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Explore Darwin’s theory of natural selection, his observations, and evidence. Compare Lamarck's evolutionary theory. Learn about the controversy, impact, and principles underlying evolution.
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What – How – Why? • What: State Darwin’s Theory of Natural Selection 2.7e, RWC -3.2f/g, 4d • How: Describe Darwin’s 2 main contributions to the study of evolution, and the evidence he provided to support his theory in a proficient CR. • Why? How did Darwin come up with this important scientific mechanism?
Evolution • Evolution: Change over time, process by which modern organisms come from ancient organisms. • What causes changes in organisms? 2 things that we have discussed that cause changes. • Mutations and Sexual Reproduction (meiosis).
What scientist is credited with evolution? • When you think of evolution, the scientist that comes to mind is ______________________.
Charles Darwin • Darwin was set to become a clergyman but loved studying nature in his spare time and therefore was invited to set sail on the H.M.S. Beagle (1831-1836) to survey the world to collect plants and animals.
Darwin’s Observations How can similar organisms live in such different locations? • 1. Patterns of Diversity Why are the frogs different from the island to the mainland? Why is there so much diversity among organisms that have similar features?
Darwin’s observations • 2. Living organisms and Fossils Does this fossil look like a modern day organism? What is the name of the animal that is fossilized here? What is the modern day animal this resembles? Does this fossil look like a modern day animal? Why doesn’t this animal exist anymore?
Darwin’s observations The islands have animals and plants different from any place in the world! AND…each island has different climates and animals and plants. 3. The Galapagos Islands Do you know where the Galapagos islands are located? How did they get to each island? How can they be so different?
Publishing • Using: • the observations from his travels • evidence he collected from his trip • Geologic observations that had already been published. • Observations from other scientists that supported his book: • “On the Origin of Species by Means of Natural Selection”
On the Origin of Species • Two main conclusions: • 1. Species evolved from a common ancestor. • Partners: Why would he think that? • 2. Method for why evolution occurred, called Natural Selection (current theory of evolution). • Based on the picture on the side, which species will continue living?
Natural Selection • Over time, Natural selection results in changes in the characteristics of a population because they increase an organisms’ ability to survive and reproduce (fitness). What 2 things cause variation again? “Survival of the fittest”. Which moth is most fit in each picture? Why?
Controversy? Many people considered Darwin to be brilliant. Others opposed his message. Why do you think his book has been controversial? Ideas about the changing of species were controversial as they conflicted with the beliefs that: 1. World was only a few thousand years old. Why would they think that? 2. Creation made humans unique unlike any other organisms.
Summary Concept Map • Conclusion: All organisms evolved from a common ancestor through the process of NATURAL SELECTION. • 1. Darwin’s travels show him that diversity of living species was greater than previously known. • 2. Each island in the Galapagos had its own type of tortoise and bird from the other islands, and these looked different from species on the mainland. • 3. Fossils found were both similar and different from modern organisms.
Objective • Why: You have to compare Darwin and Natural Selection to other scientists to ensure that you understand Natural Selection accurately. • Obj: Research the role of earlier scientists on evolutionary thought. (2.9a) • DOL: Given 2 MC & 1 CR, SWBAT determine how earlier scientists evolutionary theories were incorrect when compared to Darwin’s theory with 80% accuracy.
Before Darwin…the father of evolution was Lamarck! • The first true evolutionary theory came from Lamarck • Do you think he was right (1) or was he wrong (2) even before I tell you what happened?
Lamarck: Similar or different to Darwin? Opposite sides of the room. • His theory attempted to answer the question “How do populations change over time”? • Similar or different? • Organisms change over time • Similar or different? • Environment drives evolution of traits • Similar or different? • Common descent • Similar or different? • So far, they had the same basic principles….but there were significant differences between the two.
Lamarck: Use and Disuse and Inheritance of acquired characteristics Individuals lose characteristics they do not require (or use) and develop characteristics that are useful. Then, those acquired traits could be passed down to its offspring. For example, the giraffe needed a longer neck, so it stretches it until it became long. Then its offspring would have long necks too. How is this wrong? With your partner, come up with a real-life example of a “use” situation and describe how you know that would be impossible.
Exemplar • A blacksmith, through his work, strengthens the muscles in his arms. His sons will have similar muscular development when they mature.
Giraffes and Natural Selection • Natural Selection’s reasoning for giraffes long necks would be that • 1. There was a struggle for food in high locations. • 2. Those with longer necks were better able to compete for food than those with short necks. These reproduced and survived more than those with shorter necks. (Fitness) • 3. Long necks survived and passed on their traits to their descendants.
Water birds webbed toes • Lamarck proposed that from years of stretching their toes to swim through water, these birds stretched the skin in between their toes for better swimming.
Partners • Think of the three steps of Natural Selection. How would Darwin have proposed the water birds webbed toes evolution? • 1. The struggle to be faster in water to catch prey • 2. Those that had more webbing were faster and survived and reproduced faster (fitness). Those that didn’t had lower fitness. • 3. Higher likelihood of descended generations of water birds with webbed feet.
Overview • Why was Lamarck incorrect? • Lamarck stated that the phenotype changes the genotype. This is wrong. Instead, the genotype has to change the phenotype. • What is phenotype? What is genotype? • Lamarck said that the variation is caused by the individual organism due to the environment. This is wrong, instead, variation already existed and the only with the best variation/adaption has the higher fitness.
Check-In • 1. Lamarck’s theory of evolution includes the concept that new organs in a species appear as a result of • A. continual increase in population size. • B. the actions of organisms as they use or fail to use body structures • C. an unchanging local environment • D. the natural variations already present within the population of organisms.
Check-In • 2. Which of the following is in agreement with Lamarck but not Darwin. • A. Acquired characteristics that are inherited are the cause of evolution. • B. organisms that are fittest will survive • C. there is always a struggle to survive by all organisms • D. descent with modification happens because those organisms that are best fit will most likely survive and reproduce.
Darwin vs. Lamark • What: Research the role of earlier scientists or evolutionary thought. (2.9a) RWC -3.2f/g, 4d • How: Compose 2 real-world scenarios to illustrate each of the main evolution theories. Evaluate a classmate’s scenarios, giving 2 pieces of constructive feedback. • Why: Being able to distinguish between the arguments of people is a valuable critical thinking skill!!
Two Minds – Two Theories • Darwin vs Lamarck
Lamarck’s Hypothesis: The Inheritance of Acquired Characteristics • 1. A changing environment creates a NEED for certain features to be developed in order to survive. • 2. Through the use/non-use of features, those needed for survival are developed and maintained. • 3. The necessary features are passed onto offspring to continue development. • 4. Over many generations, enough differences develop to have a new species.
Darwin’s Hypothesis: Natural Selection • 1. Overproduction of offspring – more than can survive and reproduce. • 2. Variation – inheritable traits vary from individual to individual. • 3. Change in the environment • 4. Struggle for survival – competition within species. • 5. Survival of the fittest – those most “fit” or suited to the environmental change. • 6. The “fit” trait is passed onto offspring. • 7. If traits differ enough from original population, new species, who is better adapted to the environment, emerges.
Comparison Sample Scenarios • On your own: • Read scenario • Decide is this Lamark’s or Darwin’s work • What are key details in the scenario that supports your decision on Lamark or Darwin. • With Partner • Discuss your findings
Scenario A - Exemplar • Scenario A. • Contains the elements of Lamarck’s hypothesis: • 1) environmental change creates “need” for individuals to change • 2) by individual effort, physical changes were produced, and • 3) newly acquired physical changes somehow became genetic, and were passed on to offspring.
Scenario B – Exemplar • Scenario B. Contains the elements of Darwin’s natural selection process: • 1) inheritable variations • 2) an environmental change • 3) survival and reproduction of those with traits enabling survival in the changing environment. No mention of “need” nor individual efforts to make physical changes “in order to survive”.
Create your own scenario • Write a similar pair of scenarios describing how some particular species evolved, with a particularly conspicuous feature, (e.g. a tiger, an elephant, a hawk, a frog, etc.); do one scenario the way • Partner A: Lamarck might explain it. • Partner B: Darwin might explain it.
DOL • Which of the following is not one of Lamark’s hypothesis? • Environment changes, so the specie needs to change • Develops new features to survive • Variations are inherited • Acquired traits are passed down to offspring • Which of the following is one of Darwin’s hypothesis? • Organisms with selected traits have survival rates • Develops new features to survive • Acquired traits are passed down to offspring • New species eventually happen
DOL – 5pts GOAL – 4/5 • In a proficient CR, answer the following question: • Describe the current theory of evolution and explain in scientific terms how living things evolve over time. (2pts) Describe the observations used by Darwin to support your answer. (3pts)
Exemplar • Natural selection is the current theory of evolution, that describe that the change of organisms over time is due to their ability to survive and reproduce (Survival of the Fittest). Darwin’s observations of the variation of organisms, fossil remains, and observations from his trip to the Galapagos indicate that all organisms are related, but only those best able to survive, are still alive today.
DOL • In a CR, what was Lamarck’s overall belief about the way in which organisms changed over time, and how was this in contrast with Darwin’s theory of Natural Selection.
Exemplar • Lamarck believed that individuals lose characteristics they do not require (or use) and develop characteristics that are useful. Then, those acquired traits could be passed down to their offspring. This is in contrast to Darwin that believed that organisms are varied to begin with, and those that are best fit will pass on their genes to the next generation, those that aren’t fit will probably die due to their fitness.
