Transcript 7th grade ch. 6 sec. 2

Evidence of Evolution
Ch. 6 section 2
Interpreting the evidence
• Scientists have found a great deal of
evidence supporting evolution.
• Fossils, patterns of early development,
and similar body structures all provide
evidence that organisms have changed
over time.
Fossils
• Fossils show that organisms that lived
in the past were very different from
animals that live today.
Similarities in early
development
• Opossum, chicken, fish, salamander
• All four animals look very similar in early
development. (p.183)
• All four animals share a common
ancestor.
Similarities in body structure
• Scientists look at body structures for clues in
evolution.
• Most vertebrates have similar body
structures.
• All of these animals probably inherited a
similar structure from a vertebrate ancestor
they shared.
• Homologous Structure: similar structures that
relate species have a common ancestor.
Inferring species relationship
• Scientists have combined the evidence
from DNA, protein structures, fossils,
early development, and body structure
to determine the evolutionary
relationships among species.
Similarities in DNA
• Why do some species have similar body
structures and development patterns?
Species inherit many of the same genes
from a common ancestor.
• Scientists compare N-bases in DNA.
• Ex. Elephant is closely related to a tiny
elephant shrew. (p. 185)
Branching Tree
• Diagram that shows how scientists think
different groups of organisms are
related.
• Raccoons, lesser pandas, giant pandas,
and bears may be related.
How do new species form?
• A new species can form when a group
of individuals remains isolated from the
rest of its species long enough to evolve
different traits.