1. Unit 5 – Lecture 5

2. Speciation Speciation – creation of a new species could occur when organisms of the same species can no longer interbreed in their natural environment explains how tigers and lions can interbreed but are not of the same species – not in same environment

3. Speciation Causes for speciation: geographic isolation – physical separation of populations lead to each changing separately

4. Speciation Causes for speciation: reproductive isolation – caused by: fertilization prevention creation of sterile hybrids [mule/hinny]

5. Speciation Causes for speciation: reproductive isolation – caused by: behavioral differences nocturnal/diurnal, blooming seasons, mating rituals or choices, etc simple physical incompatibilities.

6. Change over Time Two ways of hypothesized evolutionary change: gradualism – gradual changes [microevolution] which would slowly build to change org. believed to be the major form of evolutionary change transitions are rarely seen in the fossil record

7. Change over Time Two ways of hypothesized evolutionary change: punctuated equilibrium – long periods of little change followed by short periods of intense change because of very “incomplete” fossil record according to the theory of gradualism, created by Stephen J Gould

8. Comparing Traits Comparing organisms from an evolutionary viewpoint, they can be said to exhibit convergence or divergence. Convergent Evolution organisms in similar environments have similar traits makes sense –similar adaptations needed to function

9. Comparing Traits Comparing organisms from an evolutionary viewpoint, they can be said to exhibit convergence or divergence. Convergent Evolution organisms which show convergence have analogous structures analogous structures – different structures with the same use

10. Comparing Traits Comparing organisms from an evolutionary viewpoint, they can be said to exhibit convergence or divergence. Divergent Evolution states that organisms which were once closely related become less similar over time because of geographic or reproductive isolation

11. Comparing Traits Comparing organisms from an evolutionary viewpoint, they can be said to exhibit convergence or divergence. Divergent Evolution adaptive radiation – states that this change between species happens in a short amount of time believed to occur because of change in location

12. Comparing Traits Comparing organisms from an evolutionary viewpoint, they can be said to exhibit convergence or divergence. Divergent Evolution homologous structures – similar structures have a different use assumed to be caused by evolutionary ancestry

13. Comparing Traits Comparing organisms from an evolutionary viewpoint, they can be said to exhibit convergence or divergence. Divergent Evolution homologous structures – similar structures have a different use DNA evidence doesn’t always support this theory similar structures are sometimes coded for by very different genetic information

14. Comparing Traits Vestigial Structures – multiple definitions: previously – structures which no longer are thought to provide any benefit to organisms list of nearly 200 useless structures in late 1800s to almost none now, leading to a re-vamping of the definition according to an evolutionary standpoint

15. Comparing Traits Vestigial Structures – multiple definitions: previously – structures which no longer are thought to provide any benefit to organisms list of nearly 200 useless structures in late 1800s to almost none now, leading to a re-vamping of the definition according to an evolutionary standpoint

16. Comparing Traits Vestigial Structures – multiple definitions: previously – structures which no longer are thought to provide any benefit to organisms list of nearly 200 useless structures in late 1800s to almost none now, leading to a re-vamping of the definition according to an evolutionary standpoint

17. Comparing Traits Vestigial Structures – multiple definitions: currently – structure which no longer serve in their capacity it is assumed that they had based off of comparing organs in organisms comparing their uses to their hypothesized evolutionary ancestors

18. Vestigial…or not? Appendix – breaks down cellulose in plants serves as part of the immune system in humans to make white blood cells and antibodies to fight infection

19. Vestigial…or not? Coccyx [tailbone] – continues into tail in other orgs helps anchor muscles so that we can sit and walk correctly – including the gluteus maximus btw – humans born with “tails” do not have tails in the sense of typical orgs, they are just fleshy growths.

20. Vestigial…or not? Pineal gland – secretes melatonin, an important chemical to our sleep/wake cycles [what makes you feel sleepy]

21. Vestigial…or not? Tonsils – part of immune system minimizes respiratory infections, produces antibodies first line of defense

22. Vestigial…or not? Wings in flightless birds – not for flying… but often used for balance or for sexual selection

23. Vestigial…or not? “Junk” DNA – does not code for any traits… found to have important functions in embryonic development, possibly for social functions, controlling expression of other genes

24. Vestigial…or not? Eyes in blind cave animals like fish & salamanders

25. Vestigial…or not? Sexual organs in dandelions – dandelions reproduce asexually vegetative reproduction seeds are asexually formed too

26. Vestigial…or not? Wisdom teeth human mouths now smaller than those even a few hundred years ago

27. Vestigial…or not? Male nipples – certainly don’t nurse children ALL humans are female during the first six weeks of development around 6 weeks, certain hormones are dispersed which lead to further development of a certain sex.

28. Vestigial…or not? There is no way to scientifically determine the uselessness of an organ just that no function has been found – Darwin agreed. As always, science can only work with available info and revise as necessary, which again stresses what science truly IS – the pursuit of knowledge about our world.