Determining Evolutionary Relationships Quiz

PDF page 824: To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior chapter we explored the differences between homologous and analogous traits and how they relate to convergent and divergent evolution.) Similarities among organisms stem either from shared ancestral history (homologies) or from separate evolutionary paths (analogies). Cladograms are constructed by using shared derived traits to distinguish different groups of species from one another. For example, lizards, rabbits and humans all descended from a common ancestor that had an amniotic egg; thus, lizards, rabbits, and humans all belong to the same clade. Vertebrata is a larger clade that also includes fish, lamprey, and lancelets. The closer two species or groups are located to each on a phylogenetic tree or cladogram, they more recently they shared a common ancestor. With the influx of new information, scientists can revise phylogenetic trees; for example, computer programs, such as one called BLAST, which helps determine relatedness using DNA sequencing. Typically, a phylogenetic tree is constructed with the simplest explanation of evolutionary history (maximum parsimony) and the fewest number of evolutionary steps. Understanding phylogeny extends far beyond understanding the evolutionary history of species on Earth. For botanists, phylogeny acts as a guide to discovering new plants that can be used to make food, medicine, and clothing. For doctors, phylogenies provide information about the origin of diseases and how to treat them, for example, HIV/AIDS.

PDF page 824: To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior chapter we explored the differences between homologous and analogous traits and how they relate to convergent and divergent evolution.) Similarities among organisms stem either from shared ancestral history (homologies) or from separate evolutionary paths (analogies). Cladograms are constructed by using shared derived traits to distinguish different groups of species from one another. For example, lizards, rabbits and humans all descended from a common ancestor that had an amniotic egg; thus, lizards, rabbits, and humans all belong to the same clade. Vertebrata is a larger clade that also includes fish, lamprey, and lancelets. The closer two species or groups are located to each on a phylogenetic tree or cladogram, they more recently they shared a common ancestor. With the influx of new information, scientists can revise phylogenetic trees; for example, computer programs, such as one called BLAST, which helps determine relatedness using DNA sequencing. Typically, a phylogenetic tree is constructed with the simplest explanation of evolutionary history (maximum parsimony) and the fewest number of evolutionary steps. Understanding phylogeny extends far beyond understanding the evolutionary history of species on Earth. For botanists, phylogeny acts as a guide to discovering new plants that can be used to make food, medicine, and clothing. For doctors, phylogenies provide information about the origin of diseases and how to treat them, for example, HIV/AIDS.

PDF page 824: To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior chapter we explored the differences between homologous and analogous traits and how they relate to convergent and divergent evolution.) Similarities among organisms stem either from shared ancestral history (homologies) or from separate evolutionary paths (analogies). Cladograms are constructed by using shared derived traits to distinguish different groups of species from one another. For example, lizards, rabbits and humans all descended from a common ancestor that had an amniotic egg; thus, lizards, rabbits, and humans all belong to the same clade. Vertebrata is a larger clade that also includes fish, lamprey, and lancelets. The closer two species or groups are located to each on a phylogenetic tree or cladogram, they more recently they shared a common ancestor. With the influx of new information, scientists can revise phylogenetic trees; for example, computer programs, such as one called BLAST, which helps determine relatedness using DNA sequencing. Typically, a phylogenetic tree is constructed with the simplest explanation of evolutionary history (maximum parsimony) and the fewest number of evolutionary steps. Understanding phylogeny extends far beyond understanding the evolutionary history of species on Earth. For botanists, phylogeny acts as a guide to discovering new plants that can be used to make food, medicine, and clothing. For doctors, phylogenies provide information about the origin of diseases and how to treat them, for example, HIV/AIDS.

PDF page 824: To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior chapter we explored the differences between homologous and analogous traits and how they relate to convergent and divergent evolution.) Similarities among organisms stem either from shared ancestral history (homologies) or from separate evolutionary paths (analogies). Cladograms are constructed by using shared derived traits to distinguish different groups of species from one another. For example, lizards, rabbits and humans all descended from a common ancestor that had an amniotic egg; thus, lizards, rabbits, and humans all belong to the same clade. Vertebrata is a larger clade that also includes fish, lamprey, and lancelets. The closer two species or groups are located to each on a phylogenetic tree or cladogram, they more recently they shared a common ancestor. With the influx of new information, scientists can revise phylogenetic trees; for example, computer programs, such as one called BLAST, which helps determine relatedness using DNA sequencing. Typically, a phylogenetic tree is constructed with the simplest explanation of evolutionary history (maximum parsimony) and the fewest number of evolutionary steps. Understanding phylogeny extends far beyond understanding the evolutionary history of species on Earth. For botanists, phylogeny acts as a guide to discovering new plants that can be used to make food, medicine, and clothing. For doctors, phylogenies provide information about the origin of diseases and how to treat them, for example, HIV/AIDS.

PDF page 824: To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior chapter we explored the differences between homologous and analogous traits and how they relate to convergent and divergent evolution.) Similarities among organisms stem either from shared ancestral history (homologies) or from separate evolutionary paths (analogies). Cladograms are constructed by using shared derived traits to distinguish different groups of species from one another. For example, lizards, rabbits and humans all descended from a common ancestor that had an amniotic egg; thus, lizards, rabbits, and humans all belong to the same clade. Vertebrata is a larger clade that also includes fish, lamprey, and lancelets. The closer two species or groups are located to each on a phylogenetic tree or cladogram, they more recently they shared a common ancestor. With the influx of new information, scientists can revise phylogenetic trees; for example, computer programs, such as one called BLAST, which helps determine relatedness using DNA sequencing. Typically, a phylogenetic tree is constructed with the simplest explanation of evolutionary history (maximum parsimony) and the fewest number of evolutionary steps. Understanding phylogeny extends far beyond understanding the evolutionary history of species on Earth. For botanists, phylogeny acts as a guide to discovering new plants that can be used to make food, medicine, and clothing. For doctors, phylogenies provide information about the origin of diseases and how to treat them, for example, HIV/AIDS.

PDF page 834: Imagine being the person responsible for organizing all of the items in a department store properly—an overwhelming task. Organizing the evolutionary relationships of all life on Earth proves much more difficult: scientists must span enormous blocks of time and work with information from long-extinct organisms. Trying to decipher the proper connections, especially given the presence of homologies and analogies, makes the task of building an accurate tree of life extraordinarily difficult. Add to that the advancement of DNA technology, which now provides large quantities of genetic sequences to be used and analyzed. Taxonomy is a subjective discipline: many organisms have more than one connection to each other, so each taxonomist will decide the order of connections. To aid in the tremendous task of describing phylogenies accurately, scientists often use a concept called maximum parsimony, which means that events occurred in the simplest, most obvious way. For example, if a group of people entered a forest preserve to go hiking, based on the principle of maximum parsimony, one could predict that most of the people would hike on established trails rather than forge new ones. For scientists deciphering evolutionary pathways, the same idea is used: the pathway of evolution probably includes the fewest major events that coincide with the evidence at hand. Starting with all of the homologous traits in a group of organisms, scientists look for the most obvious and simple order of evolutionary events that led to the occurrence of those traits.

PDF page 827: Figure 20.7 Bat and bird wings are homologous structures, indicating that bats and birds share a common evolutionary

PDF page 826: In general, organisms that share similar physical features and genomes tend to be more closely related than those that do not. Such features that overlap both morphologically (in form) and genetically are referred to as homologous structures; they stem from developmental similarities that are based on evolution. For example, the bones in the wings of bats and birds have homologous structures (Figure 20.7).

PDF page 827: Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. That outcome would be highly improbable. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. Misleading Appearances Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. Similarly, unrelated organisms may be distantly related, but appear very much alike. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the wing structure and embryonic origin is completely different. These are called analogous structures (Figure 20.8). Similar traits can be either homologous or analogous. Homologous structures share a similar embryonic origin; analogous organs have a similar function. For example, the bones in the front flipper of a whale are homologous to the bones in the human arm. These structures are not analogous. The wings of a butterfly and the wings of a bird are analogous but not homologous. Some structures are both analogous and homologous: the wings of a bird and the wings of a bat are both homologous and analogous. Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied.

PDF page 827: Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. That outcome would be highly improbable. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. Misleading Appearances Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. Similarly, unrelated organisms may be distantly related, but appear very much alike. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the wing structure and embryonic origin is completely different. These are called analogous structures (Figure 20.8). Similar traits can be either homologous or analogous. Homologous structures share a similar embryonic origin; analogous organs have a similar function. For example, the bones in the front flipper of a whale are homologous to the bones in the human arm. These structures are not analogous. The wings of a butterfly and the wings of a bird are analogous but not homologous. Some structures are both analogous and homologous: the wings of a bird and the wings of a bat are both homologous and analogous. Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied.

PDF page 827: Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. That outcome would be highly improbable. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. Misleading Appearances Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. Similarly, unrelated organisms may be distantly related, but appear very much alike. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the wing structure and embryonic origin is completely different. These are called analogous structures (Figure 20.8). Similar traits can be either homologous or analogous. Homologous structures share a similar embryonic origin; analogous organs have a similar function. For example, the bones in the front flipper of a whale are homologous to the bones in the human arm. These structures are not analogous. The wings of a butterfly and the wings of a bird are analogous but not homologous. Some structures are both analogous and homologous: the wings of a bird and the wings of a bat are both homologous and analogous. Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied.

PDF page 827: Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. That outcome would be highly improbable. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. Misleading Appearances Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. Similarly, unrelated organisms may be distantly related, but appear very much alike. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the wing structure and embryonic origin is completely different. These are called analogous structures (Figure 20.8). Similar traits can be either homologous or analogous. Homologous structures share a similar embryonic origin; analogous organs have a similar function. For example, the bones in the front flipper of a whale are homologous to the bones in the human arm. These structures are not analogous. The wings of a butterfly and the wings of a bird are analogous but not homologous. Some structures are both analogous and homologous: the wings of a bird and the wings of a bat are both homologous and analogous. Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied.

PDF page 827: Notice it is not simply a single bone, but rather a grouping of several bones arranged in a similar way. The more complex the feature, the more likely any kind of overlap is due to a common evolutionary past. Imagine two people from different countries both inventing a car with all the same parts and in exactly the same arrangement without any previous or shared knowledge. That outcome would be highly improbable. However, if two people both invented a hammer, it would be reasonable to conclude that both could have the original idea without the help of the other. The same relationship between complexity and shared evolutionary history is true for homologous structures in organisms. Misleading Appearances Some organisms may be very closely related, even though a minor genetic change caused a major morphological difference to make them look quite different. Similarly, unrelated organisms may be distantly related, but appear very much alike. This usually happens because both organisms were in common adaptations that evolved within similar environmental conditions. When similar characteristics occur because of environmental constraints and not due to a close evolutionary relationship, it is called an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the wing structure and embryonic origin is completely different. These are called analogous structures (Figure 20.8). Similar traits can be either homologous or analogous. Homologous structures share a similar embryonic origin; analogous organs have a similar function. For example, the bones in the front flipper of a whale are homologous to the bones in the human arm. These structures are not analogous. The wings of a butterfly and the wings of a bird are analogous but not homologous. Some structures are both analogous and homologous: the wings of a bird and the wings of a bat are both homologous and analogous. Scientists must determine which type of similarity a feature exhibits to decipher the phylogeny of the organisms being studied.

PDF page 829: occurred that caused a shift in the genetic code. An insertion or deletion mutation would move each nucleotide base over one place, causing two similar codes to appear unrelated. Sometimes two segments of DNA code in distantly related organisms randomly share a high percentage of bases in the same locations, causing these organisms to appear closely related when they are not. For both of these situations, computer technologies have been developed to help identify the actual relationships, and, ultimately, the coupled use of both morphologic and molecular information is more effective in determining phylogeny.