Phylogeny Systematics - Phylogeny and Systematics...

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Unformatted text preview: Phylogeny and Systematics Objectives D.5.1 – Outline the value of classifying organisms. D.5.2 – Explain the biochemical evidence provided by the universality of DNA and protein structures for the common ancestry of living organisms. D.5.3 – Explain how variations in specific molecules can indicate phylogeny. D.5.4 – Discuss how biochemical variations can be used as an evolutionary clock. Definitions Value of classification Studying phylogeny is a goal of systematics; phylogeny can be used to classify organisms and show relatedness. Organization of data through phylogeny (classification) … helps to identify organisms, suggests evolutionary links, and allows prediction of shared characteristics. Value of classification Studying phylogeny is a goal of systematics; phylogeny is used to classify organisms and show relatedness. Consider the discovery of a new bacterium from a sick patient: how it is related to other bacteria can suggest its pathosus- genicity and ceptibility to drugs, & it’s epidemiology. Value of classification Studying phylogeny is a goal of systematics; phylogeny is used to classify organisms and show relatedness. Consider the discovery of new dinosaur fossils: is this a new species with new evolutionary adaptations? And where does it fit in relation to other species? Value of classification Studying phylogeny is a goal of systematics; phylogeny is used to classify organisms and show relatedness. Where did birds come from? Value of classification Studying phylogeny is a goal of systematics; phylogeny is used to classify organisms and show relatedness. Where did the first primates evolve? How are humans related to apes? Who were the first humans? Universality of DNA The same DNA code is used by all organisms on Earth (universal). Identical bases: DNA has A, T, C, G; RNA has A, U, C, G. Triplets code for the same amino acids in all life. Suggests all life has a common ancestor. Universality of DNA The same DNA code is used by all organisms on Earth. Genetic transformation of E. coli with human DNA (the gene for insulin) produces a functioning insulin protein in the bacteria. Universality of DNA DNA is the material of inheritance Neo-Darwinism relates genetics to evolution. Changes in a DNA sequence over time can be used to measure the degree of relatedness. The less similarity in DNA sequences – the more distantly related. Universality of DNA Biochemical evidence provided by the universality of DNA and proteins derived from DNA show that humans are part of the tree of life. This must affect how we view ourselves and the rest of the living world. Proteins indicate phylogeny Variations in specific molecules can indicate phylogeny. DNA codes for amino acids, so the number of differences in a particular molecule can show relatedness based on DNA similarity, and produce a family tree. Evolutionary clocks Biochemical variation can be used as an evolutionary clock. Mutations lead to variations; the rate of mutation can be estimated. BUT, the mutation rate is NOT constant, so interpretation must be carefully done. Remember: gradualism vs. punctuated equilibrium Some particular genes mutate rapidly, others slowly. DNA coding for ribosomal RNA changes slowly. Mitochondrial DNA changes rapidly. Evolutionary clocks Biochemical variation can be used as an evolutionary clock. Mutations lead to variations; the rate of mutation can be estimated. Phylogeny Phylogeny based based on on differences differences in in the the protein protein sequence sequence of of cytochrome cytochrome cc Evolutionary clocks DNA mutations in the male’s Y chromosome can be used to make a map of human migration. Using mitochondrial DNA can produce a map of a woman’s lineage. Evolutionary clocks Mapping human migration using mutations in the Y chromosome or mitochondrial DNA: Phylogeny and Systematics Objectives D.5.5 – Define clade and cladistics. D.5.6 – Distinguish, with examples, between analogous and homologous characteristics. D.5.7 – Outline methods used to construct cladograms and conclusions that can be drawn from them D.5.8 – Construct a simple cladogram. D.5.9 – Analyze cladograms in terms of phylogenetic relationships. D.5.10 – Discuss the relationship between cladograms and the classification of living organisms. Definitions Cladistics: An approach to taxonomy that classifies organisms according to the relative order in time at which branches arose along a phylogenetic tree. Based upon evolutionary relationships, not morphology. It implies an order in time for common ancestors. It does not establish an absolute time frame or say one specific group member is older than another. Clade: An evolutionary branch of organisms. Can be one species, or one genus, or one family (Felidae, Hominidae) up through one kingdom. Consists of an ancestral species and ALL of its descendants. Definitions Cladogram: a phylogenetic diagram based on cladistics. Cladogram of the dog family (Canidae): Branch colors : Red = red-fox-like clade Green = South American clade Blue = wolf-like clade Orange = grey & island fox clade Dates (from fossils) are indicated at some branch points. Mya = million years ago. Homologous characteristics Features of new species are altered versions of ancestral features. Similarity in characteristics resulting from common ancestry is known as homology. Homologous characteristics derive from homologous patterns in DNA that can be useful to cladistics. All All cats cats share share aa common common ancestor ancestor Homologous characteristics Homologous structures For example, the forelimbs of humans, cats, whales, and bats share the same skeletal elements (but different functions) because they diverged from the ancestral tetrapod forelimb of the lungfish. Analogous characteristics Analogous structures are those that appear similar but derive independently from different ancestors. They indicate an evolution of unlike creatures toward life in a common environment. Don’t be mislead! A streamlined body with flippers is an adaptation for life swimming in the water. Constructing cladograms A clade consists of an ancestral species and ALL of its descendants. NOT a clade Two clades Constructing cladograms How do scientists decide on the branching sequence? 1) Sort homology from analogy. The greater the number of homologies, the closer the relationship. The more complex two similar structures are, the less likely they evolved independently. Skulls of monkeys and humans have several fused bones. Constructing cladograms How do scientists decide on the branching sequence? 1) Sort homology from analogy. 2) Identify shared derived characters. A backbone is a shared primitive character not useful in relating one vertebrate to another. Hair is a shared derived character that separates a reptile from a mammal. Constructing cladograms How do scientists decide on the branching sequence? 1) Sort homology from analogy. 2) Identify shared derived characters. 3) Perform an outgroup comparison. Include a closely-related organism outside your group of study (the lancelet in this case). Constructing cladograms 4) Translate the character table into a cladogram. 5) Make conclusions What is the order of derived characteristics? How are groups similar or dissimilar? Analyzing cladograms What is the chronological sequence of branching during evolutionary history within this group of organisms? The turtle-leopard clade includes a common ancestor that is more recent than the ancestor of the salamander-turtle-leopard clade. (No absolute dates are given.) Phylogenetic sytematics Classification based on evolutionary history is called phylogenetic systematics. Phylogeny is the evolutionary history of a species or group, based on fossils, molecular biology, anatomy, etc. All phylogenetic trees are hypotheses. New science may find new characteristics of greater importance (ex: DNA). Cladistics is one system that places groups (clades) in order. It can verify or dispute the traditional hierarchical (Linnaean) system of taxonomy. Some say do away with phyla, classes, order, etc. and use the names of clades: Vertebrata, Amniota (amniotic eggs) to classify. Phylogenetic sytematics Classification based on evolutionary history is called phylogenetic systematics. Systematists can use cladograms to place species in a taxonomic hierarchy. Phylogenetic sytematics When did major mammalian orders originate? Fossils say after the dinosaurs went extinct, 65 mya. DNA says closer to 100 mya. What is the truth? Proliferation Proliferation Fossils Fossils too too few few to to find find ...
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