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Transcript
Evolution Unit Question: To what extent does the environment influence living things over time Area of Interaction: Environment Evolution change over time. Charles Darwin??? Fact, Fiction, Theory & Law: How are they different? Fact: something that has actual existence. Ex. space exploration is now a fact b : an actual observable occurrence in our time Fiction: a: something invented by the imagination or feigned; specifically : an invented story b: fictitious literature (as novels or short stories) c: a work of fiction; especially : NOVEL Hypothesis: an interpretation of a situation a: an educated ‘best guess’ Theory: A well supported testable explanation of phenomena that have occurred in the natural world. a: a plausible or scientifically acceptable general principle offered to explain phenomena <wave theory of light> A Hypothesis becomes Theory when it is supported by a huge body of evidence after lots of testing. Law: very much like a theory, less complex a: a statement of provable scientific knowledge related to a single measurable phenomenon. ie Law of Gravity, Law of thermodynamics b: specific and measurable PBS 6 Min Vid Deep thoughts • So what is evolution? – Fact or fiction? – Hypothesis, Theory, or Law? – Is evolution debatable? • How do ideas change over time with new scientific evidence? Give examples. Evolution • Change over time • In biology it is the process by which modern organisms have descended from ancient organisms. 3 million years ago 50 million years Who is Charles Darwin? - Proposed theory to explain evolution - Theory called Natural Selection Darwin - Early Years • Terrible student – Medical school at age 16 (Edinburgh, Scotland, established 1582!-ancient university) – Skipped class to collect biological specimens – Sat in on classes in geology and botany • Father removed Darwin due to lack of academic progress Darwin – Early Years • Clergymen - University of Cambridge • Preferred competitive collecting of beetles, riding, and shooting to studying – but did graduate. Beetling was the craze at that time… Darwin – How it all started • Darwin was recommended as a naturalist and much needed gentleman’s companion to Captain Robert Fitzroy of the H.S.S Beagle • Two year voyage to chart the coastline of South America Movie Sailing the Seas…for five years! Darwin – the voyage! • Darwin methodically collected an enormous amount of specimens – Animals, fossils, rocks, etc. • He also made observations and took detailed notes • Some key specimens from the Galapagos Islands… Darwin’s Finches Galapagos Islands…great place to visit? Blue-footed Booby Galapagos Tortoise Iguanas Galapagos Islands What did he see & find? • He saw: – Living Organisms and Fossils • Fossil: preserved remains or evidence of an ancient organism – Patterns of diversity: organisms are different all over the world and on different islands of the Galapagos • Patterns of diversity example: Darwin’s Finches Other Scientists that shaped Darwin’s Ideas 1. Hutton Layers of sedimentary rock form slowly Mountains are pushed up slowly The earth changes slowly! 2. Lyell Darwin read his book right before sailing on the Beagle Volcanoes and erosion we see working today takes millions of years to make the landscape The earth is older, much older than we think Other Scientists that shaped Darwin’s Ideas 3. Malthus Population growth and food production are related Overpopulation will occur There will always be competition for food. Those that get food are the most advanced genetically 4. Lamark 1st to propose a theory of evolution, but his was WRONG! 1. Tendency towards perfection 2. Use and disuse of organs: if you stop using an organ, it will disappear 3. Passing on acquired traits: traits you get in your lifetime will be passed on to your offspring • Alfred Wallace writes Darwin – • He came up with the same ideas independently (“I think an organisms structure is related to the environment it lives in”) This forced Darwin to publish his book, On the Origin of Species, in 1859 – 21 years after the Beagle voyage! Movie So what is Darwin’s Theory? 1. There is variation within a species 2. Some traits are helpful, some are harmful. Those that are helpful will help the organism survive. Those that are harmful will cause the organism to die sooner. (natural selection) 3. Those that survive will reproduce others with the same traits 4. Over a LONG period of time, the species gradually changes. 5. All living organisms originated from one common ancestor. Natural Selection (after genetics) • Genetic mutations occur during meiosis. • Over time, natural selection causes changes in the inherited characteristics of a population (the gene pool). • Changes lead to adaptations and eventually new species! Movie V a r i a t i o n Variation: The differences in individual organisms in the same species. Same Species? Marine Flatworms snails Variation- differences • Variation is caused by: –Sexual reproduction (“shuffling the genetic deck”) –Genetic mutations (error in DNA replication or repair) Ex: Variation in height among humans Example: Peppered Moth • Black and White variations • Live mostly on white birch trees in England • Birds eat them! • Birch trees turned black from soot from nearby factories • Which moth was more likely to survive? Simulation Survival of the Fittest = Natural Selection • Species Overproduce— Most species produce more babies than can survive • Struggle for existence— Members of each species compete on a daily basis for food, living space, and other necessities • Fitness—the ability of an individual to survive and reproduce in its environment • Adaptations- inherited physical features or behaviors that become common in a population because it provides a natural selection advantage Many animals are browns and grays. Why?? Some fish lay on the sand to camoflage. A deer will lift its white tail to warn others of danger. Even eggs and babies can be camoflaged. Sometimes an animal will hi-lite one body part to save another. Phototropism -plants grow to light. Plants have adaptations, too. How is the Ghost Pipefish adapted to its’ environment? video Lesson Overview Evolution as Genetic Change in Populations How do variations become Adaptations? Normal Variation exists as a “bell shaped curve”. Variations become adaptations when they “increase the chance for survival”. Lesson Overview Evolution as Genetic Change in Populations Directional Selection Directional selection occurs when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. The range of phenotypes shifts because some individuals are more successful at surviving and reproducing than others. For example, if only large seeds were available, birds with larger beaks would have an easier time feeding and would be more successful in surviving and passing on genes. Lesson Overview Evolution as Genetic Change in Populations Stabilizing Selection Stabilizing selection occurs when individuals near the center of the curve have higher fitness than individuals at either end. This situation keeps the center of the curve at its current position, but it narrows the overall graph. For example, very small and very large babies are less likely to survive than averagesized individuals. The fitness of these smaller or larger babies is therefore lower than that of more averagesized individuals. Lesson Overview Evolution as Genetic Change in Populations Disruptive Selection Disruptive selection occurs when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle. Disruptive selection acts against individuals of an intermediate type and can create two distinct phenotypes. For example, in an area where medium-sized seeds are less common, birds with unusually small or large beaks would have higher fitness. Therefore, the population might split into two groups—one with smaller beaks and one with larger beaks. Lesson Overview Evolution as Genetic Change in Populations Genetic Drift Genetic drift occurs in small populations when an allele becomes more or less common simply by chance. Genetic drift is a random change in allele frequency. Speciation If Darwin says that we all have a common ancestor, how do we get new species? Species: group of similar organisms that can breed and produce fertile offspring Speciation: Formation of new species Members of a species may be born with Variations- gene shuffling Mutations- a genetic change Sometimes those variations/mutations are an adaptation and allow the individual to survive. The surviving individual(s) usually reproduce others like them. Those individuals without the adaptation tend to die off. Over a very long period of time, the entire species can change to have the adaptation. A necessary factor in speciation: populations become reproductively isolated Reproductive Isolation- separating a species in any way so they can’t breed with each other • • • Behavioral Isolation- (Different courtship rituals) Geographic Isolation- (Separated by rivers, oceans, mountains, etc) Temporal Isolation- separated by time (reproduce at different times of the year) What kind of speciation is this? How are these species related? Kaibab Squirrel Abert Squirrel What kind of speciation is this? Cicadas that breed every 13 years Cicadas that breed every 17 years What kind of speciation is this? The eastern meadowlark (left) and western meadowlark (right) have overlapping ranges. They have different mating songs. Speciation in Galapagos Island finches The steps of speciation in Darwin’s finches 1. Bird pushed from mainland and arrive on the islands. 2. Separation of populations (Geographical isolation) 3. Changes in the gene pool (Reproductive isolation) 5. Ecological Competition for survival (mainly food) How do scientists prove speciation occurred? Can’t state it as a fact, only an evidenced theory by: • • • • Genetic Studies Studying fossil history Presumed common ancestors Observing common traits What kind of speciation did Darwin observe in the Galapagos? Evolution Evidence -How do we know it happened? Key Concept: Darwin argued that living things have been evolving on Earth for millions of years. Now we believe it has been 3.5 billion years. Age of Earth = 5-6 billion 4 Main Proofs of Evolution 1. Fossil Record Fossils provide evidence that living things have been evolving for billions of years. Fossilization Video Archaeopteryx Fossil – 150 million years old Example: Oldest dinosaur fossil with feathers – probably evolved into birds. • The oldest fossils are 3.5 billion years old! 3.4-3.5 billion year old stromatolites composed of cyanobacteria and sediment from the Pilbara Shield of Australia Video- 11 min 2. Geographic Distribution of Living Species • Darwin saw similar organisms in different locations. • He thought: Can these organisms adapt to their local environment and change over time? Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara 3. Similarities in Body Structure a. Homologous structures – parts of different animals that develop from the same body part but have different functions. Examples: human arm, cat leg, whale fin, bat wing b. Vestigial Organs – organs that serve no useful purpose. So why are they there? Organs like: tonsils, appendix, coccyx, wisdom teeth, whale pelvis… 4. Similarities in Early Development a. Embryos (organisms in the early stages of development) of different animals look very similar. Why? Why? 1. Not all genes in an organism are turned on at the same time. They have a specific pre-arranged order that all living organism share. 2. As embryos grow, different genes turn on to make them different organisms. What about Us??? Human Evolution We have fossils of our own species(homo sapiens) dating back 100,000 years. Fossils of close relatives date back some 2 million years. Earlier hominids(primate that walks on 2 feet) date back to 6 million years Human Evolution • Australopithecus afarensis- 3 million years ago. Very small skull. Oldest full fossil reconstruction found thus far. Human Evolution • Australopithecus africans- 2 million years ago. Apelike, but bipedal locomotion. • Homo habilus- 1.8 million years ago. Handy with tools. Human Evolution • Homo Erectus- 0.5 million years ago. Thought to be first erect mammals. Wrong! - Java Man - Peking Man Human Evolution • Homo sapiens - Neanderthal Man100,000 years ago. Short, tough hunters. • Homo sapiens(cont.) - Cro-Magnon50,000 years ago. Hunters and artists. Cave paintings. - Modern humans10,000 years ago. (us) That’s the story according to scientists, anthropologists and paleontologists So, there are 2 big questions: • Did species evolve? Do they continue to evolve? • If so, what has caused the changes in species? Darwin’s Theory of Natural Selection was widely accepted from 1860-early 1900’s by those who thought evolution had occurred. 1920’s: Scopes Monkey Trial Met by a new challenger, organized religion and the creation theory. Creation Theories A force other than the natural laws of science causes evolution to occur. A creation theory may take many forms: Organized religions (Christianity, Buddhism, Muslim, etc.) or just a personal belief. Today- 2014 Both creationism and natural selection remain popular theories to explain why and how nature has changed. Many people combine both theories! What do you think?? Evolution.... a slow gradual process that ... well, Evolves!!