Homo_sapiens.html: ../ch24/24_02bBioSpeciesConceptB-U.jpg
The scientific name for humans
is Homo sapiens (kingdom Animalia).
The genus is Homo, while the specific epithet is sapiens.
binomial.html: ../ch25/25_09CarnivoraPhylogenyB.jpg
Scientific names.
The combination genus Panthera and specific epithet epithet pardus
uniquely identifies the leopard (Panthera pardus).
The genus indicates its relationship to other big cats:
lion (Panthera leo), tiger (Panthera tigris), and jaguar (Panthera onca).
The domestic cat (Felis silvestris) is in a different genus (Felis) of the cat family,
Felidae.
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The scientific name of an organism uses a binomial nomenclature
composed of its genus and specific epithet.
Thus genus Panthera and specific epithet pardus
uniquely identifies the leopard (Panthera pardus), and humans are
Homo sapiens.
The cat family, Felidae, is a sister taxon with other families
in the order
Carnivora, which is a branch of
class
Mammalia.
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| A character table can show shared derived characters inherited among organisms. A 0 indicates a character is absent; a 1 indicates that it is present. | The shared derived characters can be arranged to track descent from a common ancestor. |
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Monophyletic.
Group I (species A, B, C) is a monophyletic group, or clade,
made up of an ancestral species (X) and all of its descendant species.
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Paraphyletic.
Group II is paraphyletic:
it consists of an ancestor (X) and some (D, E, F),
but not all (excludes G), of that ancestor’s descendants.
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Polyphyletic.
Group III is polyphyletic:
it lacks a common ancestor of all the species in the group.
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A cladogram is used to track relationships by
shared derived characters inherited from a common ancestor.
Clades are defined by an evolutionary novelty at the branching point, which constitues a
shared derived character (homology) for the clade (ingroup).
An outgroup does not possess that character.
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| Constructing a cladogram. | |||
|---|---|---|---|
| (a) | Character table. A 0 indicates that a character is absent, a 1 indicates that a character is present. | (b) | Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny. |
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Similar environmental pressures and natural selection can produce similar (analogous) adaptations
in organisms from different evolutionary lineages:
convergent
evolution
An elongated body, large front paws, small eyes, thicken skin, and a tapered nose
all evolved independently in the marsupial
Australian mole and eutherian
North American mole.
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Traditional taxonomy uses a hierarchical classification
where species are placed into groups belonging to more comprehensive groups (taxa).
Starting from the most comprehensive taxon, Linnaeus classified organisms into
kingdom,
phylum,
class,
order,
family,
genus,
and
species.
Leopards and humans both belong to kingdom Animalia, phylum Chordata,
but while leopards are in order Carnivora, humans are in order Primates.
A taxon above kingdom called domain was added after Linnaeus proposed these 7 levels.
humans-fungi.html: 26_02HumansFungiTree-L.jpg
What are the evolutionary relationships among a human, a mushroom, and a tulip?
Despite appearances, molecular evidence has revealed that animals, including humans,
and fungi, such as mushrooms, are more closely related to each other than either are to plants.
life.html: 26_21-ThreeDomains-L.jpg
The tree of life.
Based on rRNA gene sequences, living organisms are divided into 3 domains:
Bacteria, Archaea, and Eukarya.
Eukarya and Archaea appear to share a common ancestor,
are more closely related to each other than to Bacteria.
Note:
Archaea and Bacteria are "prokaryotes"
that lack organelles such as a nucleus. The lack of organelles is not a
shared derived character,
thus "prokaryotes" do not constitute a clade.
molecular-DNA.html: 26_08-AligningDNA-L.jpg
Identifying homologous
DNA.
phylogeny.html: 26_11bCharTablePhylTreeB-L.jpg
A phylogenetic tree shows evolutionary relationships by homology.
A homology is a
shared derived character, such as hair among the mammals, inherited from a common ancestor.