1. Principles of Evolution Chapter 24

2. Classification of Humans KingdomAnimalia PhylumChordata ClassMammalia OrderPrimates FamilyHominidae GenusHomo Species sapiens

3. Challenges to Early Beliefs Biogeography - discovery of species in isolated locales Comparative morphology - similarities between animals, parts with no functions Fossils - deep layers with simple fossils, overlying layers with increasing complexity

4. Charles Darwin Proposed the theory of evolution by way of natural selection Influenced by –Observations made while naturalist on H.M.S. Beagle –Conversations with other naturalists –Writings of Thomas Malthus

5. Variation in Populations Individuals do not evolve; populations do Members of a population have similar traits Details of traits vary among individuals Some variation results from genetic differences (different alleles)

6. Mutation A heritable change in DNA Most are harmful Some are neutral A few are beneficial

7. Natural Selection Individuals vary Some variations are heritable Some versions of traits increase fitness Natural selection is the difference in survival and reproduction in individuals who have different versions of a trait

8. Evolving Populations A population is evolving when some forms of a trait are becoming more or less common relative to the other forms Over time, shifts in the makeup of gene pools have been responsible for the amazing diversity of life forms on Earth

9. Other Changes to Gene Pool Genetic drift –Founder effect –Virtually no Native Americans with type B blood Gene flow –Physical movement of alleles –Helps keep neighboring populations genetically similar

10. Species A genetic unit consisting of one or more populations of organisms Members can interbreed and produce fertile offspring under natural conditions Reproductively isolated from other species

11. Speciation time Atime Btime Ctime D time

12. Fossils Usually hard parts Form in sedimentary rock Stratification Fossil record is biased

13. Biogeography Distribution of plants and animals Plate tectonics

14. Comparative Morphology Homology –Similarity in body parts in different organisms –Attributable to descent from a common ancestor Analogy –Similarity in body parts in different organisms –Attributable to similar environmental pressures

15. Homologous Structures Vertebrate forelimbs

16. Comparative Embryology Early vertebrate embryos strongly resemble one another Same plan of development Fish Reptile Bird Mammal

17. Proportional Skull Changes Chimpanzee Human

18. Evidence from Comparative Biochemistry Molecular clocks –Neutral mutations Protein comparisons –Cytochrome C Nucleic-acid comparisons –Base-pairing of DNA or RNA from one species to another

19. Extinctions - End of the Line Background extinction –Local changing conditions Mass extinction –Catastrophic global event –65 million years ago –Probably asteroid impact

20. Adaptive Radiation New species of a lineage moves into a wide range of habitats Has occurred in the human lineage Homo habilis remained in Africa H. erectus went to Europe, Asia H. sapiens evolved by 100,000 years ago

21. Trends in Human Evolution Upright walking Refined hand movements Enhanced daytime vision Changes in dentition Changes in brain and behavior

22. Comparison of Skeletal Organization

23. Trend toward Longer Life Spans and Dependency

24. From Primates to Hominids 60 million years ago –Tropical forests –Small rodents, tree shrews 54 - 38 million years ago –Primates in trees 36 million years ago –Tree-dwelling anthropoids 10 - 5 million years ago –First hominoids

25. Early Earth Primitive atmosphere –H 2 –N 2 –CO –CO 2 –Probably no O 2

26. Complex Compounds Form Organic compounds may have: Formed when lightning interacted with gases in early atmosphere Assembled on clays in tidal flats Formed near hydrothermal vents

27. Emergence of First Living Cells Self-Replicating Systems –RNA –DNA Plasma Membranes –Proto-cells