Classification

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Classification

• Chapter 18

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Characteristics of Living Things
Section 1-3
Characteristic
Examples
Living things are made up of units called cells.
Many microorganisms consist of only a single
cell. Animals and trees are multicellular.
Living things reproduce.
Maple trees reproduce sexually. A hydra can
reproduce asexually by budding.
Living things are based on a universal genetic
code.
DNA Flies produce flies. Dogs produce dogs.
Seeds from maple trees produce maple trees.
Living things grow and develop.
Flies begin life as eggs, then become maggots,
and then become adult flies.
Living things obtain and use materials and energy.
Metabolism Plants obtain their energy from
sunlight. Animals obtain their energy from the
food they eat.
Stimulus Leaves and stems of plants grow toward
light.
Living things respond to their environment.
Homeostasis Despite changes in the temperature
of the environment, a robin maintains a constant
body temperature.
Living things maintain a stable internal
environment.
Taken as a group, living things change over time.
EvolutionPlants that live in the desert survive
because they have become adapted to the
conditions of the desert.
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Figure 1-21 Levels of Organization
Section 1-3
Biosphere
The part of Earth that contains all ecosystems
Biosphere
Ecosystem
Community and its nonliving surroundings
Hawk, snake, bison, prairie dog, grass, stream,
rocks, air
Community
Populations that live together in a defined area
Hawk, snake, bison, prairie dog, grass
Population
Group of organisms of one type that live in the
same area
Bison herd
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Figure 1-21 Levels of Organization continued
Section 1-3
Organism
Individual living thing
Bison
Tissues, organs, and organ systems
Groups of Cells
Nervous system
Brain
Nervous tissue
Smallest functional unit of life
Cells
Nerve cell
Groups of atoms smallest unit of most
chemical compounds
Molecules
DNA
Water
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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
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Taxonomy--system of classification

• Name organisms
• Group organisms in a logical manner
• Establishes common set of criterion regardless of
  language or country

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Classification and Phylogeny

• Common names are problematic
• vary among languages and even among regions
  within a country
• Early naming attempts were up to 20 words
• Binomial Nomenclature
• Hierarchical Classification
• Systematics Evolutionary Classification

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Linnaeuss System of Classification

• Hierarchical system including seven levels or
  taxons
• Species (most specific classification)
• Genus (related species)
• Family (related genus)
• Order (related families)
• Class (related orders)
• Phylum (related classes)
• Kingdom (related phylum--broadest category of
  classification)

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Linnaeuss System of Classification
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Hierarchical Classification

• Taxonomic categories
• Kingdom King
• Phylum Philip
• Class Came
• Order Over
• Family For
• Genus Good
• Species Spaghetti

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Figure 18-5 Hierarchical System of Classification
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Binomial Nomenclature

• Carolus von Linnaeus
• Two-word naming system-Latin
• Genus
• Noun, Capitalized, Underlined or Italicized
• Species
• Descriptive, Lower Case, Underlined or Italicized

Carolus von Linnaeus(1707-1778) Swedish
scientist who laid foundation for modern taxonomy
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Genus species

• Genus
• group of closely related species

• species
• unique to each species within the genus
• often Latinized description of some important
  trait

Homo sapiens man Ursus maritimus polar
bear Ursus arctos grizzly bear
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Which similarities are most important?

• Linnaeus group species into larger taxa according
  to visible similarities and differences
• Modern biologists now group organisms into
  categories that represent lines of phylogeny or
  evolutionary relationships (Darwin), not just
  physical similarities

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Phylogenetics

• Organisms classification should reflect
  phylogenythe evolutionary history of a species
  or taxon
• Compare visible similarities among currently
  living species or fossils from extinct organisms
• Compare patterns of embryonic development and
  ways in which different species express similar
  genes
• Compare similar chromosomes, DNA or RNA

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SystematicsEvolutionary 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

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Homologous vs. Analogous Structures

• Homologous structures share a common structure

• Analogous structures have a similar function

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Modern Evolutionary Classification

• Organisms determine who belongs to their species
  by determining with whom they will mate!
• Species is defined as a group of organisms
  capable of breeding and producing viable
  offspring (offspring that are also capable of
  reproducing)
• Taxonomic groups above the level of species are
  invented by researchers are subject to change
  as our understanding and information improves

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Evolutionary Classification

• Species within a genus are more closely related
  to each other than to species in another genus
• Members of a genus share a recent common ancestor
• Higher the level of the taxon, the farther back
  in time is the common ancestor of all the
  organisms in the taxon

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Taxonomic Diagrams
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
PhylogeneticTree
Cladogram
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Figure 18-13 Cladogram of Six Kingdoms and Three
Domains
Section 18-3
DOMAIN ARCHAEA
DOMAIN EUKARYA
Kingdoms
Eubacteria Archaebacteria Protista Plantae Fungi A
nimalia
DOMAIN BACTERIA
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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

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Classification Using Cladograms

• Identifies and considers only those
  characteristics of organisms that are
  evolutionary innovations
• new characteristics that arise as lineages evolve
  over time
• characteristics that appear in recent parts of a
  linneage but not in its older members are called
  derived characters
• Shared characters are features that all members
  of a group have in commonhair in mammals or
  feathers in birds

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Cladograms

• Help scientists understand how one lineage
  branched from another in the course of evolution
• Represents a type of evolutionary tree showing
  evolutionary relationships among a group of
  organisms
• Organisms that share one or more derived
  characters probably inherited those characters
  from a common ancestor

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Traditional Classification vs Cladogram
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Similarities in DNA and RNA

• DNA RNA are so similar across all forms of
  life, they can be used to compare organisms at
  their most basic level--their genes
• The protein myosin which humans use for muscle
  contraction is also produced by yeast to help
  internal cell parts to move
• The more similar the DNA sequences of two
  species--the more recently they shared a common
  ancestor

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Molecular Clocks

• Uses DNA comparisons to estimate the length of
  time that two species have been evolving
  independently
• Relies on a repeating process to mark
  time--mutation
• The degree of dissimilarity is an indication of
  how long ago the two species shared a common
  ancestor

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Kingdoms and Domains

• Domains are more inclusive category--larger than
  a kingdom
• Domain Eukarya
• Kingdoms Protists, Fungi, Plants, Animals
• Domain Bacteria
• Kingdom Eubacteria
• Domain Archaea
• Kingdom Archaebacteria

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Kingdoms and Domains
The three-domain system
Bacteria
Archaea
Eukarya
The six-kingdom system
Bacteria
Archaea
Protista
Plantae
Fungi
Animalia
The traditional five-kingdom system
Monera
Protista
Plantae
Fungi
Animalia
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Figure 18-12 Key Characteristics of Kingdoms and
Domains
Section 18-3
Classification of Living Things
DOMAIN KINGDOM CELL TYPE CELL
STRUCTURES NUMBER OF CELLS MODE OF
NUTRITION EXAMPLES
Bacteria Eubacteria Prokaryote Cell walls with
peptidoglycan Unicellular Autotroph or
heterotroph Streptococcus, Escherichia coli
Archaea Archaebacteria Prokaryote Cell walls
without peptidoglycan Unicellular Autotroph
or heterotroph Methanogens, halophiles
Protista Eukaryote Cell walls of cellulose in
some some have chloroplasts Most unicellular
some colonial some multicellular Autotroph or
heterotroph Amoeba, Paramecium, slime molds,
giant kelp
Fungi Eukaryote Cell walls of
chitin Most multicellular some
unicellular Heterotroph Mushrooms, yeasts
Plantae Eukaryote Cell walls of cellulose
chloroplasts Multicellular Autotroph Mos
ses, ferns, flowering plants
Animalia Eukaryote No cell walls or
chloroplasts Multicellular Heterotroph
Sponges, worms, insects, fishes, mammals
Eukarya
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Domain Bacteria Kingdom Eubacteria

• Unicellular and prokaryotic
• Thick, rigid cell walls that contain
  peptidoglycan
• Ecologically diverse
• free-living soil organisms
• deadly parasites
• photosynthetic or heterotrophic
• anaerobic and aerobic

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Domain Archaea Kingdom Archaebacteria

• Unicellular and prokaryotic
• Live in most extreme environments
• volcanic hot springs
• brine pools
• black organic mud devoid of oxygen
• Cell walls lack peptidoglycan
• Cell membranes contain lipids unique to
  archaebacteria

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Domain Eukarya Kingdom Protista

• Eukaryotic organisms that cannot be classified as
  animals, plants, or fungi
• Display greatest variety
• Share characteristics with plants, animals, and
  fungi
• Most are unicellular (except for algae)

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Domain Eukarya Kingdom Fungi

• Eukaryotic
• Heterotrophs
• Feed on dead or decaying organic matter
• Secrete digestive enzymes into their food source
  then absorb smaller food molecules into their
  bodies
• Mushrooms, yeast, mildew

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Domain Eukarya Kingdom Plantae

• Eukaryotic, multicellular
• Photosynthetic autotrophs
• Nonmotile
• Cell walls contain cellulose
• Include cone-bearing, flowering plants, mosses
  and ferns

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Domain EukaryaKingdom Animalia

• Multicellular, eukaryotic
• Heterotrophic
• Lack cell walls
• Most are motile