Transcript TRACING PHYLOGENY

Chapter 26
 Phylogeny
-- Evolutionary history of a species or
group of related species; attempts to trace
macroevolution.
 Macroevolution – Origins of broader groups of
organisms; studied in relation to major events
of environmental change.
 Systematics -- Study of biological diversity in an
evolutionary context.
 Current biological diversity reflects past
episodes of speciation and macroevolution.
 Taxonomy – Component of systematics which
includes identification and classification of
species.
 System
used today was developed by Carl Linnaeus
in the 18th century.
 Two main features: 1) sort and name separate
species, and 2) organize them into categories
based on relationships.
 Binomial nomenclature: Two-part Latin name
unique to each species.
 Ex: Genus Felis includes many species of related
organisms (cats).
 Species Felis silvestris; Felis lynx; Felis leo.
Kingdom
Animalia
Phylum
Chordata
(phyla,
plural)
Class
Order
Family
Genus (genera, pl)
Species
Mammalia
Carnivora
Canidae
Canis
Canis
familiaris
5
kingdom
system
Monera (bacteria)
Protista (algae
and protozoans)
Fungi
Plantae
Animalia
6
kingdom system
Archaebacteria
Eubacteria
Protista
Fungi
Plantae
Animalia
 Outward
similarities; embryonic development; life
cycle stages.
 Homology – similarities due to common ancestry.
 But superficial features don’t always reflect
evolutionary relationships.
 Analogy -- Similarities due to convergent evolution,
not common ancestry.
 Convergent evolution -- Similar characteristics due
to sharing similar ecological roles; natural selection
shapes adaptations.
 Phenetics:
makes no evolutionary assumptions.
 Comparison is made of as many phenotypes as
possible.
 If enough characteristics are compared, homology
will overshadow analogy.(?)
 Overall phenotypic similarity is not a reliable
indicator of phylogeny.(?)
 This may be more useful for analyzing DNA
sequence data.
 Cladistics:
classifies organisms according to
phylogeny.
 Cladogram -- a branching “family tree”.
 Each species in the cladogram has a mixture of
primitive characters that existed in the common
ancestor and characters that evolved more
recently.
 A major difficulty in cladistics is finding
appropriate categories for each branch point.