Evolution. Origins of life Origin of species (diversification of life) Origins of adaptation

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1 Evolution Origins of life Origin of species (diversification of life) Origins of adaptation

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3 The reproductive process in biology inevitably produces evolutionary change Mutations will occur: p(mutation)>0. To the extent that populations are separated from one another, divergence will occur. i.e., some amount of evolution is an inevitable result of thermodynamics associated with reproduction.

4 Evidence of Evolution Ch 24 Change through time: Fossils: extinction, transitions, environmental change Comparative studies: vestigial traits Current studies: drug resistance, etc Species are related to one another. Biogeography Homology: structural, developmental, molecular (genetic)

5 Fossils Georges Cuvier ( ) First detailed study of fossils. Comparative anatomy. Correlation of parts. Extinction.

6 Fossil dating Generic dating. P pres = P orig (2 (-age/halflife) ) Isochronic dating is better in that it avoids assumption that there was no daughter isotope at t=0, and will signal if new material was added to the site at a later date.

7 Fossil Dating Radioactive decay and absolute age: earth 4.6 by old. Life arose ~ 3.8 by ago. First Eukaryote fossils ~ 1.5 by ago. Humans diverged from other Apes ~ 5 my ago. Homo sapiens ~ 0.5 my ago.

8 Extinction The Irish elk: actually an extinct deer. Widely distributed in Pleistocene. Cuvier 1812 described fossil remains. Evidence of extinction. Many examples are now known of extinct creatures preserved as fossils from all eras.

9 Transitional forms Birds and other dinosaurs Whales and Ungulates Darwin noted that fossils in an area often resembled organisms living in the area

10 Vestigial traits Reduced or modified function. Even molecular examples: L-gulano-γ-lactone oxidase: gene required to synthesize vitamin C. non functional in humans, guinea pigs.

11 Environmental Change

12 Species are related to other Species fall into groups within groups. Indicates branching evolutionary processes; descent with modification. Doesn t occur with man-made objects or rocks and minerals. species

13 Galapagos Islands

14 Homology Genetic: even the codons (3 base code for each amino acid) are preserved across wide arrays of organisms.

15 Homology Developmental Human coccyx Gill pouches in Tetrapods (p. 512) Goethe and the sutures in the skulls of apes and humans.

16 Structural/developmental homology

17 Structural homology cont d Bone for bone homology (some fusion/ loss) across array of Tetrapods

18 Origin of Adaptation Originally thought of as design: God conferred appropriate structures on organisms. Chain of Being. Lamarck proposed Evolution to explain the nested pattern of similarity. Mechanism: use and disuse (organismal drive or will) and inheritance of acquired characteristics.

19 Darwin Malthus essay on population growth invoked the idea of competition in a high mortality environment. Developed an explicit model model of natural selection.

20 Natural selection Organisms in a population vary with respect to various traits. Some of this variation is heritable. In each generation more individuals are produced than can survive (struggle for existence) The subset that survive each generation will be enriched for heritable variation that allow them to outcompete other variants.

21 Natural selection and antibiotic resistance. Mycobacterium tuberculosus

22 TB an important disease ~ 25% of deaths in NY City in Treatment in early 20th century: pneumothorax and rest. With advent of antibiotics, TB declined in 1950s. Began to increase again in 1980s and 90s.

23 Oft repeated scenario Individual enters hospital with symtoms of TB. Treated and observed for a number of weeks until judged cured. Returns some months later with renewed case of TB unresponsive to antibiotics.

24 What happened? Did variation exist in the original infecting population? Was the variation heritable? Did the new variant affect reproductive success? Did selection occur?