A generational time scale, involving change from one generation to the next, is the time scale of evolution by natural selection. Microevolutionary and macroevolutionary patterns reflect this process on longer time scales. Macroevolution occurs when the forces of evolution work over a long period of time. Types of macroevolution include speciation, convergent evolution, and coevolution. Speciation is the evolution of a new species. For a new species to arise, some members of an existing species must change so they can no longer produce fertile offspring with the rest of the species.... Show more A generational time scale, involving change from one generation to the next, is the time scale of evolution by natural selection. Microevolutionary and macroevolutionary patterns reflect this process on longer time scales. Macroevolution occurs when the forces of evolution work over a long period of time. Types of macroevolution include speciation, convergent evolution, and coevolution. Speciation is the evolution of a new species. For a new species to arise, some members of an existing species must change so they can no longer produce fertile offspring with the rest of the species. Speciation often occurs when some members of a species break off from the rest. The splinter group evolves in isolation from the original species. The original species also continues to evolve. Sooner or later, the splinter group becomes too different to breed with members of the original species. At that point, a new species has formed. A good example of speciation involves anole lizards. There are about 150 different species of anole lizards in the Caribbean Islands. Scientists think that a single species of lizard first colonized one of the islands about 50 million years ago. A few lizards from this original species eventually reached each of the other islands, where they evolved in isolation. Anoles on different islands eventually evolved traits that prevented them from mating with lizards on other islands. They had undergone speciation. Over many millions of years, all the species of anoles known today evolved. Sometimes two species evolve the same traits because they live in similar habitats. This is called convergent evolution. Caribbean anoles demonstrate this as well. On each Caribbean island, anoles in similar habitats independently evolved the same specialized traits. For example, anoles that lived on the forest floor evolved long legs for leaping and running on the ground. Anoles that lived on tree branches evolved short legs that helped them cling to small branches and twigs. On each of the islands, there were anole species that evolved in each of these same ways. Species that often interact with each other and have a close relationship may influence each other's evolution. Examples include flowers and the animals that pollinate them. When one of the two species evolves new traits, the other species may evolve matching traits. This is called coevolution. Show less
A generational time scale, involving change from one generation to the next, is the time scale of evolution by natural selection. Microevolutionary and macroevolutionary patterns reflect this process on longer time scales. Macroevolution occurs when the forces of evolution work over a long period of time. Types of macroevolution include speciation, convergent evolution, and coevolution. Speciation is the evolution of a new species. For a new species to arise, some members of an existing species must change so they can no longer produce fertile offspring with the rest of the species. Speciation often occurs when some members of a species break off from the rest. The splinter group evolves in isolation from the original species. The original species also continues to evolve. Sooner or later, the splinter group becomes too different to breed with members of the original species. At that point, a new species has formed. A good example of speciation involves anole lizards. There are about 150 different species of anole lizards in the Caribbean Islands. Scientists think that a single species of lizard first colonized one of the islands about 50 million years ago. A few lizards from this original species eventually reached each of the other islands, where they evolved in isolation. Anoles on different islands eventually evolved traits that prevented them from mating with lizards on other islands. They had undergone speciation. Over many millions of years, all the species of anoles known today evolved. Sometimes two species evolve the same traits because they live in similar habitats. This is called convergent evolution. Caribbean anoles demonstrate this as well. On each Caribbean island, anoles in similar habitats independently evolved the same specialized traits. For example, anoles that lived on the forest floor evolved long legs for leaping and running on the ground. Anoles that lived on tree branches evolved short legs that helped them cling to small branches and twigs. On each of the islands, there were anole species that evolved in each of these same ways. Species that often interact with each other and have a close relationship may influence each other's evolution. Examples include flowers and the animals that pollinate them. When one of the two species evolves new traits, the other species may evolve matching traits. This is called coevolution.
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