Download 7 AP Bio Darwin and evolution 2015

7
A/P Biology
Darwinism/Evolution Chap. 22 pgs 465-479
Name: ________________________ Date: ___________ Periods: _______
There are several factions of beliefs among scientists about evolution:
1.) Some scientists believe that evolution is purely a function of mutation of genes at
the molecular level. Moreover, scientists believe that DNA NATURALLY
mutates on a predictable timetable - this is referred to as the “molecular clock”.
2.) Some scientists believe that evolution is predicated on over-all changes in the
environment. That is as the environment changes it (the environment) “selects”
organisms that are BEST adapted to these changes over time. This may be a
function of changes in the DNA (or genetic code) but it also may have to do with
the ability of an organism to have the “tools” to adapt to changes. So we might
venture that the change need not lie in the direct mutation of the DNA, rather the
ability of the organism to adapt. (You might argue that the DNA itself is a
measure of the ability to adapt.)
3.) Some scientists believe that there is a predisposition of the DNA for
development over time. That change is already programmed into the DNA for the
future. Some DNA already has a program inside of it that accounts for any
possible change in the environment. That is to say that some part of the
population “HAS THE POTENTIAL” to adapt to any change in the environment.
(Again, you may argue that this does not take into account huge changes in the
environment accomplished in an instant. This is the basic definition of a
cataclysmic event.) Recent evidence suggests that the DNA sequence changes
over time according to the “molecular clock” AND that the environment can then
modulate those changes through epigenetics (Internet research). An example of
this might be the “de-evolution” of eyes in “cave fish”.
4.) There are some scientists that believe in creationism. That God, or some form of
spirit or energy created all the different organisms.
5.) There are some scientists that believe there may have been some sort of
creationism AND a concomitant form of evolution thereafter. Basically an
“Intelligent Design” the basic “life” was formed or designed to evolve in a
sophisticated way.
6.) The last most recent development regarding evolution involves the concept of
epigenetics. MOST scientist DO NOT believe that epigenetics is any form of
evolution because it does NOT involve the actual change of DNA over time (i.e.
the original sequence remains the same). The difference is the expression of
genes- that is to say that genes can be turned on or off, or simply the expression of
the gene is modified. So a gene that makes one thousand molecules of insulin
may now make only one hundred molecules of insulin. The over-all concept is
that "normal" evolution; where the environment "selects the best organism to
survive over LONG periods of time (10,000 yrs to 1,000,000 yrs)" was NOT agile
enough, did not respond fast enough for organisms to survive. So there had to be
a better, faster way- via epigenetics- to change expressions of genes to survive in
a rapidly changing environment. This environmental change might be temporary
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or long term. If temporary, then the epigenetic modification "might fade" over time.
If changes were long term, then the concept of changes in the sequence of DNA over
a long period of time would take over. DNA sequence changes (or mutations) is the
true definition of EVOLUTION- and therefore eventually a new DNA sequence
would be "selected" to make an organism successful- in the mean time, epigenetics
might "fill in" as an adaptive strategy to allow an organism a better chance to survive
in the short term of evolutionary change. Epigenetics is a process where genes are
modulated using a process called methylation- adding a small "R" group (in this case
CH3-) to a gene. This addition - or subtraction may modify a gene, turn it on or turn
it off.
There is evidence that bacteria evolve over thousands of generations (a generation is
defined as the reproductive cycle of the bacteria- that is to say the “generation time” or
the time it takes to divide; one bacteria undergoing fission or division- to make two
bacteria- in some cases the generation time for a bacteria to reproduce is 20 minutes).
The bacteria evolve or alter their genetic make-up in a somewhat predictable fashion–
and the changes in the genetic material can be thought of as an evolutionary clock or
molecular clock. The definition of the molecular clock is “A measurement of
evolutionary time in nucleotide substitutions per year.” (Taken from:
http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/DefM/mol_evolutionary_clock.html) So we can deduce that since bacteria are proven to
evolve in a somewhat predictable fashion - that is their DNA sequence changes over time
(perhaps in response to the environment- or perhaps in spite of the environment), that all
organisms evolve over time. This is reasonable conclusion- BUT proving this to be the
case beyond any doubt is a monumental task. The "take home" message here is that the
shorter the generation time, the more likely you will have mutations or changes in
the DNA sequence and the more likely evolution will occur in a shorter period of
time.
Are these the ONLY beliefs that exist for the changing of species over time? Of
course not. Why can we not know how organisms got to be here? Well the simplistic
answer is, BECAUSE WE CANNOT PHYSICALLY GO BACK IN TIME AND
WITNESS THE EVENTS! We can draw inferences of evolution based on known
evidences (fossils, transitional (intermediate) species, radioactive dating, embryological
evidence, DNA/protein evidence, homologous structures, analogous structures, and
vestigial structures). We can hypothesize how life was built AND Craig Venter (look
this person up in the Internet!) has already "pieced together” an artificial life form
(bacteria) using known sequences of DNA that he strung together. Is he playing God?
There are other scientists that are approaching life from the opposite direction. They are
taking pieces of DNA away from a bacteria to find out the minimal amount of DNA
necessary for LIFE of that bacteria!
How do we “theorize” how evolution occurred? We MUST depend on evidence!
We have to look at all the different pieces of the puzzle we know of, and then figure out
what is the “most likely” chain of events based on the consensus of information from
credible sources! (THIS is also the basis for Internet Research!!!)
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We have many permutations and combinations possible.
We can look at evolution as
a series of gradual or small
changes in the environment
over time which might
allow DNA mutations to
keep up with the changes
and allow organisms to adapt by chance mutations over
millions of years. This is gradualism (see picture of
starfish above changing over millions of years). This
diagram shows two simple branches, but this is just an
example. Scientists have already found many different
variations of the starfish in very deep dives in the ocean
that show even more diversity than we ever dreamed.
(The starfish above is more than 3 feet across!)
The other theory of evolutionary change is punctuated equilibrium. (See - top.)
Some scientists believe that the Earth has undergone several cataclysmic disasters that
may have wiped out large portions of the total organisms on Earth. This may account for
the different periods of development (Mesozoic, Cambium, etc…). Basically this theory
describes a pattern of long, stable periods interrupted by brief periods of rapid changes.
It is difficult to support this theory over gradualism, but what is clear is evolution has
“appeared” to have proceeded at different rates for different organisms (at different
places on Earth and thus different environments) at different times during the long history
(4.5 billion years) of the life of the Earth. Could there be a required combination of
gradualism and punctuated equilibrium? Could there be a hybrid explanation?
So how do we perceive the evolutionary process? We can look at it more like
Darwin did on the Beagle back in 1831. We can try and make some sense out of the
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evolutionary scheme. WE CAN DOCUMENT THAT ANIMALS CHANGE OVER
TIME? HOW?
1.) Fossil records- we have found that fossils can show progression of change, and we
can document the different
ages of the progression of
the changes by dating the
fossils through radioactive
dating. The picture to the
right shows the theoretical
development of the modern
horse from Hyracotherium
(the smallest horse) to
Equuus (today’s modern
horse) dated no more than
10,000 years ago.
Though carbon-14
dating is one of the best
known ways to determine
age of a fossil-the half-life
of carbon 14 is only 5730
years. This makes the
accuracy of carbon-14
dating fairly accurate for
maybe 50,000 years.
Beyond that the accuracy
starts to fail. The reasoning
lies in the concept of
radioactive dating. When
an animal is alive, it continues to take in and expel small amounts of radioactive material
(Carbon 14 decomposes into Nitrogen 14 at a predictable rate). When an organism dies,
it ceases to take in or expel radioactive material. Radioactive dating REQUIRES us to
determine HOW MUCH radioactive material in left in an organism after a period of timeand we must compare that to the amount of decayed material (residual) that the
radioactive isotope decays to. (Example: Carbon 14 decays to Nitrogen 14.)
(Radioactive materials lose half of their molecules – called their half-life in a given
period of time. So- if we had 10 grams of radioactive Carbon 14 in a body 50,000 yrs
ago, there would only be 3.9 X 10-2 grams left. After a million years the carbon 14 would
not be able to be accurately measured!) The better radioactive testing for very old
samples, Rubidium-87 is more useful, with a half-life of 5X1010 years (50 billion years).
2.) Transitional forms and structures- If you find different forms of the same animal,
you might theorize that there was an evolutionary progression that took place. Scientists
have to make certain assumptions about how animals evolved by dating remains and
Following logical progression. It is these assumptions that make predictions somewhat
uncertain. (see the transformation of the horse (above). How do scientists “make the
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connection” between the Hyracotherium which was about SIX INCHES tall to the
Miohippus (see previous page diagram) which was about 24 inches tall? They compared
the fossil bones- looked at the skull structure, counted the vertebra and the teeth- and
found that they were related because there were so many similarities! The only
difference was the structure of the feet and the over-all height.
Scientists also make certain assumptions about origins of different species by
comparing structures that are similar. (see pic below)
Each of the different
structures that you see to
the right has the same basic
arrangement of bones.
(Similar bones are given
the same colors.)
Homologous structures
are those structures that
share a common
ancestry! They do not
have the same function
necessarily, BUT they DO
have the same form!
On the other hand,
analogous structures have
the same function, but not
the same basic formAND NOT necessarily
show the same ancestor!
Example might be the wing
of a bird and the wing of an
insect. (See picture bottom
right.)
Then there are vestigial
structures. Vestigial
structures also help us to
guess which species are
related by showing us the remnants of a structure. An example of this might be a
vestigial structure found in the whale (see next page).
The vestigial bones are remnants from the whale’s
ancestors’ life as a land animal that had hind legs at one
time. These bones are often thought of as useless BUT we
MUST understand that just because we cannot attribute a
use to these structures DOES NOT MEAN there is no use
(there may be of use in the future?)! These vestigial
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structures may have some use we do not understand or unable to measure! The vestigial
structures DO allow us to
make some assumptions about their
ancestors (that is - they were probably
land creatures). Another example of socalled vestigial structure might be the
appendix in the human or the tailbone in
the human.
3.) Comparative embryologyScientists studied the development of
multi-cellular organisms from the single
cell (zygote) to the multi-cellular stages
(definition of what embryology IS).
Comparing the development of different
animals we note certain progressions and patterns of development that lead us to believe
that these multi-cellular animals share a common ancestor. Scientists have shown that
development of organisms are controlled by a successive expression of genes (called
“HOX” –Internet research- genes) in a specific order. What scientists see is a
progression of the development of a zygote to a blastula to more complex organism
looking nearly identical- from development of worms, to development of fruit flies, to the
development of humans). No scientists can look at an untreated zygote under the
microscope and determine what organism it is. Even after it has undergone mitosis
many times and formed a ball of cells or even started to develop head and limbs, it is
difficult to determine what organism it will turn out to be. As the cells develop, we can
begin to delineate what Kingdom, what Phylum, what Class, what Order, what Family,
what Genus, and what species it is. BUT, this takes time! We have to watch the embryo
develop and wait to see what happens to start to figure out where it is heading in terms of
development. (Yes we CAN do DNA tests on the individual cells and determine what it
will be before it finishes developing- but just to look at the embryo we cannot guess.) If
we look at the embryos of different organisms at various stages of development, we
might be hard pressed to determine which is bird, which is rabbit, which is frog, etc…
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(a.) fish (b.) frog (c.) turtle (d.) bird (e.) rabbit
Even if we do a simple comparison of
the chick and the human we see many
similar features that make us think that
these two embryos have a common
ancestor. (See pictures to the right.)
If we simply look at a single cell from
ANY organism, we would be hard
pressed to determine the organism it
came from (except for certain onecelled organisms!).
4.) DNA and protein evidence:
finally, one part of the puzzle to
evolution HAS to be the basic genetic
structure of an organism. DNA
controls all that goes on in all cells. If
we examine key protein/enzymes we
can determine differences in the
sequence of amino acids. That means
that if we look at a protein called
cytochrome-C (a protein used in the
production of ATP in the mitochondria) we find 35 of the 104 amino acids in
cytochrome-C are exactly the same in dozens of species. The remaining 69 amino acids
vary from species to species.
It is expected that there are more sequence differences in distantly related
organisms than those that are closer in relationship to each other. In other words a house
cat and a lion are going to have more sequences that are alike compared to a house cat
and an octopus. We as humans are more closely related to chimpanzees than we are to
tuna. The chimpanzee and the human share nearly 98% of the same DNA sequences.
The human and tuna contain about 28-35% of the same DNA sequences. We ARE
related to the tuna in many ways (we have many of the same organ systems, a backbone
and HOMOLOGOUS structures). We certainly have MORE in common with the
chimpanzee.
If we map the number of amino acid differences (in cytochrome-C) between a
human and other organisms we might get…(see next page)
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The numbers along each line represents the number of nucleotide changes from the
“original” cytochrome “C” sequence in one celled organisms.
Such phylogenetic tree helps determine relationship and these trees correlate well with
species that appear anatomically similar.
Why do animals change?
In response to environment?
In response to mutations in genes?
Genes change in direct response to environmental factors (mutagens –Internet)?
Genes are modulated by environment- i.e. that DNA adapts?
To pick up on Darwin, we can say that animals change (or do not obviously change) to
survive. What is meant by this is that if the environment changes around an animal and
that change puts some sort of survival pressure on the animal- then the animal must either
adapt, move to a new location (where the environment is more suitable to that animal’s
survival), or DIE! As we saw in the DNA evidence of related organisms, the change in
the DNA sequence can be minute (and not obvious in the anatomy) or drastic (and very
obvious in the anatomy).
To be a successful species animals TEND to do the following:
1.) Over produce. That is more offspring are produced than can survive (either
through predation, food limitation, water limitation, nutrient limitation, or other
resource limitation). If you Over-Produce; you do not (cannot) take care of the
young for a long period of time!
2.) There is variation in offspring. Variation in offspring helps to insure that
offspring will be slightly different from the parent. This difference will allow the
offspring to be better (or possible worse) prepared to survive in an environment.
Remember, ALL environments change over time. The key is HOW FAST does
the environment change? If the environment changes EXTREMELY slowly, then
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there is little pressure for organisms that live within the environment to change.
An example would be a parasite that lives within another animal. For the most
part- the internal environment of an animal does not change significantly over a
life-time. (Exceptions to this are insects that undergo complete metamorphosis
such a caterpillar to butterfly!) The faster an environment changes, the more
pressure there is for all organisms within that environment to change. Variation
of offspring necessitates the exchange of genetic material that is Sex! Sex
promotes variation in offspring, “Fission” in the amoeba does not! (Fission is
the asexual reproduction of an organism.)
3.) There is always a struggle to survive! There are more living things than there
are resources to go around. The ultimate effect of this is competition. Not simply
competition for food (aka: resources), but competition to pass on genetic material
(i.e. offspring).
4.) Natural selection is always taking place. Organisms that have less desirable
traits for a particular environment are less fit. “Fitness” is defined as the ability
of an organism to take in enough energy to survive, grow, and reproduce.
Moreover it must provide for the offspring! It is the ENVIRONMENT
(environment is defined as EVERYTHING around an organism, both living and
non-living) that selects the best organisms to survive. That is to say that those
organisms best suited to a particular environment are more successful and have a
better chance of sending their genetic material to many offspring!
Evolution is a change in the hereditary features (-via a change in the
sequence of nucleotides in DNA-) of a group of organisms over time!
Below and on the next page are a set of graphs that “make a case” for the changes in
human brain volume over evolution of hominids. For each graph, make a case for why
these changes in brain volume might have occurred based on the graph!
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Answer the following questions here and on your scan-tron sheet.
_____ 1.) What is DNA predisposition?
a.) the ability of the DNA to change ONLY in response to the environment
b.) the change in the DNA that will occur regardless of the environment
c.) the change in the environment over time
d.) the actual structure of the DNA
e.) none of the above are correct
_____ 2.) What is “creationism”?
a.) that life began spontaneously without any outside “help”
b.) that life evolved naturally from small molecules that became organized
c.) that God created all living things
d.) that man created all living things
e.) all of the above are correct
_____ 3.) What is the molecular clock?
a.) the unpredictable change in DNA over time
b.) the change from DNA to RNA
c.) the change in DNA in response to environment
d.) a measurement of evolutionary time in nucleotide substitutions per year
_____ 4.) Gradualism is…
a.) large changes in the DNA in response to cataclysmic changes in the environment
b.) small changes in DNA in response to gradual changes in the environment
c.) small changes in DNA in response to cataclysmic changes in the environment
d.) no changes in DNA in response to no change in the environment
e.) none of the above are correct
_____ 5.) Punctuated equilibrium is a theory where…(mark one or more that are correct)
a.) organisms do not respond to cataclysmic events either through behavior or
changes in DNA
b.) organisms respond to cataclysmic disasters by changing their DNA drastically
c.) there are long stable periods of stability in the environment interrupted by periods
of rapid change
d.) surviving organisms of cataclysmic events have more of an opportunity to survive
by taking advantage of resources that are more available
e.) none of the above are correct theories
_____ 6.) Carbon-14 dating is used to determine the age of SOME fossils. If there is
64.00 grams of Carbon-14 in an animal when it dies… how much carbon-14 will be left
after 74,490 years? (Look up Radioactive Half-Life on the Internet!) Assume the halflife of Carbon-14 is 5730 years.
a.) 6.25X10-2 g b.) 7.81X10-3 g c.) 1.95X10-3 g d.) 6.10X10-5 g e.) 7.6X10-6 g
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_____ 7.) Transitional forms of fossilized skeletons can support…
a.) that organisms are related
b.) that skeletal remains demonstrated small changes over time
c.) estimation of the time it took to develop one species to the next
d.) all of the above
_____ 8.) Homologous structures are those structures…
a.) that have different structures but same function
b.) that have similar structures but may have different function
c.) that have exactly the same structures but different function
d.) that have neither the same structure nor the same function
e.) none of the above are correct
_____ 9.) Identify what the picture to the right is demonstrating:
a.) analogous structures
b.) vestigial structures
c.) homologous structures
d.) mimicry
_____ 10.) Which of the following are “vestigial structures”?
(Mark all that apply- look to Internet if you are unsure.)
a.) whale’s pelvic bone
b.) lateral lines in a shark
c.) appendix in human
d.) “melon” part of the dolphin
_____ 11.) If we look at the early embryo of a chicken and an early embryo of a human
(see page 7 of this handout) we notice a number of similarities. These similarities are
probably due to…
a.) the theory that chicks and humans have a common ancestor
b.) the fact that chickens and humans share about 78% of the same DNA
c.) the fact that chickens and humans share a lot of traits
d.) the fact that chickens produce a lot of the same proteins
e.) all of the above are correct
_____ 12.) A frog produced several hundred eggs of which perhaps 200 are fertilized and
begin to grow into tadpoles. This is an example of:
a.) over-production b.) under-production c.) response to environment d.) extinction
_____ 13.) Thomas Malthus (look this up on the Internet) theory about population and
resources were:
a.) that populations and resources grow exponentially
b.) that populations grow arithmetically and resources grow exponentially
c.) that resources grow arithmetically and populations grow exponentially
d.) that resources and populations grow arithmetically
e.) none of these are true
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_____ 14.) A bird population lived off insects at a remote pond in the mountains. A
cataclysmic event (an Earthquake) opened a passage between their pond and another
pond a few thousand feet away. The original pond where the birds lived, starts to dry up.
Frogs start to move into the original pond and start to compete for the insects. What are
the options for the birds? (Mark all that MAY apply.)
a.) the birds may start to eat frogs or other food in the area
b.) the birds may move to the other pond
c.) the birds may perish
d.) the birds may build a damn to stop the water from flowing to the second pond
e.) the birds may chase away the frogs when they try to come to the original pond
_____ 15.) In question #14… would you expect a change in the bird’s beak and claws
(the bird’s physiology) over the next 10,000 years if the insects near both ponds died off?
(For purposes of this question- we are limiting our answer to those birds that do not
migrate beyond the two ponds.)
a.) Yes, most probably b.) No, not likely c.) Not enough information to make a guess
Answer the following questions on this handout only!
_____ 16.) What is the one type of behavior (adaptation) that PROMOTES variation of
species?
a.) competition for food b.) having sex c.) binary fission d.) DNA mutation
_____ 17.) Natural selection is…
a.) when the animal is able to get food and reproduce in a controlled (artificial)
environment
b.) when an animal is able to get food but cannot reproduce because there are no
animals of the opposite sex
c.) when the environment allows an animal to have the better chance to get food and
reproduce compared to all other animals
d.) when the environment prevents any animal from finding food or reproducing
e.) when the environment encourages organisms to move to another location
_____ 18.) Evolution is a change in the hereditary features of a group of organisms over
time. In this case “time” refers to…. (NOTE: the age of the Earth is estimated at 4.5
billion years)
a.) between 1 and 10 years
b.) between 100 and 1000 years
c.) between 10,000 and 10,000,000 years
d.) between 100,000,000 yrs and 100,000,000,000
e.) “time” here refers to an infinite number
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_____ 19.) A tadpole develops into a frog after about 50-60 days (depending on
temperature and type of frog). Is THIS and example of evolution? (mark all that apply!)
a.) yes, because the tadpole changes from a gill breathing organism to a lung
breathing organism
b.) yes, because the environment the animal lives in changes
c.) no, because there is no change in DNA
d.) no, because the change only took between 50-60 days
e.) not enough information to answer this question
_____ 20.) If bacteria do NOT undergo sexual reproduction, how do they “evolve”?
a.) the DNA naturally mutates
b.) the DNA replication process is perfect
c.) the “bad” bacteria die off
d.) the good bacteria will evolve if they CAN undergo sexual reproduction
e.) none of the above are true
Answer the remaining questions on this handout only
22.) Evolution takes place when the environment changes and by our definition- the
environment is ALWAYS changing (even if you can not “see” the change). Speculate if
a parasite that lives inside your body (such as a tapeworm) would evolve. Explain your
answer.
25.) Define gradualism and punctuated equilibrium (in your own words) and defend one
of these theories of evolution!
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
26.) In your own words explain how fossil records support the idea of
evolution?_____________________________________________________
_____________________________________________________________
_____________________________________________________________
Date: _____________________
Lesson Plan for Handout #7
AP Biology
Objective: TLWD ability to determine how DNA is involved in evolution and what
evidences there are for evolution; explaining how each piece of evidence supports
Darwin’s evolutionary theory. TLWD ability to explain the four different strategies all
organisms MUST obey to be “successful” when given handout #7.
Content: Darwin, Malthus, Evolution, DNA, fossil evidence, radioactive dating, and
strategies for a successful species
Method: Powerpoint, white board, discussion
Homework: Handout #7
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