Chapter 17: Organizing Life

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Chapter 17 Organizing Lifes Diversity

• Section 1 The History of Classification
• Section 2 Modern Classification
• Section 3 Domains and Kingdoms

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17.1 The History of Classification

• Main idea Biologists use a system of
  classification to organize information about the
  diversity of living things.
• Objectives
• Compare Aristotles and Linnaeuss methods of
  classifying organisms.
• Explain how to write a scientific name using
  binomial nomenclature.
• Summarize the taxa in the biological
  classification

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17.1 The History of Classification

• Review Vocabulary
• Morphology the structure and form of an organism
  or one of its parts
• New Vocabulary
• Classification
• Taxonomy
• Binomial nomenclature
• Taxon
• Genus
• Family
• Order
• Class
• Phylum
• Division
• Kingdom
• Domain

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Early Systems of Classification

• Biologists find it easier to communicate and
  retain information about organisms when the
  organisms are organized into groups.
• Classification is the grouping of objects or
  organisms based on a set of criteria.
• Biologists use a system of classification to
  organize information about the diversity of
  living things.

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Aristotles System

• More than 2000 years ago, Aristotle developed the
  first widely accepted system of biological
  classification.
• Aristotle classified organisms as either animals
  or plants.
• Animals were classified according to the presence
  or absence of red blood.
• Animals were further grouped according to their
  habitats and morphology.
• Plants were classified by average size and
  structure as trees, shrubs, or herbs.

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Aristotles System

• System useful for organizing but it had
  limitations.
• It did not account for evolutionary
  relationships.
• Many organisms did not fit easily into
  Aristotles system such as birds that dont fly
  or frogs that live on both land and water.
• Many centuries passed before Aristotles system
  was replaced by a new system that was better
  suited to the increased knowledge of the natural
  world.

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Linnaeuss System

• In the 18th century, Carolus Linnaeus broadened
  Aristotles classification method and formalized
  it into a scientific system.
• Like Aristotle, he based his system on
  observational studies of the morphology and the
  behavior of organisms
• Linnaeuss system of classification was the first
  formal system of taxonomy.
• Taxonomy is a discipline of biology primarily
  concerned with identifying, naming , and
  classifying species based on natural
  relationships.
• A branch of the larger branch of biology called
  systematics
• Systematics is the study of biological diversity
  with an emphasis on evolutionary history.

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Linnaeuss System

• Linnaeuss method of naming organisms, called
  binomial nomenclature, gives each species a
  scientific name with two parts.
• The first part is the genus name, and the second
  part is the specific epithet, or specific name,
  that identifies the species.
• Latin is the basis for binomial nomenclature.
• Biologists use scientific names for species
  because common names vary in their use.

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Binomial Nomenclature

• Common names that lead to confusion
• Woodchuck or Groundhog
• Starfish are not fish
• Great Horned Owls do not have horns.
• Sea Cucumbers are not plants
• Scientific names eliminate confusion
• Instead of a redbird, cardinal or Northern
  cardinal having different names in different
  regions of the US, Linnaeus gave this bird its
  scientific name Cardinalis cardinalis.

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Rules of Scientific Names

• The first letter of the genus name always is
  capitalized, but the rest of the genus name and
  all letters of the specific epithet are
  lowercase.
• If a scientific name is written in a printed book
  or magazine, it should be italicized.
• When a scientific name is written by hand, both
  parts of the name should be underlined.
• After the scientific name has been written
  completely, the genus name will be abbreviated to
  the first letter in later appearances (e.g., C.
  cardinalis).

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Modern Classification Systems

• Evolution added a new dimension to Linnaeuss
  classification system.
• Organisms were no longer classified on the basis
  of morphological and behavioral characteristics
  alone.
• Evolutionary relationships are included in modern
  classification systems.

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Taxonomic Categories

• A nested-hierarchal system-each category is
  contained within another, and they are arranged
  from broadest to most specific.

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Species and Genus

• A named group of organisms is called a taxon
  (plural, taxa).
• A genus (plural, genera) is a group of species
  that are closely related and share a common
  ancestor.
• Example
• American black bear Ursus americanus
• Asiatic black bear Ursus thibetanus

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Family

• A family is the next higher taxon, consisting of
  similar, related genera.
• Example
• All bears, both living and extinct species,
  belong to the same family, Ursidae.
• All members of the bear family share certain
  characteristics they all walk flatfooted and
  have forearms that can rotate to grasp prey
  closely.

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Higher Taxa

• An order contains related families (Carnivora).
• A class contains related orders (Mammalia).
• A phylum or division contains related classes.
• The term division is used instead of phylum for
  the classification of bacteria and plants.
• The taxon of related phyla or divisions is a
  kingdom.
• The domain is the broadest of all the taxa and
  contains one or more kingdoms.

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Systematic Applications

• Scientists who study classification provide
  detailed guides that help people identify
  organisms.
• Many times a field guide will contain a
  dichotomous key, which is a key based on a series
  of choices between alternate characteristics.

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17.2 Modern Classification

• Main idea Classification systems have changed
  over time as information has increased.
• Objectives
• Compare and contrast species concepts
• Describe methods used to reveal phylogeny
• Explain how a cladogram is constructed
• Review Vocabulary
• Evolution the historical development of a group
  of organisms
• New Vocabulary
• Phylogeny
• Character
• Molecular clock
• Cladistics
• cladogram

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Determining Species

• Typological species concept
• Aristotle and Linnaeus thought of each species as
  a distinctly different group of organisms based
  on physical similarities.
• The definition of species is called the
  typological species concept.
• Based on the idea that species are unchanging,
  distinct, and natural types.

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Biological Species Concept

• The biological species concept defines a species
  as a group of organisms that is able to
  interbreed and produce fertile offspring in a
  natural setting.
• Limitations
• Wolves and dogs, as well as many plant species,
  are known to interbreed and produce fertile
  offspring even though they are classified as
  different species.
• Does not account for extinct species or species
  that reproduce asexually
• However, because the biological species concept
  works in most everyday experiences of
  classification, it is used often.

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Phylogenic Species Concept

• Phylogeny is the evolutionary history of a
  species.
• The phylogenic species concept defines a species
  as a cluster of organisms that is distinct from
  other clusters and shows evidence of a pattern of
  ancestry and descent.

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Species Concepts
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Characters

• To classify a species, scientists construct
  patterns of descent by using characters.
• Characters are inherited features that vary among
  species.
• Characters can be morphological or biochemical.

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Morphological Characters

• Shared morphological characters suggest that
  species are related closely and evolved from a
  recent common ancestor.
• Analogous characters are those that have the same
  function but different underlying construction.
  These characters do not indicate a close
  evolutionary relationship.
• Homologous characters might perform different
  functions, but show an anatomical similarity
  inherited from a common ancestor.

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Birds Dinosaurs

• Dinosaur fossils show that they share many
  features in common with birds.
• Hallow bones
• Theropods have leg, wrist, hip, and shoulder
  structures similar to birds.
• Some theropods may have had feathers
• The evidence provided by these morphological
  characters indicates that modern birds are
  related more closely to theropod dinosaurs than
  they are to other reptiles.

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Biochemical Characters

• Scientists use biochemical characters, such as
  amino acids and nucleotides, to help them
  determine evolutionary relationships among
  species.
• DNA and RNA analyses are powerful tools for
  reconstructing phylogenies.
• The similar appearance of chromosomes among
  chimpanzees, gorillas, and orangutans suggests a
  shared ancestry.

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Biochemical Characters
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Biochemical Characters

• Scientists use a variety of techniques to compare
  DNA sequences when assessing evolutionary
  relationships.
• Sequencing and compare whole genomes of different
  organisms
• Compare genome maps using restriction enzymes
• DNA-DNA hybridization during which single strands
  of DNA from different species are melted together
• Comparing the DNA sequences of different species
  is an objective, quantitative way to measure
  evolutionary relationships.

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Molecular Clocks

• Scientists use molecular clocks to compare the
  DNA sequences or amino acid sequences of genes
  that are shared by different species.
• The differences between the genes indicate the
  presence of mutations.
• The more mutations that have accumulated, the
  more time that has passed since divergence.

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The Rate of Mutation

• The rate of mutation is affected by many factors
• Type of mutation
• Where the mutation is in the genome
• Type of protein that the mutation affects
• Population in which the mutation occurs
• Molecular clocks can be valuable tools for
  determining a relative time of divergence of a
  species. They are especially useful when used in
  conjunction with other data, such as the fossil
  record.

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Phylogenetic Reconstruction

• Cladistics is a method that classifies organisms
  according to the order that they diverge from a
  common ancestor.
• Cladistics reconstructs phylogenies based on
  shared characters.
• Scientists consider two main types of characters
  when doing cladistic analysis.
• An ancestral character is found within the entire
  line of descent of a group of organisms. (Birds
  mammals backbone).
• Derived characters are present members of one
  group of the line but not in the common ancestor.
  (Birds mammals feathers hair).

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Cladograms

• Systematics use shared derived characters to make
  a cladogram.
• A cladogram is a branching diagram that
  represents the proposed phylogeny or evolutionary
  history of a species or group.
• A cladograms branches indicate phylogeny.
• The groups used in cladograms are called clades.
• A clade is one branch of the cladogram.

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Cladograms

• The greater the number of derived characters
  shared by groups, the more recently the groups
  share a common ancestor.

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17.3 Domains and Kingdoms

• Main idea The most widely used biological
  classification system has six kingdoms within
  three domains.
• Objectives
• Compare major characteristics of the three
  domains
• Differentiate among the six kingdoms
• Classify organisms to the kingdom level
• Review Vocabulary
• Eukaryote an organism composed of one or more
  cells containing a nucleus and membrane-bound
  organelles
• New Vocabulary
• Eubaceria
• Archaea
• Protist
• Fungus

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Grouping Species

• The broadest category in the classification used
  by most biologists is the domain.
• The three domains are Bacteria, Archaea, and
  Eukarya.
• Organisms are classified in domains according to
  cell type and structure.
• The most widely used biological classification
  system has six kingdoms and three domains.
• The six kingdoms are Bacteria, Archaea, Protists,
  Fungi, Plantae, and Animalia.
• Organisms are classified into kingdoms according
  to cell type, structure, and nutrition.
• Archaea are the only members of their own domain.
• Archaebacteria are unicellular prokaryotes

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Domain Bacteria

• Eubacteria, members of Domain Bacteria and
  Kingdom Eubacteria are prokaryotes whose cell
  walls contain peptidoglycan.
• Peptidoglycan is a polymer that contains two
  kinds of sugars that alternate in the chain.
• Eubacteria are a diverse group that can survive
  in many different environments.
• Aerobic (need oxygen) or anaerobic (die in
  oxygen).
• Autotrophic (produce their own food) or
  heterotrophic (get nutrition from other
  organisms).

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Domain Bacteria
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Domain Archaea

• Archaea are thought to be more ancient than
  bacteria and yet more closely related to our
  eukaryote ancestors.
• Their cell walls do not contain peptidoglycan.
• Archaea are diverse in shape and nutrition
  requirements.
• They are called extremophiles because they can
  live in extreme environments.

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Domain Eukarya

• All eukaryotes (cells with membrane-bound nucleus
  and other membrane-bound organelles) are
  classified in Domain Eukarya.
• Domain Eukarya contains Kingdom Protista, Kingdom
  Fungi, Kingdom Plantae, and Kingdom Animalia.

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Kingdom Protista

• Protists are eukaryotic organisms that can be
  unicellular, colonial, or multicellular.
• Protists are classified into three different
  groupsplantlike, animal-like, and funguslike.
• Plantlike are called algea autotrophs that
  perform photosynthesis
• Animal-lke are called protozoans heterotrophs
• Funguslike are slime molds and mildews
• Euglenoids are a type of protist that have
  plantlike and animal-like characteristics
  usually grouped with plantlike because they have
  chloroplasts and can perform photosynthesis.

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Kingdom Protista
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Kingdom Fungi

• A fungus is a unicellular or multicellular
  eukaryote that absorbs nutrients from organic
  materials in its environment.
• Member of Kingdom Fungi are heterotrophic, lack
  mobility, and have cell walls.
• Their cell walls contain a substance called
  chitin, which is a rigid polymer that provides
  structural support.
• A fungus consists of a mass of threadlike
  filaments called hyphae.
• Hyphae are responsible for the funguss growth,
  feeding, and reproduction.

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Kingdom Fungi

• Mushrooms are heterotrophic organisms.
• Some fungi are parasites - grow and feed on
  other organisms and others are saprobes get
  their nourishment from dead or decay organic
  matter.
• Fungi that live in a mutualistic relationship
  with algae are called lichens.

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Kingdom Plantae

• Members of Kingdom Plantae form the base of all
  terrestrial habitats.
• All plants are multicellular and have cell walls
  composed of cellulose.
• Most plants are autotrophs, but some are
  heterotrophic.
• Plants possess cells that are organized into
  tissues, and many plants also possess organs such
  as roots, stems, and leaves.
• Plants lack mobility, yet some plants have
  reproductive cells with flagella that propel them
  through the water.

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Kingdom Plantae
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Kingdom Animalia

• All animals are heterotrophic, multicellular
  eukaryotes.
• Animal cells do not have cell walls.
• Animal cells are organized into tissue, and most
  tissues are organized into organs.
• Animal organs often are organized into complex
  organ systems.
• Animals range in size.
• They live in the water, on land, and in the air.
• Most animals are motile, although some, such as
  coral, lack motility as adults.

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Kingdom Animalia
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Viruses - An Exception

• A virus is a nucleic acid surrounded by a protein
  coat.
• Viruses do not possess cells, nor are they cells,
  and are not considered to be living.
• Because they are nonliving, they usually are not
  placed in the biological classification system.

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