Review: a change in genes (allele freq) that produces a phenotype that is favorable (increases fitness) in a particular environment leads to natural selection (survive or not in that env ) and thus Evolution!. Have out your Microevolution HW.
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Review: a change in genes (allele freq) that produces a phenotype that is favorable (increases fitness) in a particular environment leads to natural selection (survive or not in that env) and thus Evolution!
Have out your Microevolution HW. • If you did not complete it: leave your group and go complete it. You can go through what you miss on your own after I post this power point. • If you did your HW good job! I would like you to review your answers. Pay particular attention to #5 and the scenarios/graphs you came up with. • This should take 10 minutes or less. Watch your time!
Types of Natural Selection A.) Most traits are polygenic: controlled by many genes. 1.) These traits therefore have a normal distribution and a characteristic shape when phenotypes are graphed.
B.) Natural Selection can change this normal distribution in 3 ways. Your challenge was to figure this out. I know it was probably pretty difficult but thinking is good for you! 1.) Directional Selection: individuals at one end of the curve have higher fitness than individuals at the middle or other end.
Ex: Beak Size of finches Key Directional Selection Low mortality, high fitness High mortality, low fitness Food becomes scarce. So, The population curve shifts towards one extreme of the curve. This is pretty common.
2.) Stabilizing Selection: individuals at the center of the curve have higher fitness. So, The population curve favors the middle of the curve and you lose the extremes.
Ex: Normal weight human babies vs. high or low birth weight. Human baby birth weight is the classic example. Babies that are small don’t survive as well and babies that are too big can’t get out (until C-section was developed… we could be selecting for bigger babies!) Stabilizing Selection Key Low mortality, high fitness Selection against both extremes keep curve narrow and in same place. High mortality, low fitness Percentage of Population Birth Weight
3.) Disruptive Selection: individuals at both ends of the curve have higher fitness than individuals in the middle.
Ex: Food goes from medium size seeds to large and small seeds. Birds with small & large beaks are now favored. Disruptive Selection Largest and smallest seeds become more common. Key Population splits into two subgroups specializing in different seeds. Low mortality, high fitness Number of Birdsin Population Number of Birdsin Population High mortality, low fitness Beak Size Beak Size So, The population curve increases towards two extremes. This is not as common. You should watch the Crash Course at home that I have posted at the end they have an example of a daphnia that seems to be in disruptive selection.
http://wps.prenhall.com/wps/media/objects/1110/1136802/17_3.html this is pretty slow but it does review the 3 types of selection. Watch it now. • Crash course discusses it too but that’s you tube so you’ll have to do that at home. • http://www.youtube.com/watch?v=aTftyFboC_M 8:18-12:33 c.c. types of selection
Optional Review at home: • http://www.youtube.com/watch?v=WhFKPaRnTdQ effects on allele frequency. This is also crash course. You may like a review of microevolution. Stop around 6:40 when he starts using the H-W equation.
In broader terms, these changes from generation to generation can result in speciation: the formation of new species. a. This can be thought of as descent with modification. b. Through change from generation to generation, one species may separate into two. c. This idea implies that ALL life originated from a common ancestor with speciation occurring over and over again!
Remember: Two Ways to Look At Evolution Microevolution Macroevolution The formation of new species or taxonomic groups How did animals evolve, how did mammals evolve etc. Moving on to this! We just finished this • Changes in a gene pool of a population • E.g. a population accumulating longer neck genes, darker fur genes
Macroevolution Big Changes
Macroevolution • Is concerned with how new taxonomic groups or species came to be • E.g. how did mammals evolve from ancestral reptiles (taxonomic group)
Phylogenic web quest! • Go get a copy of the web quest for you and your partner (or just you if you are working alone) • Answer all of the questions then continue this power point. Keep your web quest b/c you will be checking some of your answers. When you are done staple you and your partner’s (if you had a partner) copy together and put them in the bin. • It should take 30 minutes or less! Watch your time.
We use Phylogenetic Trees to sort organisms • A phylogenic tree is an evolutionary family tree. • Uses physical traits and/or DNA
Note Thus the answer for web quest # 4 is that it does not matter. Either order means the same thing.
Tips for Making Trees • Use your brain! • Try and think, don’t just ask • Trial and error, then double check – does your tree make sense?
There are a LOT of species • Phylogenetic trees get really, really complicated and extremely detailed • So…
The Taxonomic Groups is how we organize all the organisms on the Earth! • Domain • Kingdom • Phylum • Class • Order • Family • Genus • Species
Ex: Cat Taxonomy • Domain • Kingdom • Phylum • Class • Order • Family • Genus • species • Eukarya • Animalia • Chordata • Mammalia • Carnivora • Felidae • Felis • catus
Example FelisCatus Felis
Pneumonic Device • Dude • Kings • Play • Chess • On • Fancy • Gold • Sets Or make your own!!!
Scientific Names are based on Taxonomy • Genus species of taxonomy put together. • Ex: humans are Homo sapiens/H. sapiens • Ex: Domestic cat is Feliscatus (also called Felisdomesticus, Felissilvestrus)
So, phylogenetic trees give us the evolutionary history (the order/relationship) and taxonomy allows us to categorize the history (like the Dewey decimal system of all organisms). • Macroevolution comes down to new species…
OK stop here! • Now you need to pick up the Speciation Web Quest from the front of the room. You should work through this with your partner. • When you are done staple you and your partner’s (if you had a partner) copy together and put them in the bin. • Then come back to this power point • If for some reason you are running low on time you can go through the rest of this power point at home. Remember to pick up your HW.
Post web quest! • So, hopefully you have a pretty clear picture of speciation but the following slides are for your review
What is a species? • a group of interbreeding populations that are reproductively isolated from other groups • Appearance can be misleading in determining a species.
How Do New Species Form? • Speciation is the process by which new species form • Speciation depends on two factors • The isolation of populations must prevent gene flow and thus keep them similar • Genetic divergence must occur, driven by genetic drift or natural selection
the different pathways to speciation fall into two broad categories • allopatric speciation, the isolating mechanism is a physical barrier • sympatric speciation, isolation occurs without geographical separation
Geographical separation of a population can lead to allopatric speciation (as in the web quest example of island fruit flies) • Separation can be caused by: • Geological changes such as: • Volcanoes • Earthquakes • continental drift • change of course by rivers • Allopatric speciation is believed to be the most common type of speciation, especially among animals
Allopatric Isolation and Divergence Part of a mainland population reaches to an isolated island The isolated populations begin to diverge due to genetic drift and natural selection Divergence may eventually become sufficient to cause reproductive isolation Fig. 16-9
Isolation without geographical separation can lead to sympatric speciation too! • Sympatric speciation may occur when a geographical area contains two distinctly different habitats. • Through natural selection, individuals of the species specialize in one habitat or the other • Ex: apple vs. hawthorn tree
Sympatric Isolation and Divergence Part of a fly population that lives only on hawthorne trees moves to an apple tree The flies living on the apple tree do not encounter the flies living on the hawthorne tree, so the populations diverge Fig. 16-10
Now that we have defined a species & how they come about…how do we maintain a species?
Types of isolation? • 1) Behavioral Isolation: occurs when two populations are capable of interbreeding but have differences in courtship rituals or other behaviors. Birds of Paradise! http://www.youtube.com/watch?v=nS1tEnfkk6M
http://www.teachersdomain.org/asset/rr10_vid_reproiso/ http://www.teachersdomain.org/asset/rr10_vid_reproiso/ 2) Geographic Isolation:occurs when two populations are separated by geographic barriers. Ex: Canyon, mountain, body of water. Salamanders http://video.pbs.org/video/1300397304/ Watch this now
3) Temporal Isolation: • occurs when two populations reproduce at different times. • Ex: orchids
Mechanical isolation: structure of reproductive organs is different enough that mating cannot occur.
Gametic isolation: gametes are incompatible – even if act of mating occurs, sperm cannot fertilize egg.
Hybrids…The Grey area • This typically happens when a geographical barrier is removed. Animals that are closely related can mate and produce offspring. • These offspring are typically sterile and/or weak • A great example that works are mules. Strong and docile it’s a mix of the fragile horse (but easily trainable) and strong willed (but sturdy) donkey