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Vocabulary
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Evolution
Speciation
Fitness
Competition
Limited resources
Adaptation
Niche
Variation
Carrying capacity
Biodiversity
Natural Selection
What is Evolution?
• The study of how
species change
over time
• Life began as
simple, singlecelled organisms
that evolved to
become today’s
complex, multicellular organisms
Evolution
• New life forms come into
existence over time
• New species evolve from
pre-existing species via
modification (mutations)
• All species therefore have
descended from a
common ancestor
The End Result…
• Diversity among
species, BUT a unity
between them
(fundamental
similarities among
life processes)
• Therefore, evolution
explains the diversity
and unity of life
Darwin’s Observations:
• He studied the geology (rock
formations) and observed that
the Earth is VERY old
• He noticed that some fossils of
species found in the rocks are
VERY similar to those of
today (with some changes)
• He noticed that today’s
species are related to extinct
species
Fossil Record
• The fossil record shows
that organisms have
changed over time
• Some species that have
existed are now extinct
• Some current species
are not present in the
fossil record
• Some current species
are similar, but not
identical, to some
previous species
•Fossil layers are fossils that
formed in sedimentary rock.
•Sedimentary rock is rock that is
formed in layers by the depositing
and pressing of sediments on top
of each other
Which layer represents the oldest
fossils?
The top layers are the youngest and the
bottom layers are the oldest.
•The organisms also tend to become more
and more complex.
•From this, Darwin concluded that
organisms have not remained the same
since earth's beginning, that they have
changed a lot, gradually becoming more
and more complex. He also realized that
as new species arise, other ones become
extinct.
Evidence to Support
Theory of Evolution
• Scientists use many
forms of evidence to
support this theory.
• Scientists compare
similarities among
organisms to show
how they may have
evolved from a
common ancestor.
Comparative Anatomy
• Related organisms share a
unity of body plan
• Backbone, rib cage, and
arrangement of internal
organs are similar in fish,
amphibians, reptiles, birds
and mammals
• Among vertebrates,
forelimbs have the same set
of bones, whether it is used
for swimming, walking,
flying, hanging or grabbing
• Therefore, forelimbs are
HOMOLOGOUS structures
Homologous Structures
• Bones are structurally
similar, but have
different functions
• Ex: forelimbs of birds
and mammals
• Pelvic bones in whales
are homologous to
cows
Vestigial Structures
• Structures which
have become reduced
in size and are no
longer of use, or have
diminished in
function than they
did in the past
Comparative Embryology
• Related organisms
develop similarly
• All vertebrate
embryos develop
gill-like structures
even though only
fish have gills as an
adult
Comparative Biochemistry
• Basic cell structure is almost
universal
• All living things use the
same basic biological
molecules for similar
functions
• Ex: DNA stores genetic info.,
proteins serve as enzymes,
carbohydrates and fats used
for storage, lipids used to
build membranes
• Metabolic systems such as
photosynthesis and
respiration are similar
among species
Comparative DNA
• Many organisms
have similar DNA
sequences
So…. If we are all related from a
common ancestor then how do
we become different???
Lamarck and Darwin had 2
different ideas for how this
occurred.
Darwin’s Finches
• While on the Galapagos
Islands, he found 14
different species of finches,
all descended from a
common ancestor
• All 14 species of “Darwin’s
finches” have beaks
adapted to specific tasks
related to a specific
environment and ecological
niche
Define the following terms:
1. Overproduction
2. Variation
3. Competition
4. Natural Selection
5. Adaptation to the environment
6. Fitness
Natural Selection
• It was once thought that
species could evolve based
on their needs.
• However, today we know
that this does not happen
• Charles Darwin proposed a
mechanism by which
organisms evolve (and called
it Natural Selection)
1. Overproduction:
• More offspring
are produced,
than can
actually survive
“Of course, long before you
mature, most of you will be eaten”
2. Competition: Since more
are produced than survive,
there is a competition for
resources.
Competition
•Resources are fixed. (food,
shelter)
•Many more individuals are
produced than can survive
•Population grows to a limit
•Individuals must compete
•There is a struggle for
survival
Sources of Variation
•Sexual Reproduction
•Mutations
Reproduction
• We know that sexual
reproduction and random
genetic change (mutations)
result in variations among
individuals
• We also know that the
genetic instructions for our
traits are passed on to new
generations in the form of
genes (DNA)
• The genes that give the
organisms an advantage
have an adaptive value and
are passed on to future
generations
Sources of Genetic Variation
• Meiosis and Sexual
Reproduction
– Both processes allow
for genetic shuffling
Sources of Genetic Variation
• Mutations – random
changes in the DNA
base sequences
– They can only be passed
on to future generations
if they occur in the
gametes
Why are variations good?
• Variations lead to
biodiversity.
• The more variations in
organisms, the more
stable the ecosystem is
because variations
increase the likelihood
that some organisms
will survive and create
new future generations
Fitness: What does it mean?
Some individuals have traits which make
them better at surviving. (physical or
behavioral)
This results in differential reproduction
Fitness is linked to a particular
environment.
The Beaks of Finches State Lab
What variations do you see in this population?
Why does variation exist in this population?
Examine the tools and decide which you think
will be the best for picking up small seeds. Give
reasons.
Choose a tool which will be least successful in
picking up small seeds. Explain why.
Do you think these differences are important and
why?
Round 1: No competition
Use your beak to pick up the small seeds and place them IN
the petri dish. You will have a limited amount of time and you
must pick up an average of 20 seeds to survive.
Evolution of Giraffes
• Darwin’s explanation of evolution as applied to giraffes.
• Each generation of short-necked giraffes had slight variations in the lengths
of their necks.
• Only those with the longer necks survived the process of natural selection
and produced the next generation, which started out with slightly longer
necks.
• The long-necked individuals in the 2nd generation were again favored by
natural selection, resulting in even longer necks in the 3rd generation
Extra Credit Question for the test
• Choose one of the “stories” from the film
Voyage to the Galapagos and explain how
evolution is occurring in these populations
• Use specific examples and include the
following terms:
– Natural Selection
– Fitness
– Adaptation
How fast does evolution occur?
• In organisms that
reproduce few
offspring and have
long life cycles,
evolution takes
place very slowly.
• Ex: Humans
How fast do species evolve?
• Evolution is much
faster in organisms
with short life
cycles that produce
many offspring
• Ex: Resistance in
bacteria and insects
Bacteria Resistance
• In bacteria we see evolution
taking place with the
appearance of antibiotic
resistant bacteria.
• When a colony of bacteria
form, some may have natural
variations that make them
better adapted.
• When antibiotics are taken,
the antibiotic resistant
bacteria are not killed.
• They then can reproduce
creating a population
dominated by antibiotic
resistant bacteria
Insecticide Resistance
• When insecticides are used,
some insects have variations
that make them immune to
the insecticide.
• These insects are not killed.
• They survive and reproduce
creating a new population of
insects that are insecticide
resistant
Gradualism:
• The slow and steady
evolution of species over
time
• Many small changes over
millions of years
• Eventually, population will
evolve into new species
• Driven by natural selection
Punctuated Equilibrium:
• Evolution is rapid
and could take place
in one generation
• Driven by small
number of genetic
changes (mutations)
• Occurs when there is
severe environmental
change-(asteroid
impact)
What is Speciation?
• The formation of a new species
What factors can lead to the
evolution of a new species
(speciation)?
Factors leading to speciation:
1. Geographical Isolation
• When two
populations
are
separated by
a
geographical
barrier (such
as rivers or
mountains)
2. Ecological Competition
• Competing for the
same resources forces
one to either adopt a
new food source or
become EXTINCT
3. Behavioral Isolation
• When two species have differences
in courtship rituals
Blue-Footed Booby Dance
4. Temporal Isolation(reproductive
isolation)
• When two
different species
reproduce at
different times
• They are fertile
at different
times of the year
Mechanical Incompatibility
• Body parts
(sex organs)
simply do not
match up
Reproductive isolation
Results from
Isolating mechanisms
Which include
Behavioral isoloation
Geographical isolation
Temporal isolation
All can result in the formation of a new species!!!
Darwin’s theory of Evolution
includes
Variety-organisms
differ as a result of
sexual reproduction
and mutations
Overproduction
causes
Favorable
adaptations lead to
better fitness
competition
Evolution
A
C
B
I
G
J
D
E
F
H
Read the following story:
You are a bear-eating monster. There are two kinds of bears:
happy bears and sad bears. You can tell the difference
between them by the way they hold their hands. Happy bears
hold their hands high in the air, and sad bears hold their
hands down low. Happy bears taste sweet and are easy to
catch. Sad bears taste bitter, are sneaky, and are hard to
catch. Because of this, you eat only happy bears. New bears
are born every 'year' (during hibernation) and the birth rate
is one new bear for every old bear left from the last year.
These characteristics are controlled by one gene loci and there
are two alleles. The allele for paws down (D) is dominant and
the allele for paws up (d) is recessive.
Essential Questions: What kinds of factors affect the
evolution of a species?
How do they affect the frequency of alleles in the gene
pool?
Terms to be familiar with:
1. Genetic Variation
2. Gene pool
3. Natural Selection
4. Selecting Agent
5. Phenotype
6. Genotype
What are the 2 different types of bears based on
their observable characteristics?
Sad,
grumpy
bears
If Happy bear phenotype is the recessive
condition what is their genotype?
What is the genotype of the Sad bear?
Happy Bears
Procedure:
• Obtain an initial population of 12 bears from your teacher.
DO NOT EAT THE BEARS UNTIL INSTRUCTED TO
DO SO!!!
• Record the number of happy bears, sad bears and the total
number of bears in this population in the data table.
• Paws Down (Grumpy, bad tasting)Paws Up (d)(happy,
sweet
• Eat 3 happy bears. (If you do not have three happy bears,
then eat the difference in sad bears.) You will receive 3
replacement bears for your new population. Record the
number of bears in the new population.
• Eat 3 happy bears once more. Again if you do not have 3
happy bears then eat the difference in sad bears. You will
receive 3 replacement bears for your third population.
Record the number of bears in population #3.
Paws Down
(Grumpy, bad tasting)
Paws Up (d)
(happy, sweet tasting)
Number of each in
population #2
Number of each in
Population #3
Total in the class
population
5. Graph your results using a histogram. Graph each
population separately and note trends evident from the
initial population to population #3.