Transcript Classification of Living Things

Classification of Living Things
Chapter 20
Taxonomy
• Identifying, naming and classifying organisms
• Latin base
• Aristotle
– first to classify, divided into 14 major
Categories
– Subdivided them according to size
• John Ray
– All organisms should have a set name
– Divided them into groups based on how
he thought they were related
Carolus Linnaeus 1707 - 1778
• Binomial nomenclature – 2 part name
– Genus – contains many species
– Specific epithet (1 species)
• Usually descriptive, can have geographic
descriptions
• When writing a scientific name
– Genus capitalized
– Species lower case
– Italics, underlined if handwritten
Published Systema Naturae in 1735
species
• Interbreed and share the same gene pool
• Subspecies
– Variant types of organisms of a species that tend to
interbreed where their populations overlap
• They could actually be different species
• hydridization
Classification categories
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Species
Genus
Family
Order
Class
Phylum
Kingdom
Domain
More than 30 categories: super, sub, infra
Organisms put in categories based on characters,
structural, chromosomal, or molecular features
Phylogenetic trees
• Systematics – study of the diversity of organisms
at all levels of organization
– Taxonomy and classification
– Goal: determine phylogeny – evolutionary history
• Represented by Phylogenetic tree
• Shows divergence from a common ancestor
• Derived characters – individual characteristics
Tracing phylogeny
• Record data from:
– Fossil evidence
– Homology
– Molecular data
• Using this information you can determine
common ancestors and classify organisms
accordingly
Homology
• Includes comparative anatomy and embryological
evidence
• Sometimes homology is challenging because of
– Convergent evolution – having the same or similar
characters but distantly related due to adaptation to
the environment
• Analogous structures – having same function but
do not have common ancestor (wings of
bat/insect)
– Parallel evolution – similarity in structure in related
groups that cannot be traced to common ancestor
Molecular data
• Protein comparisons - limited
• RNA and DNA Comparisons
– DNA-DNA hybridization: compare single strands
from different organisms and allowed to combine, if
closely related, strands will stick together
– Nucleotide sequences
• Molecular clocks – nucleic acid changes used to
indicate relatedness and evolutionary time
Cladistic Systematics
• Willi Hennig
• Uses shared derived characters to classify
organisms and construct a cladogram
• Objective because it lists characters used to
construct cladogram
• Figure 20.11, table 20.2
Phenetic systematics
• Species are classified by the number of their
similarities
• Count the # of traits the two species share and
estimate the degree of relatedness
• Figure 20.10
Traditional systematics
• Mainly use anatomical data to classify organisms
• Stress common ancestry and degree of structural
difference among divergent groups
• Not as strict as cladists
Classification systems
• Began with 2 kingdoms: animal and plant
• 1880 Ernst Haeckel:
– Added kingdom Protista
– unicellular, microscopic
• 1969: RH Whittaker – expanded system to 5
kingdoms: monera, protista, fungi, plantae and
animalia
– Based on type of cell, complexity, type of nutrition
3 Domain system
• Late 1970’s Carl Woese
• Used rRNA sequencing
• Proposed 2 groups of prokaryotes because they
were so different
• Domains:
– Archea – prokaryotes that are not bacteria
– Bacteria – mostly prokaryotic bacteria
– Eukarya – contains Protista, Fungus, Plantae and
Animalia