Unit: Evolution Aim: What evidences do we have to show that evolution takes place?

1. Unit: EvolutionAim: What evidences do we have to show that evolution takes place? The Nature of Change and Variation

2. What is Evolution? • Change in living things over time

3. Why study evolution? • Evolutionary concepts underpin much of modern biology - you can’t fully understand current trends in biology if you don’t understand evolution

4. In the early days... • Prior to 1760 -people believed organisms were fixed- that is they didn’t change • 1744-1829 – Jean Baptiste Lamarck • Evolution through the inheritance of acquired characteristics • Traits acquired during an organism’s life could be passed on to their offspring • Giraffes long necks explained by repeated stretching • hypothesis rejected

5. Types • Macroevolution = speciation – the formation of new species. The change in species over time • Microevolution-changes in genes/alleles within a population.

6. Charles DarwinAlfred Wallace • Descent with modification. • The Origin of Species. 1859 • Species were not created in their present forms but evolved from an ancestral species. • Natural selection, the mechanism by which change occurs (Explanation of how evolution occurs).

7. Evidence of Change • Fossil Record • Embryology • Molecular Biology-Amino Acids, Nucleotides, DNA sequencing, mitochondial DNA • Anatomy

8. Fossil Record • Fossils are a major source of information about changes in life during the distant past • In general, fossils show that life has increased in diversity and complexity over time

9. Fossil Record • Interpretation of the distribution of fossils in the rock initially based on the principle of superposition - in undisturbed rock layers, older fossils will be found lower in the rock than younger fossils -radiometric dating confirms this • In general older life forms tend to be less complex • Periods of diversity are interrupted by mass extinctions – followed by new life forms • Fossil Record is incomplete – estimated only 1 in 10,000 extinct species are represented – Why?

10. Embryology • All vertebrate embryos have • Gill slits on sides of the throat • Post anal tail • The fact that organisms without gills, or tails have them as embryos is taken as evidence of a common ancestry with organisms that had both • Which is the fish, rabbit, human, chicken, tortoise?

12. Comparative Anatomy • Similarities in structure between organisms was used to determine evolutionary relationships

13. Other Proof From Anatomy • Vestigial structures – structures that are greatly reduced with little or no function - they are thought to be left over from ancestors • Pelvis and leg bones in snakes • Reduced toe in horse • Appendix in human • Coccyx (tail bone) in humans • Human male nipples

14. Vestigial Structures

15. Comparative Anatomy • Analogous Structures • Similar function but different structure - • Insect’s wing, Bird’s wing and Bats wings – all allow flight, but are structurally different • Eyes of Molluscs and Vertebrates – both allow sight, but are different in structure

16. Comparative Anatomy • Homologous Structures • Have a similar structure but different function • The forelimbs of vertebrate animals all have the same structural design, but they have different functions • This similarity of structure shows a common ancestry

18. Molecular Biology Comparisons of the sequences of amino acids in proteins or nucleotides in DNA can show the relationships between organisms - the number of differences in the sequences of amino acids or nucleotides indicates how closely related two organisms are

19. Hemoglobin Comparison Species AA differences from humans Gorilla 1 Rhesus Monkey 8 Mouse 27 Chicken 45 Frog 67

21. Cladogram (family tree) created from a fossil record

22. Bird Evolutionary Tree Trees/cladograms are also created using comparative DNA sequences. If the DNA is very similar to each other, it means they share a fairly recent common ancestor.