The History and Classification of Life

1
The History and Classification of Life

• Modern Biology
• Chapters 14 18
• Biology Exploring Life
• Sections 15.3,15.4,16.1,16.2,17.5

2
Taxonomy

• Branch of biology that names and groups organisms
  according to their characteristics and
  evolutionary history
• Aristotle
• Plants and animals only
• Common names only
• Vary from one locale to the next
• May not describe species accurately (ex.
  Jellyfish)

3
Carolus Linnaeus

• Developed system of grouping organisms into
  nested hierarchical categories, each more
  specific than the last, according to
  morphological features
• Seven levels (taxa) of classification
• Kingdom, phylum/division, class, order, family,
  genus, species
• Binomial nomenclature
• Scientific name of an organism
• Two partsgenus and species
• Italicized or underlined
• Genus capitalized
• Latinized (understood worldwide)

4
Systematics

• Phylogenetic approach to taxonomy that reflects
  the evolutionary history of organisms
• Phylogenetic tree
• Family tree that shows the evolutionary
  relationships hypothesized to exist among groups
  of organisms, based on evidence from
• Paleontology (fossil record)
• Morphology (homologous structures)
• Embryology
• Molecular biology (DNA, RNA, proteins,
  chromosomes)

5
Cladistics

• Phylogenetic classification system that uses
  shared derived characters to establish
  evolutionary relationships
• Features that apparently evolved only within the
  group under consideration (ex. Bird feathers)
• If shared, then probably inherited from a common
  ancestor
• Cladograms
• Groups and derived characters appeared in the
  order shown by the branch points.
• Only groups branching above a listing of a
  derived character share that character.

6
Modern Classification Systems

• Six kingdoms
• Archaebacteria
• Eubacteria
• Protista
• Fungi
• Plantae
• Animalia
• Three domains (based on ribosomal RNA sequence
  comparisons)
• Archaea
• Bacteria
• Eukarya

7
Radioactive Dating

• Isotopes
• Atoms of the same element that have different
  mass numbers (P N)
• Ex. Carbon-12 and carbon-14
• Radioactive isotopes
• Isotopes that have unstable nuclei and tend to
  undergo radioactive decay
• Half-life length of time it takes for one-half
  of any size sample of an isotope to decay (ex.
  Carbon-14 has a half-life of 5715 years.)
• Estimated age of Earth 4.0-4.5 billion years

8
The First Organic Compounds

• Alexander Oparin
• Hypothesized that Earths early atmosphere
  contained ammonia, hydrogen gas, water vapor,
  methane, and other hydrocarbons
• Stanley Miller and Harold Urey
• Tested Oparins hypothesis using an apparatus
  that was a model for the atmospheric conditions
  of early Earth
• Products of spark-induced chemical reactions
  included a variety of organic compoundssuch as
  amino acids, ATP, and nucleotides
• Extraterrestrial origin

9
Microspheres and Coacervates

• Membrane-bound structures that form
  spontaneously, without enzymes specified by
  genetic information
• Can grow or bud
• Can take up certain substances from their
  surroundingsperhaps ribozymes (self-replicating
  RNA molecules that act as enzymes, discovered by
  Thomas Cech)
• Close the gap between nonliving chemical
  compounds and cellular life

10
The First Cells

• Prokaryotes
• Anaerobic heterotrophs, about 3.5 billion years
  ago
• Anaerobic chemoautotrophs
• Ancestors of modern archaebacteria
• Evolved to help prevent organic molecule
  depletion
• Aerobic photoautotrophs
• Ancestors of modern cyanobacteria (a group of
  eubacteria)
• Evolved to help prevent oxidation of essential
  organic compounds

11
The First Cells (continued)

• Ozone production
• Sunlight splits O2 into O
• O reacts with O2 to form O3
• Biosphere became oxygen-rich and UV-protected,
  paving the way for life on land (not just in the
  water)

12
The First Cells (continued)

• Eukaryotes endosymbiotic theory
• Aerobic prokaryote gave rise to mitochondria
• Photosynthetic prokaryote gave rise to
  chloroplasts
• Evidence in modern mitochondria and chloroplasts
• Independent replication
• Independent genome of circular DNA

13
Colonization of Land

• Multicellular life in the seas
• Algae
• Cambrian explosion rapid speciation of many
  aquatic invertebrates and vertebrates (jawless,
  cartilaginous, and bony fishes)
• First organisms with adaptations for life on land
• Plants and fungi mycorrhizae
• Invertebrate animals arthropods (crustaceans,
  arachnids, centipedes, millipedes, and insects)

14
Colonization of Land (continued)

• Terrestrial vertebrates
• Amphibians
• Reptiles
• Birds
• Mammals