1. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Human Evolution and PREHISTORY Chapter Three: BIOLOGY AND EVOLUTION Link to the Canadian Association for Physical Anthropology Link to the Canadian Association for Physical Anthropology

2. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Chapter Preview What Forces Are Responsible For The Diversity Of Primates In The World Today? What Is Evolution? How Does Evolution Produce New Forms of Organisms? What Are The Forces Responsible For Evolution?

3. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. PRIMATES Our group of animals is so diverse because it is a product of evolution “Descent with modification” (Charles Darwin)

4. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE CLASSIFICATION OF LIVING THINGS Linnaeaus classified living things:  as a way of creating order and naming the plants and animals to the glory of God’s creation  on the basis of overall similarities in small groups, or species

5. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE CLASSIFICATION OF LIVING THINGS Modern classification  distinguishes superficial similarities (analogies) from basic ones (homologies)  homologous structures are possessed by organisms that share a common ancestry  analogous structures may look similar and may serve the same purpose, but do not arise in similar fashion from a common ancestor

6. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE CLASSIFICATION OF LIVING THINGS On the basis of homologies, as in Linnaeus’ system groups of like species are organized into larger groups, genera (singular, genus) Species  Population or group of populations capable of interbreeding but that is reproductively isolated from other such populations

7. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE CLASSIFICATION OF LIVING THINGS Characteristics used by Linnaeus to classify: 1.Body structure 2.Body function 3.Sequence of bodily growth

8. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE CLASSIFICATION OF LIVING THINGS Characteristics used by Modern Taxonomy: 1.Body structure, function and growth 2.Chemical reactions of blood, protein structure, genetic material, parasite comparison

9. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE DISCOVERY OF EVOLUTION Creationism In Linnaeus’ time species were thought to be unchangeable since the time of creation Today creationism is supported by fundamentalist Christian groups like the Creation Research Society (CRS) Creationism is based on a belief system rather than on scientific evidence

10. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE DISCOVERY OF EVOLUTION 18 th Century Influences Lamarck – species can change Cuvier – different sedimentary layers held different types of fossils, consistent with existing 18 th century view called catastrophism (evidence of new acts of divine creation) Lyell – gradual process shaped the earth over a long period of time and are no different today, uniformitarianism

11. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. THE DISCOVERY OF EVOLUTION  By the 19 th century many naturalists had come to accept the idea that life had evolved  Charles Darwin and Alfred Russell Wallace independently discovered how evolution works  Their idea was natural selection

12. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Natural Selection Darwin and Wallace based their idea on two observations: 1.All organisms display a range of variation 2.All organisms have the ability to expand beyond their means of subsistence

13. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Natural Selection The evolutionary process through which factors in the environment exert pressure that favours some individuals over others to produce the next generation

14. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. ORIGINAL STUDY The Unsettling Nature of Variational Change  Before Darwin evolution was seen as moving in predictable fashion, and ultimately, to humans at the pinnacle  Darwin introduced the idea of “undirected variation”, of which only a selected portion was passed on to the next generation  The difficulty lies in seeing human evolution as unpredictable and nonprogressive in nature

15. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Gene Portion of DNA molecule containing several base pairs that directs the synthesis of a protein, e.g. gene for ABO blood type

16. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Mendel Law of Segregation  Genes, or the units controlling the expression of visible traits, retain their separate identities over generations

17. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Mendel Law of Independent Assortment  Genes controlling different traits are inherited independently of one another

18. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY DNA -- A complex molecule with information to direct the synthesis of proteins and the ability to produce an exact copy of itself RNA – carries instructions from DNA to make amino acids

19. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Genetic Code  Three-base sequence (codon) of a gene that specifies production of an amino acid  Amino acids strung together make a protein

20. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Genome The complete sequence of DNA for a species Human Genome 3 billion chemical bases, with 30,000 functioning genes 30,000 genes account for 1-1.5% of the human genome The rest is non-coding“junk DNA” (see Applied Box)

21. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Two types of genes are responsible for what organisms actually become: Structural genes – contribute directly to actual formation of the structure, e.g. eye colour Regulatory genes – control expression or activity of other genes, e.g. homeobox genes control whether an organism has fins or legs

22. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Chromosomes Long strands of DNA in a protein matrix 23 pairs in humans Each chromosome in the pair contains genes for the same traits, e.g. gene for A-B-O blood group Variant forms of these genes are called alleles, e.g. A, B and O

23. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Mitosis Cell division that produces new cells having exactly the same number of chromosome pairs, and hence, genes as the parent cells Meiosis Cell division that produces the sex cells, each of which has half the number of chromosomes, and hence genes, as the parent cell

24. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Homozygous Refers to a chromosome pair that bears identical alleles for a single gene, e.g. each of the pair has an A allele Heterozygous Refers to a chromosome pair that bears different alleles for a single gene, e.g. one chromosome has A allele, one has O allele Genotype actual genetic makeup of an organism, e.g. AA or AO

25. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Law of dominance and recessiveness Certain alleles are able to mask the presence of others; one allele is dominant, the other is recessive Phenotype The physical appearance of an organism; may or may not include recessive alleles

26. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. HEREDITY Polygenetic inheritance Two or more genes (as opposed to just two or more alleles) work together to produce one particular phenotype, e.g. skin colour, stature

27. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. POPULATION GENETICS Concept of the population A group of individuals within which breeding takes place It is within the population that natural selection takes place, and at this level that evolutionary change occurs

28. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. POPULATION GENETICS The stability of the population In theory, the gene pool of a population should remain the same generation after generation, i.e. the alleles should occur in the same frequency Gene pool The genetic variants available to a population

29. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. The Hardy Weinberg Principle The percentage of individuals that are homozygous dominant, homozygous recessive, and heterozygous will remain the same from one generation to the next provided certain conditions are met: Random mating Large population No new variants Equal survival and reproductive success

30. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. EVOLUTIONARY FORCES Sources of change: 1.Mutation – chance alteration that produces a new gene 2.Genetic drift – chance fluctuations of allele frequencies in the gene pool 3.Gene flow – introduction of new alleles from nearby populations 4.Interspecies gene transfer – transfer of DNA between species 5.Natural selection – adaptation

31. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. NATURAL SELECTION Evolutionary process through which the environment exerts pressure that selects some individuals over others to reproduce 1.Directional selection – a particular allele may be favoured 2.Disruptive selection – individuals at both extremes of the distribution are favoured 3.Stabilizing selection – populations are already well adapted

32. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Adaptation and Sickle-cell Anemia In malarial areas of the world selection favoured heterozygous individuals (Hb A Hb S ) because of an increased ability to survive the effects of the malarial parasite Culture played an important role with respect to this biological adaptation

33. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. SPECIATION Gradualism if isolated over a long period of time, species evolve from subspecies (or races) through accumulation of genetic differences races – in biology, populations within a species that are capable of interbreeding but may not regularly do so **this concept has no biological validity in humans; races are merely social categories

34. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. SPECIATION Punctuated Evolution  new species appear quickly, in geological terms, and this dramatic change lasts for a long time with little significant change  rapid appearance of novelty likely due to involvement of homeobox genes

35. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. ISOLATING MECHANISMS Factors that separate breeding populations, leading to the appearance first of divergent races and then divergent species  Geographical  Anatomical structure  Early miscarriage of offspring  Early death of offspring due to weakness/maladaptation  Sterility of hybrid offspring  Genetic  Social Isolating factors:

36. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Divergent or Branching Evolution Isolation may cause a single ancestral species to give rise to two or more descendant species This divergent evolution is probably responsible for much of the diversity of life today

37. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. Convergence Two distant forms develop greater similarities because their structures serve similar functions, e.g. birds and bats

38. COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED. NEXT TIME: Monkeys, Apes, and Humans: The Modern Primates