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SPECIATION/MACROEVOLUTION The Creation of species Hi, Donald Duck here. I was just telling my uncle, Professor Ludwig von Drake from Vienna Austria that I had to give a talk about evolution to a bunch of teenagers. When he noticed how much trouble I was having preparing for the talk, he volunteered to give the talk instead. Hope you can understand him, he’s got an accent, but he’s also really smart. Bye, I’m off for a date with Daisy. Hello, I am Professor Ludwig von Drake, und I um here to describe zee speciation concept. I must warn you that we will be discussing the key process in macroevolution called SPECIATION. Hopefully you have an understanding of the evolution concept. Now in my first discussion of species I show you zee mating and reproduction of zee species. Your job is to match zee correct mates together. If correct, you vill have identified zee species und you vill get new little vuns. + = + = = + Good, you have correctly classified zee species using how zey look = MORPHOLOGY MORPHOLOGICAL SPECIES CONCEPT Classify species mainly on visible anatomical characters to define species. Morpho mean shape, form, appearance Logo mean word. So appearance word. Organisms are classified in the same species if they appear identical by morphological (anatomical) criteria. Thus it is a population or group of populations that differs morphologically from other populations. For example, we can distinguish between a chicken and a goose because they have different shaped bills and the duck has webbed feet. Carl Linnaeus vas svedish ya! He was also know as Carl von Linne. The von denoted after he was ennobled, in 1761 and he shortened the Linnaeus to Linne. You now know zee method used by Carl Linnaeus to classify species. He developed a zystem of taxonomy to classify every living thing . Zis vas done vay back in 1735 It was based on MORPHOLOGY. Now shall ve continue vith my little game? Vait a minute. Zay all look different. Zee difference is between zee sexes called Sexual Dimorphism. We now have to rely of whether zey reproduce! + = + = + = No Offspring DIFFERENCE ---SEXUAL DIMORPHISM Notice from the previous slide, there where inappropriate mates chosen. In nature this would not happen. MATE RECOGNITION SPECIES CONCEPT A group of organisms that are known to recognize one another as potential mates. Like the isolation species concept above, it applies only to organisms that reproduce sexually. Now we have arrived at the final definition for zee species. A species must reproduce und produce offspring Vait, Vait, Vhat are you doing. Those don’ t go together! Zey are different -----species? Yes zey are different species because the mules cannot reproduce. Now on to my final, final definition of species + Female Horse = Male donkey + Male mule = NO OFFSPRING Female mule BIOLOGICAL SPECIES CONCEPT Two populations that can and do interbreed in nature and produce fully fertile offspring. In the population, there is an absence of gene flow between members of different species. It, however, is insufficient for asexually reproducing organisms. Also, it does not distinguish between the theoretical possibility of interbreeding and the actual likelihood. It also does not apply to species that hybridize to produce polyploid individuals. Even in World War II, 14,000 mules were used as they were able to travel through thick jungle and rugged mountains that were impossible for vehicles, and even horses, to cross. Some say they are stubborn, but this is due to their intelligence and knowledge of self preservation. My new final definition of species is ...What the heck are you doing now? Stop doing zat, zey are different --species? Lets see, zey can reproduce, produce offspring who are fertile.....But zis is not happening in zee wild! It is not natural. It is zee result of human intervention! + = Female tiger Male lion + Male liger = Female liger + Male tiger Male liger Liger cubs = Female lion Tigon cub Female liger Did you know that Ligers are the world’s largest cats? It's pretty much my favorite animal. It's like a lion and a tiger mixed... bred for its skills in magic Now vut has just happened? You are mating tigers and lions and lions and tigers and ligers and liger and tigons and tigons. I am going crazy! Is a tiger a lion? Is a lion a tiger? Zey look different. You mean Charles Darwin? Ya, ya, ya, Charles Darvin. Darwin says –species variations Are tigers and lions the same species? They must be, zey produce fertile offspring. But I know zey are not the same species. I need to talk to that Darvin Guy! How about Haldane? Who is zis Haldane fella? J.B.S. Haldane was a genetics and population genetics pioneer from 1892-1964 Vhat did he do? He developed Haldane’s Rule. According to Haldane, males are the heterogametic sex, in that they have XY sex chromosomes, whereas females are homogametic, with XX chromosomes When in the F1 offspring of two different animal races one sex is absent, rare, or sterile, that sex is the heterozygous [heterogametic] sex. Ex. From genetics, more males are colour blind or hemophiliacs –thus heterogametic -still rare As species differentiation further progresses, parental genetic differentiations generate anatomical, physiological or psychological differences that result in mating incompatibilities. The "postzygotic barriers" (hybrid sterility and hybrid inviability), are replaced by "prezygotic barriers" (e.g. mating incompatibilities). "I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other ... It does not essentially differ from the word variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for convenience sake." Post = after Zygotic = first cell barrier After zygote fertilization, offspring are produced, but are sterile. Pre=before Vait a minute, enough of zis hocus pokus mumbo jumbo! I am giving a talk to high school students, not brain surgeons. Vhat does all zis mean? Zygotic= first cell barrier Barrier to prevent fertilization in the first place—even though offspring can be produced STEP 1 Postzygotic barrier = sterile offspring like the mule They mate to produce offspring but the offspring are infertile. STEP 2 Prezygotic barrier = lack of contact in the wild (ex live in different areas) A prezygotic isolating mechanism would prevent fertilization of the egg. Prezygotic Barriers The species are separated by: ECOLOGICAL SEPARATION – Different locations or niches TEMPORAL SEPARATION- Different breeding season BEHAVIOURAL SEPARATION – specific mating rituals required MECHANICAL SEPARATION – size of reproductive organs incompatibilities MORPHOLOGICAL SEPARATION – body size and shape incompatibilities GAMETIC SEPARATION – sperm incompatible to egg Boy, am I glad I don’t have to take your exam. Oh, excuse me, where was I now. Oh yes, I need my final, final, final definition of a species. A species can be defined as all members of groups or populations zat interbreed or have the ability to interbreed vith each other under natural conditions. Zeir offspring must also be fertile. Zee liger is not a species because, notice, it says NATURAL conditions, und lions and tigers are kept separate by ECOLOGICAL barriers as mentioned in zee previous slide. CAUTION – IMPORTANT POINT The mule cannot mate with either the horse or the donkey. There is no gene flow, and this is a new more accurate way of defining a species. In addition the liger cannot mate with either the lion nor the tiger, so it is the same effectively as the mule example. This hybrid has REDUCED HYBRID FERTILITY . They cannot produce offspring when then mate with either parental species- genes cannot flow. CAUTION – IMPORTANT POINT REDUCED HYBRID VIABILITY The genes of different parent species may interact to produce offspring. The hybridization, however, impairs the offspring’s development. Hybrids do not complete development or are weak or frail. (postzygotic barrier) HYBRID BREAKDOWN The first generation hybrids are viable and fertile, but when they mate with each other or either parent species, offspring of the next generation are feeble or sterile. (postzygotic barrier) See you in part two. SPECIATION PART 1 END