1. Theory of Evolution

2. THEORY OF EVOLUTION The theory of evolution is scientists explanation of how living things began. Also called organic evolution LIVING ORGANISMS HAVE CHANGED GRADUALLY OVER TIME TO FORM NEW ORGANISMS THAT ARE MORE COMPLEX.

3. Jean-Baptiste de Lamarck Jean-Baptiste de Lamarck (lived before Pasteur) – French scientist credited with one of the first theories of evolution Believed that organisms change over time from simple to more complex by passing on acquired traits to offspring. Believed that as environment changed, organisms changed their behavior to survive. As they used a body part for survival, it would improve and be passed down. If they no longer needed a body part or organ, it would go away.

4. Giraffes Example: Lamarck believed that giraffes got their long necks in order to eat leaves found in tall trees. They continued to stretch their necks and over time the necks grew and were passed down to offspring.

5. In the Beginning – Some Say The atmosphere of the early earth was very harsh. It was extremely hot and wet and contained little free oxygen. It was not suitable for life.

6. But where did the first living thing come from? Organic evolution is when one living thing comes from another. But where did the first living thing come from? Alexander Operin and J. B. S. Haldane developed a hypothesis (Operin-Haldane Hypothesis) that life started from chemicals in the atmosphere reacting to form organic compounds. This is chemical evolution. They never tested the hypothesis.

7. Organic Molecules In1953, Stanley Miller and Harold Urey created an experiment that showed atmospheric gases could react with one another to form small organic molecules. They placed ammonia, methane, and hydrogen in a closed container. Then they heated it and added electricity to simulate lightning on Earth. They found amino acids and sugars after a few days.

8. Next step The next step in evolution was for organic molecules to develop lipid membranes around them. These were called protocells

9. First true cells The first cells were anaerobic (without oxygen), heterotrophic (cannot make their own food) prokaryotes (simple cell with no nucleus or organelles) that used chemosynthesis to produce energy. Chemosynthesis – “ate” organic compounds for food. The first cells would have been classified as bacteria.

10. Second Cells Eventually, these bacteria cells evolved to create their own food. These are called autotrophs – some use chemosynthesis and others use photosynthesis (carbon dioxide plus water yields glucose). o Because photosynthesis releases free oxygen, many scientists believe that these photosynthetic bacteria formed the atmosphere we know today.

11. Oxygen – Not so good Free oxygen is very destructive because it reacts with everything. Prokaryotes would have had to develop a way to protect themselves. Scientists theorize that they evolved to use the oxygen to produce energy. Now they would be called aerobic cells.

12. Prokaryotes to Eukaryotes How did cells continue to evolve to become complex eukaryotes with organelles? Anaerobic cell engulfs aerobic cell (eats it) The aerobic bacteria that is eaten becomes what is now a mitochondria (creates energy for the larger cell) = aerobic eukaryotic cell

13. Endosymbiotic Theory This is a symbiotic relationship – both partners benefit Then an aerobic eukaryote engulfed a photosynthetic bacterium which turned into a chloroplast (another symbiotic relationship). This formed an autotrophic eukaryote that gave rise to plant cells.

14. Endosymbiotic Theory summarized Anaerobic Cell eats Aerobic cell (bacteria) Aerobic cell becomes mitochondria and now we have an aerobic eukaryotic cell Some become animal cells Others eat a photosynthetic bacteria Photosynthetic bacteria becomes a chloroplast. Now we have photosynthetic eukaryotic cells that become plant cells.

16. Other Theories Panspermia – belief that life originated in outer space Organic compounds were found in a meteorite that landed in Australia in 2008

17. Fox Sidney Fox – Performed experiments that caused amino acids to form spherical membranes that are semipermeable – could have formed protocells.

18. Not Yet Scientists have been unable to explain how RNA or DNA formed as of yet to confirm any type of chemical evolution theory.

19. Evidence of Evolution

20. The theory of evolution offers an explanation for the existence of all living organisms on the Earth today and in the past It supposes that present day organisms have all been derived from organisms that lived in the past By a series of very small changes over millions of years new species have developed from previous species* Over a period of about 3000 million years, many new species have been produced and many have become extinct. We know a great deal about the organisms that lived millions of years ago from studying their fossilised remains. 2 Theory of evolution

21. There are many ways in which an organism can be fossilised One of these ways is shown in the next sequence of slides In principle, a fossil is formed when an organism dies, its body is enclosed in mud, or sand. The soft parts decay but some of the hard parts (skeleton, shells, seeds) are preserved The mud or sand eventually becomes rock and the hard parts of the organism are mineralised. When the rock is exposed as a result of earth movements or erosion, the fossil remains can be dug out and studied. 3 Fossil formation

22. Living fish A Dies Enclosed in sediment Hard parts fossilised Living fish B Dies Enclosed in sediment Hard parts fossilised Fish B becomes a fossil much later than fish A The sediment eventually becomes rock The deeper the rock layer, the older the fossil 4 Process of fossilisation

23. living fish sediment from river fish skeleton partly buried by sediment 5 Sedimentation

24. fish skeleton fossilised older sediment becomes rock more recent sediment collects 6 Layers of sediment

25. land raised above water level recent rock older rock 7 Earth’s crust movement

26. earth movements fracture rock fossilised skeleton exposed 8 Fractured rock

27. When rock strata become exposed, it can be assumed that, in most cases, the lowest layers are the oldest* This means that the fossils of organisms preserved in the lowest layers represent animals and plants that lived many millions of years ago rock strata of increasing age 9 Rock strata © Alan Richardson

28. This is a fossil of a fish which lived 40 million years ago 10 Fossil fish

29. This is a reconstruction, from fossil remains, of an ‘armour-plated’ fish which lived 350 million years ago dorsal fin The fish which gave rise to fossils such as this, were very different from today’s fish 11 Fossil fish reconstruction

30. By studying the type of fossils and the abundance of each species in the different strata, it is possible to build up a picture of how the populations of organisms changed over millions of years The next slide shows how this picture appears for vertebrate animals The width of each band represents the relative abundance of the organisms as judged by their fossil remains. For example, 100 million years ago there were many more species of reptiles than there are today Mammals do not appear at all in rocks older than about 3 million years 12 Vertebrate sequence

31. Relative number of species 400 million years ago fish amphibia reptiles birds mammals 100 million years ago 200 million years ago 300 million years ago o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o Possible lines of evolution 13 Vertebrate fossil record

32. Interpretation of the fossil record (1) In interpreting the fossil record, it must be borne in mind that: fossils will be formed only in places and at times when conditions are suitable for fossilization. So they may not be representative of the organisms living at that time 1 only the skeletons, shells and other parts resistant to decay will be preserved 2 fossils are found only if they are exposed by Earth movements or erosion 3 very few fossils have been found which show intermediate stages between different groups of organism 4 14 Interpretation (1)

33. Interpreting the fossil record (2) Despite its gaps, the fossil record does show that, over millions of years: organisms became more numerous and more diverse, i.e. many more species came into existence 1 organisms became more complex 2 although very few organisms found as fossils are alive today, there are many basic similarities in the body structure of the fossils and similar organisms living today 3 although they are few, there are fossils which show characteristics intermediate between major groups 4 15 Interpretation 2

34. feathers claws thin ribs teeth long tail wing-like forelimbs Reptile-like features Bird-like features Replica of Archaeopteryx fossil; half bird half reptile © Alan Richardson 16

35. Evidence from comparative anatomy Fish, amphibia, reptiles, birds and mammals all have vertebral columns, skulls, brains, circulatory systems and many other features in common This suggests that they all arose from a common ancestral form rather than arising independently. The same reasoning can be applied to other groups of organisms such as insects which have most of their anatomical features in common Although these features are superficially different there is a basic pattern underlying them all 18 Comparative anatomy

37. Vertebrate limbs The basic pattern of the vertebrate limb is represented by the human arm skeleton shown below ball and socket joint hinge joint single bone two bones group of small bones five jointed digits 17 Vertebrate forelimb

38. The forelimbs of the following vertebrates show the basic pattern of limb bones with modifications which are adapted to their methods of locomotion. LizardBird DolphinBat The basic pattern suggests they have evolved from a common ancestor 19 Modified limbs

39. Another important line of evidence for evolution comes from DNA analysis Any permanent change in form or function of an organism must be preceded by a change in its DNA Organisms which have much of their DNA in common must be closely related, i.e. they have split from a common ancestor comparatively recently (in geological terms) For example, humans and chimpanzees have 99% of their DNA in common which suggests a close relationship and relatively ‘recent’ divergence from a common ancestor DNA evidence 20 DNA evidence

40. The next slide shows the widely accepted pathway of evolution for plants and animals Only a few of the main types of organisms are shown 21 Evolutionary pathways

41. Mammals Flatworms Annelids InsectsCoelenterates Fish Birds Reptiles Crustacea Amphibia Single celled organisms MonocotsHerbsShrubsTrees Dicots Flowering plants Conifers Mosses LiverwortsAlgae Ferns Fungi Multicellular plants Multicellular animals Mollusc 22 Evolutionary pathways 2

42. The accepted view of evolution 26 ‘Correct’ evolutionary sequence