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Evidence for Evolution
FOSSIL EVIDENCEProvides TRANSITIONAL LINKS
Archaeopteryxlinks reptiles and birds
Anatomical Evidence
HOMOLOGOUS
STRUCTURES
ANALOGOUS
STRUCTURES
structures that are similar
because they were inherited
from a COMMON ANCESTOR
similar in function, but NOT
inherited from a common
ancestor
NOTE: similar structure, but NOT
always function!
NOTE: similar FUNCTION, but not
STRUCTURE
More Anatomical Evidence:
Vestigial Structures
Vestigial Structures are
undeveloped structures
that were functional in
some ancestor, but are
no longer needed in that
organism.
EMBRYOLOGYsuggests common ancestors
BIOGEOGRAPHICAL EVIDENCE
 When we study the distribution of plants and animals on the
planet, we notice:
 Animals evolved differently in each of the
biogeographical regions
 We see evidence that as the continents drifted, organisms
were separated and evolved.
BIOCHEMICAL EVIDENCE
 Almost all living things use the same biochemical
molecules
 DNA, Protein, ATP
 Vast diversity came about by only slight differences in the
same genes

The more closely “related” the organisms are, the more similar
their DNA
Patterns of Evolution
Macroevolution refers to large-scale evolutionary
patterns and processes that occur over long periods
of time.
Macroevolution
Six important topics in macroevolution are:






extinction
adaptive radiation (divergent evolution)
convergent evolution
coevolution
punctuated equilibrium
changes in developmental genes
Gradualism
Punctuated Equilibrium
Gradualism
 Organisms go through gradual and continuous change
Punctuated Equilibrium
 Organisms go through fast periods of change, followed by
long periods of no change (according to fossil record)
Extinction
More than 99% of all species that have ever lived are
now extinct.
Extinction
Mass extinctions:
 provide ecological opportunities for organisms
that survived
 result in bursts of evolution that produced many
new species
Patterns of Evolution:
1. Convergent Evolution
 Convergent Evolution: When 2 or more unrelated species
become more similar due to similar adaptations to their
environment.
Patterns of Evolution:
2. Divergent Evolution-Adaptive Radiation
 Divergent Evolution:
when related species
become more different
as they adapt to different
environments
 Divergent evolution leads
to Adaptive Radiation
Coevolution
Sometimes organisms that are closely connected to one
another by ecological interactions evolve together.
The process by which two species evolve in response to
changes in each other over time is called coevolution.
Adaptive Radiation of Mammals
Ancestral Mammals
This diagram shows part of the adaptive radiation of mammals, emphasizing current hypotheses about how a group of ancestral
mammals diversified over millions of years into several related living orders. Note that the dotted lines and question marks in this
diagram indicate a combination of gaps in the fossil record and uncertainties about the timing of evolutionary branching.