1. Homology/Analogy Natalia Alvarez Kevin Coleman 2006 Botany 940 Evidence for evolution

2. Homolog structure: Similar structure and position, but different function Courtesy of Prof. Ken Sytsma http://evolution.berkeley.edu Analog structure: Similar function, but different origin

3. Homology How can we explain this? Hypotheses?? Courtesy of Prof. Ken Sytsma

4. Homology Archetypal explanation “The same organ in different animals under every variety of form and function.” (Owen,1843) Common ancestry “A structure is similar among related organisms because those organisms have all descended from a common ancestor that had an equivalent trait. “ (Darwin,1859) Homology in character evolution. Staton, July 2000

5. Wells’ Critique: Circular definition Homology/Common ancestor “Features are homologous because they are inherited from a common ancestor” Common ancestry is inferred using homologous features. Features can be tested by “Multiple ad hoc hypothesis of homology” (Kluge 1997) Origin of arthropod compound eye. Oakley,2002.

6. How would you test common ancestry?

7. Fossil record –Structure and position –behavioral patterns

8. Fossil record -Fossil intermediates –Behavioral patterns Dinosaur Bird Alligator

9. How would you test common ancestry? Fossil record –Structure and position –behavioral patterns Genetics

10. Wells’ Critique: Genetics Assumption: homologous features are programmed by similar genes Problems 1. Similar genes determine radically different structures. 2. Organisms with different genes produce similar structures. Example: Pax6 in fruit flies, mice and humans

11. Genetics: Homolog structures and genes Is there a correlation between genotype and phenotype? Pax6 in fruit flies, mice and humans: "master regulator of eye development“ (qtd. in Displan,1997). Downstream genes are not the same, thus determines different structures. http://big.big.or.jp/~mastakeu/pax6.html http://www.umich.edu/~mmgmed/faculty/glaser/glaser2-resprojects.html

12. How would you test common ancestry? Fossil record –Structure and position –behavioral patterns Genetics Developmental pathways

13. Wells’ Critique: Developmental Pathways Assumption: homologous features should develop in similar ways Problems 1. Similar pathways may produce very dissimilar features. 2. Similar features are often produced via very different pathways. Haeckel’s drawings Gilbert, S. F. 1997. http://7e.devbio.com/about.php

14. Developmental pathways: shared features, shared early developmental features,presence and sequence of development stages. http://www.natcenscied.org/icons/icon4haeckel.html

15. How would you test common ancestry? Fossil record –Structure and position –behavioral patterns Genetics Developmental pathways others?

16. Analogy Different structures which perform the same function (Owen, 1843) Convergence: Similarities between organisms that evolved independently. Tasmanian wolfMexican wolf Foquieria – Foquieriaceae North America Allauidia – Didieriaceae Madagascar