1. 10/21/2015Jean Goliath 20101 EVIDENCE FOR EVOLUTION 10/21/20151 LIFE SCIENCES EVOLUTION COURSE MAY 2010

2. 10/21/2015Jean Goliath 20102  Palaeontology  Comparative Anatomy  Comparative Embryology  Comparitive Biochemistry  Biogeography 10/21/20152

3. Jean Goliath 20103  Palaeontology – study of plant/animal fossils  Palaeontologist – scientist who studies fossils.  Fossils - Remains, imprints, traces of organisms that are usually preserved in rocks.  Fossilisation – entire process by which dead organisms or their parts are transformed into fossils.  Fossil record: The observed remains of once-living organisms taken as a whole. 10/21/20153 http://kim.wits.ac.za/index.php?module=news&ac tion=viewstory&id=gen11Srv0Nme53_81569_12 70732348 FOSSIL EVIDENCE

4. 10/21/2015Jean Goliath 20104  Fossils are most commonly found in sedimentary rocks.  Sedimentary rocks are formed when clay and sand particles (SEDIMENTS) are carried from one place to another by water/wind - they pile up.  Sediments harden over years because of the weight of overlying sediments and form shale, sandstone and limestone.  Fossils are also found in other places e.g. tree resin, ice etc. 10/21/20154

5. Jean Goliath 20105  Plant/animal dies and rapidly covered with sediments  Soft tissues decay with the help of micro-organisms  Hard body parts e.g. bone, teeth, shells etc. remain intact as organic material is hardened or replaced by minerals.  More layers of sediments form over years  Layers compressed  Sediment solidifies and forms sedimentary rock  Movement of earth pushes sedimentary rock to the surface  Fossils exposed to surface by erosion of rock layers. 10/21/20155

6. Jean Goliath 20106  Fossils offer evidence of previous life on earth- geological time scale  Fossils help us find out the progressive changes within an animal or plant group.  Age of geological strata.  Information about climate and environment.

7. 10/21/2015Jean Goliath 20107  Body fossils – complete organisms preserved in ice, resin etc. OR parts of the organism e.g. shells  Cast fossils – Hard parts decomposes and leave and imprint or mould. Mould filled with minerals  Trace fossils - signs or marks of organism that lived previously e.g. fossilized footprints 10/21/20157

8. Jean Goliath 20108  Conditions for fossilisation not favourable  All fossils were NOT found yet  All organisms are not fossilised – some are eaten by predators, some decay quickly  Incomplete fossils  Problems in identifying fossils 10/21/20158

9. Jean Goliath 20109  Relative dating – sedimentary layers laid down first are the oldest, those laid down last is younger.  Radiometric dating – Decay of radioactive elements/isotopes  Halflife – rate of decay of a radioactive isotope, amount of time it takes to break down half of the atoms of radioactive material to its decay product Oldest sediments Parent daughter Most recent sediments

10. 10/21/2015Jean Goliath 201010 Radioactive isotopeHalflife 238 U decays to 206 Pb4500 million years 14 C decays to 14 N 5 730 years 234 U decays to 207 Pb 704 million years Question: The halflife of 14 C is 5 730 years and the halflife of 234 U is 704 million years. Explain which of 14 C or 234 U should be used to calculate the age of dinosaur fossils.

11. 10/21/2015Jean Goliath 201011  Uranium will be used because dinosaurs became extinct approximately 65 million years ago and 14 C can only measure up to 5 370 years ago.

12. 10/21/2015Jean Goliath 201012 During each equal time unit, one half-life, the proportion of parent atoms decreases by 1/2

13. 10/21/2015Jean Goliath 201013  When embryos of vertebrates are compared to one another in an early stage, they show a number of similarities

14. 10/21/2015Jean Goliath 201014

15. 10/21/2015Jean Goliath 201015  Earnest Haeckal (1834 – 1919) - claimed that “the development of an individual (ontogeny) reflects the stages through which the individual’s species has passed during its evolution (phylogeny)” The different stages in early development of an organism correlates with the adult forms of that organisms’ ancestors.  The idea is that vertebrates developed from a common ancestor

16. 10/21/2015Jean Goliath 201016  Name characteristics shown by embryos of different vertebrates that scientists use as evidence that these animals might have a common ancestor  Gill slits, tail, notochord, fish-like heart

17. 10/21/2015Jean Goliath 201017  Homologous structures – structures that are similar in structure but may have different functions e.g. forelimbs of most vertebrates, indicative of common ancestry

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19. 10/21/2015Jean Goliath 201019  Analogous structures – structures that differ in structure but resemble each other in function e.g. wings of birds and butterflies – not related Wings

20. 10/21/2015Jean Goliath 201020  Vestigial structures – structures diminished over evolutionary time, no longer perform the same function as in other organisms, must have been important in some ancestral form but became redundant in later species e.g. vestigial hind limbs of whales. Hindlimb femur pelvis Question Suggest why a vestigial structure, once it has been reduced, may not disappear altogether

21. 10/21/2015Jean Goliath 201021  The genes for vestigial hind limbs are still present in the species OR  The vestigial structure is no longer an advantage/disadvantage and are therefore not selected for or against.

22. 10/21/2015Jean Goliath 201022  Biochemical composition of most living organisms are remarkably similar  Strengthen the idea of a common ancestor  Characteristics that indicate possible common origin of different organisms include identical DNA structure, similar sequence of genes, identical protein synthesis etc.  Cytochrome C- similar amino acids in cytochrome C of different organisms.

23. 10/21/2015Jean Goliath 201023  The study of the distribution of plants and animals across the Earth.  Different but closely related species are found in similar biomes and have similar features adapting to that biome  Probably developed from common ancestral species.

24. 10/21/2015Jean Goliath 201024 Biogeographical Distribution The distribution of species around the world suggests that modern forms evolved from ancestral populations and spread out (radiated) out into new environments. Good examples are found on islands offshore from large continental land masses: Galapagos Islands Cape Verde Island

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26. 10/21/2015Jean Goliath 201026 CAN YOU SPOT THE FOSSIL(S) ? Australopithecus sediba

27. 10/21/2015Jean Goliath 201027 THANK YOU