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CH. 23: EVOLUTIONEvolutionary Changes
TYPES
Fossil Record Biogeography Convergent Evolution Selective Breeding Homologies
Anatomical Developmental Molecular
FOSSIL RECORD
Shows timeline of successive evolutionary change
Transitional fossils Intermediate states Exhibit characteristics of
ancestors as well as descendants
BIOGEOGRAPHY
Geographic distribution of species Extinct and living Reveal patterns of evolution
Endemic Species Found only in a particular location Isolated
CONVERGENT EVOLUTION
Organisms with similar characteristics that are not evolutionarily related
Similar environments with similar adaptive pressures.
Suggests adaptation as an evolutionary force
Similar features are termed analogous structures (convergent traits)
SELECTIVE BREEDING
Human Controlled Called “artificial selection”
Human breeders determine reproduction Surviving traits are human-desired
Augmentation of already present genetic variation
HOMOLOGIES
Similar traits between two species Descent from a common ancestor Featured observed
Anatomical Homologies Developmental Homologies Molecular Homologies
ANATOMICAL HOMOLOGIES
Observations of anatomical structures between species
Similar patterns exhibited within features
Homologous Structures Same traits may be modified for
different functions in successive species
VESTIGIAL STRUCTURES
Structures resembling those of a species’ ancestors but lacking a function in the species itself.
Evolutionary relics Structures were functional in ancestral species, but lost
function as the species changed lifestyle Structure does not disappear but is degenerated by
mutations
DEVELOPMENTAL HOMOLOGIES
Species that appear very differently as adults can bear striking similarities in the embryonic stage
Similarities are temporary and are lost during development.
Traits indicate evolutionary ancestors
MOLECULAR HOMOLOGIES
Observations of features at the molecular level All organisms use DNA as genetic material RNA carries information for proteins as functional products
Certain biochemical pathways are universal These features arose very early in the history of life Analysis of genetic sequences reveals evolutionary
relatedness Closest relatives have higher percentage of identical sequences