1. Evolution and Genetics Part 2

2. Overview Creationism and Evolution Genetics Population Genetics Mechanisms of Genetic Evolution Human Biological Adaptation

3. Theories of Origin 4 Theories 1. Living things could have always existed on earth with no beginning. 2. Ancestors of the earth’s plants and animals could have come from some other world. 3. Life could have originated on earth at some remote time in the past. (evolution theory) 4. All forms of life were brought into existence during a period of special creation by a supernatural God.

4. Condensed Version 1. Evolution – no God – spontaneous generation 2. Creation – God – supernatural origin.

5. Evolution – the gradual development of all forms of life by natural processes from common ancestral form, which itself had arisen by natural processes from complex chemicals in the earth’s primeval ocean (original matter came into existence by spontaneous generation) Creation (special) – all forms of life. Basic laws were brought into existence by special creative and integrative processes, which are no longer in operation by acts of a supernatural God.

6. Creationism and Evolution Creationism: biological similarities and differences originated from creation Creation: October 23, 4004 BC, at 9 am (James Ussher and John Lightfoot – Biblical scholars Calculations based on genealogy

7. Carolus Linnaeus 1 st comprehensive and influential classification of plants and animals Physical characteristics Creators plan and had not changed

8. Fossils raised doubts Why weren’t the animals still around? What happened to them? Catastrophism Fires, floods, and other catastrophes, including the biblical flood involving Noah’s ark, had destroyed the species After each destruction, God created again How did some animals manage to survive? Some ancient species lived in isolated areas Some species were on Noah’s ark

9. Evolution Transformism Alternative to creationism Charles Darwin Influenced by his grandfather – Zoonomia (1794): common ancestry with animals Charles Lyell – uniformitarianism: the present is the key to the past (Principles of Geology) Natural forces have shaped the earth Casts doubt on the fact that the world is only 6,000 years old

10. Natural Selection Nature selects the forms most fit to survive and reproduce in a given environment Competition for strategic resources: those necessary for life (food, space)

11. Example: Giraffes In any group of giraffes, there is always a variation in neck length. When food is adequate, the animals have no trouble feeding themselves. But in times when there is pressure on strategic resources, so that their dietary foliage is not as abundant as usual, giraffes with longer necks have an advantage. They can feed off the higher branches. If this feeding advantage permits longer-necked giraffes survive and reproduce even slightly more effectively than shorter-necked ones, the trait will be favored by natural selection. The giraffes with longer necks will more likely to transmit their genetic material to future generations than will giraffes with shorter necks.

12. Incorrect theory: Inheritance of acquired characteristics; the idea that each generation, individual giraffes strain their necks to reach just a bit higher. This straining somehow modifies their genetic material. Over generations of strain, the average neck gradually gets longer through the accumulation of small increments of neck length acquired during the lifetime of each generation of giraffes. This is not how evolution works. If it did work in this way, weight lifters could expect to produce especially muscular babies. Workouts that promise no gain without the pain apply to the physical development of individuals, not species.

13. 1.There is variation in traits. For example, some beetles are green and some are brown. Color variation in these beetles 2.There is differential reproduction. Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do. Differential reproduction 3.There is heredity. The surviving brown beetles have brown baby beetles because this trait has a genetic basis. Heredity of the traits of the beetles who survive 4.End result: The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown. Eventually, the advantageous trait dominates

14. Genetics DNA molecules make up genes and chromosones (basic hereditary units) Mutations (biochemical changes) provides variety on which natural selection operates Mendelian genetics: studies the ways in which chromosomes transmit genes across generations Population genetics: investigates natural selection and others causes of genetic variation, stability, and change in breeding populations

15. Mendel’s Experiments Read the paper on Mendel’s Experiments. Answer: Imagine the some of the seven traits that Mendel studied in pea plants were determined by genes on the same chromosome. How might have his results have differed? Explain.

16. Population Genetics Studies stable and changing populations in which most breeding normally takes place Gene pool – the “pool” of genetic material available Natural selection, mutation, random genetic drift and gene flow

17. Mechanisms of Genetic Evolution Natural Selection Harmful recessive genes can’t be eliminated from the gene pool if they are masked Genotypes and phenotypes Genotypes – hereditary factors (genes and chromosomes) Phenotypes – organism’s evident biological characteristic Identical Twins Same genotype, different phenotypes

18. Phenotypes Outward physical appearances Internal organs, tissues and cells Biological reactions are not automatic Reactions to food, heat, sunlight Human biology has plasticity Changes when being affected by environmental factors

19. Question Give three examples of how and why identical genotypes might develop different phenotypes. (Identical twins and clones have identical genotypes.)

20. Directional Selection Long-term selection of the same trait(s) Most adaptive traits remain Environment must stay the same Selection operates in competition in mating Colorful birds Humans – learned + biological responses

21. Question Are humans more or less adaptable than other species? What makes us so adaptable? Think of another species that are more adaptable than we are and explain any mechanism that they use to adapt.

22. Mutations Changes in the DNA molecules of which genes and chromosomes are built Occur in about 5% of sex cells Advantage: adapative advantage Disadvantage: deviate from the types that have been selected over generations

23. Random Genetic Drift Change in allele frequency that results from chance (not natural selection) Common in small populations

24. Gene Flow The exchange of genetic material between populations of the same species Origins of species Group of related organisms who members can interbreed to produce offspring that can live and reproduce Has to be able to reproduce over time EX: horses and donkeys = mule (mules are sterile) Lions + tigers Speciation – formation of a new species

25. Speciation Species cannot exchange genes Must evolve independently Genetic isolation Geographic isolation

26. Human Biological Adaptation Genetically transmitted diseases Genetic discrimination Eugenics – genetic improvement by encouraging the reproduction of individuals with favored features and discouraging that of individuals with features deemed undesirable http://www2.webster.edu/~woolflm/forcedsterilization.html Sterilization in the US

27. Clones Genetic enhancement Cell is taken from a donor animal and inserted into an egg cell whose genetic material has been removed Ethics of Human cloning Who would raise them? What would be the legal status? Would they be people or products? Would they be free or products? Would they be free humans or entities designed to satisfy wishes and medical needs others? What do you think about the ethics of human cloning?

28. Genes and Disease When there is not effective drugs… Genetic resistance is significant EX: HIV People that develop AIDS varies Rate of how quickly disease progresses varies Industrialized nations have treatment Could surpass smallpox epidemics Large shift in gene frequencies

29. Facial Features Natural selection Long noses – arid areas Membranes and blood vessels inside the nose moisten the air as it is breathed in. Long noses are also adaptive in cold environments, because blood vessels warm the air as it is breathed in. This nose distance from the brain, which is sensitive to the bitter cold, from raw outer air. Thomson’s nose rule – average nose length tends to be longer in areas with lower mean annual temperatures Tooth size Big teeth - Native Australian hunters and gatherers (sand and gritty food)

30. Size and Body Build Bergmann’s Rule: the smaller of 2 bodies similar in shape has more surface area per unit of weight Sheds heat more efficiently Average body size tends to increase in cold areas and do decrease in hot areas Pygmies live in hot climates and weigh only 90 pounds

31. Allen’s Rule: relative size of potruding body parts – ears, takes, bills, fingers, toes, limbs – increase with temperature Humans: slender bodies with long digits and limbs have an advantage in tropical climates More efficient heat dissipation Eskimos: short limbs and stout bodies conserve heat better Cold areas: population tend to have larger chests East African Nilotes – tall, linear bodies with long extremities

32. Lactose Tolerance Phenotypical adaptation: adaptive changes during the individual’s lifetime Milk contains lactose Lactase is needed to digest milk All animals have it except humans

33. Review Questions 1. What is the most convincing argument for creationism? 2. What is the most convincing argument for evolution? 3. Describe Darwin’s theory. 4. Are humans more or less adaptable than other species? Explain. 5. Which of the mechanisms of genetic evolution acts to prevent speciation? Explain it. 6. How would you design the ideal body for a very cold climate? How about for a very hot climate? 7. Give an example of a biological trait that depends on physiological adaptation.