Evolution Evidence
The theory of evolution states that
all organisms on Earth have
descended from a common
ancestor
Support for Evolution
1. The Fossil Record
(Fig. 15.4 p. 423)
–Fossils show that ancient
species share similarities with
species that live on Earth today
Glyptodont
Armadillo
2. Comparative Anatomy
(Fig. 15.6 p. 425)
a) Homologous structures
develop from similar tissues in
early developmental stages of
the organism, but meet
different needs in the adult.
Homologous Structures
Fig. 15.6 on p. 425
• Q: What is similar about each of
these?
• Similar bone structure, from same
tissue
• Q: What is different about each of
these?
• Perform different functions – grab,
walk, fly
b) Vestigial structures are features of
ancestors that no longer have a
function for that species and will
become smaller over time until they
are lost
• Ex: Humans → appendix, tailbone
(Table 15.2 p. 425)
Snakes →tiny bones where legs
used to be
Vestigial Structures
Other Vestigial Structures
• Vestigial Pelvis bone and femur in whales
Other Vestigial Structures
c) Analogous structures look similar in
appearance and function, but are
developed from anatomically
different parts
–They are used for the same purpose
and similar in construction, but not
inherited from a common ancestor.
• Ex: eagle wing vs. beetle wing
(Fig. 15.7)
bird wing vs. bat wing
Analogous Structures
3. Comparative Embryology
(Fig. 15.8 p. 426)
• Embryology is the study of embryos
• Embryo = early, pre-birth stage of an
organism’s development
• Vertebrate embryos have similar
structures during certain stages of
development, but become totally
different structures in the adult form.
Comparative Embryology
Comparative Embryology
Human embryo
Chick embryo (LM)
Pharyngeal
pouches
Post-anal
tail
Q: What do similarities in early
development indicate?
• The organisms have similar genes
controlling early development.
Q: What do these similar genes indicate?
• These organisms have a common
ancestor.
Q: Why do the embryos become different
as they develop?
• Different genes start to contribute or
become “expressed” in the organism.
4. Comparative Biochemistry
(Fig. 15.9 p. 427)
• Evolutionary theory predicts
molecules in species with a recent
common ancestor should share
certain amino acid sequences.
• The more closely related the species
are, the more amino acid sequences
they have in common.
5. Geographic distribution
(Fig. 15.10 p. 427)
• Evolution is linked to climate and plate
tectonics which explains many ancestral
relationships and geographic
distributions seen in fossils and living
organisms.
–For example: South American animals
are more similar to other South
American animals than to animals in
Europe.
Mara –
South America
Rabbit – Europe
Adaptation
• An adaptation is a trait influenced
by natural selection that increases
an organism’s reproductive
success.
• Fitness: The ability of an
organisms to survive and
reproduce
–how much a certain trait
appears in the next generation;
measured by the amount of
offspring
• Camouflage: adaptation that allows a
species to blend in with their
environment.
• Why?
–Hide from predators/prey, more
survive to reproduce
• Ex: Arctic fox
(Fig. 15.11 p. 428)
Leafy sea dragon
• Mimicry: one species changes to
look like another species
• Ex: Harmless snake “mimics” a
poisonous snake so predators
leave it alone(Fig. 15.12 p. 429)
Western Coral
Snake
(poisonous)
California
Kingsnake
• Antibiotic resistance:
–Some species of bacteria that
originally were killed by
antibiotics (like penicillin) have
evolved to be drug resistant
–For nearly every antibiotic, there
is at least one species of
resistant bacteria
• Example: Tuberculosis (TB)