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Part I Macroevolution Macroevolution- is the process of speciation or making a new species. A species is a group of interbreeding organisms that produce viable, fertile offspring in nature. Members of a species will interbreed with one another but not other organisms outside of the species. If a new species evolves, then for some reason it can no longer interbreed with the species it was once a part of. This is due to changes in the gene pool and microevolution. Macroevolution- is the process of speciation or making a new species. A species is a group of interbreeding organisms that produce viable, fertile offspring in nature. Members of a species will interbreed with one another but not other organisms outside of the species. If a new species evolves, then for some reason it can no longer interbreed with the species it was once a part of. This is due to changes in the gene pool and microevolution. These closely related animals are in the genus Canis but do not interbreed with one another in nature. They are separate species. Speciation-2 types I. Anagenesis- is the accumulation of changes in one species that leads to another species. The changes that accumulated from the Hyacotherium-> Equus (modern horse) is an example of anagenesis. Speciation-2 types I. Anagenesis- is the accumulation of changes in one species that leads to another species. The changes that accumulated from the Hyacotherium-> Equus (modern horse) is an example of anagenesis. II. Cladogenesis- is the budding of a one or more new species from a species that continues to exists. This results in biological diversity. a. Allopatric speciation-Speciation occurs because a group has been separated from the parent group. b. Sympatric speciation-speciation occurs even though the two groups are still living in the same area. Sympatric-Living in the same geographic area Allopatric-Groups living in 2 different geographic areas II. Cladogenesis- is the budding of a one or more new species from a species that continues to exists. This results in biological diversity. a. Allopatric speciation-Speciation occurs because a group has been separated from the parent group. b. Sympatric speciation-speciation occurs even though the two groups are still living in the same area. Sympatric-Living in the same geographic area Allopatric-Groups living in 2 different geographic areas A. Allopatric Speciation- First step 1. Geographic Isolation-(extrinsic isolating mechanism). Two populations must become geographically isolated from one another. If the groups become sympatric again one of two things resultA. They have become separate species, and they can no longer interbreed B. They have not changed enough and still can interbreed They remain the same species. Islands produce some of the most profound examples of speciation due to geographic isolation. A. Allopatric Speciation- First step 1. Geographic Isolation-(extrinsic isolating mechanism). Two populations must become geographically isolated from one another. If the groups become sympatric again one of two things resulta. They have become separate species, and they can no longer interbreed b. They have not changed enough and still can interbreed They remain the same species. Islands produce some of the most profound examples of speciation due to geographic isolation. Why does speciation occur after geographic isolation 1. Founder effect- The population that left the original group will have different allelic make-up from the original group 2. The 2 groups will now experience different mutations 3. The 2 groups will now experience different selection pressures being in different environments. i.e.The classic example are the finches of the Galapagos Islands. There are 14 different species of finches and 25 islands. One would expect that each island would have only one species, however, each island has more than one species of finch and larger islands may have as many as ten. The process one species going to a new area and evolving into several new species is called adaptive radiation. Why does speciation occur after geographic isolation 1. Founder effect- The population that left the original group will have different allelic make-up from the original group 2. The 2 groups will now experience different mutations 3. The 2 groups will now experience different selection pressures being in different environments. i.e.The classic example are the finches of the Galapagos Islands. There are 14 different species of finches and 25 islands. One would expect that each island would have only one species, however, each island has more than one species of finch and larger islands may have as many as ten. The process one species going to a new area and evolving into several new species is called adaptive radiation. Finches 1-9 are all tree finches. Finch #1 is vegetarian and the others insects but they differ in the types of insects they each eat which is also reflected in the size of their beaks. On islands where two or more of these finches exists, the differences in the beak size is even more pronounced. Finch #2 is in a genera all its own as its characteristics are more warbler like. Finch #8 has its own genera as it is the only finch found on the Cocos island 700 km from the Galapagos Islands. The second large group of finches are ground finches 10-14. Some live on seeds and the others on cactus flowers. Smaller beaks are specialized for small seeds and larger beaks for large seeds. Darwin found 14 different species of finches in these islands. He also saw adaptive radiation in tortoises and the mocking bird on the Galapagos Islands. How it happens-Changes occur so that 1. interbreeding does not occur or 2. no viable offspring or 3. no fertile offspring in nature 1. Ecogeographic isolation- The two populations have become so specialized for different environments, that once the barrier is removed the 2 species will never become sympatric. Species A can not live where species B lives. Their genetic differences prevents gene flow Ex.Plantus occidentalis (sycamore) found in the eastern United States and. Plantus orientalis (oriental plane tree) found in the Mediterranean area can form fertile hybrids but these areas are so different from one another that they can survive in one another's habitat How it happens-Changes occur so that 1. interbreeding does not occur or 2. no viable offspring or 3. no fertile offspring in nature 1. Ecogeographic isolation- The two populations have become so specialized for different environments, that once the barrier is removed the 2 species will never become sympatric. Species A can not live where species B lives. Ex. Plantus occidentalis (sycamore) found in the eastern United States and. Plantus orientalis (oriental plane tree) found in the Mediterranean area can form fertile hybrids but these areas are so different from one another that they can survive in one another's habitat 2. Habitat isolation- the two species have developed a preference for 2 different habitats. Even if the species become sympatric, the probability that they will meet and mate is low. Ex-Bufo woodhousei and Bufo americanus are 2 closely related toads. B. woodhousei likes to reproduce in quiet water of stream whereas B. americanus likes to reproduce in shallow rain-pools. They remain separate species. 2. Habitat isolation- the two species have developed a preference for 2 different habitats. Even if the species become sympatric, the probability that they will meet and mate is low. Ex-Bufo woodhousei and Bufo americanus are 2 closely related toads. B. woodhousei likes to reproduce in quiet water of stream whereas B. americanus likes to reproduce in shallow rain-pools. They remain separate species. 3. Seasonal isolation- the two species have developed different times of the year to mate *if the species become sympatric they will seldom mate. There are four species of frogs from the genus, Rana, each of these frogs mates at different times of the year. 3. Seasonal isolation- the two species have developed different times of the year to mate *if the species become sympatric they will seldom mate. There are four species of frogs from the genus, Rana, each of these frogs mates at different times of the year so they do not mate with one another. 4. Behavioral Isolation- Behavior during mating is important. If courtship behavior has changed during separation, and now when the groups are sympatric mating will not occur, two new species are formed. i.e.There are 12 fiddler crabs (Uca) species found on a beach in Panama. The male for each species has a distinctive display which includes waving its claw, elevating the body, and moving around the burrow. 4. Behavioral Isolation- Behavior during mating is important. If courtship behavior has changed during separation, and now when the groups are sympatric mating will not occur, two new species are formed. i.e.There are 12 fiddler crabs (Uca) species found on a beach in Panama. The male for each species has a distinctive display which includes waving its claw, elevating the body, and moving around the burrow. 5. Mechanical isolation- There is a physical, biological structure that prevents mating i.e. size, fit of genitalia organs (lock and key) found in snails, insects and plants. 6. Gametic isolation- Even if mating occurs; a biolgical mechanism will prevent the sperm or pollen from reaching the eggs i.e. When Drosophila virilis and Drosophila americanus mate, the sperm a immobilized so that they never reach the eggs. 5. Mechanical isolation- There is a physical, biological structure that prevents mating Ex. size, fit of genitalia organs (lock and key) found in snails, insects and plants. 6. Gametic isolation- Even if mating occurs; a biolgical mechanism will prevent the sperm or pollen from reaching the eggs Ex. When Drosophila virilis and Drosophila americanus mate, the sperm a immobilized so that they never reach the eggs. The next isolating mechanisms result in an embryo and are called a post-zygotic isolating mechanism. This exacts significant cost from the individual. 7. Developmental isolation- If fertilization occurs, the development of the embryo can be irregular and the embryo dies be irregular and the embryo aborted. When goats and sheep mate, they produce embryos that die before birth. 8. Hybrid inviability- Even if a hybrid is produced, it may not make it to a reproductive age because it is weak, and irregular, etc. i.e.When tobacco hybrids are successful, they often result in - tumors in their vegetative parts. Usually no flowering occurs and no reproduction occurs. The next isolating mechanisms result in an embryo and are called a post-zygotic isolating mechanism. This exacts significant cost from the individual. 7. Developmental isolation- If fertilization occurs, the development of the embryo can be irregular and the embryo dies be irregular and the embryo aborted. When goats and sheep mate, they produce embryos that die before birth. 8. Hybrid inviability- Even if a hybrid is produced, it may not make it to a reproductive age because it is weak, and irregular, etc. i.e.When tobacco hybrids are successful, they often result in - tumors in their vegetative parts. Usually no flowering occurs and no reproduction occurs. 9. Hybrid sterility- some hybrids produce superior offspring but the offspring are sterile A mule is the result of female horse crossed with a male donkey. Mules are sterile- (Hinny is the offspring of a female donkey and a male horse) *no gene flow Horse is on the left, donkey is in the center and the mule is on the right. 9. Hybrid sterility- some hybrids produce superior offspring but the offspring are sterile A mule is the result of female horse crossed with a male donkey. Mules are sterile- (Hinny is the offspring of a female donkey and a male horse) *no gene flow Horse is on the left, donkey is in the center and the mule is on the right. II.Sympatric Speciation-no geographic isolation is necessary. Polyploidy-instant speciation and occurs in plants. 1. Autopolyploidy- the number of chromosomes double in the offspring due to total nondisjunction during meiosis i.e. Primrose- 2N=14 chromosomes. Nondisjunction occurrs and there are now primroses that are teteraploid. 4N=28 discovered by Hugo deVries. II.Sympatric Speciation-no geographic isolation is necessary. Polyploidy-instant speciation and occurs in plants. 1. Autopolyploidy- the number of chromosomes double in the offspring due to total nondisjunction during meiosis i.e. Primrose 2N=14 chromosomes. Nondisjunction occurrs and there are now primroses that are tetraploid. 4N=28 discovered by Hugo deVries. 2. Allopolyploidy- involves the multiplication(doubling) of the number of chromosomes in a hybrid between 2 species due to nondisjunction. Ex-Plant A has 12 chromosomes and plant B has 8 chromosomes. Nondisjunction occurs and the egg has 12 chromosomes instead of 6. The pollen has 8 chromosomes instead of four. When plant A pollinates plant B the resulting new seed and then plant will have a total of 20 chromosomes. Alloploidy plants are usually more vigorous than the parents. Examples are oats, potatoes, bananas, barley, plums, apples, sugar cane, coffee and wheat. 2. Allopolyploidy- involves the multiplication(doubling) of the number of chromosomes in a hybrid between 2 species due to nondisjunction. Ex-Plant A has 12 chromosomes and plant B has 8 chromosomes. Nondisjunction occurs and the egg has 12 chromosomes instead of 6. The pollen has 8 chromosomes instead of four. When plant A pollinates plant B the resulting new seed and then plant will have a total of 20 chromosomes. Allopolyploidy plants are usually more vigorous than the parents. Examples are oats, potatoes, bananas, barley, plums, apples, sugar cane, coffee and wheat. The tempo of evolution 1. Gradualism- (Darwin) evolution works on large populations over a large expanse of time. The populations slowly accumulate changes and evolve. 2. Punctuated equilibrium-(Gould) evolution is often rapid. This change occurs after some crises in the environment. This may reduce the population size. Once natural selection occurs and populations evolve, then the population may stay static or not change for long periods of time. The tempo of evolution 1. Gradualism-(Darwin) evolution works on large populations over a large expanse of time. The populations slowly accumulate changes and evolve. 2. Punctuated equilibrium(Gould) evolution is often rapid. This change occurs after some crises in the environment. This may reduce the population size. Once natural selection occurs and populations evolve, then the population may stay static or not change for long periods of time. The fossil record supports both tempos. Let’s see what we know http://www.proprofs.com/quizschool/story.php?title=_33334