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Diversity of Life: Introduction to Biological Classification

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1 Diversity of Life: Introduction to Biological Classification
By Deanne Erdmann, MS Image References Weller, K. Dairy Cow. USDA Agricultural Research Service. Retrieved from Nichols, B. Seedless grapes. USDA Agricultural Research Service. Retrieved from Richard, B. Leaf Beetle. USDA Agricultural Research Service, APHS. Retrieved from BioEd Online

2 Why Do We Classify Organisms?
Biologists group organisms to represent similarities and proposed relationships. Classification systems change with expanding knowledge about new and well-known organisms. Tacitus bellus Why Do We Classify Organisms? Predict behavior Evolutionary relationships Understand organisms Classification is always a work in progress To understand how and why organisms function the way they do, and how they interact with one another, we must observe patterns in development and evolution. Think about the scope of the Life Science Content Standards: understanding the cell; molecular basis of heredity; biological evolution; interdependence of organisms, matter, and energy; organization in living systems; and behavior of organisms. Classification is a scientific approach to grouping organisms based on current knowledge gathered from all of these fields. It is more important to understand how and why classification systems are organized than to memorize each individual level. Classification systems encompass a wide, dynamic body of knowledge that is being modified continually. References National Research Council. (1996). National Education Standards. Washington D.C.: National Academy Press. Image reference Bauer, S. Tacitus bellus. USDA Agricultural Research Service. Retrieved from BioEd Online

3 History of the Kingdom System
The two kingdom system was accepted by biologists until 1866, when German biologist Ernst Haeckel proposed moving all single-celled organisms to the kingdom Protista In 1938, American biologist Herbert Copeland argued that the prokaryotes deserved their own kingdom, called Monera. Prokaryotes are single-celled organisms that do not have membrane-bound nuclei or organelles In 1959, American ecologist Robert Whittaker proposed that because of how they feed, fungi should be placed into their own kingdom apart from plants. The kingdom Fungi includes molds and mushrooms. In 1977, rRNA research by Carl Woese revealed two genetically different groups of prokaryotes. His findings led scientists to split the kingdom Monera into two kingdoms, called Bacteria and Archaea.

4 Leucaena leucocephala
Classification Binomial Nomenclature Two part name (Genus, species) Hierarchical Classification Seven Taxonomic Categories Systematics Study of the evolution of biological diversity Leucaena leucocephala Lead tree Classification Classification systems attempt to solve the problem of providing meaningful groupings of organisms. The Swedish scientist, Carolus von Linnaeus, is credited with introducing binomial nomenclature and hierarchical classification as an organized way of naming and describing organisms and their relationships to one another. Binomial nomenclature refers to the use of a two-part name for each species (one name designating genus and one designating species). Linnaeus described a hierarchical classification system using seven taxonomic categories, or taxa (Kingdom, Phylum, Class, Order, Family, Genus, Species). Beginning with species, each category becomes progressively more comprehensive. For example, while the leopard, tiger and domestic cat all belong to different genera, they are grouped together in the same family. Taxonomy is the science of classification. When taxonomic systems include hypothesized evolutionary relationships among groups, the field generally is referred to as Phylogenetics. Systematics is a larger field involving classifying organisms based on their phylogenetic relationships. Systematics can be thought of as the study of biological diversity and how that diversity evolved. In a sense, Charles Darwin introduced systematics in his revolutionary work, The Origin of Species. He wrote, “The natural system is founded on descent with modification; that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parent, and, in so far, all true classification is genealogical” (Darwin, 1859). References Campbell, N. E. & Reece, J. B. (2002). Biology (6th ed.). Benjamin Cummings. Darwin C. (1859).The Origin of the Species. London, England: Pengin Books. Image Reference Bauer, S. Leucaena leucocephala. USDA Agricultural Research Service. Retrieved from BioEd Online

5 Binomial Nomenclature
Carolus von Linnaeus Two-word naming system Genus Noun, Capitalized, Underlined or Italicized Species Descriptive, Lower Case, Underlined or Italicized Carolus von Linnaeus ( ) Swedish scientist who laid the foundation for modern taxonomy Binomial Nomenclature Early naturalists identified plants and animals by observable structural similarities and referred to organisms using long complicated phrases. This was known as the “polynomial system.” In this system, a plant might be described by phrases of 12 or more words. It is not surprising that polynomial names could become very complex and were often misinterpreted when translated from one language to another. In the 1700s, Carolus von Linnaeus, sometimes referred to as the Father of Classification, described a binomial system, which was published in his early work, System Naturae (1735). Although he created the two-word system as a short-cut for users of this work, the system was rapidly adopted as a manageable way of naming species. In the binomial nomenclature system, genus and species—just two names—replace the long string of words used in the polynomial system. The meaning of words can differ from language to language and from country to country. For example, in Great Britain, the word “buzzard” refers to an organism Americans call a hawk. For this reason, scientific names are written in Latin to maintain a uniform system of naming across all languages. In the binomial system, genus is always a noun, underlined (or italicized), and capitalized; species is a descriptive term, underlined (or italicized), and not capitalized. Some examples of binomial names include: Quercus rubra (red oak), Panthera pardus (leopard), or Homo sapiens (human). References Johnson, G. B. & Raven, P. H. (2004). Biology, Principles and Explorations. Holt, Rinehart, and Winston. Linne, Carl von. (1735). System Naturae. Nieuwkoop:De Graaf. Image reference Roslin, A. (1775) Carl von Linné. Retrieved from BioEd Online

6 Hierarchical Classification
Taxonomic categories Kingdom King Phylum Philip Class Came Order Over Family For Genus Good Species Soup Hierarchical Classification Carolus von Linnaeus created a hierarchical classification system using seven taxonomic categories, or taxa (Kingdom, Phylum, Class, Order, Family, Genus, Species). These categories are based on shared physical characteristics, or phenotypes, within each group. Beginning with kingdom, each successive level of classification becomes more and more specific. Organisms within the same order have more in common with one another than organisms within the same class. For example, all species of bears are mammals, but not all mammals are bears. A useful pneumonic tool to help students remember the hierarchical classification system is: “King Phillip Came Over For Good Soup,” with the first letter of each word representing each category, beginning with kingdom and ending with species. References Campbell, N. E. & Reece, J. B. (2002). Biology (6th ed.). Benjamin Cummings. BioEd Online

7 Kingdoms and Domains BioEd Online The three-domain system
Bacteria Archaea Eukarya The six-kingdom system Bacteria Archaea Protista Plantae Fungi Animalia The traditional five-kingdom system Kingdoms and Domains In the 18th Century, organisms were considered to belong to one of two kingdoms, Animalia or Plantae. As biologists gathered more information about the diverse forms of life on Earth, it became evident that the two-kingdom system did not accurately reflect relationships among different groups of organisms, and the number of kingdoms increased. In 1969, Robert Whittaker proposed a five-kingdom system consisting of monerans, protists, fungi, plants and animals. In the last few years, comparative studies of nucleotide sequences of genes coding for ribosomal RNA and other proteins have allowed biologists to recognize important distinctions between bacteria and archaebacteria. The graphic on this slide illustrates the phylogenetic relationships drawn from this information using a three-domain and a six-kingdom arrangement, compared to the traditional five kingdom system. References Woese, C. R. & Fox, G. E. (1977). Phylogenetic structure of the prokaryotic domain: the primary kingdoms. Proceedings of the National Academy of Sciences of the United States of America. 74(11), Monera Protista Plantae Fungi Animalia BioEd Online

8 Systematics: Evolutionary Classification of Organisms
Systematics is the study of the evolution of biological diversity, and combines data from the following areas. Fossil record Comparative homologies Cladistics Comparative sequencing of DNA/RNA among organisms Molecular clocks Systematics: Evolutionary Classification of Organisms Evolutionary classification, or phylogenetics, creates classification that represents hypothesized relationships among groups of organisms. Systematists use a combination of fossil records, comparative anatomy, cladistical analyses and molecular data to understand the patterns of relationships among organisms. The fossil record is an accumulation of all fossils found within layers of sedimentary rock and helps to reconstruct a geological time scale. Fossils are the remnants or impressions of organisms that lived in the past. Homologies are similarities among species attributed to the inheritance of a feature from a common ancestor. Important information about common ancestry can be discovered by comparing different organisms’ anatomical, embryological and molecular homologies. A classic example of homologous structures is the comparison of the basic groups of bones in the forelimbs of different groups of vertebrates (whale, alligator, penguin and human). Although each forelimb is adapted for a different use, the bones are formed in the same way during embryological development, suggesting descent from a common ancestor. Cladistics is based on the idea that members of a group share a common evolutionary history and are more closely related to members within their group than to other organisms. These groups are recognized as sharing unique, derived features not present in distant ancestors. A cladogram is a branching diagram that illustrates hypothesized relationships based on shared, derived characteristics. Comparative sequencing: Scientists also can compare DNA and RNA sequences among different organisms to unravel evolutionary relationships and common ancestry. These sequences can be used in comparison studies to determine phylogenetic relationships that can not be compared between morphological or fossil data. Ribosomal RNA, chloroplast DNA, and mitochondrial DNA have proven particularly useful in these kinds of studies. Molecular clock studies compare sequences of macromolecules (proteins and nucleic acids) among species, assuming that these macromolecules evolve at constant rates throughout time, and for different lineages. Changes in sequences (nucleotide or amino acid substitutions, or mutations) are used to develop ideas about the evolutionary divergence of species. The molecular clock hypothesis has been a powerful technique for determining evolutionary events of the remote past for which the fossil record and other evidence is lacking or insufficient. The reliability of this hypothesis is currently under debate in the scientific community. References Campbell, N. E. & Reece, J. B. (2002). Biology (6th ed.). Benjamin Cummings. Judd, W. S., Campbell, C. S., Kellogg, E. S., Stevens, P.F., & Monoghue, M. J. (2002). Plant Systematics: A Phylogenetic Approach, (2nd ed.). Sinauer Associates, Inc. BioEd Online

9 Taxonomic Diagrams BioEd Online Phylogenetic Tree Cladogram
Mammals Turtles Lizards and Snakes Crocodiles Birds Mammals Turtles Lizards and Snakes Crocodiles Birds Phylogenetic Tree Cladogram Taxonomic Diagrams Sometimes, biologists group organisms into categories that represent common ancestries, not just physical similarities. Early naturalists used physical characteristics and later, fossil data, attempting to represent evolutionary relationships among organisms. Today, modern classification systems use fossil data, physical characteristics and DNA/RNA information to draw increasingly more accurate branching diagrams. Phylogenetic trees, or phylogenies, represent hypothesized evolutionary relationships among organisms and may include extinct as well as modern species. Cladograms are based only on characteristics observable in existing species. The branching patterns in a cladogram are defined by the presence of unique, evolving innovations (derived characteristics) shared by all members of the group. References Campbell, N. E. & Reece, J. B. (2002). Biology (6th ed.). Benjamin Cummings. Judd, W. S., Campbell, C. S., Kellogg, E. S., Stevens, P. F., & Monoghue, M. J. (2002). Plant Systematics: A Phylogenetic Approach, (2nd ed.). Sinauer Associates, Inc. Image References Dykinga J. Buffalo. USDA Agricultural Research Service. Bauer, S. Turkey. USDA Agricultural Research Service. Alligator, unknown NOVA Development Corp. (1995) Insects & Reptiles #0517. Art Explosion, Volume 2 Clip Art NOVA Development Corp. (1995) Insects & Reptiles #0557. Art Explosion, Volume 2 Clip Art BioEd Online


11 Dichotomous Keys Identify Organisms
Dichotomous keys versus evolutionary classification Dichotomous keys contain pairs of contrasting descriptions. After each description, the key directs the user to another pair of descriptions or identifies the organism. Example: 1. a) Is the leaf simple? Go to 2 b) Is the leaf compound? Go to 3 2. a) Are margins of the leaf jagged? Go to 4 b) Are margins of the leaf smooth? Go to 5 Dichotomous Keys of Identify Organisms Identification is the process of finding the named group to which an organism belongs. Dichotomous keys are useful tools to help identify different organisms and usually are found in field guides. Identification in the field is based on features that are observable to the eye; therefore, it is important to remember that a key is an identification tool and is not synonymous with phylogenetic diagrams, which communicate hypothesized evolutionary history. Dichotomous keys are constructed of contrasting pairs of statements. To use a dichotomous key, begin with the first pair of statements and follow the directions at the end of each statement until you reach the name of the organism you are trying to identify. With each new organism, always start at the beginning of the key (1a and 1b). The ability to use dichotomous keys is an important skill and should be incorporated into instruction throughout the year. It is important to note that when constructing a dichotomous key, each pair of contrasting descriptions must deal with the same characteristic. For example the margin of the leaf might be used for the first pair of descriptors, and the shape of the leaf might be used for another pair. An incorrect pair of statements might be: 1a) Is the leaf heart shaped? 1b) Are the edges lobed? References Campbell, N. E. & Reece, J. B. (2002). Biology (6th ed.). Benjamin Cummings. BioEd Online

12 Dichotomous key


14 Plant Phyla bryophyta Filicinophyta Coniferophyta Angiospermophyta

15 Bryophyta (“bryo-”: moss)
mosses, liverworts and hornworts stems radial symmetry (mosses) stems bilateral symmetry (liverworts), no lignin no true leaves or roots no cuticle. reproductive structure are called sporangium which are on long stalks with capsules on end. In this image the spore is released from the sporangium to develop into another plant. Mosses Plants in the moss phylum are non-vascular and do not have seeds, roots or flowers. They do not have stems or leaves either, but are capable of photosynthesis. Mosses do not grow upright, and instead grow in an outward manner, anchoring themselves to a base through which they absorb the necessary nutrients and moisture. Mosses may grow in a variety of climates, including deserts and rain forests, as well as tropical and polar regions. They serve an important ecological role because they are able to grow on rocky surfaces, so they are often the first plant species to move into an area. As they begin to die and decompose, mosses help with the formation of soil that allows other plant species to grow in the area. In addition, mosses help recycle nutrients for forest vegetation and maintain proper moisture levels in the soil.

16 Filicinophyta (ferns)
leaves roots non woody stems divided leaves height up to 20 m reproduction: sporangia (sori) contain reproductive spores Ferns Like mosses, plants in the fern phylum do not have seeds or flowers, but ferns have a vascular system which is used to carry fluids throughout the plant. Ferns reproduce via spores that are found on the underside of their leaves. According to the American Fern Society, there are over 12,000 species of ferns, and most are perennial. Some, however, are evergreen or deciduous. Ferns grow in a variety of environments, including rocky areas, woodlands and bogs. In general, wild ferns thrive in wooded areas with high humidity. They also do well in soil that is slightly acidic, which helps the plants drain properly and retain moisture. Because of their adaptability, ferns are often used as house or landscape plants. They should be kept in shaded areas, where sunlight is filtered.

17 Coniferophytes (conifers and pines)
trees (100m), shrubs, woody (lignin) stems, waxy narrow needle like leaves. vascular system (tracheids) reproduction: monoecious, microsporophylls (male) non motile gametes often with air bladders for water/ air dispersal. macrosporophylls (female) ovule on cone scale Conifers Conifers, also known as gymnosperms, are a phylum of vascular plants that contain seeds but do not grow flowers. The seeds are commonly referred to as "naked" because they are not protected by flowers or fruit tissue. Instead, many conifers use a cone-like structure, such as a pine cone, to produce their seeds. Others use a berry-like structure. Conifer plants may grow as either trees or shrubs, and usually have leaves that have a needle-like appearance. Common species of conifer plants include pine, spruce, cedar, fir, yew and juniper. They can grow in a variety of climates, but most species prefer full sun.

18 Angiospermophyta (flowering plants and grasses)
roots stems leaves. vascular bundles (xylem/ phloem ) waxy cuticle, annual or perennial up to 100m reproduction: ovules in an enclosed carpel structure. pollen grains produced from anthers variety of pollen transfers vectors Flowering Plants Flowering plants make up the most complex phylum in the plant kingdom. Also known as angiosperms, these are vascular plants that contain seeds and flowers. They reproduce by growing their seeds inside an ovary which is located inside their flowers. Once the seed is fertilized, the flower falls off and the seed grows into a fruit. Some flowering plants grow two seed leaves and are known as dicot plants, while others begin with only one seed-leaf and are known as monocots. Most flowering plants are dicots, but some notable monocots include irises, lilies and orchids. Flowering plants can grow in a wide range of environments, but typically require greater care than non-flowering plants to remain healthy.

19 Animal Phyla (just the invertebrates for now…)
Porifera (sponges) Cnidaria (jellyfish…) Platyhelminthes (flatworms) Annelida (segmented worms) Mollusca (snails, clams, octopus…) Arthropoda (insects, crustaceans, spiders...) Porifera Modern Latin, neuter plural of porifer, from Latin porus "pore, opening" (see pore (n.)) +-fer "bearing" (see infer). Related: Poriferal. Cnidaria (n.) phylum of stinging invertebrates, from Modern Latin cnida, from Greek knide "nettle," from stem of knizein "to scratch scrape." Related: Cnidarian. (silent “c”) Platyhelminthes – platy: “flat”, helminthes: “worm” Mollusca (n.) 1797, from Modern Latin mollusca, chosen by Linnaeus as the name of an invertebrate order (1758), from neuter plural of Latin molluscus "thin-shelled," from mollis"soft" (see melt (v.)). Linnæus applied the word to a heterogeneous group of invertebrates, not originally including mollusks with shells; the modern scientific use is after a classification proposed 1790s by French naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier ( ). annelid (n.) "segmented worm," 1834, from French annélide, source of the phylum name Annelida, coined in Modern Latin 1801 by French naturalist J.B.P. Lamarck ( ), from annelés "ringed ones" (from Latin anulus "little ring," a diminutive of anus; see anus) + Greek eidos "form, shape" (see -oid) Arthropoda (n.) 1870, Modern Latin, literally "those with jointed feet," coined 1845 by German zoologist Karl Theodor Ernst von Siebold ( ) from Greek arthron "a joint" (seearthro-) + podos genitive of pous "foot" (see foot (n.)).arthropod (n.) 1877, from Modern Latin Arthropoda, literally "those with jointed feet," biological classification of the phylum of segmented, legged invertebrates; see Arthropoda




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