Chapter15 evolution(darwin)
- 1. Chapter 15: Darwin’s Theory of Evolution Pages 368-386
- 2. Chapter 15-1: The Puzzle of Life’s Diversity Pages 369-372
- 4. Evolution Definition: change over time, the process by which modern organisms have descended from ancient organisms
- 5. The Theory of Evolution helps us understand how: • fossils fit into life’s history • bacteria become resistant to antibiotics & insects to pesticides • determine the relationships among the different groups of organisms on Earth
- 6. Charles Darwin • Born Feb.12, 1809 in England • Sailed on the H.M.S. Beagle in 1831 for a 5 year voyage around the world • Made many observations & collected evidence that caused him to hypothesize about how life changes over time • His observations were influenced by reading the ideas of other scientists
- 9. Scientific beliefs before Darwin: • Species were unchanging – the same organisms always existed. • Earth was about 10,000 years old.
- 10. Darwin’s Observations 1. A large variety of organisms inhabit the Earth • Example: He collected 68 species of beetles in 1 day in a rainforest in Brazil 2. Organisms were well suited for the different environments in which they were found • Examples: On the Galapagos Islands, t ortoises from different islands have different shaped shells & neck lengths and different finches (birds) have different shaped beaks
- 11. Fossils • Definition: preserved remains of ancient organisms • Fossil evidence raises many questions: • Why have so many species disappeared? • How do extinct organisms relate to living organisms? • Darwin based most of his beliefs on the fossils he found and wondered if animals on different islands once belonged to the same species
- 12. Review: Species Definition: organisms belong to the same species if they can interbreed (produce fertile offspring) under natural conditions
- 13. Good News: We are skipping Chapter 15-2.
- 14. To summarize Chapter 15-2: Many scientists contributed ideas that helped frame Darwin’s theory, ideas such as: 3) The Earth is actually millions of years old and is still changing… 4) Organisms acquired or lost certain traits during their lifetime that could be passed onto offspring, thus changing a species (later proved false)… 5) If a population grows unchecked, sooner or later, food and space will run out…
- 15. Chapter 15-3: Darwin Presents His Case Pages 378-386
- 16. Vocabulary 15-3 natural variation struggle for existence fitness adaptation survival of the fittest natural selection common descent homologous structure vestigial organ
- 17. Darwin’s Book • Darwin collected his ideas and published the book “On the Origin of Species” which proposed: – A mechanism of evolution he called natural selection, based on three major principles – That the process of evolution has been taking place for millions of years
- 18. Principle #1: Natural Variation • Definition: differences among individuals of a species • Darwin argued that natural variation is found in all species • These “variations” can be passed on to the next generation
- 19. These natural variations occur through: • Sexual reproduction • Independent assortment of chromosomes • Segregation of alleles • Crossing-over during meiosis • Mutations in DNA
- 20. Principle #2: Struggle for Existence Members of each species compete for living space, food, and other things needed for them to: SURVIVE AND REPRODUCE.
- 21. Principle #3: Survival of the Fittest 1) The greater fitness an organism has, the more likely it is to survive in an environment (i.e. “win the struggle”). Fitness: is the ability of an organism to survive and reproduce in an environment 2) Fitness is the result of adaptations . Adaptations: any inherited characteristic that increases an organism’s chance of survival • Example: can be physical (porcupine quills) or behavioral (hunting in a pack)
- 22. Darwin’s Theory of Evolution by Natural Selection • Individuals with high levels of fitness survive and reproduce the most offspring – survival of the fittest. • Individuals not suited to their environment (low fitness) either die or produce small number of offspring.
- 23. Common Ancestry • Definition: all living organisms are related to one another • Common descent: all species – living and extinct – came from common ancestors
- 25. 1. The Fossil Record • Fossil: preserved remains of an ancient organism; formed by sediment settling over remains • Fossil records are incomplete – many organisms have lived and died and were never preserved • Fossils in the same layer of rock lived at the same time • Shows how some organisms change slowly over time • Show how complex animals and plants of today were preceded by simpler ones
- 28. The “fishapod”…375 million years old…may be the link between water and land.
- 29. “Ida”…47 million years old…possibly the missing link in primate evolution.
- 31. 2. Geographic Distribution of Species • Isolated land areas and island groups evolve their own distinct plants and animals fit to the environment • The same kinds of fossils are found in areas which were once connected (ex. Pangaea, the “supercontinent”) but now separated as a result of continental drift
- 34. 3. Homologous Body Structures & Vestigial Organs • Many different organisms have similar body structures – which may perform different functions but are constructed of the same basic bones and tissues • Vestigial organ: organ that is so reduced in size it does not perform a function
- 37. 4. Embryonic Development • Embryos of closely related organisms have similar early stages of development
- 39. 5. Molecular Analysis • If two species have genes and proteins sequences that match closely, biologists conclude that the sequence was copied from a relatively recent common ancestor