Download Evidence of Evolution

EVIDENCE OF EVOLUTION
Key Concepts
• What evidence supports the theory
of evolution?
• How do scientists infer evolutionary
relationships among organisms?
• How do new species form?
Key Terms
Homologous Structures
– Body parts that are structurally similar
in related species.
Key Terms
Branching tree
– A diagram that shows how scientists
think different groups of organisms are
related.
Identifying Supporting
Evidence
• Identifying supporting evidence
helps us understand the relationship
between the facts and the
hypothesis.
• Evidence consists of facts that can be
confirmed by testing or observation.
Supporting Darwin’s Theory
• Fossils show that organisms that lived in
the past were very different from
organisms alive today.
• Patterns of early development show that
some different organisms look similar
during their early stages.
• Similar body structures in different species
show that the organisms shared a
common ancestor.
Interpreting the Evidence
• FOSSILS
• EARLY
DEVELOPMENT
• BODY STRUCTURE
FOSSILS
• The preserved remains
or traces of an
organism that lived in
the past.
• Fossils show that
organisms that lived
in the past were very
different than
organisms alive today.
• Scientists use fossils to
infer the structures of
ancient organisms.
EARLY DEVELOPMENT
(embryology)
• Scientists compare the
early development of
different organisms to
make inferences about
evolutionary relationships.
• Similarities in early
development among
different organisms
suggests that they are
related and share a
common ancestor.
BODY STRUCTURE
(homologous structures)
• Darwin compared body
structures of living species
when observing the species
on the Galapagos Islands.
• Body structure is an
organism’s body plan, how
its bones are arranged.
• Similarities in body
structure provide evidence
that organisms evolved
from a common ancestor.
Species Relationships
• Fossils, early development patterns,
and body structure provide evidence
that evolution has occurred.
• Scientists also have used these kinds
of evidence to infer how organisms
are related to one another.
New Evidence
•DNA
•Protein
Structure
Similarities in DNA
• Scientists compare the
genes of different species
to determine how closely
related the species are.
• The more similar the
sequence of bases in the
DNA, the more closely
related the species are.
• The more similar the order
of amino acids (codes for
proteins) in the DNA, the
more closely related the
species are.
Combining Evidence
• The use of DNA and protein structure
has confirmed conclusions that
scientists had already based on
fossils, embryos, and body structure.
• The use of DNA and protein structure
has also caused scientists to “revise”
the branching trees of some species.
Branching Trees
• Branching trees
show common
ancestry
(phylogeny).
• Evolution is about
gradualism and
phylogeny.
How Do New Species Form?
(speciation)
• A new species can
form when a group of
individuals remains
isolated from the rest
of its species long
enough to evolve
different traits.
• Isolation/Separation
– River
– Volcano
– Mountain range
Convergent Evolution
• The process whereby organisms not closely
related, independently evolve similar traits as a
result of having to adapt to similar environments
or ecological niches.
Divergent Evolution
(adaptive radiation)
• The process by which related species evolve
different traits.
Gradualism
Evolution occurs
slowly but steadily.