Speciation

1. Speciation 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.