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