Evolution B-LS4-1 PDF

Evolution B-LS4-1 Charles Darwin Charles Darwin - created the Theory of Evolution. Darwin wrote many of the premises of 'The Theory of Evolution by Natural Selection' ○ He did this by noting differences in the beaks of closely related finches while studying in the Galapagos...

Evolution B-LS4-1 Charles Darwin Charles Darwin - created the Theory of Evolution. Darwin wrote many of the premises of 'The Theory of Evolution by Natural Selection' ○ He did this by noting differences in the beaks of closely related finches while studying in the Galapagos Islands. Evolution Scientific studies in the fields of anatomy, embryology, biochemistry, and paleontology have all contributed scientific evidence for the theory of evolution. Field of Anatomy -The field of anatomy (the study of the structures of organisms) provides one type of data for the support of biological evolution. Scientists consider homologous structures as evidence of an evolutionary relationship between two groups of organisms (for example two species or two families). ○ Organisms that have diverged from a common ancestor often have homologous structures (similar characteristics resulting from common ancestry). The greater the numbers of shared homologous structures between two species, the more closely the species are related. Evolution Many species have vestigial organs (structures with little or no function to the organism) that are remnants of structures that had important functions in ancestors of the species. The vestigial organs of one species are often homologous structures that are shared in related species for which the structure has remained functional. The study of the anatomy also reveals that species living in different locations under similar ecological conditions may evolve similar structures and behaviors. Such structures, called analogous structures, describes body structures that look alike and serve similar functions, but are not descended from a common ancestors. Evolution Field of Embryology -The field of embryology (the study of the embryonic development of organisms) provides another type of data for the support of biological evolution by comparing the anatomies of embryos (an early stage {pre-birth, pre-hatching, or pre-germination} of organism development). Sometimes similarities in patterns of development or structures that are not obvious in adult organisms become evident when embryonic development is observed. The embryos of vertebrates are very similar in appearance early in development but may grow into different structures in the adult form. These similar structures of these embryos may suggest that these species evolved from common ancestors Evolution Field of Biochemistry - The field of biochemistry (the study of the chemical processes in organisms) studies genes and proteins to provide support for biological evolution. The more similar the DNA and amino acid sequences in proteins of two species, the more likely they are to have diverged from a common ancestor. Biochemistry provides evidence of evolutionary relationships among species when anatomical structures may be hard to use. For example, when species are so closely related that they do not appear to be different, or when species are so diverse that they share few similar structures. Evolution Field of Paleontology - Paleontology (the study of prehistoric life) is another tool that scientists use to provide support for biological evolution. The fossil record provides evidence of life forms and environments along a timeline and supports evolutionary relationships by showing the similarities between current species and ancient species. ○ The most accurate way to determine relationship is by examining genetic or protein sequences. The fossil record is not complete because most organisms do not form fossils. Many of the gaps in the fossil record have been filled in as more fossils have been discovered. In general, the older the fossils, the less resemblance there is to modern species. Evolution Scientists study data from a variety of fields to determine the phylogeny (evolutionary history) of a species or a group of related species. The central ideas of evolution are that life has a history — has changed over time — and that different species share common ancestors. Evidence of the shared history is found in all aspects of living and fossil organisms (physical features, structures of proteins, sequences found in RNA and DNA). Scientists must use multiple sources of evidence in drawing conclusions concerning the evolutionary relationship among groups of organisms. Evolution For example: Field of Anatomy: Phylogenies can be constructed by assuming that anatomical differences increase with time. The greater the anatomical similarity, the more recently a pair of species shares a common ancestor. ○ The accumulation of evolutionary differences over time is called divergence. ○ Anatomical structures that share a common evolutionary history but not necessarily the same function are termed homologous. Evolutionary biologists make observations on as many anatomical structures as possible to construct phylogenies. Sometimes individual structures may suggest evolutionary relationships that differ from the bulk of the evidence. This may result from convergence. Convergence occurs when organisms with different evolutionary histories adapt to similar environments. Anatomical structures that have different evolutionary origins (genetics) but have similar functions Evolution Field of Embryology: By comparing characteristics of embryonic development, scientists are able to compare anatomical structures to construct phylogeny. Field of Biochemistry: Phylogenies can be constructed by assuming that differences in DNA, proteins, and other molecules increase over time. The greater the overall genetic similarity, the more recently a pair of species shares a common ancestor. The time since a pair of species has diverged can be estimated under the assumptions of a “molecular clock.” Evolution Even though a comparison of the DNA sequences of two species provides some of the most reliable evidence, there are challenges inherent in this approach as well. ○ Because genes evolve at different rates, it may be difficult for scientists to identify the molecules that yield information about the group of organisms at the scale under study. ○ Different assumptions about the details of molecular evolution can yield different phylogenetic trees. ○ Natural selection can cause convergence in molecules, just as it causes convergence in anatomical structures. Evolution Field of Paleontology: The fossil record provides information regarding the dates and order of divergence for phylogenies. Transitional fossils (fossils that show links in traits between groups of organisms used to document intermediate stages in the evolution of a species) confirm evolutionary relationships. The primary challenge for using the fossil record as a map of evolutionary history is that the record is incomplete. Evolution Even though millions of fossils have been discovered by scientists, many environmental conditions must be met in order for a fossil to form, and the chance of all of these conditions coming together at one time is rare. The fossil record favors the preservation of species that existed for a long time, were abundant and widespread, and had hard shells or skeletons. Fossils that allow scientists to fill gaps in the record are continually being discovered. Evolution Understand that one piece of evidence does not ensure an accurate picture of the history of the evolution of a particular group of organisms, but as scientists collect many pieces of evidence from many fields, the reliability of a particular hypothesis becomes greater and greater. The more evidence scientists can gather from different fields of science, the more reliable their information becomes in regards to evolutionary relationships. The evolutionary theory is a well-documented explanation that accounts for a wide range of observations made by scientists in many fields of science. No scientist suggests that all evolutionary processes are understood; many unanswered questions remain to be studied and analyzed. Evolution A phylogenetic tree is a scientific diagram that biologists use to represent the phylogeny (evolutionary history of a species) of organisms. It classifies organisms into major taxa (groups) based on evolutionary relationships. Phylogenetic trees are used to classify species in the order in which they descended from a common ancestor using physical characteristics. Speciation could be thought of as a branching of a family tree then extinction is like the loss of one of the branches. Evolution Some phylogenetic trees only express the order of divergence of a species. They do not attempt to show relative or absolute time frames. These are called cladograms. Evolution Some phylogenetic trees indicate an estimated time of divergence. The tree below shows the relative time that species diverged. ○ The branch between humans and whales is almost at the top of the line, while the branch between birds and tyrannosaurs happens about midway up the line, indicating that birds and tyrannosaurs diverged much sooner than humans and whales diverged. From phylogenetic trees, the following information can be determined: Which groups are most closely related? Which groups are least closely related? Which group diverged first (longest ago) in the lineage? Evolution One of the main challenges to the classification of the Earth’s biodiversity is that species are becoming extinct at an increasing pace. As knowledge of biodiversity increases, revisions to taxonomic systems are continually being proposed. Biologists regularly revise the many branches of the phylogenetic tree to reflect current hypotheses of the evolutionary relationships between groups. Additionally, information gained from DNA sequencing has contributed to many revisions of phylogenetic hypotheses. Evolution The most recent classification scheme includes; ○ Three domains (Bacteria - single celled, Archaea(similar to bacteria), and Eukarya - multicellular) ○ Six kingdoms (Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia).