1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero D1 & D3 Objectives Human Evolution and the Origin of Life on Earth

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Conditions on early Earth made the origin of life possible Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages: 1. Abiotic synthesis of small organic molecules 2. Joining of these small molecules into polymers 3. Packaging of molecules into “protobionts” 4. Origin of self-replicating molecules

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Synthesis of Organic Compounds on Early Earth Earth formed about 4.6 billion years ago, along with the rest of the solar system Earth’s early atmosphere contained water vapor and chemicals released by volcanic eruptions Experiments simulating an early Earth atmosphere produced organic molecules from inorganic precursors, but such an atmosphere on early Earth is unlikely

4. LE 26-2 Water vapor CH 4 NH 3 H2H2 Electrode Condenser Cold water Cooled water containing organic molecules Sample for chemical analysis H2OH2O

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extraterrestrial Sources of Organic Compounds Some organic compounds from which the first life on Earth arose may have come from space Carbon compounds have been found in some meteorites that landed on Earth

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Instead of forming in the atmosphere, the first organic compounds may have been synthesized near submerged volcanoes and deep-sea vents Video: Hydrothermal Vent Video: Hydrothermal Vent Video: Tubeworms Video: Tubeworms

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The “RNA World” and the Dawn of Natural Selection The first genetic material was probably RNA, not DNA RNA molecules called ribozymes have been found to catalyze many different reactions, including: – Self-splicing – Making complementary copies of short stretches of their own sequence or other short pieces of RNA

8. LE 26-5 Nucleotides Template 3 3 55 Ribozyme (RNA molecule) Complementary RNA copy

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protobionts Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure Experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds For example, small membrane-bounded droplets called liposomes can form when lipids or other organic molecules are added to water

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Early protobionts with self-replicating, catalytic RNA would have been more effective at using resources and would have increased in number through natural selection

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis and the Oxygen Revolution The earliest types of photosynthesis did not produce oxygen Oxygenic photosynthesis probably evolved about 3.5 billion years ago in cyanobacteria

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Effects of oxygen accumulation in the atmosphere about 2.7 billion years ago: – Posed a challenge for life – Provided opportunity to gain energy from light – Allowed organisms to exploit new ecosystems

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosymbiotic Origin of Mitochondria and Plastids The theory of endosymbiosis proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.4: Eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes Among the most fundamental questions in biology is how complex eukaryotic cells evolved from much simpler prokaryotic cells

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The prokaryotic ancestors of mitochondria and plastids probably gained entry to the host cell as undigested prey or internal parasites In the process of becoming more interdependent, the host and endosymbionts would have become a single organism

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Key evidence supporting an endosymbiotic origin of mitochondria and plastids: – Similarities in inner membrane structures and functions – Both have their own circular DNA

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The absolute ages of fossils can be determined by radiometric dating The magnetism of rocks can provide dating information Magnetic reversals of the magnetic poles leave their record on rocks throughout the world

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Half-Life Definition – thanks to D. Bio notes half-life- the amount of time required for 1/2 of a radioactive sample to decay to its stable form

19. LE 26-7 1 Accumulating “daughter” isotope Remaining “parent” isotope 2 1 4 1234 1 8 1 16 Ratio of parent isotope to daughter isotope Time (half-lives)

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Derived Characters of Primates Most primates have hands and feet adapted for grasping Other derived characters of primates: – A large brain and short jaws – Forward-looking eyes close together on the face, providing depth perception – Well-developed parental care and complex social behavior – A fully opposable thumb

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Derived Characters of Hominids A number of characters distinguish humans from other hominoids: – Upright posture and bipedal locomotion – Larger brains – Language capabilities – Symbolic thought – The manufacture and use of complex tools – Shortened jaw

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

23. PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero LE 34-41 Paranthropus robustus Homo ergaster Homo sapiens Homo neanderthalensis ? Paranthropus boisei Australopithecus africanus Kenyanthropus platyops Australopithecus garhi Australopithecus anamensis Homo habilis Homo erectus Homo rudolfensis Australopithecus afarensis Ardipithecus ramidus Orrorin tugenensis Sahelanthropus tchadensis Millions of years ago 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two common misconceptions about early hominids: – Thinking of them as chimpanzees – Imagining human evolution as a ladder leading directly to Homo sapiens

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Incompleteness of fossil record The fossil record often shows apparent trends in evolution that may arise because of adaptation to a changing environment The fossil record is based on the sequence in which fossils have accumulated in such strata Fossils reveal ancestral characteristics that may have been lost over time

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Perry, G. H., et al. (2007). Diet and the evolution of human salivary amylase gene copy number. Nat. Genet. doi: 10.1038/ng2123 Traditionally, it was believed that our ancestors evolved a large brain to accomodate language and tool use. But in recent years, a number of theories have focused on the role of diet in human brain evolution. During the course of human evolution, changes in diet were brought about by the control of fire, the domestication of plants and animals, and the development and mastery of stone tool technology. According to one theory, increased consumption of meat by our ancestors provided the additional energy needed for brain expansion. (Cooking would have further increased the amount of calories obtained from meat.) Another holds that a switch to a seafood-rich diet would have provided polyunsaturated fatty acids which, when incorporated into nerve cell membranes, would have made the brain function more efficiently.

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparison of genetic and cultural evolution GENETICCULTURAL The product of natural selectionThe product of learning. the transmission of acquired behaviour characteristics DarwinianLamarkian Innate not modified during the organism’s life time Learned during the life time Passed on through hereditary information Passed on to kin (family), social group, population, within a generation and between generations Slow changeFast change © 2008 Paul Billiet ODWSODWS

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The relative importance of genetic and cultural evolution for humans Not limited to humans examples found amongst birds and non-human primates Genetic evolution determines features such as basic anatomy e.g. maximum cranial capacity that in turn will determine “intelligence”. This sets the possible scope of cultural evolution Hominid cultures are associated with particular cultures: