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Review of Natural Selection
Evidence for Evolution
Evidence for Evolution
Evidence for Evolution
 Darwin argued that living things have
been evolving on Earth for millions of
years.
 Evidence for this can be found in
1.
2.
3.
4.
Fossil Records
Geographic distribution of living things
Homologous structure of organisms
Similarities during development or
(embryology)
Evidence for Evolution
 1. Fossil evidence
provides an
incomplete record of
early life.
 Fossils can include
any evidence of life,
such as imprints and
remains of organisms.
Evidence for Evolution
 This evidence must be
interpreted to form an
overall picture of how
species changed over
time (evolved)
 By examining the fossil
record, scientists have
concluded that
evolution happens in a
simple to complex
pattern and life
emerged from sea to
land.
Evidence for Evolution
 Fossils must be dated to
help establish a time
frame for the existence of
a species.
 There are two methods of
determining the age of
fossils.
Evidence for Evolution
 In relative dating the exact
age of the fossil cannot be
determined, only the order of
appearance as compared to
other fossils found in nearby
rocks.
 Fossils occur in layers of
sedimentary rock.
 The fossils near the top will be
more recent than fossils in
lower layers of rock.
Fill It In …
Explanation of the
fossil diagram:
Evidence for Evolution
 Radioactive dating
gives a more exact
age using the
natural decay of
radioactive isotopes
in organisms.
Evidence for Evolution
 2. Biochemical
similarities include
comparisons of DNA
and the resulting amino
acid sequences for
certain, shared proteins.
 This is considered one
of the most reliable and
objective types of
evidence used to
determine evolutionary
relationships.
Evidence for Evolution
 In general, the fewer
differences found
between two species,
the closer the
evolutionary
relationship.
Evidence for Evolution
Fill It In …
Explanation of the amino
acid sequence diagram:
Evidence for Evolution
 3. Shared
anatomical
structures supports
some type of
evolutionary
relationship.
Evidence for Evolution
 Structures with a similar
bone arrangement are
called homologous
structures.
 A similar bone
arrangement, even if the
functions are different,
supports evidence from a
common ancestor.
Homologous Structures
 Homologous Structures- different mature forms
but develop from the same embryonic tissue
 Similar function
 Found on different species
 Thought to be inherited by a common ancestor
Comparative Anatomy
 Vestigial organs- are no longer used by the
organism
 Have shrunk in size
 May only be a trace left behind
 Why?
 Example- Whale Hip,
Human tail bone
Comparative Anatomy
 Analogous structure- Similar function
 Found in different species
 Inherited by a DIFFERENT ancestor
Fill It In …
Explanation of the
bone diagram:
Evidence for Evolution
 Structures that perform
the same function (ex.
flying) but are very
different anatomically (ex.
bird wing vs. butterfly
wing) are called
analogous structures.
 This supports evolution in
similar habitats though
not from a recent
common ancestor
Evidence for Evolution
 Vestigial structures (ex.
Appendix or tail bone in
human) are not
functional in that
organism, but may
represent a link to a
previous ancestor.
Human Vestigial Organs
Evidence for Evolution
Fill It In …
Example of vestigial structure:
Embryology
 Embryology- is an
organisms
development
 ALL vertebrate
embryos have gill
pouches- thought to
be inherited from a
common ancestor
 Embryonic tissue
develop in the same
order
http://www.pbs.org/wgbh/evo
lution/library/04/2/l_042_02.h
tml
Check Yourself!
1. Name the two methods by which fossils may be
dated.
2. How do biochemical similarities support the
theory of evolution?
3. What does similar bone structure (even if the
function is different) suggest about two species?
Check Yourself!
1. Name the two methods by which fossils may be
dated.
RELATIVE DATING &
RADIOACTIVE DATING
2. How do biochemical similarities support the
theory of evolution?
3. What does similar bone structure (even if the
function is different) suggest about two species?
Check Yourself!
1. Name the two methods by which fossils may be
dated.
RELATIVE DATING &
RADIOACTIVE DATING
2. How do biochemical similarities support the
theory of evolution? FEWER DIFFERENCES =
CLOSER EVOLUTIONARY RELATIONSHIP
3. What does similar bone structure (even if the
function is different) suggest about two species?
Check Yourself!
1. Name the two methods by which fossils may be
dated.
RELATIVE DATING &
RADIOACTIVE DATING
2. How do biochemical similarities support the
theory of evolution? FEWER DIFFERENCES =
CLOSER EVOLUTIONARY RELATIONSHIP
3. What does similar bone structure (even if the
function is different) suggest about two species?
EVOLUTION FROM A COMMON ANCESTOR
Does evolution still happen
today?
 As long as variation,
overproduction,
competition, natural
selection and mutations
occur, evolution will
occur.
 Because evolution
leading to speciation
happens over such a
long period of time,
speciation is not readily
observable within a lab.
Does evolution still happen
today?
 Natural selection, one
of the main
mechanisms of
evolution, is observable
in some populations.
 For example, the
evolution of resistance
to chemicals:
Resistance- Standard
Resistance -TedTalk
Does evolution still happen
today?
 Farmers use pesticides
to eliminate insects.
 In a population of
insects, some
individuals will possess
genetic immunity to
certain chemicals.
Does evolution still happen
today?
 When the chemicals are
applied, the individuals
with genetic immunity
will survive and
reproduce, passing this
resistance to the next
generation of offspring.
 Over time, more
individuals are born with
this immunity, rendering
the pesticide useless.
Does evolution still happen
today?
 Antibiotics are drugs that
fight bacterial infections.
 Within any population there
is genetic variation.
 In the case of antibiotic
resistance, some bacteria
are genetically more
resistant to the antibiotic than
other bacteria
Does evolution still happen
today?
 If the amount of antibiotic
delivered is too low or the
full course not completed,
only those least resistant
will die.
 The surviving, resistant
bacteria will reproduce.
Does evolution still happen
today?
 With future applications of
antibiotics the population is
selected to become more
and more resistant.
 The overuse of antibiotics
has led to many resistant
strains of bacteria.
Antibiotic resistance
Brainpop- antibiotic
resistance
Fill It In …
Definition of antibiotic resistance:
CAUSE of resistance:
EFFECT of resistance:
CAN WE SEE EVOLUTION?
1. YES! Antibiotics are good for ridding us of
bacteria but are agents of natural selection.
They select out of a population the weaker
bacteria while the more resilient (mutant)
bacteria survive and reproduce. This can occur
b/c some have medicine destroying enzymes or
eat the drug as food. Some TB causing bacteria
are resistant to all three drugs developed.
http://www.pbs.org/wgbh/evoluti
on/library/10/4/l_104_07.html
http://www.pbs.org/wgbh/evoluti
on/library/01/1/l_011_20.html
http://www.pbs.org/wgb
h/evolution/library/10/4/l
_104_09.html
Check Yourself!
1. What is a pesticide?
2. Why do some insects become resistant to
pesticides?
3. What is an antibiotic?
4. What has led to the many resistant strains of
bacteria?
Check Yourself!
1. What is a pesticide? CHEMICAL USED TO
ELIMINATE PESTS
2. Why do some insects become resistant to
pesticides?
3. What is an antibiotic?
4. What has led to the many resistant strains of
bacteria?
Check Yourself!
1. What is a pesticide? CHEMICAL USED TO
ELIMINATE PESTS
2. Why do some insects become resistant to
pesticides? SOME POSSESS GENETIC
IMMUNITY TO CERTAIN CHEMICALS
3. What is an antibiotic?
4. What has led to the many resistant strains of
bacteria?
Check Yourself!
1. What is a pesticide? CHEMICAL USED TO
ELIMINATE PESTS
2. Why do some insects become resistant to
pesticides? SOME POSSESS GENETIC
IMMUNITY TO CERTAIN CHEMICALS
3. What is an antibiotic? DRUG THAT FIGHTS
BACTERIAL INFECTIONS
4. What has led to the many resistant strains of
bacteria?
Check Yourself!
1. What is a pesticide? CHEMICAL USED TO
ELIMINATE PESTS
2. Why do some insects become resistant to
pesticides? SOME POSSESS GENETIC
IMMUNITY TO CERTAIN CHEMICALS
3. What is an antibiotic? DRUG THAT FIGHTS
BACTERIAL INFECTIONS
4. What has led to the many resistant strains of
bacteria? THE OVERUSE OF ANTIBIOTICS