EVIDENCE FOR EVOLUTION

1. EVIDENCE FOR EVOLUTION Scientific evidence to support the Theory of Evolution by Natural Selection

2. FOSSIL EVIDENCE • FOSSILS – are the mineralized remains or traces (tracks, imprints) of animals, plants or other organisms • THE FOSSIL RECORD –fossils found in rock strata that show a sequence or history of life on Earth Trilobite fossil found in Burgess Shale

3. BURGESS SHALE FOSSILS • The Burgess Shale is a middle Cambrian site (~540 MYA) • One of the few places in the world where difficult-to-preserve soft-bodied organisms of our past were preserved Some of the fossils found here are now long extinct and are unlike anything presently existing

4. THE FOSSILS RECORD PROVIDES US WITH THE FOLLOWING EVIDENCE: • Fossils found in young layers of rock (ie closer to the surface) tend to be more similar to present day organisms • Fossils appear in chronological order (oldest ancestors in deepest layers • Not all organisms appear in the fossil record at the same time – ie fish are the oldest vertebrates – then in subsequent layers amphibians, reptiles, mammals and birds

5. TRANSITIONAL FOSSILS • Transitional fossils are fossils that show intermediary links between groups of organisms • They can provide a link between the past and present Archaeopteryx – a transitional fossil because of its characteristics of both reptiles (dinosaurs) and birds

6. ARCHAEOPTERYX – transitional fossil

7. TRANSITIONALFOSSILS EXAMPLES • Example: Basilosaurus and Dorudon were ancient whales with tiny hind limbs – living entirely in water • Ambulocetus – a more recent ancestor, had heavier leg bones and lived in both water and on land

8. ANOTHER TRANSITIONAL FOSSILS: TIKTAALIK - The tiktaalik was an ancient tetrapod - It was thought to have descended from lobe-finned fishes - They lived in oxygen-poor water - used their lobe fins to live partly on land-possibly gave rise to amphibians

9. BIOGEOGRAPHY – the study of the past and present geographical distribution of organisms. • Darwin and Wallace observed that many species evolve in one location and spread out to other areas • Darwin found 14 different species of finch – he theorized all evolved from one common ancestral finch ADAPTIVE RADIATION – Diversification of a common ancestral species into a variety of species

10. BIOGEOGRAPHY -left: cactus from S.America -right: cactus from Australia

11. BIOGEOGRAPHY Top: Canary Island lizard Bottom: West African lizard

12. BIOGEOGRAPHY • Fossils of the same species can be found on the coastline of neighbouring continents • Example: Cynognathushas been found in Africa and S.America • At one time, all continents were joined (Pangea – 250 MYA) -a depiction of the Earth 250 MYA – continents were joined together

13. Cynognathus– ancient reptile -distribution of ancient organisms Cynognathus crateronotus

14. HOMOLOGOUS STRUCTURES Vertebrate forelimbs can be used for many different functions: • Flying (birds, bats) • Swimming (whales) • Brachiation (monkeys) • Running (horses, dogs) HOWEVER: they ALL contain the same set of bones organized in similar ways – WHY? Homologous structures are similar in structure but often differ in function

15. HOMOLOGOUS STRUCTURES Homologous structures provide evidence for a common ancestor amongst all vertebrates

16. ANALOGOUS STRUCTURES Analogous Structures Structures that evolve separately to perform a similar function are analogous. The wings of birds, bats, and insects, for example, have different embryological origins but are all designed for flight. Bird: feathers Bat: skin Butterfly: chitin

17. VESTIGIAL STRUCTURES Vestigial structures are thought to have had a purpose at one time in our ancestry, but no longer have a specific function (eg) human appendix

18. VESTIGIAL STRUCTURES “c” indicates the Underdeveloped hind legs Of the baleen whale The muscles connected to the ear of a human do not develop enough to have the same mobility as those of the monkey

19. EMBRYOLOGY • The embryos of different vertebrates show similar stages of embryonic development • Neck pouches – in humans become ears & throat - in fish become gills - Similarities among embryos point to a common ancestor

20. EMBRYOLOGY Can you tell which embryo is which? A – cat C - horse B – cow D - human

21. MOLECULAR BIOLOGY & GENETICS • Many organisms share similar cellular components such as: • Proteins – long chains of amino acids used for building & repair • Enzymes – made from proteins – they control many biochemical reactions in the cell • DNA – genetic material found in the nucleus The DNA of chimpanzees & humans is ~ 98% identical

22. HEMOGLOBIN • Hemoglobin—the oxygen-transport protein that gives blood its red color—got its start at about the time life originated on earth, nearly four billion years ago. Now it is almost ubiquitous, appearing in the cells of plants, animals and even bacteria, and a study of this protein affords scientists a rare glimpse back as well as forward in time. A look at the ancestral hemoglobins indicates that newly arising proteins co-opt the chemistry of older ones and gain new functions through structural alterations. But these studies have revealed an additional way to modify function. Scientists are coming to the realization that changes in a protein's regulation—the when and how of its expression—can also give rise to functional differences. The surprise, says the author, is that these regulatory changes outpace structural ones—an important lesson for students of molecular evolution and a possible indicator of where protein evolution will go in the future. http://adsabs.harvard.edu/abs/1999AmSci..87.....H hemoglobin (found in RBCs) is used to bond to O2

23. EVOLUTION: the change in the inherited traits of a population from generation to generation Above:hominid evolution