Biological Classification

1
Biological Classification
2
Why Do We Classify Organisms?

• Biologists group organisms to organize and
  communicate information about their diversity,
  similarities and proposed relationships.
• Classification systems change with expanding
  knowledge about new and well-known organisms.
• Approximately 1.75 million species have been
  classified so far.

Tacitus bellus
3
History of Classification

• Aristotle (2000 y.a.) classified organisms as
  either plants (by size) or animals (red-blooded
  or not).

4
History of Classification

• In the 1700s and 1800s
• Carolus Linnaeus, a Swedish botanist, used
  similarities and differences in morphology and
  behavior to classify birds.
• Linnaeus developed the first taxonomy system and
  made it possible to include evolutionary
  principles in classification in the 1800s.
• Jean-Baptiste Lamarck, Charles Darwin, and Ernest
  Haeckel introduced classification systems based
  on evolutionary relationships to organize
  biological diversity.

5
Scientific Names

• Carolus von Linnaeus devised the currently used
  binomial nomeclature.
• Two-word naming system
• Genus
• Noun, Capitalized, Underlined or Italicized
• Species
• Descriptive, Lower Case, Underlined or
  Italicized
• Ex.
• Genus Homo or Homo
• Species sapiens or sapiens
• Complete scientific name of species
• Homo sapiens or Homo sapiens
• Abbreviated form H. sapiens or H. sapiens

Carolus von Linnaeus(1707-1778) Swedish
scientist who laid foundation for modern taxonomy
6
Hierarchical Classification into Taxa

• Taxonomists classify organisms by dividing them
  into smaller groups based on more specific
  criteria. A named groups of organisms is a
  taxon.
• Taxonomic categories (taxa)
• Kingdom King
• Phylum Philip
• Class Came
• Order Over
• Family For
• Genus Green
• Species Spaghetti
• Beginning with species, each category becomes
  progressively more comprehensive. Ex. while the
  leopard, tiger and domestic cat all belong to
  different genera, they are grouped together in
  the same family.

7
Modern Classification - Species Concepts
8
Modern Classification Systems / Disciplines of
Biology

• Systematics is the branch of biology concerned
  with the study of biological diversity.
• Taxonomy is the part of systematics concerned
  with identifying, naming, and classifying species
  based on morphological and behavioral
  similarities and differences.
• Binomial Nomeclature is used to name species
  using two words, genus and species.

Populus tremuloides Quaking Aspen
9
SystematicsEvolutionary Classification of
Biodiversity

• Systematics is the study of the evolution of
  biological diversity, and combines data from the
  following areas
• Fossil record
• Comparative homologies, morphological characters
  (traits) derived from common ancestry
• Cladistics, the study of evolutionary
  relationships between species based on shared
  characters (inherited traits)
• Biochemical characters, such as comparative
  sequencing of DNA/RNA among organisms
• Molecular clocks

10
Comparing Morphological Characters
11
(No Transcript)
12
A Molecular Clock

• The rate at which mutations occur varies
  depending on
• Type of mutation
• Location of mutation in the genome
• Type of protein affected
• Population in which the mutation occurs
• This inconsistency makes molecular clocks
  difficult to read.
• Molecular clocks are often used along with the
  fossil record and help determine when a species
  evolved.

13
Taxonomic Diagrams based on Phylogeny
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Mammals
Turtles
Lizards and Snakes
Crocodiles
Birds
Cladogram a branched diagram that shows the
proposed phylogeny (evolutionary history) of a
species nodes represent common ancestors
Phylogenetic Tree a form of cladogram nodes
represent common ancestors
14
Lily Cladogram
The closer two groups are, the larger the number
of characters they share.
15
Dichotomous Keys Identify Organisms

• Dichotomous keys are tools used to identify
  organisms field guides contain dichotomous keys.
• Dichotomous keys contain pairs of contrasting
  descriptions - choices between two options.
• After each description, the key directs the user
  to another pair of descriptions or identifies the
  organism.
• Example (identifying a plant using its leaf)
  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

16
Kingdoms and Domains
The three-domain system
Bacteria
Archaea
Eukarya
The six-kingdom system
EuBacteria
Archaeabacteria
Protista
Plantae
Fungi
Animalia
The traditional (now outdated) five-kingdom system
Monera
Protista
Plantae
Fungi
Animalia
17
Kingdom Eubacteria (Domain Bacteria)

• Prokaryotes whose cell walls contain
  peptidoglycan, a protein-sugar polymer that is
  porous and strong
• All unicellular, mostly heterotrophic, some
  autotrophic
• Disease-causing bacteria and many harmless
  bacteria found in the environment are in this
  kingdom
• Kingdom Archaebacteria (Domain Archaea)
• Prokaryotes, thought to be more ancient than
  bacteria, no peptidoglycan in cell walls
• All unicellular, mostly heterotrophic, some
  autotrophic (including chemotrophic)
• Called extremophiles because they can live in
  the most extreme environments on earth, such as
  hot springs, salty lakes, thermal vents on the
  ocean floor, and the mud of marshes
• All bacteria reproduce asexually (binary
  fission), many also sexually (conjugation)

18
Kingdom Protista

• Eukaryotes that differ significantly from each
  other but do not fit into any other kingdom
• Unicellular, colonial, or multicellular
  organisms, but their cells cannot form true
  tissues/organs
• Autotrophic or heterotrophic
• Reproduce sexually and asexually using spores,
  cysts, gametes
• Classified into three groups by trophism
  fungus-like, plant-like, and animal-like

19
Kingdom Fungi

• Eukaryotes whose cells can form true tissues /
  organs
• Cell walls contain chitin, a rigid polymer that
  gives structural support
• All heterotrophic / decomposers secrete
  digestive enzymes onto their food and absorb the
  nutrients (extracellular digestion)
• Most multicellular, a few unicellular (yeasts)
  all sessile (cannot move)
• Reproduce sexually and asexually by spores,
  fragmentation/regeneration

A mushroom is a fungus.
20
Kingdom Plantae

• Eukaryotes whose cells can form true tissues /
  organs
• Autotrophs - form the basis of all land
  ecosystems and a few heterotrophs (yes, some
  plants are parasites!)
• All multicellular and sessile (cannot move)
• Reproduce sexually and asexually (spores, seeds,
  cuttings, etc.)

A leaf is a plant organ.
21
Kingdom Animalia

• Eukaryotes whose cells form true tissues / organs
• All multicellular
• All heterotrophic
• Most motile (can move)
• Most reproduce sexually,some asexually

22
(No Transcript)