Evolution

1. Evolution Darwin & Natural Selection

2. Broad concept • Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

3. Learning Objectives • Explain how evolution is demonstrated by evidence from the fossil record, comparative anatomy, genetics, molecular biology, and examples of natural selection

4. What is evolutionary theory? • Evolution = change over time • Evolution is often called the “unifying theory of biology” because it organizes all of the observations gathered by biologists and proposes and explanation for those observations. • Two men that made important contributions to the theory of evolution are Lamarck and Darwin.

5. 3.8 billion years ago This is our current "best guess" for the beginning of life on Earth. 530 million years ago • The first true vertebrate – an animal with a backbone – appears

6. What ideas preceded evolution? • Before Darwin, most people believed that living things had been created no more than 2000-3000 years ago. • BUT…old fossils were being discovered that were MILLIONS of years old. • Why did so many species disappear and are they related to living species?

7. Fossils • When an organism dies, it's bone structure is often preserved when debris or dirt packs on top of it for thousands - millions of years. • This is how researchers know what many of the dinosaurs looked like, which led to discovery of how they lived and interacted with the ecosystem.

8. What ideas preceded evolution? • 1795 - James Hutton: proposed that Earth had to be much older than ~3000 years old • 1830 - Charles Lyell: proposed that geologic features on Earth change over time… so Darwin wondered if life changed too!

9. What ideas preceded evolution? • 1809 - Jean-Baptiste Lamarck: “Use/Disuse Theory”…first ‘evolution-like’ theory • If an organism used/did not use a particular feature in its lifetime, this use/disuse would be passed on to offspring • (If a man was a bodybuilder, his child would be naturally muscular.) • WRONG!!! (but it was an interesting idea)

10. What ideas preceded evolution? • 1798 - Thomas Malthus: if the human population grew continuously, we would hit the Earth’s carrying capacity and people would die. • Darwin thought… • “WHY haven’t plants/animals grown continuously over time? WHAT causes some to survive and others to die?

11. Darwin’s Background • Born in England, 1809 • Studied Medicine at Edinburgh University • Transferred to Cambridge University – earned a degree in theology. • the study of religious faith, practice, and experience; especially: the study of God and of God's relation to the world • Studied to be a Minister Library of Congress, Prints and Photographs Division [reproduction number, e.g., LC-USZ61-104].

12. Darwin • Darwin was a naturalistwho observed many species. • He is famous for his trips to the Galapagos Islands, his observations of the finches (and other animals) and the book he wrote: The Origin of Species

13. Three Main Parts of Charles Darwin’s Life 1809 – 1831: Age 0 - 22 Childhood, education, college 1831 – 1836: Age 22 to 27 Voyaging on the HMS Beagle 1836 – 1882: Age 27 to 73 Scientist and author

14. Darwin’s Schooling 1817 – 1818: Attended day-school of Reverend Case 1818 – 1825: Attended Shrewsbury School, a boarding school run by Dr. Samuel Butler (grandfather of the Samuel Butler who wrote Erewhon and The Way of All Flesh). He could readily walk back home from this school, although he was a boarder. 1825 – 1827: Studied medicine at University of Edinburgh, where his father and brother had studied, but discovered medicine was not to his liking. 1828 – 1831: Attended and graduated from Cambridge University (theology) intending to become a clergyman.

15. Darwin’s Expedition - 1831 • Hired as a Naturalist on H.M.S. Beagle • Job was to collect specimens • Sailed on fiveyear scientific expedition around the world • Main mission of the Beagle was to chart the South American coastline • Down east coast of South America • Up pacific coast to Galapagos Islands • Made stops on mainland and islands • Observed variety of life and habitats • Collected fossils, rocks, plants & animals

17. Galapagos Islands • a group of 18 islands in the Pacific off South America (500 miles off coast of Ecuador). Formed by volcanoes & geologic uplift between 8-90 million years ago.

18. Galapagos Islands • Animal Species include: finches, green turtle, land iguanas, marine iguanas, Galapagos penguin, lava gulls, sea lions, whale, red-footed & blue-footed boobies, frigates, tortoises, waved albatross, pelicans, sharks, rays, flamingos, crabs • Most of these animals live only on these islands! However, they look like species living on the mainland

20. Lonesome George • The last known individual of the Pinta Island tortoise which is one of eight to fifteen subspecies of Galápagos tortoise • Rarest creature in the world! • ~90 - 100 years old!!!! • First seen in 1971 & relocated for his safety to the Charles Darwin Research Station, George was penned with two females of a different subspecies… no viable eggs • Recently – other subspecies/Pinta hybrids with ~1/2 of George’s genotype have been discovered. Died June 2012

21. Galapagos giant tortoises • Evolved from a common ancestor that arrived from the mainland (likely a pregnant female or breeding pair) • Original ancestor was much smaller and evolved into the present-day giants. Gigantism evolves because there is no longer any need to hide from predators and because there are no other similar animals to compete with for food. • The tortoises spread around the islands and evolved differently in order to adapt to the different environments

22. Shells • Some tortoises developed domed carapaces (top shells) while other developed saddleback carapaces. (along with variations in between) • Domed – turtles can retreat back into their shell (protection). Low vegetation • Saddleback– due to higher vegetation on drier islands, tortoises needed a longer neck to s-t-r-e-t-c-h

23. 250,000 down to 15,000 • ~250,000 tortoises inhabited the islands when they were discovered. • 12-15 subspecies • Today only about 15,000 are left  • Now only 11 subspecies • After the arrival of humans… • Hunting tortoises for meat! • Whalers would capture hundreds and keep on ships for food • Destruction caused by goats released in 1950’s – invasive species! • Competed for food • Other invasive species – pigs, dogs, cats, rats, plants

24. Darwin’s observations of finches (birds) on the Galapagos Islands led him to believe that different species may have descended from a common ancestor.

26. Relationship between species (beaks) & food

27. Darwin’s finches • Darwin’s conclusions • variations in beaks • differences in beaks in the original flock • adaptations to foods available on islands • natural selection for most fit • over many generations, the finches were selected for specific beaks & behaviors • offspring inherit successful traits • accumulation of winning traits:both beaks & behaviors • separate into different species

28. Warbler finch Cactus finch Woodpecker finch Sharp-beaked finch Small insectivorous tree finch Small ground finch Warbler finch Large insectivorous tree finch Cactus eater Medium ground finch Tree finches Ground finches Insect eaters Seed eaters Large ground finch Vegetarian tree finch Bud eater From 1 species to 14 species… natural selection for best survival & reproduction variation

29. Darwin’s view of Evolution • Darwin • giraffes that alreadyhave long necks survive better • leave more offspring who inherit their long necks • variation • selection & survival • reproduction & inheritance of more fit traits

30. According to Darwin, giraffes get taller over time due to Natural Selection

31. Natural selection is the process by which those heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. It is a key mechanism of evolution.

32. It follows logically that … Some individuals will be better suited to their environment - they will survive and reproduce more successfully than individuals without those characteristics Future generations will thus contain more genes from better-suited individuals. As a result, characteristics will evolve over time to resemble those of the better-suited ancestors.

33. Survival of the Fittest • the environment limits the growth of population by increasing the rate of death or decreasing the rate of reproduction, or both. • Organisms with certain (+) variations survive, reproduce, and pass their variations on to the next generations. • Organisms without these variations are less likely to survive and reproduce.

34. Darwin Presents His Case • Darwin returns to England in 1836 with specimens from around the world. • On the Origin of Species: • book – foundation of evolutionary biology. HUGE impact on science!!! • 1859 – published • Topics included… • NATURAL SELECTION • PHYSICAL EVIDENCE FOR EVOLUTION

35. Darwin was afraid to publish his work! • Why????? • during the first half of the 19th century the English scientific establishment was closely tied to the Church of England, while science was part of natural theology. • Ideas about the transmutation of species (evolution) were controversial as they conflicted with the beliefs that species were unchanging parts of a designed hierarchy and that humans were unique, unrelated to animals.

36. On the Origins of Species • Darwin's book introduced the scientific theory that populationsevolveover the course of generations through a process of natural selection. • included evidence that he had gathered on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence, and experimentation

37. On the Origin of Species • the evidence he presented generated scientific, philosophical, and religious discussion.

38. Darwin Presents His Case • Artificial selection: nature provides genetic variation and humans select desirable traits for further mating…crops/livestock were undergoing an “artificial evolution”! • Struggle for existence: animals survive that are better adapted for their environment (faster, camouflaged, smarter etc.) than those who are not (slower, weaker etc.)

39. Darwin Presents His Case • Survival of the fittest: individuals with adaptations that enable fitness survive and reproduce most successfully • Also called - NATURAL SELECTION • The mechanism of evolution! • Adaptation= an inherited characteristic • Fitness= ability of an organism to survive in its environment and reproduce

40. Darwin Presents His Case • Over time, Natural Selection results in changes in the inherited characteristics (the genes) of a population! • Descent with modification: each species in existence today came from other species over time…they just changed in some way(s) • Every living thing has a common, single ancient organism it descended from • Think about it… there had to be a first cell !

41. Darwin’s Evidence of Evolution EVIDENCE: • 1) Fossils: a person can “see” an organism evolving through history by looking at fossils of different ages • 2) Geographic distribution: UNRELATED animals/plants were living in areas of the world with similar environments

42. Darwin’s Evidence of Evolution • 3) Homologous body structures: organs or limbs differ in form or function, but contain SAME basic structures • Turtle leg, alligator leg, bird wing, human finger all have similar bone structure and likely all came from a specific ancient fish fin • 4) Embryology: early embryos of many animals look almost EXACTLY the same!

43. Homologous Structures

46. Sharks & Dolphins are ANALOGIES • They may share the same basic shape, but underneath their skins, sharks and dolphins are very different!

48. HOMOLOGY • In everyday life, people look like one another for different reasons. • Two sisters, for example, might look alike because they both inherited brown eyes and black hair from their father. • On the other hand, two people attending an Elvis impersonators' convention may look alike because they are both wearing rhinestone studded suits and long sideburns. The similarity between the sisters is inherited, but the similarity between the Elvis impersonators is not.

49. Summary of Darwin’s Theory • Heritable variations exist among individuals. • The students in a classroom all look different • Organisms compete to survive and reproduce. • A sunflower produces hundreds of seeds but only a % germinate • Through natural selection, the fittest individuals (best suited to environment) reproduce and pass traits to their offspring. • Tall sunflowers produce tall sunflower seeds • Species evolved from common ancestors. • Bat, human, alligator, primate all evolved from same ancestor!