Notes: Evolution & Natural Selection

1. Notes: Evolution & Natural Selection

2. Charles Darwin His father was a wealthy doctor and wanted Charles to become a doctor. At age 16, he went to Medical School. In 1827, his father sent him to become a priest. In 1831, a friend asked him to go on a ocean trip as an unpaid naturalist.

3. Other Scientists and Evolution • Hutton- Geologist who studied how geologicalforces shaped Earth • Earth processes happen very slowly • Earth must be older than a few thousand years • Lyell- Geologist who said that in order to understand the past, we must observe how geological processes shape the earth today. If Earth can change over time, so must life. • Examples: volcanoes, earthquakes

5. Lamark was a French naturalist who… • Claimed that organisms tend to be complex and perfect and are therefore unchanging. • Use and disuse- Lamark thought that animals could change their bodies by using them in new ways. Example: animals could use front limbs as wings and develop flight. • Inheritance of acquired traits- Lamark though that all changes could be inherited. For example, if you lift weights, your children would inherit your muscles. • Lamark’s ideas are not scientifically accepted today!

6. Darwin’s Voyage on the HMS Beagle The purpose of Darwin’s trip was to draw accuratemaps of the region. Darwin was to collect specimens and document the plant and animallife.

7. Darwin’s original beliefs Divine creation - each species was created by God, unchanging and existing as it was originally created. However, on the voyage, his beliefs began to change when he got to the Galapagos Islands.

8. Darwin’s Finches The finches showed convincing evidence that species evolve.

9. Darwin was struck by the fact that the animals of the Galapagos Islands resembled those of the nearby coast of South America. Darwin hypothesized that ancestors of the Galapagos Islands must have migrated to the island and the population slowlychanged after they arrived.

10. Darwin published his book in 1844: On the Origin of Species by Means of Natural Selection.

11. Darwin’s Theory of Natural Selection • There is variation within any species • All organisms tend to over-reproduce • There is a struggle for survival • The fittest survive • The environment determines who is the fittest

12. 1. Variation exists within every population 1. Ladybugs have different spots

13. 1. Variation exists within every population 2. Zebras all have different stripes

14. 2. All species tend to produce more offspring than they can SUPPORT 3. Frog eggs 1. Turtle eggs 2. Insect eggs 4. Baby mice

15. 3. There is a Struggle for Survival • To eat • To drink • Territory • To mate

16. 4. The fittest will survive

17. 4. The fittest will survive Healthy or sick horse?

18. 5. Nature (the environment) will determine which organism is the fittest to Survive 1. long neck giraffes survive over short neck giraffes.

19. Evidence of Natural Selection in our lifetime The Peppered Moth in England Before the industrial revolution After the industrial revolution

20. Explanation for the peppered moth There was variation in the moth population to begin with, some were black and some were white. This variation was due to randommutations.

21. Beforethe industrial revolution, the bark of the tree bark was white in color. The white moths then were easily camouflaged,survived, and reproduced. Black moths were rare.

22. Afterthe industrial revolution, the trees became covered in soot/pollutionfrom all of the factories and the trees turned black. Now the black moth were easily camouflaged, survived, and reproduced. White moths were rare.

23. How does the peppered moth illustrate natural selection? There was variationin the population to begin with (some white, some black). Moths tend to over-reproduce. Therefore there is a struggle for survival. The fittest(those that were camouflaged the best) survived. The environment determined which moths were the most fit.

24. How Do New Traits Appear? • Recall that all genes have at least 2 alleles (forms) • All organisms have additional “invisible variation” due to small biochemical differences • Mutations- Random mutations also occur as a result of mistakesin DNA replication or due to environmental factors. • Gene Shuffling- homologous chromosome pairs move independently during meiosis- the 23 pairs in humans can produce 8.4 million different gene combinations!

25. Natural Selection may lead to Speciation Speciation - the evolution of a new species

26. The process of speciation • Geographic Isolation - when two populations become isolated by a geographic barrier such as mountains. Geographic Isolation

27. Reproductive Isolation - Sometimes when populations have been separated for a long, long time, they become so different that they can no longer breed and produce fertile offspring. Same species now, but may become two different ones.

28. 1.Horse and Donkey = MuleMule is infertile (can’t reproduce) mule donkey horse

29. Lion and Tiger = LigerLiger is often infertile (there have been successful breedings)

30. 2. The Kaibab and Abert Squirrels Became reproductively isolated by huge mountains

31. 3. Wood and Leopard Frogs Wood frogs Leopard frogs Seem to be the same species, but they breed at different times of the year.

32. Speciation-When two populations become so different that they can no longer breed and produce fertile offspring. They are then considered two separate species.

33. Speciation in Finches

34. Types of Selection • Directional Selection- when individuals at one end of the curve in a population have higher fitness than in the middle or other end. • Example: Supply of small seeds is low, birds with larger beaks can still feed, birds with smaller beaks cannot. We will see higher numbers of birds with larger beaks.

35. Disruptive selection- When individuals at the upper and lower ends of the curve have higher fitness than in the middle. • Example: If medium seeds are scarce, small and large seeds are plentiful, birds with small or large beaks will be most fit. Medium beaks will not be as numerous.

36. Stabilizing selection- when individuals in the center of the curve have higher fitness than those at the ends. • Example: babies with very low birth rate may not survive while very large babies may have trouble being delivered. Average sized babies are most fit.