BI102 - Week 6
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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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