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Evolution DARWIN’S THEORY OF EVOLUTION • THE PUZZLE OF LIFE’S DIVERSITY • BIOLOGICAL DIVERSITY – variety of living things. – – – How did all these different organisms arise? How are they related? What scientific explanation can account for the diversity of life? • A. Scientific facts, observations, and hypothesis known as evolution theory • EVOLUTION – change over time, modern • • • • organisms have descended from ancient organisms THEORY – well supported explanation of phenomena that have occurred in the natural world Evolution: Videos for Students: Evolving Ideas Evolution: Isn't Evolution Just a Theory? Video 1 BRAIN TEASER *HAVE STUDENTS NAME DIFFERENT ANIMALS • *ASK: WHAT DIFFERENT WAYS DO THESE ANIMALS USE TO MOVE ABOUT? • *WHAT TRAITS DOES EACH ANIMAL HAVE THAT HELP IT MOVE ABOUT AS IT DOES? • OBSERVING VARIATION SUCH AS THIS WAS INSTRUMENTAL IN DARWIN’S DEVELOPING HIS THEORY OF EVOLUTION VOYAGE OF THE BEAGLE • - voyage around the world – Darwin would collect plant and animal specimens at each port – Study and record information DARWIN’S OBSERVATIONS Evolution #2: Who was Charles Darwin? - YouTube – In 1 day in the Brazilian forest Darwin collected 68 different beetle species – Patterns of diversity • Plants and animals seemed remarkably well suited to whatever environment they inhabited – WHY WERE NO RABBITS IN AUSTRALIA DESPITE THE PRESENCE OF HABITATS THAT SEEMED PERFECT FOR THEM? – WHY WERE THERE NO KANGAROOS IN ENGLAND? Living organisms and fossils Evolution Primer #3 How Do We Know Evolution Happens YouTube • Fossils – preserved remains of ancient organisms – WHY HAD SO MANY OF THESE SPECIES DISAPPEARED? – HOW WERE THEY RELATED TO LIVING SPECIES? The methods are all based on radioactive decay: • Certain naturally occurring elements are radioactive, and they decay, or break down, at predictable rates. • Chemists measure the half-life of such elements, i.e., the time it takes for half of the radioactive parent element to break down to the stable daughter element. Sometimes, one isotope, or naturally occurring form, of an element decays into another, more stable form of the same element. • By comparing the proportions of parent to daughter element in a rock sample, and knowing the half-life, the age can be calculated. • Older fossils cannot be dated by carbon-14 methods and require radiometric dating.Scientists can use different chemicals for absolute dating: • The best-known absolute dating technique is carbon-14 dating, which archaeologists prefer to use. However, the half-life of carbon-14 is only 5730 years, so the method cannot be used for materials older than about 70,000 years. • Radiometric dating involves the use of isotope series, such as rubidium/strontium, thorium/lead, potassium/argon, argon/argon, or uranium/lead, all of which have very long half-lives, ranging from 0.7 to 48.6 billion years. Subtle differences in the relative proportions of the two isotopes can give good dates for rocks of any age. Galapagos Island • Different islands, close together, very different climates – Hot dry barren WHAT TRAITS DO YOU THINK AN ANIMAL MIGHT NEED TO SURVIVE ON A HOT DRY ROCKY ISLAND? Conserve water, protection from sun, make use of scarce resources – Sparse vegetation – Rainfall, different assortment of plants and animals – Rich vegetation for tortoise to reach WHAT TRAITS DO YOU THINK AN ANIMAL MIGHT NEED TO SURVIVE ON A RICH VEGETATED ISLAND? Move in trees, dim, damp conditions – Tortoises varied from island to island Pinta Pinta Island Marchena Tower Intermediate shell Fernandina James Santa Cruz Isabela Santa Fe Hood Island Floreana Isabela Island Dome-shaped shell Hood Saddle-backed shell The journey home • After returning Darwin began to wonder if animals living on different islands had once been members of the same species? – Would have to have been an original species Questions • 1. How did Charles Darwin change our view of the living world? • 2. How did tortoises and birds differ among the islands of the Galapagos? • 3. What is evolution? Why is evolution referred to as a theory? • 4. What is a fossil? • 5. Darwin found fossils of many organisms that were different from any living species. How would this finding have affected his estimates of biological diversity? Answers • • • • • 1. Darwin hypothesized that animals could undergo change through time. This was in contrast to the prevailing view that organisms do not change 2. Tortoises and birds showed variation that reflected the island they lived on or the type of food they ate 3. Evolution, or change over time, is the process by which modern organisms have descended from ancient ones. Evolution is referred to as a theory because it is a well-supported explanation of phenomena that have occurred in the natural world 4. A fossil is the preserved remains of an ancient organism 5. It would have increased his estimates of biological diversity! IDEAS THAT SHAPED DARWIN’S THINKING People believed all forms of life and earth had been created only a few thousand years ago Since creation nothing hand changed, example a robin today looks and sounds like a robin from the beginning of time Fossils found????????? WHAT DID SUCH FOSSIL EVIDENCE INDICATE ABOUT LIFE IN THE PAST?? SEVERAL PERIODS OF CREATION AND CATASTROPHIES AN ANCIET CHANGING EARTH • JAMES HUTTON AND CHARLES LYELL – Together, Hutton and Lyell helped scientists recognize the earth is millions of years old, the process that changed earth in the past are the same processes that operate in the present. Hutton’s Theory of Geological change, 1795 – Layers of rock are moved by forces beneath earths surface » Pushed up from seafloor to make mountains » Rocks shaped by natural forces, rain, heat and cold temperature, this weathers rock extremely slow » Proposed earth to be much more then a few thousand years old Lyell’s “Principles of Geology” – – – Scientists must explain past events in terms of processes that they can actually observe, since process that shaped the earth millions of years ago continue in the present Darwin witnessed a volcanic eruption Darwin wrote about an earthquake » ? If we saw these things what can we explain about geology? » ? If the earth could change overtime, might life change as well? » Thought: Lyell realized that it would have taken many, many years for life to change in the way he suggested, this would have been possible only if the Earth were extremely old. Sea level Sea level Sedimentary rocks form in horizontal layers. When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers. As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed. New sediment is then deposited above the exposed older rock surface. Lamarcks Theory of Evolution – Among the first scientists to recognize that living things change over time, and that all species were descended from other species – Animals adapted to their environments, – 1809 – Year Darwin was born – Lamarck proposed that by selective use or disuse of organs, organisms acquired certain traits during their lifetime. These traits could then be passed on to one’s offspring’s. Overtime this process led to change in a species. » Figure 15.7 and explanation!!! Figure 15–7 Lamarck’s Theory of The acquired Evolution 3.characteristics, 2. Because the a large front claw has been used repeatedly, it becomes larger 1. Male crab uses its small front claw to attract mates and ward of predators. claw, is then passed on to the crab’s offspring. Tendency towards perfection – All organisms trying to be perfect • Example – an ancestor of a bird wanted to fly, the organism continued to try and over generations finally could fly • Scientists believe that insects were the first animal to fly. They had a covering down the sides of their bodies used to protect their spiracles, breathing apparatus, eventually they were able to lift these up and used to glide, then used to flap to help them fly for short periods of time. What do we as humans think of as perfect? • Use and Disuse – Organisms could altar shape or size of particular organs by using their bodies in new ways. » Example – appendix, wisdom teeth Inheritance of acquired traits – Example – an animal sometime during it’s lifetime, alters a body structure – leading to longer legs, of fluffier feathers ? If you became a body builder would your children have muscles when they are born??? Evaluating Lamarck’s theory Incorrect, an animals behavior and activity have no effect on it’s inheritable characteristics adapted to environment » » » » BUILDING SCIENCE SKILLS Challenge students to design an experiment to test lamarck’s theory of the inheritance of acquired traits. Students’ experimental designs should include a hypothesis, procedure, and possible outcomes. Ask: WHAT SPECIES WOULD YOU USE, AND WHAT VARIABLE WOULD YOU TEST? Cut off the tails of adult mice and then observed whether the offspring of the mice also had short tails. Have students explain how the different possible outcomes of their experiment would or would not support Lamarck’s theory Population Growth – 1798, Thomas Malthus observed that babies were being born faster than people dying – Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone – ? WHAT WORKS AGAINST GROWTH? WAR, FAMINE, DISEASE – Darwin noticed this worked more strongly with plants and animals than humans. ? WHY DO HUMANS PRODUCE FEWER OFFSPRING? Questions 1. What two ideas from geology were important to Darwin’s thinking? 2. According to Malthus, what factors limited population growth? 3. According to Lamarck, how did organisms acquire traits? 4. Why was Lamarck’s theory of evolution ultimately discredited? 5. Malthus formed his theory by studying factors that control the population growth of humans. How might factors operating on organisms in nature differ from those of Malthus theory? Answers • 1. Earth is very old, and the same processes that shaped the Earth millions of years ago continue in the present • 2. Malthus thought that war, famine, and disease limited population growth • 3. Lamarck thought that organisms acquired traits by using their bodies in new ways. For example, birds might transform their front limbs into wings by trying to use the limbs for flying • 4. Lamarck’s theory was discredited because we now know that acquired characteristics are not inherited. • 5. Factors operating on organisms in nature might include competition and predation instead of famine and war • What did such fossil evidence indicate about life in the past? • Some organisms in the past had no modern representatives, and that some organisms may have become extinct Darwin Presents his case Darwin returned 1836 with lots of specimens His mocking birds resulted in 3 separate species found no where else in the world Birds he thought were wrens, warbles, and blackbirds were all finches and found no where else Tortoises, marine iguanas – all species looked similar to ones from South America yet clearly different Phenotypes adapt in response to the environment, with new and useful traits arising. Publication of “On the origin of Species” He wrote in notebooks his findings, but did not publish Discussion: Darwin’s reluctance to publish his work is a good example of how science is influenced by its social context. Question: what current areas of scientific research are controversial, much as evolution was controversial in Darwin’s time? Answer??? 1858, Darwin received an essay from Alfred Russell Wallace, it summarized thoughts on evolutionary change that Darwin had been mulling over for 25 years, Darwin published 18 months later, “On the origin of Species” Natural Variation and Artificial Selection Natural Variation – defined as differences among individuals of a species in nature – – – Example – zebras, inherits genes that give it a distinctive patterns of stripes some cows give more milk, some plants bear larger fruits these traits can be inherited farmers would use selective breeding to determine which natural variation that they found, example – only fastest horses, cows that gave the most milk were allowed to produce off spring Artificial Selection – nature provided the variation among different organisms and humans selected those variations that they found useful. – How is this used today? HowStuffWo rks Videos "Cool Underwater Creatures" Evolution: Library: Evolution of Camouflage Artificial Selection – This process can lead to great differences. In some cases, a single ancestral species has given rise to a variety of modern plants. Evolution by Natural Selection Evolution Primer #4 How Does Evolution Really Work Natural Selection - YouTube The struggle for existence Darwin was convinced that a process like artificial selection worked in nature Struggle for existence – members of each species compete regularly to obtain food, living space, and other necessities of life. Prey that are faster, better camouflaged or better protected can avoid being caught Predators that are faster or outsmart the prey can catch more prey Survival of the fittest how well suited an organism is to its environment fitness – the ability of an individual to survive and reproduce in its specific environment adaptation – an inherited characteristic that increases an organisms chance of survival figure 15 – 12 statement and over head survival of the fittest – individuals better suited to their environment, high levels of fitness, survive and reproduce most successfully Natural Selection – survival of the fittest, takes place with out human control or direction Overtime, natural selection causes a change in the inherited characteristics of a population. It directs these changes in ways that increase a species fitness in its environment ?What did Darwin mean when he described certain organisms as “more fit” than others? A. he meant organisms that are better suited to their environment Weird True & Freaky: Bear vs Caribou : Video : Animal Planet Wildlife in disguise: Amazing animal camouflage – YouTube David Gallo shows animal camouflage YouTube Descent with modification Each living species has descended with changes from other species over time All living organisms are related to one another Back in time ancestors were shared by tigers, panthers, and cheetahs Common descent – common ancestors of living things Tree of life – links all living things on earth Evidence of evolution • Darwin argued that living things have been evolving on earth for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early development. • Fossil record • Different layers of rock had been formed at different times in earths history • figure 15.13 overhead • ? what are the major changes that occurred as these cephalopods evolved • they gradually evolved longer, more coiled shells. Sexual Selection • Evolution: Library: Tale of the Peacock Geographic distribution of living species • ? why can two species that look very different from each other be more closely related than two other species that look similar to each other? • it depends on the environments in which the species evolved • • • • • • • • • • • Similar Species in Similar Environments The existence of similar but unrelated species was a puzzle to Darwin. Later, he realized that similar animals in different locations were the product of different lines of evolutionary descent. Here, the beaver and the capybara are similar species that inhabit similar environments of North America and South America. The South American coypu also shares many characteristics with the North American muskrat. Interpreting Graphics Which animal has a larger geographical range, the coypu or the muskrat? Homologous body structures Similarities among body parts of animals with backbones the limbs differ greatly in form and function, yet they are all constructed from the same basic bones. Over head forelimbs of vertebrates ?what similarities in the limbs suggest that they developed from the same basic structure? The number and placement of the bones ?what are some major changes in bone structure that occurred as these vertebrates evolved along different paths? ?what is the scientific explanation for these similarities? Each of these limbs has adapted in ways that enable organisms to survive and reproduce in different ways in different environments Figure 15–15 Homologous Body Structures Turtle Alligator Bird Typical primitive fish Mammals ►Homologous structures – structures that have different mature forms in different organisms but develop from the same embryonic tissue ►Vestigial organs – organ that serves no useful function in an organism, so reduced in size that it is just a trace of a homologous organ in another species ►?How might vestigial organs provide clues to an animal’s evolutionary history? ►They might indicate a change in the animal’s environment or behavior ►? How can biologists use the idea of homologous structures to determine whether particular species are closely related? ►The similarities and differences of homologous structures provide evidence for how recently species last shared a common ancestor ► ► Video 3: How do we know evolution happens? Evolution: Library: Whale Evolution Vestigial Organs These three animals are skinks, a type of lizard. In some species the skinks, legs have become vestigial. They are so reduced that they no longer function in walking. In humans, the appendix is an example of a vestigial organ because it carries out no function in digestion. Inferring How might vestigial organs provide clues to an animal’s evolutionary history? Similarities in Early Development Overhead comparing vertebrate embryo development ?why might you expect the embryos of fishes to be more similar to the embryos of sharks than to the embryos of humans? Because fishes and sharks shared a more recent common ancestor Why Does Evolution Matter Today? • Evolution: Why Does Evolution Matter Now? • Video 6 Summary of Darwin’s theory Individual organisms in nature differ from one another. Some of this variation is inherited Example Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce Example More organisms are produced than can survive. Members of each species must compete for limited resources Example Because each organism is unique, each has different advantages and disadvantages in the struggle for existence Example Individuals best suited to their environment survive and reproduce most successfully. The characteristics that make them best suited to their environment are passed on to offspring. Individuals whose characteristics are not as well suited to their environment die or leave fewer offspring. Example Species change over time. Over long periods, natural selection causes changes in the characteristics of species, such as in size and form. New species form, and other species disappear. Example Species alive today have descended with modifications from species that lived in the past. Example All organisms on Earth are united into a single tree of life. Example QUESTIONS???? 1. What types of evidence did Darwin use to support his theory of change over time? 2. How is artificial selection dependent on variation in nature? 3. The theory of evolution by natural selection explains, in scientific terms, how living things evolve over time. What is being selected in this process? 4. What is the struggle for existence? How is it related to Malthus’s work? 5. Compare and contrast Darwin’s theory of evolution with that of Lamarck. How are they similar? How are they different? . Answers 1. He used the fossil record and the geographical distribution of living species 2. In artificial selection, nature provides the variation among different organisms. Humans select those variations that they find useful. 3. a species’ fitness in its environment 4. the struggle for existence is competition between members of the same species for food, living space, and other needs. The greater the population pressure on food and other resources, the greater the competition. Malthus argued that population pressure keeps human population numbers in check. 5. a. Both states the organisms change to adapt to their environments. Lamarck thought organisms acquire certain traits in their lifetime. Darwin thought that, overtime, natural selection causes a change in the inherited characteristics of a population Evolution Primer #7: Why Is Evolution Controversial Anyway? - YouTube The Simpsons - Homer Evolution - YouTube