Ch 25 - Ch. 25 Scientists are becoming interested in...

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Ch. 25 Scientists are becoming interested in studying the evolutionary history of organisms and tracing their roots back to common ancestors. Phylogeny is the process of tracing evolutionary history of a species or group of species. Systematics is the analytical approach to understanding evolutionary relationships and diversity between organisms alive and extinct. Use fossil record and morphological characteristics to discover which organisms are related. Molecular systematics is a new process of comparing the DNA and RNA of organisms to determine their relationships to one another. Also compares relationships between genes and entire genomes. Fossils, morphological characteristics and molecular data are all used to compare organism’s relationships to each other. Sedimentary rock forms the best fossils. Sediment from rivers accumulates in ocean and pile up and cause fossils to form in the bottom of the oceans. Fossil record is based on the sequence of the fossils that have built up in these strata. Fossil record is incomplete because favors organisms that were abundant and lived a long time and had hard bones and skeletons. Had to die in right place as well for fossils to form. Homologies are characteristics that different species that are closely related share because they diverged from common ancestors. Morphological homologies are similar structures that closely related organisms share. Ex. Bones of forelimbs of mammals. Caused by divergence from common ancestor. Molecular homologies are similar DNA or RNA sequences in organisms that are related. May not look the same but can be related through DNA from common ancestor. Analogy is similar morphological structures due to convergent evolution. Similar environmental pressures create organisms with similar structures. Homoplasies are analogous structures that have evolved independently. Ex. Bats and
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Ch 25 - Ch. 25 Scientists are becoming interested in...

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