Understanding Evolution: Changes in Life Forms and Controversies

2. What is Evolution? • Change over time • The theory of evolution proposes that modern forms of life have descended from earlier forms of life and changed as they descended. • What caused the “changes” or differences in traits? • MUTATIONS!! • Can we control this?

3. Why is the Theory of Evolution so Controversial? • People have varying beliefs on the origin of life due to religion. • Biological evolution does not study the origin of life. It only studies the changes in life forms since their origin.

4. Mechanisms that drive evolution? • Mutation= random changes in the DNA • Natural Selection • Gene Flow= movement of alleles into or out of a population • Genetic drift= changes in the alleles of a population due to random events (i.e. natural disaster. Important terms to know: • adaptation- A characteristic that increases fitness. • fitness- The ability to survive.

5. What is natural selection? • A theory introduced by Charles Darwin • A process that increases or decreases the presence of a trait depending on the trait’s ability to keep the organism alive and reproducing. • 3 conditions must be met for natural selection to occur: • Variation in characteristics (due to mutations) • Differences in fitness • Heritability (can be passed down to offspring) of the characteristic

6. Examples of Natural Selection • Galapagos finches= different beaks • Male peacocks= varying brightness in their feathers • Giraffes= varying neck length • Sharks= white on the underside and blue/gray on top • Humans= varying resistance to malaria • Bacteria= antibiotic resistance

7. Natural Selection Lab

8. Natural Selection Lab

9. How do we know if evolution has occurred? • The Hardy-Weinberg Principle calculates genetic variety in a population. If the genetic variety remains constant from one generation to the next, it is said to be in Hardy-Weinberg equilibrium (not evolving). • The H-W equation is: q2 + 2pq + p2= 1 (or 100%)

10. Hardy-Weinberg continued… q2= the frequency of homozygous recessive individuals. 2pq = the frequency of heterozygous individuals. p2= the frequency of homozygous dominant individuals.

11. Hardy-Weinberg Goldfish Lab

14. Evidence of Common Ancestry • The theory of evolution states that all living things have descended from another life form, just as you have descended from your parents and they descended from their parents. • The evidence that supports this theory includes: • Fossils • DNA • Embryo structure • Comparative anatomy

15. Cladogram • Evolutionary relatedness between organisms can be demonstrated on a diagram called a cladogram. • Organisms with similar characteristics are placed more closely on the diagram because they are thought to have evolved more closely to one another. • As an organism evolves, there is a new branch on the cladogram. • Characteristics that evolve between species are called derived characters.

16. Insect Cladogram Activity

17. Insect Cladogram Activity

20. Evidence of Common Ancestry- Fossil Record • Layers of rock contain fossils • new layers cover older ones • creates a fossil record over time • fossils show a series of organisms that have lived on Earth

21. Evolution from sea to land • Fossils are also evidence of transitional (in between) forms. • In 2006, there was the fossil discovery of the missing link between sea and land animals • 4 limbs • called Tiktaalik

22. Evidence of Common Ancestry- Comparative Anatomy Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors

23. How could thesevery different animalshave the same bones? Compare the bones • Limbs of different animals that perform different functions are built with the same bone structure

24. Homologous structures • Structures that come from the same origin • homo = same • logous = information • Forelimbs of humans, cats, whales, & bats are homologous structures. • same internal structure but different functions • evidence of common ancestor • The greater the # of homologous structures between organisms, the more closely related they are.

25. But don’t be fooled by these… • Analogous structures • look similar on the outside • have the same function • different internal structure • This means they do not have a close evolutionary relationship How is a birdlike a bug?

27. Vestigial organs • Structures of modern animals that have no function • evolutionists believe that these were functional in ancestors • evidence of change over time • some snakes & whales have pelvis bones & leg bones of walking ancestors • eyes on blind cave fish • human tail bone

28. Vestigial organs • Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land!

29. Evidence of Common Ancestry- Embryology • Development of an embryo tells an evolutionary story • The greater the # of similar structures during embryo development, the more closely related they are.

31. Dog Human Macaque Bird Frog Lamprey 8 32 45 125 67 0 10 20 30 40 50 60 70 80 90 100 110 120 Evidence of Common Ancestry-Biochemistry • Comparing DNA & protein structure • Every living thing uses the same genetic code! • The fewer the number of differences in the amino acid sequence of common proteins, the more closely related organisms are. number of amino acids different from human hemoglobin

32. What 2 organisms on the chart above are the most alike in terms of DNA? • What 2 organisms are the least alike? • What is the turtle’s closest relative? Why does this data make sense?

33. What data from whole genome sequencing can tell us about evolution of humans

34. Example: the Evolutionary Hypothesis of Common Ancestry Chromosome Numbers in the great apes: human (Homo)46chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48 Testable prediction: If these organisms share a common ancestor, that ancestor had either 48 chromosomes (24 pairs) or 46 (23 pairs).

35. Fusion Homo sapiens Inactivated centromere Telomere sequences Ancestral Chromosomes Chromosome Numbers in the great apes (Hominidae): human (Homo) 46chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48 Centromere Telomere Testable prediction:Common ancestor had 48 chromosomes (24 pairs) and humans carry a fused chromosome; or ancestor had 23 pairs, and apes carry a split chromosome.

36. Human Chromosome #2 shows the exact point at which this fusion took place “Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).” Homo sapiens Inactivated centromere Telomere sequences Chr 2 Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

37. Building “family” trees Evolution evidence can be used to create family trees. Closely related species are branches on the tree — coming from a common ancestor

38. Human Impact on Evolution- Selective Breeding Humans create the change over time “descendants” of the wolf

39. Artificial Selection …and the examples keep coming! I liked breeding pigeons!

40. Insecticide resistance • Human activities like spraying crop fields with insecticides leads to: • The survival of insects that are resistant to the insecticide • Resistant survivors reproduce • Resistance is inherited • Insecticide becomes less & less effective