Today is Thursday, September 18 th , 2014

1. In This Lesson: Speciation (Lesson 3 of 3) Today is Thursday,September 18th, 2014 Pre-Class: How would you define a species?

2. Today’s Agenda • The Origin of Species • Well, not Darwin’s work. Just his work. • Where is this in my book? • Chapter 24.

3. By the end of this lesson… • You should be able to identify the point at which evolution has created a new species. • You should be able to distinguish between microevolution and macroevolution. • You should be able to distinguish between homologous structures and analogous structures. • You should be able to tell me why this is wrong: http://si.wsj.net/public/resources/images/PT-AO773_EVOLUT_F_20100521192057.jpg

4. Macro- and Microevolution • So far we’ve actually discussed both of these. • Microevolution is the small, short-term changes in a population. • Macroevolution is the long-term change in a population leading to the development of a new species, which is called speciation. • (we’ll define species later) • What’s the difference? • Time and scale.

5. Macroevolution/MicroevolutionCase in Point http://4.bp.blogspot.com/-zTFRKQESx9w/UQEoSRCnKnI/AAAAAAAANnI/U2c3Y8R1ES0/s400/archaeopterix1.jpg Archaeopteryx – the first bird: The development of the feathers was microevolution; the rise of birds was macroevolution. http://en.wikipedia.org/wiki/Archaeopteryx#mediaviewer/File:Archaeopteryx_lithographica_%28Berlin_specimen%29.jpg

6. Evolutionary Time • Speciation occurs either by… • …cladogenesis, when one species splits into two or more species. • …anagenesis, wherein one species simply evolves on its own into a distinct new species.

7. Tree of Life Darwin had the idea of speciation in his earliest notes. The trunk of the “tree” is the distantly related common ancestor to all other branches. The closer the branches, the more recently they diverged.

8. Tree of Life • Any branch that doesn’t make it all the way to the top represents an extinction. • You can also trace the path back to the common ancestor.

9. Tree of Life platypus monkey shark goldfish frog chicken alligator pig cow Egg-Layers Mammals Less Cowish More Cowish More modern cladograms (tree of life-like diagrams) look like this:

10. Species • Ernst Mayr proposed the most concrete species definition in 1942: • A population whose individuals can interbreed AND produce fertile offspring. • There are some issues with this, but it works pretty well for currently-living creatures. • We’ll outline those issues later.

11. Mule • Horse + Donkey http://cloud.equinenow.com/140171_1/mare_mule_horse.jpg

12. Liger • ♂ Lion, ♀ Tiger http://2.bp.blogspot.com/__jinAaXs1i4/TGzaZyBwtmI/AAAAAAAAAI8/bMYSAFod7bw/s640/Liger4.jpg

13. Tiglon • ♂ Tiger, ♀ Lion http://www.metrolic.com/wp-content/uploads/2010/09/Tiglon20.jpg

14. Zedonk • Donkey + Zebra http://4.bp.blogspot.com/_p5mAt9Tofmg/TFf_sh1ENTI/AAAAAAAAAt4/ZM0AlU4z9gU/s320/zedonk+trimmed.jpg

15. What do all those creatureshave in common? • Sterility. • If two animals can produce offspring, that’s not good enough. • They need to produce fertile offspring that can reproduce on their own. • Until that point, they are considered separate species.

16. Barriers • So what are some barriers to reproduction? • Pre-Zygotic Isolation (reproduction/birth preventers) • Geographic isolation • Ecological isolation • Temporal isolation • Behavioral isolation • Mechanical isolation • Gametic isolation • Post-Zygotic Isolation (barriers to birthed offspring) • Reduced hybrid viability • Reduced hybrid fertility

17. Geographic Isolation • Some kind of physical barrier preventing interaction: • Example: Harris’s Antelope Squirrel lives across a canyon from a close relative, the White-Tailed Antelope Squirrel.

18. Uh…hold on a sec. I can’t think of a good place to put these two vocabulary words so I’m puttin’ ‘em here. Allopatric speciation is when you get a new species due to a geographic divide. Sympatric speciation is when you get a new species that lives in the same area.

19. Allopatric Speciation Case in Point • The Mexico-United States border. • Jaguars range throughout Central and South America, and historically have been in North America too. • The construction of some of the U.S. border fence has isolated only a few (<5) individuals in Arizona. • Local extinction likely, but allopatric speciation is a possibility. http://s1.reutersmedia.net/resources/r/?m=02&d=20071008&t=2&i=1901911&w=580&fh=&fw=&ll=&pl=&r=2007-10-08T163501Z_01_N08297982_RTRUKOP_0_PICTURE0

20. Ecological Isolation • No big physical barrier, but the niches occupied by each species are different. • Example: 2 species of Thamnophis garter snake live in the same area but one is aquatic and one terrestrial.

21. Temporal Isolation • Time-based isolation – species’ breeding schedules just don’t line up. • Example: Eastern and Western Spotted Skunks actually have an overlapping range but not overlapping mating periods.  Mates in Winter Mates in Summer  Eastern Spotted Skunk Western Spotted Skunk http://www.julielarsenmaher.com/wp-content/uploads/2012/09/Julie-Larsen-Maher-6637-Eastern-Spotted-Skunk-03-05-10.jpg

22. Behavioral Isolation • Some kind of behavior or display is necessary for mating. • Example: Blue-tongued skinks are thought to have blue tongues in part to identify one another. http://www.lafebervet.com/wp-content/uploads/2011/05/BlueTongueSkink.jpg

23. Behavioral Isolation Lacewing Courtship Calls Differing Meadowlark Calls Eastern Meadowlark Western Meadowlark • Other examples: • Courtship displays. • Mating calls.

24. Mechanical Isolation Male reproductive organs of the Damsel fly • Morphological (shape) differences prevent mating. • Example: Monkey flowers attract different pollinators but may live near one another. • Example: Damselflies’ sex organs are differently-shaped preventing interbreeding.

25. Gametic Isolation • Sperm cannot fertilize eggs. • Biochemical Barrier: Sperm can’t penetrate eggs. • Chemical Incompatibility: Sperm can’t survive in female reproductive tract. • Example: Aquatic creatures that release sperm into open water only fertilize females of their species.

26. Gametic Isolation • Species may differ in chromosome number: • Dog: 78 Chromosomes (39 pairs) • Orangutan: 48 Chromosomes (24 pairs) • Mouse: 40 Chromosomes (20 pairs) • Strawberry: 56 Chromosomes (7 groups of 8 - octoploid) • Adders-tongue fern: 1200 or 1260 Chromosomes

27. Post-Zygotic Isolation • Suppose a hybrid (offspring of two separate species) actually is born. What could go wrong? • Reduced Viability • Offspring are frail/can’t survive well. • Example:Interbred salamander species. Offspring often don’t complete development. • Reduced Fertility • Offspring are sterile. • Example:All those animals from before.

28. Aside: Chromosome Number • Horses: 64 Chromosomes • Donkeys: 62 Chromosomes • Mules: 63 Chromosomes • It’s amazing mules can even be born!

29. Back to the Species Definition • All those breeding-related things really help define a species…if it’s a sexually-reproducing organism. • No love for the asexual reproducers. • Oh, pun! • Fossils are also a bit of a challenge. • Some alternate definitions could be useful.

30. Alternative Species Definitions • Ecological Concept • Defines species by role relative to other species. • Morphological Concept • Defines species by similar body structures. • Genealogical Concept • Defines species by similar DNA. • Pluralistic Concept • Some/all of the above.

31. Aside: Cows and Platypuses • When you actually start digging around in creatures’ DNA, you get surprising results. Here are two: • “Cows are 25% Snake” article • Platypus DNA contains segments associated with mammals, birds, and reptiles. • Plus they’ve got 10 sex chromosomes. So there’s that. http://1.bp.blogspot.com/-2zq5eXFKk5E/Tc6GeJUi5fI/AAAAAAAAAro/ad_I1NKNF8c/s1600/Platypus+003.jpg

32. Speciation Rate • Over time, the splitting and rise of new species is referred to as adaptive radiation. • The “radiation” part refers to the diversification of organisms as they speciate. • Typically speciation is FAST. • Exactly how fast/sudden adaptive radiation occurs is a matter of debate, however. http://www.mcatzone.com/uploads/gloss/adaptive_radiation.gif

33. Gradualism vs.Punctuated Equilibrium • Gradualism is the idea that change occurs very slowly but at a somewhat constant rate. • Supporters include Charles Darwin and Charles Lyell. • Punctuated equilibrium, on the other hand, states that changes occur rapidly when speciation occurs, but then does not change much thereafter. • Supporters include Stephen J. Gould and Niles Eldredge.

34. Punctuated Equilibrium? • Time is on the X-axis. • The yellow stripe highlights a relatively brief period of divergent evolution, which is when species branch off from one another. • The opposite of divergent evolution is convergent evolution, and both terms typically refer to traits of populations rather than actual species. • Bats and birds both developing wings is a case of convergent evolution because they evolved to become more similar to one another. http://evolution.berkeley.edu/evosite/evo101/VIIBDiversityclades.shtml

35. The Kitchen SinkFinal Assorted Notes • Evo-Devo • Short for Evolutionarydevelopmental biology. • A field that uses development stages in an individual’s life to learn about evolutionary changes in the species. • Heterochrony • Evolution-produced changes in developmental timing in an organism. • Paedomorphosis • When adult organisms retain features that were considered juvenile in their ancestors.

36. Closure • Think back to middle school evolution. • You learned about homologous and analogous structures. • Homologous structures are…? • Structures that are similar because they developed in a common ancestor. • The fins of a whale and arms of humans are homologous structures. • Analogous structures are…? • Structures that just look similar, but don’t have common ancestor significance. • Bird wings and bat wings evolved independently.

37. Closure Deux • HHMI – Stickleback – Speciation