Transcript Evidence for evolution

GENETIC CHANGE IN A
POPULATION OVER
TIME
Types of evidence of evolution

Fossils
 Homologies
 Anatomical
 Molecular
 Developmental
 Biogeography
 Observable Events
Fossil Record
Helps scientists understand pathway of evolution
 Paleontology
 Fossil
 Remains: ex. bone, tooth, or shell
 Traces: ex. burrow, footprint, or imprint
Fossil Record


Most fossils are
found in layered
sedimentary rock
Oldest fossils are
in the lowest layer
 Newest fossils are
in the top layer
Fossil Record

Comparing fossils
from different
layers shows:
Life on Earth has
changes
Increased
number of life
forms
Fossil evidence
Reduction of toes over
time
Anatomical Homologies

Homologous
Structures: Similar
structure but different
function

Shows:
 Similar genes
 Common ancestor
Turtle
Alligator
Bird
Mammal
Anatomical Homologies
Vestigial Structure: Body part reduced in function in
a living organism but may have been used in an
ancestor
 Shows: Organisms evolutionary past

Whale pelvis
& tailbone
humans
Developmental Homologies

Shows:
 Similar genes
 Common ancestor
Developmental Homologies
Fish, reptiles, birds, & mammals
(yes, even us!) all have a tail,
limb buds & pharyngeal
pouches in the early stages of
development
Molecular Homologies

DNA & the genetic code
 DNA codes for amino acids
 “Universal” Genetic code
proteins
The similarity in DNA shows:
A probable common ancestor for all life on
Earth
Molecular Homologies

The amino acid
sequence in a
particular protein is
compared between
organisms.
45
27
67
1
Number of differences from human
hemoglobin
Molecular Homologies

Comparing amino acid sequence shows:
 Closeness of
relationship
 A probable
common
ancestor
Amino Acid Difference in Hemoglobin Compared with Human
Human hemoglobin has 146 amino acids
Species

Amino Acid
Sequencing is
probably the
STRONGEST
evidence for
relationships among
organisms.
Gorilla
Differenc
e
1
Rhesus
Monkey
Mouse
27
Chicken
45
Frog
67
Lamprey
125
8
Molecular Homologies

A
CLADOGRAM: diagram that
shows the evolutionary
relationship among a group of
organisms.
B
Where would the
common
ancestor
be?
What
organism
belongs
at each branch?
C
E
F
50
40 30
20
10
100
150
Common
ancestor
D
Number of Amino Acid Differences
0
G
Biogeography

Geographic distribution

organisms living far apart may be similar
because they share a common ancestor
Observable Events
Some changes in species have been
observed and studied
 Shows: Evolution is an ongoing process

Peter & Rosemary
Grant’s Study of Beak
Size Shift in Darwin’s
Finches
H. Kettlewell’s Study
of Peppered Moth
Color Shifts