1. Evolution

3. What is Evolution?  Evolution is the change in a species over time.  More specifically, it is the change in inherited characteristics in a species over the course of generations

4. Who Was Charles Darwin?  Charles Darwin was an English scientist who proposed a theory to explain how organisms change over time  In 1831 he set sail on a five year voyage throughout the world and visited several continents and many remote islands  During these visits he made many observations of the plants and animals that he encountered throughout the world  In 1859 he published his famous work “On the Origin of the Species” in which he proposed the Theory of Evolution

5. Theory of Evolution  Darwin based his theory on two ideas :  Variations - Differences among individuals of a species  Natural Selection - Nature selects any trait that increases an organism’s ability to survive and reproduce

6. Natural Selection  The theory of evolution and natural selection are based on the following ideas:  Overproduction within a population  Competition within a species  Survival of the Fittest

7. Overproduction  More offspring are born than can possibly survive to reproduce themselves  For example, if all the offspring of bacteria, insects, dandelions, rabbits, etc. survived, they would overrun the earth!  This DOES NOT happen!

8. Competition  In our world there is a finite (limited supply) of resources  As a result, individuals within a particular species are constantly competing for resources such as food, water, shelter, and mates!  There is simply not enough to go around!

9. Survival of the Fittest  The individuals who survive are those who are most adapted to exist in their environment  This is due to the possession of adaptations (differences in form) that maximize their fitness  Fitness is the ability for an individual to survive and reproduce in its specific environment

10. Adaptive Value  Any trait that helps an organism survive and reproduce under a given set of environmental conditions is said to have adaptive value  According to Darwin’s theory, a changing environment will select certain traits and behaviors of organisms that allow them to survive and reproduce

11. Examples of Traits: Peppered Moths  The Industrial Revolution in England covered the trees in dark soot.  Light colored moths were now more easily spotted by predators (birds), and were killed off at higher frequencies.  Dark colored moths were now camouflaged, and more of them survived to pass their genes onto their offspring.  Over time, the majority of peppered moths in England were dark colored Peppered Moth Video Clip

12. Examples of Traits  Bacterial Resistance to Antibiotics

13. Examples of Traits  Galapagos Finches  The finches on the Galapagos island are adapted to eating different kinds of food

14. Examples of Behaviors  Nest building behavior in birds- those birds which build the best nests are able to reproduce better  Fighting behavior among walrus populations for a harem of females- the stronger, healthier males will mate with the most females  Correct blinking rate behavior between male and female fireflies to find each other and mate  Kangaroo Boxing Kangaroo Boxing

15. Genetics and Evolution  As Darwin developed his theory of evolution following his return to England in 1836, he worked under a serious disadvantage: He did not know how heredity worked.  Although Mendel’s work on inheritance was published in the 1860’s, its importance was not recognized until after 1900.  Without an understanding of heredity, Darwin was unable to explain two important factors.  First, he did not know the source of variation that was so central to his theory.  Second, he could not explain how inheritable traits were passed from one generation to the next.

16. How are New Traits Created in Offspring?  During meiosis (remember crossing over !) new combinations of genes occur. This is called genetic recombination. These genes can be passed on to the offspring.  Random mutations of genes in the gametes can create new traits in the offspring. The mutations are changes in the base pairs of DNA that can occur randomly or from exposure to radiation.

17. Genetics and Evolution  If a random mutation or a product of genetic recombination creates a new trait in an offspring that is advantageous for survival, that offspring will have a much greater likelihood of reproducing and passing its genes on to future generations  As time and generations continue, this advantageous trait (or variation) will increase in frequency in the population, and may even lead to the creation of a new and species. This is called speciation.  Anole Lizards Speciation Anole Lizards Speciation

18. Evidence for Evolution  Geologic Record  Geographic Distribution of Living Species  Homologous Body Structures  Vestigial Structures  Comparative Embryology  Comparative Biochemistry

19. Geologic Record  Some evidence for evolution comes from fossils.  Fossils are traces or remains of once-living organisms that have been preserved by natural processes  Fossils that have formed in different layers of rock show how species have evolved over time

20. Evolution of the Chambered Nautilus

22. Geographic Distribution  Different species on different continents look and behave in similar manners  These species evolved into similar organisms because they were exposed to similar pressures of natural selection

23. Beaver- North America Capybara- South America

24. Homologous Body Structures  Structures of different organisms that are similar in form but may differ in function  They show that these organisms may have shared a common ancestor

25. Vestigial Structures  A structure that no longer serves a purpose in an organism but is present because it once was useful in the organisms evolutionary past  Ex: Whales with tiny pelvic bones, species of snakes with tiny legs, birds that have wings but cannot fly (penguins, ostriches)

26. Vestigial Structures

28. Comparative Embryology  Comparing embryos of different organisms can indicate they may have shared a common ancestor

29. Comparative Biochemistry  Comparing the molecular makeup of an organism such as proteins, enzymes, and other body chemicals  The greater the similarity, the more closely related the organisms are and the greater the likelihood they share a common ancestor  Ex: Every organism on this earth contains genetic material in the form of DNA or RNA

30. Comparative Biochemistry

31. Comparing DNA Sequences  The more similar the DNA sequence is between two species, the more closely related they are  For example, humans and chimps share about 98% of the same DNA!  Even stranger, humans share 50% of their DNA with fruit flies!

32. Human vs. Chimpanzee Genome  Comparing Human and Chimp Genome Comparing Human and Chimp Genome

33. Origin of Life on Earth  All life on earth is said to have evolved from one common ancestor  In Earth’s primitive environment, the first organisms to evolve were simple single-cellular organisms 3.8 billion years ago  Those single-cellular organisms evolved into multi-cellular organisms that became increasingly more complex  Today, every living species is a descendant of this first life form  Animation: Origin of Life Animation: Origin of Life

34. Evolutionary Models  Simple branching diagrams can be used to represent the evolutionary relationships among different species  These diagrams are called phylogenetic trees

35. Branching points represent ancestors common to species at the ends of these branches. Ends of branches represent species that are alive today. Based on this tree, are lizards more closely related to turtles or to birds?

36. 1.List the letters of species that are presently alive: 2.Which species is the one common ancestor to all the other species? 3.Which two species are more closely related, F and G, or F and L? 4.List all of the common ancestors of species L and N:

37. Human Influence on Evolution  Selective Breeding, or artificial selection, is when humans, not the natural environment, select the organisms that have certain advantageous traits and decide which ones will survive and pass on those traits to their offspring. This results in livestock breeds and crops that are different from their wild ancestors

39. Human Influence on Evolution  Genetic Engineering- humans manipulate genes (ex: cloning, recombinant DNA) to produce new varieties of plants and animals

40. Lamarck’s Theory of Acquired Characteristics  An organism can pass on characteristics that it acquired during its lifetime to its offspring  Proposed by Frenchman Jean-Baptiste Lamarck in the early 1800s  Two Parts:  Use and Disuse - individuals lose characteristics they do not require and develop characteristics that are useful  Inheritance of acquired traits - individuals inherit the traits of their ancestors

41. Example of Lamarckism  Giraffes stretching their necks to reach leaves high in the trees are able to strengthen and gradually lengthen their necks  Any offspring produced by these giraffes will inherit these characteristics and also have long necks

43. Extinction  Extinction is the disappearance of an entire species  It typically occurs when the environment changes  Sometimes, the environment changes so much that there are no longer any members of the species that are adapted to survive  Based on the fossil record, the majority of the species that have ever lived on Earth, are now extinct  Resurrecting the Extinct Resurrecting the Extinct