1. Do Now What different ways do these animals use to move about? What traits does each animal have that help it move about as it does?

2. Unit 5 Evolution Ch. 15 Darwin’s Theory of Evolution

3. The Puzzle of Life’s Diversity  Evolution - modern organisms have descended from ancient organisms (change over time)  Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world

4. Voyage of the Beagle  Charles Darwin contributed most to our understanding of evolution  He made observations & collected evidence that led him to propose a hypothesis about the way life changes over time

5. Voyage of the Beagle  That hypothesis, now supported by a large amount of evidence, has become the theory of evolution

6. Darwin’s Observations  Darwin collected the preserved remains of ancient organisms - Fossils  Some of these fossils resembled organisms that were still alive  Others looked unlike any creature ever seen

7. Darwin’s Observations  The Galapagos Islands influenced Darwin the most  He observed that the characteristics of animals & plants varied among the different Islands

8. Darwin Presents His Case  Darwin published the results of his work in a book, On the Origin of Species  In his book, he proposed a mechanism for evolution called natural selection  He stated that evolution has been taking place for millions of years, & continues in all living things  Friday “Dangerous Mind” Movie on Darwin (complete worksheet) Remember!!! Reward Friday

9. Home Work (Monday)  Computer time required at home or library. One page required Choose 1 to write about  Compare Darwin’s and Wallace’s theories.  Compare and contrast both Darwin’s and Wallace’s careers and background.  Genetics Test

10. An Ancient, Changing Earth  Hutton & Lyell helped scientists recognize that Earth is millions of years old  They also noted that the processes that changed Earth in the past are the same processes that are changing Earth now

11. Lamarck’s Evolution Hypothesis  The year that Darwin was born, Lamarck published his hypothesis  He proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime  Over time, this process led to change in a species

12. Lamarck’s Explanation

13. Population Growth  English economist, Malthus, published a book, noting that babies were being born faster than people were dying  He stated that if the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone

14. Inherited Variation & Artificial Selection  Artificial selection - nature provided the variation, & humans selected those variations that they found useful  It has produced diverse plants & animals by selectively breeding for different traits

15. Evolution by Natural Selection  Struggle for existence - the members of each species compete regularly to obtain food, living space, & other necessities of life  Predators that are faster & better at catching prey are more likely to survive

16. Evolution by Natural Selection  Fitness - the ability of the organism to survive & reproduce in its specific environment.  Fitness is the result of adaptations

17. Evolution by Natural Selection  Adaptation - any inherited characteristic that increases an organisms’ chance of survival  Successful adaptations allow organisms to become better suited to their environ. & thus better able to survive

18. Evolution by Natural Selection  Individuals that are better suited to their environ., with adaptations that enable fitness, survive & reproduce most successfully - Survival of the Fittest

19. Evolution by Natural Selection  Since it is similar to artificial selection, Darwin referred to survival of the fittest as - Natural Selection  In both AS & NS, only certain individuals of a population produce new individuals

20. Evolution by Natural Selection  However, in NS, the traits being selected, & therefore, increasing over time, contribute to an organism’s fitness  NS takes place without human control or direction

21. Evolution by Natural Selection  NS results in changes in the inherited characteristics of a population, that increase a species’ fitness in its environ.  Over time, NS produces organisms that have different structures, & occupy different habitats

22. Evolution by Natural Selection  As a result, species today look different from their ancestors  Each living species has descended, with changes, from other species over time - Descent with Modification

23. Evolution by Natural Selection  Descent with modification also implies that all living organisms are related to each other  Common descent - all species (living & extinct) were derived from common ancestors

24. Evidence of Evolution  Darwin argued that living things have been evolving on Earth for millions of years  Evidence of this could be found: in the fossil record, the geographical distribution of living species, homologous structures of living organisms, & similarities in early development

25. Evidence of Evolution  The Fossil Record:  Darwin noticed that the sizes, shapes, & varieties of related organisms preserved in the fossil record, changed over time

26. Evidence of Evolution  Geographic Distribution of Living Species:  Darwin realized that similar animals in different locations were the product of different lines of evolutionary descent

27. Evidence of Evolution  Homologous Body Structures:  Homologous structures - structures that have different mature forms but develop from the same embryonic tissues  Not all homologous structures serve important functions  Organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs

28. Homologous Structures

29. Evidence of Evolution  Homologous Body Structures:  Vestigial organs - may resemble miniature legs, tails, or other structures, a trace of a homologous structure

30. Evidence of Evolution  Similarities in Early Development:  The early stages or embryos, of many animals with backbones are very similar

31. Summary of Darwin’s Theory  Individual organisms differ, & some of this variation is heritable  Organisms produce more offspring than can survive, & many that do survive do not reproduce

32. Summary of Darwin’s Theory  Because more organisms are produced than can survive, they compete for limited resources  Individuals best suited to their environ., survive & reproduce most successfully

33. Summary of Darwin’s Theory  These organisms pass their heritable traits to their offspring  This process of NS causes species to change over time

34. Summary of Darwin’s Theory  Species alive today are descended with modification from ancestral species that lived in the distant past  This process, where diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life