EVOLUTION
1809 - Lamarck’s Theory
2 Major Principles:
•
Use and Disuse
•
•
The more an animal uses a body part, the more
developed it becomes (and vice-versa)
Inheritance of Acquired Characteristics
•
Characteristics an organism develops or
acquires in its lifetime can be passed on to its
offspring
I. What is Evolution?
•
The slow, gradual change in a species over time.
•
‘Slow’ means thousands to millions of years (in most cases)...
•
Species with short reproductive rates; like bacteria, evolve
quickly. Bacteria reproduce about every 20 minutes.
•
Just in the last few millions of years, hundreds of species
have become extinct- while hundreds of others have
developed.
•
How do we know evolution is happening? Let’s look at the
evidence…
I. Evidence for Evolution
II. Fossil Evidence
•
Definition: Any trace or remains of an organism that
has been preserved by natural processes.
•
Studying fossils allows scientists to compare the
remains of ancient organisms with present day
species to determine evolutionary relationships.
•
Fossils form from amber, ice, tar, petrification, bones
buried under sedimentary rock.
•
The older the fossil, the deeper it will be buried.
Fossil Evidence
III. How do we KNOW????
evolutionary relationships
Evidence can be:
Structural
Molecular/ Biochemical
Structural Evidence
Homologous Structures: Similar internal
structure, but different form and function.
Structural Evidence
Analogous structures: Similar external form
and function, but different internal structure.
BOTH FLY- BUILT DIFFERENTLY
Structural Evidence
Vestigial
structures:
Structures that are
remnants of
structures that
were functional in
ancestral forms,
but are now
reduced in size
and serve little or
no purpose.
• DO THE TOP “10”
Structural Evidence
Embryological evidence: Comparing embryos at
various stages of development may show similarities
not present after birth.
WHO
DOES
THIS
GUY
LOOK
LIKE?
??
IV. Molecular Evidence
Gel electrophoresis: Technique used to
separate DNA fragments according to their
size.
-
+
Molecular Evidence
DNA sequencing:
A
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-T-G-G-C-C-T-C-A-T-A-T-A-G-G-C-C-G-C-T-A-T-C
B
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-C-G-G-C-C-T-C-A-T-A-T-A-G-G-C-A-G-C-C-A-T-C
C
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-T-G-G-C-C-T-C-T-T-A-T-A-G-G-C-G-G-C-T-A-T-C
How many differences are there between sequence A and B?
Molecular Evidence
DNA sequencing
A
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-T-G-G-C-C-T-C-A-T-A-T-A-G-G-C-C-G-C-T-A-T-C
B
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-C-G-G-C-C-T-C-A-T-A-T-A-G-G-C-A-G-C-C-A-T-C
C
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-T-G-G-C-C-T-C-T-T-A-T-A-G-G-C-G-G-C-T-A-T-C
How many differences are there between sequence A and B?
Molecular Evidence
DNA sequencing
A
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-T-G-G-C-C-T-C-A-T-A-T-A-G-G-C-C-G-C-T-A-T-C
B
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-C-G-G-C-C-T-C-A-T-A-T-A-G-G-C-A-G-C-C-A-T-C
C
A-G-C-T-A-G-G-C-C-A-T-G-T-A-T-A-A-T-G-G-C-C-T-C-T-T-A-T-A-G-G-C-G-G-C-T-A-T-C
Between B and C?
Molecular Evidence
Protein analysis or Amino Acid Sequencing
Carp
Bullfrog Alligator Mouse
Human
24
19
14
9
Mouse
19
10
9
0
Alligator
18
11
0
Bullfrog
19
0
Carp
0
The numbers represent the number of
differences between protein samples.
Human
0
What next?
V. Charles Darwin
The Father of Evolution
• Born February 12, 1809
•
1831- 1836 Served as
naturalist aboard the
HMS Beagle
•
1835 Arrived in the
Galapagos Islands
• 1859 Published On the
Origin of Species…
•
1882 Died and buried in
Westminster Abbey
Charles Darwin
•
Darwin’s thoughts
on Natural Selection
explained a lot about
evolution, but he
didn’t explain the
mechanism by
which traits change
over time.
•
The field of Genetics
explains this…
MUTATIONS. (they are
not always bad!).
Darwin’s and His Theory of
Evolution (summarized in 5 major points)
1. OVERPRODUCTION: Most
species produce far more offspring
than can survive. Those that die
are considered ‘weak.’ These
weak organisms do not live long
enough to reproduce. Therefore,
weak traits are weeded out of the
species.
Darwin’s Points…
2. COMPETITION:
Since living space
and food are limited (limited
resources), offspring must compete
for resources. Those who are good
at competition survive long enough
to reproduce.
Darwin’s Points…
3. VARIATIONS & ADAPTATIONS:
The characteristics of the individuals
in any species are not exactly alike.
Those individuals that have
favorable variations (adaptations),
will have a greater chance of living
long enough to reproduce.
Darwin’s Points…
4. NATURAL SELECTION:
Organisms with variations that make
them better adapted to their
environment survive and reproduce;
passing on these favorable traits to
their offspring.
Types of Natural Selection
DIRECTIONAL- an extreme phenotype becomes
favorable ex… long neck giraffes
Types of Natural Selection
STABILIZING- the average phenotype becomes
favorable and the extremes are unfavorable
Ex. Widow tail bird
Types of Natural Selection
DISRUPTIVE- two opposite phenotypes become favorable and the
average is unfavorable
Ex. Bird beaks- small seeds and large seeds on an island.. What
beaks work? Medium beaked birds would have to compete with
both large and small beaks.
Darwin’s Points…
5. SPECIATION:
Over many
generations, favorable adaptations
gradually accumulate in the species
and bad traits disappear.
Eventually, the accumulated
changes become so big that the
result is a new species.
Now, who wants to play a
game?
I wanna
play!
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play
VI. The Rate of Evolution
How Fast is Evolution Occurring?
•
There are TWO
theories… scientists
cannot seem to agree
on which one is correct.
•
THEORY #1:
•
GRADUALISM (based
on Darwin’s
ideas)…species arise
through gradual
accumulation of small
variations… evolution is
slow and continuous
over millions of years.
The Rate of Evolution
•
How Fast is Evolution Occurring?
THEORY #2
(Steven Gould)…
• PUNCTUATED
EQUILIBRIUM
species remain the
same (in equilibrium)
for extended periods
of time- evolution
occurs quickly for
short periods of
time.
VII. Sources of
Genetic Variation
•
MUTATIONS: Random changes in the genetic makeup of
an organism. (Actually a rare event, but causes new traits to
arise).
•
GENETIC RECOMBINATION: Gametes uniting during
fertilization. (Included within this is concept are meiosis and
crossing over).
• MIGRATION: New traits being brought into a population or
taking traits out of a population. Has the greatest effect on small
populations.
•
GENETIC DRIFT: Affects small populations; changes in the
gene pool due to storms, a catastrophe, etc. Harmful because it
tends to decrease the gene pool. Not significant in large
populations.
Peppered Moth
CLICK ON THE PICTURE TO SEE AN
ANIMATION
VIII. The Modern
Theory of Evolution
•
Focuses on the population rather than the
individual.
•
Population Genetics: The study of changes in the
genetic makeup of populations.
•
Frequencies: how often a particular allele (trait) is
found within a population.
•
Gene Pool: the total of all the alleles present in a
population.
•
Mathematically explained by Hardy- Weinberg. See
Packet.
IX. ADAPTATIONS
•
STRUCTURAL
ADAPTATIONS:
Involves parts of the
body ( wings for flying,
fins for swimming).
•
PHYSIOLOGICAL
ADAPTATIONS:
Involves metabolism of
the organism (poison
venom).
•
Other adaptations are
mating, behavioral,
hibernation, etc.
•
Bald eagle adaptations
to the right…
X. ADAPTIVE RADIATION
•
DEFINITION: The emergence of many species
from a common ancestor that was introduced to
a new environment.
•
Example: Darwins Finches… 14 finch species
diverge from one common ancestor on the South
American Mainland. Each species became
specialized feeders for their particular
environment.
ADAPTIVE RADIATION
Imagine these are beaks…
Some are great for big
seeds…
While others are best for little ones
Without the best beak for the
available food source…
Some finches
will not
survive to
pass their
unfavorable
traits on to
offspring.
XI. Two more concepts…
1.
Convergent
Evolution: Natural
selection that causes
non- related species to
resemble one another.
2. Coevolution: Two or
more species evolve in
response to each other
through competitive or
cooperative
adaptations. Example
are flowers and their
pollinators.
GENE POOL- the total of all the alleles present in a
population