Transcript Systematics * biodiversity + evolution

SYSTEMATICS –
BIODIVERSITY +
EVOLUTION
Chapter 22
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
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
Domain
Eubacteria
(bacteria)
Domain
Archaea
The three domains
Common ancestor
of all living organisms
Domain
Eukarya
Eubacteria
Archaebacteria
Protista
Plantae
Protista
The six-kingdom
system of classification
Common ancestor
of all living organisms
Animalia
Common ancestor
of all eukaryotes
Fungi
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
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
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
Three kinds of taxonomic groupings:
1.
•
2.
•
3.
•
•
•
Monophyletic taxon
Ancestral species and all its descendants (see figure 22-6a p 428)
• Example: mammals
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
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
Evolutionary
relationships
Taxon III
Taxon I
1
2
"Taxon II"
3
C
4
5
6
Common
ancestor
to groups
2 and 3
E
Common ancestor
to groups 5 and 6
D
Common ancestor
to groups 4, 5, and 6
B
A
Common
ancestor
Common ancestor
to all groups except 1
Common ancestor
to all groups
Two approaches to the classification
of reptiles birds, and mammals.
Common
ancestor
Birds
Dinosaurs
Crocodiles
Snakes
Lizards
Mammals
Reptiles
Two approaches to the classification
of reptiles birds, and mammals.
C
E
D
B
A
Common
ancestor
Birds
Dinosaurs
Crocodiles
Snakes
Lizards
Mammals
Reptiles