Classification of organisms
Taxonomy & Systematics
Characteristics of organisms
- Similarity in basic life processes
- Large number of different adaptations
- Central Unity of Life with a large number of modifications
- Major goal of biology is to study this diversity and
find order & relationships among organisms
Branches of biology that specialize in finding order
- Taxonomy - classification & naming organisms
- Systematics - study of evolutionary relationships among
organisms, arranging organisms into groups that reflect phylogeny (evolutionary
relatedness)
- Both use the species as basic unit of classification
Species
- Natural unit of evolution
- Different species concepts
- Organisms do not display continuous variation - naturally
divided into many distinct & separate types - species
- Are currently 1.5 million species
- Estimated that some 4-10 million species exist
Naming species
- Use the binomial system originated by Linnaeus in 1700s
- Each species name consists of 2 latinized words: genus
& species epithet
- Genus is capitalized
- Both words are italicized or underlined
Species names
- Canis familiaris is
species name for dog
- Can be abbreviated as C. familiaris, never as
familiaris
- Scientific names are important - each species has only
one - not used more than once
- Common names can lead to confusion
Classification
- Species grouped in a hierarchical classification system
- Organisms grouped together based on similarities
Hierarchy of classification
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Taxa for cat
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species - basic unit
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Felis catus
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genus -similar species
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Felis
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family - similar genera
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Felidae
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order - similar families
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Carnivora
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class - similar orders
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Mammalia
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phylum - similar classes
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Chordata
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kingdom - similar phyla
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Animalia
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Taxonomy vs Systematics
- Taxonomy - group organisms based on similarities in traits
- may be artificial
- Systematics - group organisms based on phylogenetic relationships
- Must try to recognize differences between superficial
& phylogenetic similarities
Analogous structures
- Have common function, but basic differences in structure
& evolutionary history
- Superficial similarities resulting from convergent evolution
- Examples: wings
of birds & insects
- body form of swimming animals
Systematics
- Goal is to group taxa together in monophyletic taxa (a
single ancestor gave rise to all species in the taxon)
- Polyphyletic taxon - derived from 2 or more ancestral
forms not common to all members
- Currently uses cladistics
- Identifies
- specialized features which evolved recently
- generalized features which evolved long ago
- Group species on basis of specialized features (shared
derived characters)
Classification of organisms
- Use all types of traits including molecular ones (DNA
base sequences)
- With more information, classification can change
- Examples - concepts of kingdoms has changed as we find
out more about organisms
Kingdoms
- Originally - Plants & Animals (Linneaus)
- With the discovery of microorganisms, some had characteristics
of both plants & animals - 3 kingdom proposal (1800s)
- Plant
- Animal
- Protista (Protoctista)
- 5 kingdom system (1960s)
- Monera - prokaryotes
- Protista - unicellular eukaryotes
- Plants - multicellular autotrophs
- Fungi - mulitcellular heterotrophs, absorptive
- Animals - multicellular heterotrophs, ingestive
Domains
- Recent evidence has indicated that there are 2 groups
of prokaryotes that are more different from each other than eukaryotes
- Divided into 3 domains
Kingdoms
- One proposal has divided organisms into 6 kingdoms (others
have more)
Classification
- In addition, there are the viruses - not included with
other organisms
- Do not use binomial system with viruses
- In BSC 116, you will examine characteristics of different
organisms - primarily plants & animals
Remember - Final Exam - Friday, May 11, 2-4:30