Chapter 22 SYSTEMATICS – BIODIVERSITY + EVOLUTION.
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Transcript of Chapter 22 SYSTEMATICS – BIODIVERSITY + EVOLUTION.
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Chapter 22
SYSTEMATICS – BIODIVERSITY + EVOLUTION
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Taxonomy – naming, describing, and classifying organisms
•Naming:•Worldwide system recognized by all scientists•Binomial nomenclature -1st developed by Carolus Linnaeus•2 part name: Genus + specific epithet = scientific name•Genus name capitalized; species name not; both underlined or italics; both derived from Latin or Greek
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Classifying – group organisms into meaningful categories• Taxon – group (pl. taxa) – Linnaeus also established a hierarchy• Kingdom, phylum, class, order, family, genus, species
• Currently we include a larger category above kingdom – domain• (Dumb King Phillip came over for good spaghetti)• We have three domains:• Eubacteria (aka bacteria) prokaryotes• Archaea • Eukarya – plants, animals, protists, fungi
• New proposal – group organisms into clades – a set of organisms with a common ancestor (more on this later)• Important – Figure 22-3 + Table 22-2, page 424
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The three domains
Common ancestorof all living organisms
DomainArchaea
DomainEubacteria(bacteria)
DomainEukarya
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The six-kingdom system of classification
Eubacteria Archaebacteria Protista Plantae Protista Animalia Fungi
Common ancestorof all living organisms
Common ancestorof all eukaryotes
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Phylogeny – using systematics to describe the evolutionary history of life on Earth
• Based on available data – changed to adjust to new information•Homology – helpful similarities • Structures that are found in 2 or more groups that share a recent common ancestor• Example: wing of a bat and a bird•Homoplasy – not helpful similarities• Superficial similarity due to convergent evolution rather than descent from a common ancestor• Example: wing of a bird and a butterfly• The difference between these is not always easy to see
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So, we want to make an evolutionary ‘family tree’…
• The branches use two set of features:• Shared ancestral characters – plesiomorphic characters• Found in all descendants from a particular ancestor (everyone on that ‘branch’)• Example: vertebral column – all vertebrates have this
• Shared derived characters – synapomorphic characters• Found in 2 or more taxa with a recent common ancestor (smaller ‘branches’)• Example: middle ear bones found in all mammals; identifies the branch between reptiles and mammals
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Can we use molecular information? Of course!•Molecular systematics compares macromolecules, especially DNA, RNA, and amino acid sequences•Molecular clocks can be used to establish how long 2 groups have been evolving separately from each other (assuming a constant rate of change)•rRNA sequences – have been studied extensively and used as molecular clocks
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Three kinds of taxonomic groupings:1. Monophyletic taxon• Ancestral species and all its descendants (see figure
22-6a p 428)• Example: mammals
2. Paraphyletic taxon• Common ancestor and some but not all descendants• Not used in cladistics• Example: reptiles – because birds are in a separate
taxon despite the fact that they share a common ancestor with reptiles
3. Polyphyletic group • ‘accidentally’ put organisms in groups even though
they do not share a common ancestor, perhaps because of homoplastic features • Example: the Protista Kingdom• This is avoided in cladistics because it does not show
evolutionary relationships
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Evolutionary relationshipsTaxon III
Commonancestor
Common ancestorto groups 4, 5, and 6
Common ancestorto groups 5 and 6
Common ancestorto all groups
Common ancestorto all groups except 1
Commonancestorto groups2 and 3
A
B
D
EC
1 2 3 4 5 6
Taxon I "Taxon II"
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Two approaches to the classification of reptiles birds, and mammals.
Mam
mal
s
Liz
ard
s
Sn
akes
Cro
cod
iles
Din
osa
urs
Commonancestor
Bir
ds
Reptiles
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Two approaches to the classification of reptiles birds, and mammals.
A
B
D
EC
Mam
mal
s
Liz
ard
s
Sn
akes
Cro
cod
iles
Din
osa
urs
Commonancestor
Bir
ds
Reptiles