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BI102 - Week 6

by: Markhame

BI102 - Week 6 BI 102

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Contents: Darwin's life Darwin's Work Genetic Drift Darwin Today Speciation Species Defined Paths to Speciation Examples of Speciation Hybrids
General Biology - Genetics
Dr. Lesley Blair and Mark Lavery
Class Notes
Biology, bi102, BI101, Oregon State University, OSU, Oregon State, Science, Lesley Blair, Blair
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This 6 page Class Notes was uploaded by Markhame on Friday February 12, 2016. The Class Notes belongs to BI 102 at Oregon State University taught by Dr. Lesley Blair and Mark Lavery in Winter 2016. Since its upload, it has received 25 views. For similar materials see General Biology - Genetics in Biology at Oregon State University.


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Date Created: 02/12/16
Bio102 ‐ Week 6  Thursday, February 11, 2016  9:57 AM        Tuesday       2/9/2016                                                     Darwin  Monday, Week 7 ‐ Exam #2  → Covers weeks 4, 5, and 6    Darwin was a person of his time → His research was of his time  → This is why he was more received than Mendel, who was ahead of his time.        Darwin's Life    19th Century Inheritance  Blending theory → sperm and eggs came together and just kinda blended ‐ the offspring was a mix of the parents  Darwin attempts to expand on this theory → Pangenisis Theory   Of course, this theory was also wrong     Mendel's Laws are published at the same time and these are actually right  Of course, no one notices Mendel's work until quite some time later.     19th Century Evolution  Geology is coming up and suggesting that species changes over time.  Jean‐Baptiste Lamark → Researcher that gets a lot of research right, but he got evolution wrong  Theory of Acquired Characteristics → his theory  Species change by passing on the characteristics they acquire  Example: Giraffes → "Giraffes stretched out their necks and so their offspring were born with stretched necks" no, that's like saying that when you work out and gain muscles, your child will be born with muscle. Nope.    → Darwin is born into incorrect theories of inheritance and evolution, but also born into a family with history of people trying to explain nature and wealth. Many men in the families are doctors or clergymen.   We have record back to when Darwin was 5 years old that he was interested in nature.   His father wanted him to be a doctor, so he gets sent to university to do just that.  He goes to Cambridge to be a doctor, but he is just horrified of this, so instead he skips class to hunt and fish → but he takes a natural history class and falls in love with the college's collection of nature paintings and research.  His dad figures out Darwin's not going to be a doctor, so he switches him over to Religious studies.   Of course he isn't doing well in this either.   Darwin wants to travel to some islands after graduation instead of getting work.     HMS Beagle → the ship Darwin takes, it's a coastline ship that maps coastlines  The captain takes Darwin on (his father pays for it), and Darwin has a contract where he gets to take samples   The voyage was supposed to take 2 years but ended up taking 5 years, charting all around the bottom of South America, Australia, and South Africa ‐ finally  coming back to Brazil and then back to Europe.  Famously, Darwin writes about Tortoises on the Galapagos Islands  He thinks "Why are there different Tortoises on different islands?"  He's sending his research back to the university, and his professor is actually publishing and selling his work → Darwin is becoming famous while he's away.  Through pondering about extinct species relative to species he was seeing, he decided to try and build a "Tree" of how he thinks they're related.     → 20 years go by after this research. What does he do??    1. Studies Barnacles → in a tiny area of coastline of England, there's over 200 different species of barnacles.     2. Pigeon Breeding → In this time period, pigeons are many things (pretty, food, messengers, etc), Artificial Selection    3. Studies Orchids → Cataloguing the species all around England and their pollinators.     4. Asked by Museum to look at finches from Galapagos  He's not had much experiences in the islands, but he remembers how the finches on every island had different phenotypes.    → He's been writing a book for a long time, and it's a massive book that Darwin is afraid to publish.   Alfred Wallace → contacts Darwin about his ideas of how species can change  Darwin studies this work, and is upset because this kid has similar work that Darwin had not published.  So, Darwin tells other people and suggests that both pieces of work should be published together.  Note: Wallace's paper wasn't as developed as Darwin's   Darwin's research is incredible well‐done and written in depth and etc.       Darwin's Work  The Origin of Species → Clarified laws (description) of evolution  Aspects of species can change over time  Everyone agrees with this  Species descend from a common ancestor  This isn't as well‐known by many people  But after a few decades, most people are understanding this part  Also provides Theory → Natural Selection  This is the part that isn't accepted as readily by people      NATURAL SELECTION    → Individuals within species vary    → Some of the variation is passed on to offspring    → Not all offspring survive (Darwin understood this personally due to his own children)    → Individuals that survive and reproduce are (somehow) more fit than those that die  This selection is not random    Note: Darwin married his first cousin and had children, but Darwin understood inbreeding  So he understanding and makes the connection that many of his own children didn't survive because they were inbred    → The law is incredible well‐received by scientists, Theory was not    → Descent with modification  Genetic Drift  → Argument that variation is the beginning of selection  In fact, it's necessary    → Evolution: Allele frequencies change over time  Some alleles are surviving over others into new generations    → However, sometimes natural disasters do have a hand in wiping out entire allele variations  This is called Genetic Drift → Survival of the luckiest    Key: Changes in allele frequency can be random  Darwin Today  Galapagos Islands → massive increase in tourism    1970s → Researchers decided they should go to the islands and study Darwin's organisms like tortoises and finches, instead of studying them as museum artifacts.  The islands were relatively still untouched (until tourism)  Medium Ground Finch   1976 ‐ The researchers chose an island that's relatively difficult to get to so as to not have human trafficking.  Found 751 ground finches  1978 ‐ returned to the island, and there had been a flood since they left. Found 90 surviving finches with larger beaks → Allele frequencies can change rapidly  Grad students stay on the islands after this, observing the finches.   Evolution is not always directional, often just fluctuates based on environment  Ex: During dry years, beak size goes down; during wet years, beak size goes up  Thursday - 2/11/16    Species formation → Speciation   Reproductive isolation can lead to speciation  Species Defined    *Species is a human word ‐ only humans recognize this concept, other animals really don't.       Species: Individuals that can successfully interbreed      Lake Victoria → 200+ different species of Cichlids (fish)  Coloration differences and behavioral differences show us they're different species      → Different species can look similar (so there is a bit of a struggle telling if something is a different species or just a variation)  Ex: Coral Snake vs Milk Snake → One is severely poisonous (Coral), and usually is identified by "Red next to yellow, you're not a lucky fellow" right?  Nope → There are variations of milk snakes that can look even more venemous than coral snakes  Even if phenotypically different, they can be the same species    How do new Species Form?    Reproductive Isolation → they stop breeding together; Stops movement of alleles (gene flow) between populations  Ex: Beetles ‐ how did we end up with so many different species of beetles?   Stopping of breeding with own species, and starts breeding with another species that creates mixed DNA offspring that can also have mutations  Mutations accumulate until there are significant differences (and this likely causes them to stop breeding together)      Ongoing Speciation experiment:                                                                                                                                                             Mutations occur frequently    Reproductive isolation  Alfalfa & Bees  Gene flow between transgenic and "conventional" species  It's pollinated by bees, so it ends up with DNA from other plants  GMA Alfalfa alleles flow up to 100 meters → Bee flight range  Pollen traps allowed university researchers to learn just how far bees will fly  They underestimated this, by not considering wind being able to aide bees flight    Paths to Speciation  Deer Mice:   Two different species of deer mice can almost be indiscernible phenotypically  But when they're put in a controlled environment together, they try to kill each other because their smells are not familiar.   This is because these two different species of deer mice are separated in nature by The Rocky Mountains    Two different ways speciation occurs:    → Allopatric Speciations: Different Locations  A species gets physically separated and end up forming two different species while apart    → Sympatric Speciation: Same location  New species arise within another species      Examples:     Squirrels in the Grand Canyon (allopatric)  (South rim) Abert vs (North rim) Kaibab squirrel    Apple Orchards ‐ Hawthorne maggot flies (sympatric)  Hawthorne vs Apple trees  Some of the maggot flies transferred to apples  Those that have been eating the apples are separating from the ones that eat hawthorne      Sympatric Speciation: Reproductive Isolation forms???    1.Temporal Isolation   a.Example: Frogs ‐ mating calls rise up at different times of year than other species, less likely than cross‐mating    2.Behavioral Isolation  a.Example: Fireflies ‐ To humans, firefly lights might look the same but there are actually different species that have different types of glow patterns that are mating signs. Females are genetically programmed to mate only with the males of their species by their glowing patterns.    3.Mechanical Isolation  a.Species simply just don't fit together and the gametes just do not come together  b. Example: Orchids (and pollinators) ‐ different pollinators carry the pollen within specific species (pheropmones put out by the flowers attract specific kinds of pollinators)  Examples of Mutations and Speciation:    Point mutations → Accumulation of base mutations over time (small mutations)  Chromosomal mutations → sudden, fast, and massive mutations    *These mutations can lead to Speciations    Chromosomal Mutations in Speciation → Happens in plants mostly; often a meiotic error  * POLYPLOIDY  This can keep happening over and over again and produce hybrids  Like in wheat:        Animal Speciation → often much slower    More often occurring with small, slow point mutations    Ex: Horseshoe Crabs  Progression → One species kinda just becomes another  Horseshoe crabs today look a lot like their ancestors    Adaptive Radiation → One species becomes many  Ex: Hawaiian honeycreepers   Hybrids  When humans get involved and cause speciation → Hybrids happen in animals  Humans bring together two different species that would never usually mate in the natural wild      Example: Bengal Cats  → Asian Leopard cat  x  Domestic cat    → Not all of our hybrids work  Ex: Mules (Donkey  x  horse)  Wrong number of chromosomes (Horse ‐ 2n = 64; Donkey ‐ 2n = 62)  Mules are sterile → they come out with an odd number of chromosomes (2n = 63)  **But we can apparently clone mules** 


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