Download Evidence Supporting Evolution

Evidence Supporting
Evolution
Section 14.2
Fossil Record to Support
Evolution
Preserved remains or markings left by organisms
Most fossils are found in sedimentary rocks
Younger rock layers usually are layered on top of
older ones (Law of Superposition)
Positions of fossils in the rock strata can reveal
their relative age
The fossil record provides evidence of Earth's
changing life
Law of Superposition Diagram
Where would the
fossils be the
youngest?
Where would the
fossils be the
oldest?
Geographic Distribution
Differences and similarities between
organisms in different parts of the world.
These observations suggested to Darwin
that today's organisms evolved from
ancestral forms.
Geographic distribution of organisms serves
as a clue to how modern species may have
evolved
Similarity in Structure
Certain similarities in structure among species
provide clues to evolutionary history
Forelimbs of all mammals consist of the same
skeletal parts (homologous structures)
evolution is a remodeling process (“descent w/
modification”)
Vestigial structures: homologous structures that have a
major function in one species but are not important in a
related species
Cont
Section 14.2
Similarities in Development
Embryos of closely related organisms often have
similar stages in development
Called Embryology
Ex. All vertebrates have an embryonic stage when
pouches appear on the sides of the throat
Yet, the similarities of these structures during
development support other evidence that all
vertebrates evolved from a common ancestor.
Molecular Biology
If two species have genes and proteins with
sequences that match closely = sequences must
have been inherited from a relatively recent
common ancestor.
The greater the number of differences in DNA
and protein sequences between species = less
likely they share as close a common ancestry.
See Fig. 14-16
This table shows the results of a comparison of the
amino acid sequences of hemoglobin in humans
and other vertebrates.
Using DNA to Identify Relationships
Between Species
Organism
1
2
3
4
5
DNA Sequence
ABCDEFG
AbcdefG
ABCDefG
ABCDEfG
ABCdefG
Draw a flow chart showing how these organisms
relate to each other. Place the common ancestor
(1) at one end and move outward.
Concept Check 14.2
1.
Why are older fossils generally in deeper rock layers than younger
fossils?
2.
How can evolutionary theory explain why Australia is home to
relatively few native placental mammals?
3.
What are homologous structures?
4.
What can you infer about species that differ significantly in their
DNA sequences?