so uniform and gradual that their rates and effects must balance out over time Mechanisms of change are constant over time Proposed that the same geological processes operating today as in the past, and at the same rate Their ideas strongly influenced Darwin’s thinking Darwin agreed that if geological change results from AP Biology slow, continuous actions rather than sudden events, then the earth must be older than originally thought Idea of gradual change – slow accumulation of small changes could ultimately produce profound changes Age of the earth was important for Darwin – unless Earth was very old – he could not envision how their would be time for evolution to occur Before Darwin….. Lamark (1744-1829) Developed a comprehensive theory as to HOW life evolved over time 1. Use and Disuse – parts of the body that are used become larger/stronger and those that are not used will deteriorate 2. Inheritance of acquired characteristics – modifications that an organism acquires during its lifetime can be passed on to its offspring AP Biology 3 AP Biology – Chapter 22 Then along comes Darwin… 1831-1836 AP Biology 22 years old! Charles Darwin (1809-1882) Galapagos Islands (540 miles west of South America) Fascinated by the unusual organisms he found there Finches and fauna unique to Island but resemble mainland Geographical distribution of species may lead to development of new species as each population adapts to local conditions AP Biology Charles Darwin (1809-1882) Adaptations – characteristics of organisms that enhance their survival and reproduction in specific environments The finches’ various beaks and behaviors are adapted to the specific foods available on their home islands Natural Selection Darwin’s explanation of how adaptations arise centered on natural selection A process in which individuals with certain inherited traits leave more offspring than individuals with other traits AP Biology 4 AP Biology – Chapter 22 Then along comes Darwin… & those dang finches! Descendant species Warbler finch Cactus finch Ancestral Woodpecker finch species Sharp-beaked finch ef Cactus eater Insect eaters Seed eaters Vegetarian tree finch AP Biology es ch fin Tr e Small ground finch r Warble finch nd ou Gr Large insectivorous tree finch in ch es Small insectivorous tree finch Medium ground finch Large ground finch Bud eater Correlation of species to food source Rapid speciation: new species filling niches, because they inherited successful adaptations. AP Biology radiation Adaptive Beak variation in Galapagos finches (a) Cactus eater. The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. AP Biology (c) Seed eater. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. (b) Insect eater. The green warbler finch (Certhidea olivacea) uses its narrow, pointed beak to grasp insects. 5 AP Biology – Chapter 22 “The Origin of Species” Darwin developed 2 main concepts: 1. Descent with modification – all organisms related through descent from unknown prototype that lived in the past Diverse adaptations accumulated as descendants from this common ancestor moved into various habitats over millions of years Adaptation – inherited variation that increases an organisms likelihood of surviving to reproduce AP Biology “The Origin of Species” Darwin developed 2 main concepts: 2. Natural Selection – proposed mechanism to explain the observable patterns of evolution Darwin described 4 observations of nature from which he drew 2 inferences: Observation 1 – Members of a population often vary greatly in their traits (much of this variation is inherited) Observation 2 – Traits are inherited from parents to offspring Observation 3 – All species are capable of producing more offspring than their environment can support (all species have the reproduction potential to increase their population size exponentially if all individuals born reproduce) Observation 4 – Owing to lack of food or to other resources, many of these offspring do not survive (natural resources are limited) AP Biology “The Origin of Species” Inference 1 – individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals More individuals are produced than the environment can support leading to a struggle for existence with only a portion of individuals surviving Not everyone has the same success of reproducing Those individuals whose inherited variations are better suited to their environment are more likely to survive and reproduce (passing on alleles to offspring) Survival of the fittest – is not random but in based on the environment Inference 2 – This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations. Gradual change in a population. AP Biology 6 AP Biology – Chapter 22 Natural Selection Variations arise by chance but natural selection is not random since environmental factions set criteria for reproductive success Natural selection is possible due to variations and over production Individuals do NOT evolve – Populations evolve Natural Selection can amplify or diminish only heritable traits Environmental factors vary from place to place over time – the traits that are favored depend on the environmental context AP Biology Signs of Evolution 1. Direct observations of Evolutionary Change Direct observation of natural selection leading to adaptive evolution in many studies a. Research on wild guppy populations – impact of predators on guppies – guppies have variable color patterns Color patterns controlled by genes that in the wild, are only expressed by male guppies Female guppies are attricated to male guppies with bright colors However bright colored guppies also attract predators Observed that the color patterns of male guppies corresponded with intensity of predation Hypothesized that intense predation caused natural selection to favor drab colors in male guppies AP Biology Signs of Evolution b. Evolution of Drug-Resistant HIV Evolution of drug resistant pathogens. Particular problem with bacteria and viruses that reproduce rapidly - individuals resistant to a particular drug can increase rapidly HIV – numerous drugs to combat HIV, but using these medications selects for viruses resistant to the drugs Natural selection is a process of editing rather than a creative mechanism A drug does not create resistant pathogens, it selects for resistant individuals that were already present in the population Natural selection depends on time and place – favors characteristics that provide advantage in the current, local environment AP Biology 7 AP Biology – Chapter 22 Natural selection in action MRSA AP Biology Signs of Evolution 2. Fossil Record Sedimentary rock layers Shows that past organisms differed from living organisms Shows that many species have become extinct Shows that species have evolved over time Documents the origins of major new groups of organisms AP Biology AP Biology Why should extinct species & living species be found on the same continent? 8 AP Biology – Chapter 22 1. What are the lines of evidence that support Darwin’s ideas? Fossil record 550 500 Body size (kg) 450 Equus 400 350 300 250 Merychippus 200 Mesohippus Hyracotherium 150 100 50 Nannippus 60 AP Biology 55 50 45 40 35 30 25 20 15 10 5 0 Millions of years ago Signs of Evolution 3. Homology Characteristics present in an ancestral organism are altered (by natural selection) in its decendants over time exposed to different environemntal conditions Realted species can have characterisits with a similarity even though they have different functions Similarity resulting from common ancestry Homologous Structures Ex: Forelimbs of all mammals, including humans, cats, whales, bats show same arrangement of bones Similar structure but very different function AP Biology 3. What are the lines of evidence that support Darwin’s ideas? Anatomical evidence AP Biology 9 AP Biology – Chapter 22 Homologous structures spines leaves succulent leaves Don’t forget our plant friends! AP Biology needles tendrils colored leaves Homology Analogous Structures Similar functions, NO common ancestor Ex: wings of a bird vs. butterfly wings Vestigial Structures Remnants of features that served important functions in the organism’s ancestors No current use to the organisms (had a function in the past) Ex: appendix (in humans) Molecular Biology Similarities among organisms at the molecular level DNA, RNA AP Biology Analogous structures Convergent Don’t be fooled byevolution their looks! Those & tails Does fins this mean & sleek they bodies have a are recent common ancestor? analogous structures ! Solving a similar problem with a similar solution AP Biology 10 AP Biology – Chapter 22 Vestigial organs These are Why would whales remnants of have pelvis & leg bones structures that were if they were always functional in sea creatures? ancestral species AP Biology Evolutionary Tree Representation of the pattern of descent from common ancestors and the resulting homology Diagram that reflects evolutionary relationships among groups of organisms Figure 22.19 in your textbook AP Biology Building “family” trees AP Biology 11 AP Biology – Chapter 22 Convergent Evolution The independent evolution of similar features in different lineages Natural selection affects independently evolving species in similar environments in similar ways Evolved independently from different ancestors, yet they have adapted to similar environments in similar ways Resemblance is said to be analogous NOT homologous Species share features but NO common ancestor AP Biology Convergent evolution These animals look very similar but does that mean they have a recent common ancestor? marsupial mammals What is this evidence of? placental mammals AP Biology Signs of Evolution 4. Biogeography Geographical distribution of species Influenced by many factors: Continental drift – slow movement of Earth’s continents over time About 250 million years ago these movements united all of Earth’s landmasses into a single large continent, called Pangea 200 million years ago Pangea began to break about By 20 million years ago, the continents we know today were within a few hundred kilometers of their current locations Use continental drift - Can predict where fossils of different groups of organisms might be found AP Biology 12 AP Biology – Chapter 22 Biogeography Can also use our understanding of evolution to explain biogehgraphic data Endemic – islands generally have many species of plants and animals that are endemic – they are found nowhere else in the world As Darwin explained in his book – most island species are closely related to species found on the mainland AP Biology Conclusion…. What is theoretical about Darwin’s view of life? Darwin’s theory is supported by a large amount of evidence Effects of natural selection can be seen and tested in nature The word theory is much more than a hypothesis Darwin originally thought evolution was a slow process Natural selection is not the only mechanism responsible for evolution AP Biology “There is grandeur in this view of life….[in which] endless forms most beautiful and most wonderful have been, and are being, evolved.” Charles Darwin The Origin of Species AP Biology Campbell Chapters 22-24 13 AP Biology – Chapter 22 Review/Wrap Up Slides AP Biology Big Idea 1 The process of evolution drives the diversity and unity of life cells DNA AP Biology What are the 4 lines of evidence that support Darwin’s ideas?… Human Macaque Dog Bird 8 32 45 Frog Lamprey 67 125 0 10 20 30 40 50 60 70 80 90 100 110 120 AP Biology 14 AP Biology – Chapter 22 Evolution of birds Archaeopteryx lived about 150 mya links reptiles & birds Smithsonian Museum, AP Biology Washington, DC Evolution of land animals 2006 Fossil Discovery of Early Tetrapod “Tiktaalik” “missing link” from sea to land animals from swimming (0 legs) to walking (4 legs) AP Biology Evolution of marine mammals But then, they actually found my fossil! At first, I was just a Biology joke! AP Land Mammal ? ? e re th re a Whe sitional tran sils? fos ? ? Aquatic Mammal 15 AP Biology – Chapter 22 2. What are the lines of evidence that support Darwin’s ideas? Terminal bud Lateral buds Cabbage Artificial selection Brussels sprouts Leaves Flower cluster Kale Cauliflower Stem Flower and stems Broccoli Wild mustard Kohlrabi AP Biology Selective breeding the raw genetic material (variation) is hidden there AP Biology Parallel/convergent evolution Niche Burrower Placental Mammals Mole Anteater Anteater Nocturnal insectivore Mouse Climber Australian Marsupials Convergent evolution of analogous Marsupial mole burrowing characteristics Numbat Marsupial mouse Spotted cuscus Lemur Glider Stalking predator AP Biology Chasing predator Flying squirrel Sugar glider Ocelot Tasmanian cat Wolf Tasmanian “wolf” 16 AP Biology – Chapter 22 4. What are the lines of evidence that support Darwin’s ideas? Human Macaque Dog Bird Frog Lamprey The sequence in Why&compare DNA proteins is a molecular DNA & proteins across species? record of evolutionary relationships. Comparative hemoglobin structure 8 32 45 67 125 Why compare these genes? 0 10 20 30 40 50 60 70 80 90 100 110 120 compare common genes Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans C (respiration) cytochrome AP Biology hemoglobin (gas exchange) "Nothing in biology makes sense except in the light of evolution." -- Theodosius Dobzhansky March 1973 Geneticist, Columbia University (1900-1975) AP Biology Evolution is "so overwhelmingly established that it has become irrational to call it a theory." -- Ernst Mayr What Evolution Is 2001 Professor Emeritus, Evolutionary Biology Harvard University (1904-2005) AP Biology 17