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Chapter 15 Evolution Section 1: Darwin’s Theory of Natural Selection Section 2: Evidence of Evolution Section 3: Shaping Evolutionary Theory Click on a lesson name to select. • Evolution of the Cell phone Click on a lesson name to select. Chapter 15 Evolution 15.1 Darwin’s Theory of Natural Selection Darwin on the HMS Beagle Darwin’s role on the ship was as naturalist and companion to the captain. His job was to collect biological and geological specimens during the ship’s travel. Who was Charles Darwin • Charles Darwin was a major pioneer in Biology! Chapter 15 Evolution 15.1 Darwin’s Theory of Natural Selection The Galápagos Islands Darwin began to collect mockingbirds, finches, and other animals on the four islands. He noticed that the different islands seemed to have their own, slightly different varieties of animals. Chapter 15 Evolution 15.1 Darwin’s Theory of Natural Selection Almost every specimen that Darwin had collected on the islands was new to European scientists. Populations from the mainland changed after reaching the Galápagos. Chapter 15 Evolution 15.1 Darwin’s Theory of Natural Selection Darwin Continued His Studies Darwin hypothesized that new species could appear gradually through small changes in ancestral species. Darwin inferred that if humans could change species by artificial selection (the process of selective breeding of organisms to produce offspring with desired characteristics ), then perhaps the same process could work in nature. Video • NOVA – The eye 3 examples of Natural Selection • Variation in Nature – Darwin pointed out that in Nature inherited variation was common • Struggle for Existence – Darwin realized that high birth rates and a shortage of life’s basic needs forced organisms into a constant struggle for existence • Natural Selection – Darwin proposed that generation after generation, the struggle for existence selects the fittest individuals to survive in nature – Video Chapter 15 Evolution 15.1 Darwin’s Theory of Natural Selection Natural Selection Individuals in a population show variations. Variations can be inherited. Organisms have more offspring than can survive on available resources. Variations that increase reproductive success will have a greater chance of being passed on. Bird of paradise Chapter 15 Evolution 15.1 Darwin’s Theory of Natural Selection The Origin of Species Darwin published On the Origin of Species by Means of Natural Selection in 1859. Darwin’s theory of natural selection is not synonymous with evolution. It is a means of explaining how evolution works. • Evolution of Dance Charles Lyell • Darwin studied Lyell’s work while on the Beagle • Lyell put forth arguments that the Earth was older than people originally thought • Today's accepted age of the Earth of 4.55 billion years was determined by C.C. Patterson using Uranium-Lead dating on fragments of the Canyon Diablo meteorite and published in 1956 KT Boundary Lyell – He argued that the modern world must have been shaped by the same geological forces that can be seen in action today • EX: erosion in river valleys, volcanic eruptions, earthquakes – If Earth can change over time, why not the life on Earth as well? Chapter 15 Evolution 15.2 Evidence of Evolution Support for Evolution The fossil record Fossils provide a record of species that lived long ago. Fossils show that ancient species share similarities with species that now live on Earth. Glyptodont Armadillo • Tiktaalik – Intermediate Species? • Fossil Finding • LETS FIND SOME FOSSILS Fossils • Sometimes Geologic processes such as earthquakes etc. can thrust up fossils that formed under ancient rivers, oceans and lakes so that they reside on dry land OR – These bodies of water can dry up over time so that fossils are accessible • Petoskey stones Fossils • Layers of rock from 3 billion years ago often contained fossils • They are commonly found in sedimentary rocks – Form when silt, sand or clay builds up in the bottom of a river, lake or ocean – As sediments pile up, pressure on the lowers layer turn them into rocks such as sandstone or limestone • Layers like a cake Relative Dating • Each layer has it’s own time period in history – The hard pieces such as teeth and bone are preserved • Each fossil appears at one time and disappears at another – Scientists can distinguish groups of fossils in specific rock layers – These rock layers can be arranged in Chronological (Time) order to compare the ages of the fossils found in one layer to another layer • RELATIVE DATING-not exact Absolute/Radioactive Dating • How do scientists calculate the age of the Earth? – 100 Years ago Scientists discovered that certain elements are radioactive (they break down from an unstable form to a more stable form over time. • Measured in a unit called Half-Life • Act as a series of clocks by which they can measure the age of rocks – After 1 million years, ½ of a sample may be still radioactive – After 2 million years, ¼ of the same sample = radioactive – After 3 million years, 1/8 ……..and so on! Absolute/Radioactive Dating • Carbon-14 is a Radioactive element we take in from the atmosphere • When an organism dies-stops taking in C-14 – Half life=5770 years • At the end of 5770 years, half of C-14 is converted into Nitrogen-14=more stable – By comparing the Carbon-14 to the Nitrogen-14 scientists can estimate the age of the fossil • Absolute Dating • This is how the Geologic Time Scale came about!! Cambrian Explosion Chapter 15 Evolution 15.2 Evidence of Evolution Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors. Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms. Anatomically similar structures inherited from a common ancestor are called homologous structures. They have similar structures and different functions (bat wing and human hand) Reptile or Bird? • Archaeopteryx • The name Archaeopteryx means ‘ancient wing’, and this animal may be the most famous fossil find of all time. Archaeopteryx was thought to have been the first known bird until the discovery of Protoavis in 1986. It was larger than a crow and had sharp teeth, a long bony tail and three clawed fingers. Although Archaeopteryx could probably fly a few feet, it was not capable of flight like a true bird. Archaeopteryx lived in the Late Jurassic period, and specimens have been found in limestone deposits in Bavaria, West Germany. The first specimen was discovered in 1861, and since then six skeletons have been found. Legs on a snake? Ajolote Mexican Mole Lizard Archaeopteryx Homologous Structures Chapter 15 Evolution 15.2 Evidence of Evolution Vestigial Structures Structures that are the reduced forms of functional structures in other organisms. Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost. (tail bone, wisdom teeth, baby toe?!) Chapter 15 Evolution 15.2 Evidence of Evolution Analogous structures can be used for the same purpose and can be superficially similar in construction, but are not inherited from a common ancestor. Show that functionally similar features can evolve independently in similar environments Chapter 15 Evolution 15.2 Evidence of Evolution Comparative Embryology Vertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in the adult forms. Review What type of animal is this? Homologous or analogous? Chapter 15 Evolution 15.2 Evidence of Evolution Comparative Biochemistry Common ancestry can be seen in the complex metabolic molecules that many different organisms share. Chapter 15 Evolution 15.2 Evidence of Evolution Comparisons of the similarities in these molecules across species reflect evolutionary patterns seen in comparative anatomy and in the fossil record. Organisms with closely related morphological features have more closely related molecular features. So in Summation….. • Evolution is based on scientific discovery and facts! – Fossils – Comparative Anatomy – Biochemistry – Embryology! • Stop 3/19 Gene Pool • Sum of all Genes in a population – The population evolves not the individual! • A population in which the frequency of alleles (form of a gene) does not change from generation to generation it is said to be in: – GENETIC EQUILIBRIUM Common Descent • Darwin further argued that just as each living organism is the descendant of its parents and grandparents • Each living species has descended from other living species over time – COMMON DESCENT Altering the Genetic Equilibrium • Genetic Drift: alteration of allelic frequencies by chance processes – Amish population – its possible that in a small population, a larger population will inherit recessive alleles for shorter arms or legs, or dominant alleles for extra fingers and toes Altering the Genetic Equilibrium • Reproductive Isolation: preventing formally interbreeding organisms from producing fertile offspring – Tree Frogs – If one group evolves the behavior of mating in the fall while another mates in the spring….they will be reproductively isolated Species diversify when introduced into new Environments! • The process of Evolution of an ancestral species into an array of species that occupy different niches is called – ADAPTIVE RADIATION – Just like the Finches! Adaptive Radiation is an Example of Divergent Evolution • Divergent Evolution – The pattern of evolution in which species that once were all similar to the ancestral species become more and more distinct • Species begin to adapt to different environmental conditions and change according to the pressures of Natural Selection • Ring Species Counterpart to Divergent Evolution • Convergent Evolution!!!! • The pattern of evolution in which distantly related organisms evolve similar traits! • EX: Fins! EVIDENCE OF EVOLUTION • FOSSILS • ANATOMY – HOMOLOGOUS STRUCTURES – ANALOGOUS STRUCTURES – VESTIGIAL STRUCTURE – EMBRYOS http://evolution.berkeley.edu/evolibrary/home.php WHAT IS ANOTHER EXAMPLE OF VESTIGIAL STRUCTURES? OTHER EVIDENCE OF EVOLUTION • FOSSILS • ANATOMY – HOMOLOGOUS STRUCTURES – ANALOGOUS STRUCTURES http://evolution.berkeley.edu/evolibrary/home.php OTHER EVIDENCE OF EVOLUTION • FOSSILS • ANATOMY – HOMOLOGOUS STRUCTURES http://evolution.berkeley.edu/evolibrary/home.php OTHER EVIDENCE OF EVOLUTION • FOSSILS • ANATOMY – HOMOLOGOUS STRUCTURES – ANALOGOUS STRUCTURES – VESTIGIAL STRUCTURE – EMBRYOS • BIOCHEMISTRY – WHAT 2 THINGS? http://evolution.berkeley.edu/evolibrary/home.php EVIDENCE OF EVOLUTION • STRUCTURAL ADAPTATIONS – MIMICRY – CAMOUFLAGE – Chameleon http://evolution.berkeley.edu/evolibrary/home.php http://science.howstuffworks.com/animal-camouflage2.htm Chapter 15 Evolution 15.2 Evidence of Evolution Types of Adaptation An adaptation is a trait shaped by natural selection that increases an organism’s reproductive success. Fitness is a measure of the relative contribution an individual trait makes to the next generation. Chapter 15 Evolution 15.2 Evidence of Evolution Mimicry One species evolves to resemble another species. Western coral snake California kingsnake Chapter 15 Evolution 15.2 Evidence of Evolution Camouflage Allows organisms to become almost invisible to predators Leafy sea dragon Camouflage Video • Video • The secret behind (octopuses') color capability is special skin cells called chromatophores. – Each chromatophore consists of three bags of pigment. – By squeezing or expanding the bags, octopuses can change the color displayed by each cell, allowing millions of subtle combinations. – Since each cell is controlled separately, they can create remarkably sharp displays. In addition, reflective coatings under the cells help enhance the effect. – Taken by Jerry Michalski Cuttlefish Camo New York Times • Video Decorator Crab Decorator Crab • Nat Geo Video – Decorator crab Camouflage – blending in How has predation influenced evolution? Adaptations to avoid being eaten: spines (cactii, porcupines) hard shells (clams, turtles) toxins (milkweeds, some newts) bad taste (monarch butterflies) camouflage aposematic colors mimicry Aposematic colors – warning Is he crazy??? Mimicry – look like something that is dangerous or tastes bad Mimicry – look like something that is dangerous or tastes bad Mullerian mimicry – convergence of several unpalatable species Mimicry – look like something that is dangerous or tastes bad Batesian mimicry – palatable species mimics an unpalatable species model mimics mimic model Chapter 15 Evolution 15.2 Evidence of Evolution Consequences of Adaptations Some features of an organism might be consequences of other evolved characteristics. They do not increase reproductive success. Features likely arose as an unavoidable consequence of prior evolutionary change.