Taxonomy Biology 2 Mr. Greene Unit 10 Bellringer Look through this chapter and list the name of each type of organism illustrated, such as cactuses,
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Taxonomy Biology 2 Mr. Greene Unit 10 Bellringer Look through this chapter and list the name of each type of organism illustrated, such as cactuses, bees, humans, oaks, etc. Suggest reasons why a scientific method of clasification is useful to study these organisms. Key Ideas Why do biologists have taxonomic systems? What makes up the scientific name of a species? What is the structure of the modern Linnaean system of classification? Taxonomy the classification of organisms The Need for Systems About 1.7 million species have been named and described by scientists. Scientists think that millions more are undiscovered. Biologists use taxonomic systems to organize their knowledge of organisms. These systems attempt to provide consistent ways to name and categorize organisms. Taxonomic systems do not use common names, which may be confusing because they are different in different places. What's in a Scientific Name? scientific name - the two-word name each organism on Earth is assigned all biologists over the world use these names binomial nomenclature – the system of assigning names genus = 1st word = describes organism in a general way group of organisms that share major characteristics First letter is ALWAYS CAPITALIZED species = 2nd word = identifies the exact kind of living thing each different kind of organism ALWAYS LOWER CASE The correct name MUST include both parts of its scientific name SCIENTIFIC NAMING RULES 1. Must be Latin or constructed using Latin rules 2. Two different organisms cannot be assigned the same name 3. Organisms of the same genus must have different species names 4. Organisms of different genera CAN have the same species name e.g. green anole lizard = Anolis carolinensis chickadee = Parus carolinensis 5. Pick name that relates to organisms location, trait, etc. e.g. Tyrannosaurus rex = tyrant-lizard king Why are names in Latin? Latin was used in academic circles in the Middle Ages when scientists began naming organisms. Hence, it was easier to communicate regardless of language barrier. Easier to keep names for all 1.7 million organisms in Latin then renaming them Who Created the System? Carl Linnaeus - Swedish botanist long names were used before he came along (some up to 15 words long) When reading or writing scientific names, remember the following: if the genus/species is already given you can abbreviate the genus e.g. Homo sapiens = H. sapiens based on physical, genetic, biochemical and behavioral similarities taxon – each level of the naming system Biological Hierarchy of Classification Taxanomic Hierarchy Kingdom Phylum Class Order Family Genus Species North America United States Ohio Lake Mentor Center Street 6477 Animalia Chordata Mammalia Primates Hominidae Homo Homo sapiens Sam gave Fred one copper padlock key. King Philip came over from Geneva, Switzerland. Classification of Ursus arctos Grizzly bear Black bear Giant panda Red fox KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos Abert squirrel Coral snake Sea star Classification of a Bee Panthera leo? Part One Panthera leo? Part Two The Linnaean System The category domain has been invented since Linnaeus’ time. This category recognizes the most basic differences among cell types. All living things are now grouped into one of three domains. The Linnaean System, continued A species is usually defined as a unique group of organisms united by heredity or interbreeding. In practice, scientists tend to define species based on unique features. For example, Homo sapiens is recognized as the only living primate species that walks upright and uses spoken language. Summary Biologists use taxonomic systems to organize their knowledge of organisms. They attempt to provide consistent ways to name and categorize organisms. All scientific names for species are made up of two Latin or Latin-like terms. In the Linnaean system of classification, organisms are grouped at successive levels of a hierarchy based on similarities in their form and structure. The eight levels of modern classification are domain, kingdom, phylum, class, order, family, genus, and species. Bellringer Write the names of as many different kinds of cats as you can think of. Most cats belong to the same genus, Felis. Identify which cats you think belong to the same species. Key Ideas What problems arise when scientists try to group organisms by apparent similarities? Is the evolutionary past reflected in modern systematics? How is cladistics used to construct evolutionary relationships? What evidence do scientists use to analyze these relationships? Traditional Systematics Scientists have traditionally used similarities in appearance and structure to group organisms. However, this approach has been problematic. Some groups look similar but turn out to be distantly related. Other groups look different but turn out to be closely related. For example, dinosaurs were once seen as a group of reptiles that became extinct millions of years ago. Birds were seen as a separate, modern group that was not related to any reptile group. Fossil evidence has convinced scientists that birds evolved from one of the many lineages of dinosaurs. Some scientists classify birds as a subgroup of dinosaurs. Problems with Traditional Classification based on structure how would you classify dolphins? with fish because of aquatic life and limbs that look like fins with mammals because warm blooded and breathe air Phylogenetics Scientists who study systematics are interested in phylogeny, or the ancestral relationships between species. Grouping organisms by similarity is often assumed to reflect phylogeny, but inferring phylogeny is complex in practice. Reconstructing a species’ phylogeny is like trying to draw a huge family tree over millions of generations. Not all similar characteristics are inherited from a common ancestor. Consider the wings of an insect and the wings of a bird. Both enable flight, but the structures of the two wings differ. Fossil evidence also shows that insects with wings existed long before birds appeared. Phylogenetics, continued Through the process of convergent evolution, similarities may evolve in groups that are not closely related. Similar features may evolve because the groups have adopted similar habitats or lifestyles. Similarities that arise through convergent evolution are called analogous characters. Phylogenetics, continued Grouping organisms by similarities is subjective. Some scientists may think one character is important, while another scientist does not. For example, systematists historically placed birds in a separate class from reptiles, giving importance to characters like feathers. Fossil evidence now shows that birds are considered part of the “family tree” of dinosaurs. This family tree, or phylogenetic tree, represents a hypothesis of the relationships between several groups. Cladistics Cladistics is a method of analysis that infers phylogenies by careful comparisons of shared characteristics. Cladistics is an objective method that unites systematics with phylogenetics. Cladistic analysis is used to select the most likely phylogeny among a given set of organisms. Cladistics, continued Cladistics focuses on finding characters that are shared between different groups because of shared ancestry. 1 Tetrapoda clade 2 Amniota clade 3 Reptilia clade 4 Diapsida clade 5 Archosauria clade A shared character is defined as FEATHERS & TOOTHLESS BEAKS. ancestral if it is thought to have evolved in a common ancestor of both groups. SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS BEHIND THE EYE EMBRYO PROTECTED BY AMNIOTIC FLUID A derived character is one that evolved in one group but not the other. FOUR LIMBS WITH DIGITS DERIVED CHARACTER Cladistics, continued For example, the production of seeds is a character that is present in all living conifers and flowering plants, and some prehistoric plants. Seed production is a shared ancestral character among those groups. The production of flowers is a derived character that is only shared by flowering plants. Cladistics, continued Cladistics infers relatedness by identifying shared derived and ancestral characters among groups, while avoiding analogous characters. Scientists construct a cladogram to show relationships between groups. A cladogram is a phylogenetic tree that is drawn in a specific way. Cladistics, continued Organisms are grouped together through identification of their shared derived characters. All groups that arise from one point on a cladogram belong to a clade. A clade is a set of groups that are related by descent from a single ancestral lineage. Cladistics, continued Each clade is usually compared with an outgroup, or group that lacks some of the shared characteristics. The next slide shows a cladogram of different types of plants. Conifers and flowering plants form a clade. Ferns form the outgroup. Cladogram: Major Groups of Plants Traditional Classification Versus Cladogram Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM Traditional Classification Versus Cladogram Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM Cladogram: Major Groups of Plants Inferring Evolutionary Relatedness, continued Morphological Evidence Morphology refers to the physical structure or anatomy of organisms. Large-scale morphological evidence, like seeds and flowers, have been well studied. Scientists must look carefully at similar traits, to avoid using analogous characters for classification. Inferring Evolutionary Relatedness, continued An important part of morphology in multicellular species is the pattern of development from embryo to adult. Organisms that share ancestral genes often show similarities during the process of development. For example, the jaw of an adult develops from the same part of an embryo in every vertebrate species. Inferring Evolutionary Relatedness, continued Molecular Evidence Scientists can now use genetic information to infer phylogenies. Recall that as genes are passed on from generation to generation, mutations occur. Some mutations may be passed on to all species that have a common ancestor. Similarities in DNA and RNA often you cannot compare organisms that are diverse (i.e. elephants and an amoeba) all organisms use DNA and RNA to pass on info and to control growth and development DNA and RNA are a good way of comparing organisms humans – a gene that codes for myosin (protein in muscles) yeast – has same gene that codes for myosin that enables internal cell parts to move Molecular Clocks models that use DNA comparisons to estimate then length of time that two species have been evolving independently i.e. pendulum clock it marks time with a swinging pendulum molecular clock marks time by mutations Inferring Evolutionary Relatedness, continued Genetic sequence data are now used widely for cladistic analysis. First, the sequence of DNA bases in a gene (or of amino acids in a protein) is determined for several species. Then, each letter (or amino acid) at each position is compared. Similarities in Amino Acid Sequences Inferring Evolutionary Relatedness, continued At the level of genomes, alleles may be lost or added over time. Another form of molecular evidence is the presence or absence of specific alleles—or the proteins that result from them. From this evidence, the relative timing between genetic changes can be inferred. Inferring Evolutionary Relatedness, continued Evidence of Order and Time Cladistics can determine only the relative order of divergence, or branching, in a phylogenetic tree. The fossil record can often be used to infer the actual time when a group may have begun to “branch off.” For example, using cladistics, scientists have identified lancelets as the closest relative of vertebrates. Inferring Evolutionary Relatedness, continued The oldest known fossils of vertebrates are about 450 million years old. But the oldest lancelet fossils are 535 million years old. So, these two lineages must have diverged more than 535 million years ago. Inferring Evolutionary Relatedness, continued DNA mutations occur at relatively constant rates, so they can be used as an approximate “genetic clock.” Scientists can measure the genetic differences between taxa and estimate time of divergence. Inferring Evolutionary Relatedness, continued Inference Using Parsimony Modern systematists use the principle of parsimony to construct phylogenetic trees. This principle holds that the simplest explanation for something is the most reasonable, unless strong evidence exists against that explanation. Given two possible cladograms, the one that implies the fewest character changes between points is preferred. Summary Scientists traditionally have used similarities in appearance and structure to group organisms. However, this approach has been problematic. Grouping organisms by similarity is often assumed to reflect phylogeny, but inferring phylogeny is complex in practice. Cladistic analysis is used to select the most likely phylogeny among a given set of organisms. Biologists compare many kinds of evidence and apply logic carefully in order to infer phylogenies. Bellringer What are the six kingdoms representing life on Earth? Key Ideas Have biologists always recognized the same kingdoms? What are the domains and kingdoms of the three-domain system of classification? Updating Classification Systems For many years after Linnaeus created his system, scientists only recognized two kingdoms: Plantae and Animalia. Biologists have added complexity and detail to classification systems as they have learned more. Many new taxa have been proposed, and some have been reclassified Sponges, for example, used to be classified as plants. Microscopes allowed scientists to study sponge cells. Plantae Scientists learned that sponge cells are much more like animal cells, so today sponges are classified as animals. Animalia Updating Classification Systems, continued In the 1800s, scientists added Kingdom Protista as a taxon for unicellular organisms. Soon, they noticed differences between prokaryotic and eukaryotic cells. Scientists created Kingdom Monera for prokaryotes. Plantae Animalia Protista Updating Classification Systems, continued By the 1950s, Kingdoms Monera, Protista, Fungi, Plantae, and Animalia were used. In the 1990s, genetic data suggested two major groups of prokaryotes. Kingdom Monera was split into Kingdoms Eubacteria and Archaebacteria. Plantae Animalia Protista Monera Fungi What Is a Species? basic unit of evolution gives rise to new genera, families, etc. new hierarchy results when enough changes have been made to species organisms that are able to interbreed to produce fertile offspring works for most animals horse and zebra have offspring that are sterile dogs, coyotes, wolves can interbreed and make a hybrid dogs – different breeds is not the same thing as different species Concept Map Living Things are characterized by Eukaryotic cells and differing Important characteristics which place them in Cell wall structures such as Domain Eukarya Prokaryotic cells which is subdivided into which place them in Domain Bacteria Domain Archaea which coincides with which coincides with Kingdom Eubacteria Kingdom Archaebacteria Kingdom Plantae Kingdom Fungi Kingdom Protista Kingdom Animalia The Three-Domain System As biologists saw differences between two kinds of prokaryotes, they saw similarities among eukaryotes. A new system divided all organisms into three domains: Bacteria, Archaea, and Eukarya. Today, most biologists tentatively recognize three domains and six kingdoms. Phylogenetic Diagram of Major Groups of Organisms The Three-Domain System, continued Major taxa are defined by major characteristics, including: Cell Type: prokaryotic or eukaryotic Cell Walls: absent or present Body Type: unicellular or multicellular Nutrition: autotroph (makes own food) or heterotroph (gets nutrients from other organisms) The Three-Domain System, continued Related groups of organisms will also have similar genetic material and systems of genetic expression. Organisms may have a unique system of DNA, RNA, and proteins. The following slide shows major characteristics for organisms in each domain and kingdom. Kingdom and Domain Characteristics 1/2) Monera evolved from a common unicellular ancestor 4 million years ago lack nuclei lack organelles oldest forms of life ARCHAE A) Archaebacteria unicellular and prokaryotes and found in extreme environments gave rise to eukaryotes and evolved before oxygen filled atmosphere cell walls lack peptidoglycan extremophiles BACTERIA B) Eubacteria unicellular and prokaryotes with 5,000 species thick, rigid cell walls with peptidoglycan common environments gave rise to eukaryotic cell organelles both autotrophic and heterotrophic forms some require oxygen and some do not The Three-Domain System Domain Eukarya is made up of Kingdoms Protista, Fungi, Plantae, and Animalia. Members of the domain are eukaryotes, which are organisms composed of eukaryotic cells. These cells have a complex inner structure that enabled cells to become larger than the earliest cells. This complex inner structure also enabled the evolution of multicellular organisms. All eukaryotes have cells with a nucleus and other internal compartments. Also, true multicellularity and sexual reproduction only occur in eukaryotes. EUKARYA 3) Protist greatest variety some unicellular; some are not some autotrophic; some heterotrophic ancestors of plants, fungi, and animals includes protozoa (amoeba and paramecium); algae (kelp and seaweed) EUKARYA 4) Fungi heterotrophic most are multicellular and feed on dead/decaying organic matter secrete digestive enzymes into food source they then absorb smaller food molecules into their bodies mushrooms, yeast (unicellular), molds thin filaments that penetrate the soil or decaying organisms 70,000 species EUKARYA 5) Plant multicellular, photosynthetic autotrophs nonmotile (unable to move place to place) mosses, ferns, flowers, trees most grow on dry land, some grow in water have cell walls which contain cellulose green algae are their ancestors 350,000 species EUKARYA 6) Animal multicellular and heterotrophic 1 million known species evolved in the ocean no cell walls nearly all have a nervous system of some sort 1 million species Cladogram of Six Kingdoms and Three Domains DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms DOMAIN BACTERIA Eubacteria Archaebacteria Protista Plantae Fungi Animalia Summary Biologists have added complexity and detail to classification systems as they have learned more. Today, most biologists tentatively recognize three domains and six kingdoms. Domain Bacteria is equivalent to Kingdom Eubacteria. Domain Archaea is equivalent to Kingdom Archaebacteria. Domain Eukarya is made up of Kingdoms Protista, Fungi, Plantae, and Animalia.