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Human Evolution
1
Genetics
2
Mutations
3
Natural Selection
4
Darwinism/Lamarck’s Theory
5
Taxonomy
6
Traits and Punnett Squares
7
Evolution of Diets
8
Evolution of Diseases
9
Immigration
10
Emigration
11
Paleoanthropology
12
Development of the Brain
13
Evolution of Behavior
14
Human Genome Project
15
Glossary
16
About the Authors
18
Image Credits
19
It is widely accepted in science
that the Homo sapiens, or
humans, that we see today are
descended from primates like
the chimpanzee. The oldest
human-like fossils have been
found in the Middle East, leading scientists to think that the first ape-humans came
about in this area of the world. Although scientists may know where and how
humans evolved from our ape ancestors, why this occurred is still unclear. Many
theories of human evolution haved been proposed, each outlining a situation that
could have caused primates to evolve into such a unique species. Scientists are still
working today to find the theory that best matches all of the changes that are
present between apes and humans, especially the difference in intelligence.
Savanna theory: Millions of years ago, apes may have moved to the savanna
due to changes in climate. The need to hunt for food and to see over the tall
grass led to the development of bipedalism as well as tool-making and
cooperation. The heat of the savanna caused them to lose their hair in the
interest of staying cool.
Aquatic Ape theory: Evidence supports the theory that our ape ancestors
lived half in the water and half on land. Our skin doesn’t shift around like a
cat’s or dog’s. Only marine mammals have this trait. Standing upright allows
us to wade farther into the water. We have no fur like other marine mammals.
Our strange nostrils allow us to dive underwater.
To this day, scientists are in a heated debate over which theory is better.
Another semi-aquatic species of ape exists that is
strikingly similar to humans in physical characteristics.
The skull on the left is of Homo floresiensis, the
humanlike creature that lived on the island of Flores in
Indonesia. The species is now extinct, but by analyzing
the fossils left behind, scientists can conclude many
aspects of their physique and behavior. The skull on the
right is a human skull.
Genetics, the science of genes, heredity, and
variations, is a subset of modern science that has
evolved greatly since the 19th century. Starting with
Gregor Mendel’s pea plant experiment in 1868,
moving to Watson and Crick and their DNA
discovery in 1953, and finally the sequencing of the
entire genome in 2003, genetics constantly changes
every year. Our understanding of how traits are
passed on from generation to generation has evolved
since Mendel pioneered genetics research in 1868.
DNA, or deoxyribonucleic acid, is
the basis behind what drives genetics. All of
the genes that exist in the bodies of
organisms are coded for by nucleotides in
the DNA. Along with proteins and RNA, it
is one of the essential building blocks for
life. The double helix shape of the DNA
strand is unique, and it is well suited for
storing biological information. When
organisms pass on traits to the next
generation, DNA is where these traits are
stored.
Sometimes, internal or external factors can lead to the denaturing of the
proteins in the body. This will lead to mutations in the genes of an organism.
These mutations can lead to the production of offspring that have a deformation
or a neurological disease. Mutations can either remove or add extraneous bits of
DNA to the strand, and this can lead to the formation of cancer cells or
abnormalities
in
the
body.
However, these genetic variations
sometimes lead to good things as
well. The immune system is formed
through a series of mutations in the
body; evolution also happens
because of mutations.
Natural selection is also aided
by the positive side effects of genetic mutations. In the genome of the cell,
denatured proteins cause there to be an increase in genetic variation amongst the
alleles. Polyploidy, or the instance where an organism has an extra mutated set
of chromosomes, is a result of a genetic
mutation. However, this mutation is
absolutely necessary for natural selection in
organisms. This also relates to epigenetics
in the evolutionary sense. Epigenetics is the
study of the change in gene expression as
caused by mutations and natural selection.
The results of the mutations are passed
down through genes in a process called
heredity. Epigenetic factors alter the genes
that are being passed on to the next
generation, altering the phenotype of the
offspring.
Natural selection is one of the major mechanisms of evolution. It occurs
when one phenotype in a species is more likely to survive than others. Because of
their higher rate of survival, this phenotype may reproduce more successfully than
the others and slowly dominate the gene pool. Other scenarios can cause natural
selection as well, such as when a specific phenotype is less likely to survive than
the others.
Natural selection can only occur when a population is under stress.
Otherwise, all of the phenotypes would survive and reproduce regardless of their
advantages or disadvantages. Stress can come in many forms for a population,
such as competition, predators, pollution, and disease. The peppered moths below
show an example of how different phenotypes can have an advantage under some
circumstances:
The right-most picture shows a
simulation of the natural habitat of the peppered
moth, with a background colored like a tree. It
is much easier to see the black moths on this
background than the camouflaged white ones!
However, the habitat of the peppered moth has
become polluted and covered with ash from
nearby factories. Now, their habitat looks much
more like the picture on the left.
In both scenarios, it is the more obvious moths that would be noticed first by hungry
birds; therefore, the camouflaged color is more likely to survive and reproduce.
Charles Darwin is the name that most
people associate with evolution. He spent
many years studying species on the
Galapagos Islands, where most of the
evidence for his theories was found. He
noticed differences in the finches on each
island that seemed to reflect their diets. This
gave him the idea that there may be some
method of inheritance that allows
individuals with certain desirable traits to
pass them on to offspring. He wrote a book
about his theories, The Origin of Species, in
which he described this “natural selection.”
Lamarck, an English scientist of
the 1800s, was one of the pioneers in this
concept of evolution. Before Lamarck, it
was universally accepted in science that
all organisms were static. In his novel
proposal, Lamarck stated that any
changes that occurred during the life of
an individual would be passed on to its
offspring. In his famous example, he
described how this theory would apply to
giraffes. Over time, horses would have
stretched out their necks trying to reach
for higher food. This change would
accumulate over time to cause the
characteristics we see today. Lamarck’s
theory is clearly incorrect, but this new
idea inspired many others to study the
same concepts.
There are countless species of organisms on this planet, including bacteria,
animals, plants, and many other categories. How do scientists organize all this
information? It is a daunting task that some people devote their lives to; these
people study taxonomy, the classification of organisms. There exists a hierarchy of
categories that all organisms fit into. This system creates a tree of organisms, with
subcategories branching off of categories. Organisms that share a category have
certain characteristics in common, such as cell structure.
Using this system of taxonomy, each species on the planet can be given a
unique name, called their binomial nomenclature. This Latin term simply means that
a name consisting of two parts is given to them. The first is the genus to which the
species belongs, while the second is the name of the species. These are also called
the scientific names of organisms because they are used as a standard name in
science. If binomial nomenclature did not exist, then scientists from different
countries would have different names for the same organism, causing unnecessary
confusion. In fact, you have probably heard many of these binomial nomenclatures;
the name given to humans is Homo sapiens!
Punnett squares are diagrams that are used to predict the result of the
breeding of two organisms. In the square, one maternal allele is crossed with
one paternal allele for the same trait, and the resulting cross is determined inside
the square. From the results of the Punnett Square, scientists can accurately
determine the relative probability of
each trait being passed down to the
offspring. The squares are best
exemplified by Gregor Mendel’s pea
plant heredity experiment because the
results are also referred to as
Mendelian Inheritances.
There are two different types of Punnett Squares, monohybrid cross and
dihybrid cross. A monohybrid cross is used when the trait that is being crossed
has alleles in the form of BB, Bb, or bb. This type of cross is a 2 x 2 square, and
there are 4 outcomes from the cross. More often than not (75%), the phenotype
for the offspring is going to express the dominant allele for the trait. A dihybrid
cross is when 2 independent traits get crossed in the same Punnett Square. This
means that there are 16 outcomes in the resulting cross. Often this type of cross
is only used when there exist 2 traits that are being
studied concurrently and are independent of each
other. No other times are suitable for using the
dihybrid cross. Both types of squares have results
consistent with Mendelian Inheritance patterns.
The diets of humans have improved drastically since the first records of
Australopithecus diets were released. Our eldest ancestors, even dating back to
primates, typically ate a diet that consisted of fruits, nuts, and berries. People
were scavengers back then, and their bodies were more adept to eating objects
that we wouldn’t consider eating today. They still ate eggs, insects, and small
animals, but their meat consumption is far below what it is today. Hominids
from as early as 3.9 million years ago have
shown signs that they created tools and ate
meat.
Ancient
humans
consumed
significantly more protein and vitamins
than we do at the present. They ate
whatever was available to them, and that
allowed them to survive and evolve into us
Homo sapiens today.
There are organs found in the body today that are completely unused,
these are referred to as vestigial organs. These vestiges are remnants of highly
used organs that our ancestors used to eat their food. The appendix is considered
a vestigial organ because it was at one point used to grind up the bones
consumed during a meal. Hominids would eat a lot of raw meat and animal
bones, and the appendix would crush up those bones. Wisdom teeth are also
vestiges because they were used to grind up plant cellulose. Now, human jaws
and diets have adapted so that these organs are no longer necessary. However,
they still exist in the body
currently. The evolution of diets
helped speed up the development
of humans, and there are still
remnants of how we used to be
present in us today.
Disease can often affect evolution through means of natural selection.
There are many example of this throughout human history, where people with
certain phenotypes are more likely to survive an epidemic. In Africa, where a
disease called malaria is devastating many communities, the presence of a
genetic mutation called sickle-cell anemia is on the rise. Sickle-cell anemia
causes the blood cells to be misshapen and not function correctly. An individual
who is homozygous for this trait will have serious healthy complications;
however, an individual who is heterozygous for this trait will have half sicklecells and half normal cells. It turns out that these heterozygotes are immune to
malaria because there are not enough healthy blood cells present for malaria to
infect. Through the force of natural selection, this disease has changed the course
of evolution!
Malaria is caused by a parasite transmitted
from the bite of a mosquito. Symptoms
include: fever, fatigue, headaches, and death
in severe cases.
In the cases where a disease is caused by another organism, such as a
bacterial infection, it is possible for their evolution to be affected as well! Bacteria
that live in our body do not want to cause harm; in fact, they would rather live in
symbiosis with us, getting their nutrients without having to fight our immune
system. Because of this, phenotypes of bacteria that do not hurt us are naturally
selected for. Over time, this causes the symptoms of a disease to weaken. For
example, the respiratory disease Tuberculosis used to be a gruesome and fatal
disease that affected all parts of the body. Today, these bacteria live exclusively in
the lungs for most cases.
Immigration is the entrance of new individuals into a population. This process
can bring many new things into a community that could potentially change the
course of evolution, such as genetic mutations, disease, or competition. When
analyzing population dynamics, immigration is often grouped with births because
both of these cause an increase in population.
The introduction of new species to an environment can cause drastic changes
in any aspect from geology to food availability. In the famous example at
Yellowstone National Park, grey wolves were reintroduced into the park in order to
control the elk population. By reducing the population of elk, they reduced the stress
on the willow tree population, thinking that this would increase the population.
However, the wolves were also eating the beaver that were redirecting the flow of
water from the river with their dams. Now the willow trees do not have enough
water! Aside from the ecological repercussions, the new population of wolves is
attacking the livestock in nearby ranches.
A species can be invasive if it adversely
affects the ecosystem that it immigrates to. The
carpenter ant was accidentally introduced to the
Southern United States when a crate infested with
them was brought overseas on a ship. Today, the
population of ants is rapidly increasing as they
infest and destroy buildings.
Emigration is the converse of immigration; individuals that emigrate from a
population are leaving that area and moving somewhere else. Emigration is often
coupled with deaths to give a total population decrease when analyzing population
dynamics.
Emigration primarily affects evolution through genetic drift, where the gene
pool is changes due to circumstance in a small population. In a process called the
founder effect, a small population may emigrate to an area where a this species is
not already established.
The gene pool in this
new area will be very
volatile because of its
remoteness from the
original population and
the random chance
factor of which
individuals did the
emigrating.
For
example,
the
diagram to the right shows
an example of the founder
effect, where a small
population crosses the river
and reproduces there. By
random chance, this small
population happened to have
more red individuals than
blue. Because of this, the
gene pool of the new
population is significantly
different from the original.
Paleoanthropology is the study of our distant ancestors
from millions of years ago, when humans looked more like
primates than Homo sapiens. Scientists are discovering how
humans evolved from apes in the same way that they learn about
dinosaurs: by digging up fossils and analyzing them in many
different ways.
One of the oldest and most famous fossils of an early
human was found in 1974 in Ethiopia (see map). This skeleton
was named “Lucy” after the Beatles song “Lucy in the Sky with
Diamonds.” By studying her bones, scientists could infer a few
things about her life: Lucy had long arms and ape-like facial
features, along with an ape-sized brain; however, her pelvis and
knee structure show that she walked upright on two legs.
Neanderthal is a term used to describe the early man, caught between a
human and an ape. Most people think of these people as cavemen, sitting around
their campfires living without emotions or technology. Recent evidence shows
that there may be more to Neanderthals than we expected. Scientists have found
a fossilized skeleton of a primitive man with serious damage to his face and
skull. Although this man would have been crippled and possibly paralyzed by
this incident, his skeleton suggests that he lived about 40-50 years, a ripe old age
for this time period. How could he have survived in his condition? Perhaps some
younger individuals took care of the man, suggesting that these supposedly
primitive people had a sense of community and were capable of helping one
another.
The brain of our ancient ancestors was quite different from our brains
today. Brains in ancient times were not much larger than those of a chimpanzee
or gorilla. The growth of the brain is often attributed to a neurological process
called neuroplasticity. When a brain becomes more complex because of new
experiences, it requires the neuronal
connections to constantly be rearranged.
This constant reorganization of the
synapses causes the brain to grow and
take up more room in the cranium. The
skull will also evolve and expand with
the brain. This is why the head shape of
ancient humans is different from the
way it is now. As time goes on and the
brain rewires itself again and again,
future generations of people will have
different shaped heads.
Sociobiology, a subset of evolutionary
biology, looks into the assumption that behavior is
a result of evolution. The social behavior of
ancient hominids, specifically in their rituals,
fights, hunts, and societies, is the primary area
covered by sociobiologists. As an organism grows
and evolves, certain behavioral traits get passed
on from generation to generation, each time
getting honed by natural selection. For example,
ancient hominids did not have the knowledge or
the behavioral traits
to
perform
the
complex
mating
rituals (now called
dating) that Homo sapiens go through in everyday
lifestyles. The mindset that we get in when we
like someone is different from the mindset of a
Homo habilis when he/she liked another hominid.
As time went on, the ones that exhibited the more
favorable traits survived because of natural
selection.
With the natural selection of the stronger
genes wiping out the weaker genes out of the gene
pool, the weaker ones that survive need to exist in a metaphorical ecological
balance. This means that in the case where there is a sudden expansion of
altruistic traits, there is an equal expansion of traits that are dependent on those
initial traits to survive. Instinctive and intuitive behaviors, being more like a “go
getter” than a “follower,” are more likely to survive because of both altruism
and sociobiology. Many scientists believe that social behaviors evolve sort of
like adaptations, where the more protective and assertive social traits survived.
One of the greatest biological acheivements in the past 30 years was the
Human Genome Project. First proposed by the Reagan Administration in 1987,
the goal of the project was to accomplish something never before done in the
history of humanity: sequencing the genome of a human, comprising every
single gene and protein found in the body of an individual .
Think this is an easy task? Guess again! There are over 20,000 known
genes in the body that needed to be identified and sequenced. On top of that,
there were also billions of nucleotides needing to be sequenced! This was of
great importance to science because the results would allow people to better
understand many diseases associated with the human body.
The entire project itself spanned 13 years from 1990 to 2003. It cost over
$3 billion and was 99.99% accurate to the average human genome! Since the
first sequencing of the genome was completed in 2003, technology has
advanced to the point that a complete sequencing can now be done for as little
as $10,000 in just 3 months.
The project has provided many people with
crucial information that has led to many
important discoveries in the last few years.
Scientists and doctors who had access to the
findings from an online database were able to use
the information for diagnosing and discovering
new genes and technologies that have already
saved countless lives. With many more new
technologies still in clinical trials, and novel
oncogenes (genes which lead to cancer) still lying
inert in the body, the genome project will
continue to pay dividends for years to come.
Since its
completion in
2003….
- 1,800 new disease genes
have been discovered
- 2,000 new genetic tests
have been created
- 350 new biotechnology
devices have been
designed
- Malignant genes in
inherited diseases have
been discovered 128
times faster
- 2 new diseases have
been completely
identified
Phenotype – n. the set of observable characteristics of an individual resulting from the
interaction of its genotype with the environment.
Epidemic – n. a widespread occurrence of an infectious disease in a community at a particular
time.
Sickle-cell anemia – n. a severe hereditary form of anemia in which a mutated form of
hemoglobin distorts the red blood cells into a crescent shape at low oxygen levels. It is
commonest among those of African descent.
Heterozygous – adj. having two different alleles of a particular gene or genes, and so giving rise
to varying offspring.
Homozygous – adj. having two identical alleles of a particular gene or genes and so breeding
true for the corresponding characteristic
Malaria – n. an intermittent and remittent fever caused by a parasite that invades the red blood
cells and is transmitted by mosquitoes in many tropical and subtropical regions. The parasite
belongs to the genus Plasmodium (phylum Sporozoa) and is transmitted by female mosquitoes of
the genus Anopheles
Tuberculosis – n. an infectious bacterial disease characterized by the growth of nodules
(tubercles) in the tissues, especially the lungs. The disease is caused by the bacterium
Mycobacterium tuberculosis
Natural selection – n. the process whereby organisms better adapted to their environment tend
to survive and produce more offspring. The theory of its action was first fully expounded by
Charles Darwin, and it is now regarded as be the main process that brings about evolution.
Taxonomy – n. the branch of science concerned with classification, especially of organisms;
systematics.
Binomial nomenclature – n. the system of nomenclature in which two terms are used to denote
a species of living organism, the first one indicating the genus and the second the specific
epithet.
Paleoanthropology – n. the branch of anthropology concerned with fossil hominids.
Neanderthal – n. an extinct species of human that was widely distributed in ice-age Europe
between circa 120,000 and 35,000 years ago, with a receding forehead and prominent brow
ridges. The Neanderthals were associated with the Mousterian flint industry of the Middle
Palaeolithic.
Nucleotide – n: any group of molecules that form the building blocks of DNA and RNA when
linked together. They comprise a phosphate group, the bases (adenine, cytosine, guanine, and
thymine), and a pentose sugar.
Genome – n: a full set of chromosomes; all the inheritable traits of an organism.
Allele – n: any of several forms of a gene, usually arising as a result of a mutation, that is
responsible for hereditary variation in an organism.
Neuroplasticity – n: the ability of the nervous system to restore, strengthen, or rearrange
neuronal connections after a stimulus or brain injury
Synapse – n: a region where nerve impulses are transmitted and received. This encompasses the
axon terminal of a neuron that releases neurotransmitters in response to an impulse along with
the gap where neurotransmitters travel, the adjacent membrane of an axon, and the dendrite.
Vestige – n: a degenerate or imperfectly developed organ or structure that has little or no utility.
However, this organ was used in preceding evolutionary forms of the organism for useful
functions.
Sociobiology – n: the study of social behavior in animals with emphasis on the role of behavior
in survival and reproduction.
Epigenetics – n: the study of heritable changes that occur without a change in the DNA
sequence.
Mutation – n: the sudden departure from the parent type in one or more heritable characteristics,
caused by a change in a gene or chromosome.
Genetics – n: the science of heredity, dealing with resemblances and differences of related
organisms resulting from the interaction of their genes and the environment.
Melody Spencer
Melody is a 17-year-old student at the Mass
Academy of Math and Science. She lives in
West Brookfield, MA with her parents and
younger brother. With a passion for both
computer science and biology, she hopes to
find a career that combines the two, such as
bioinformatics. Aside from academics, she
enjoys long-distance running and art. She also
works as a page at her local library.
Gregory Konar
Gregory is a 17-year-old student at Mass
Academy. He lives in Marlborough, MA
with his parents and sister. He is a 2-time
International Science Fair participant in
the category of Medicine and Health
Sciences. He is extremely passionate
about cancer biology, and he hopes to find
a career in cancer biological research.
Outside of school, he enjoys hiking,
hurdling, and playing music. He will be
volunteering at UMASS Cancer Biology
labs this summer. He also umpires in
Metrowest for girls’ softball.
Cover :
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http://www.learner.org/courses/biology/images/archive/fullsize/1678_fs.jpg
http://creatia2013.wordpress.com/2013/03/12/dna-is-like-a-computer-program-but-far-farmore-advanced-than-any-software-weve-ever-created-bill-gates/
http://physicsandcake.files.wordpress.com/2010/02/neurons.jpg
http://yellowscene.com/wp-content/uploads/2009/02/caveart1.jpg
Human Evolution
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http://sciencebasedlife.wordpress.com/2010/12/18/ten-consequences-of-human-evolution/
http://en.wikipedia.org/wiki/Homo_floresiensis
http://room42.wikispaces.com/Savanna+Geography http://camprrm.com/2009/09/doublelake-campground/
Genetics
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http://www.chrismadden.co.uk/cartoon-gallery/genetics-cartoon-the-printer-in-a-geneticslaboratory-printing-out-with-the-paper-forming-a-double-helix-spiral/
http://ghr.nlm.nih.gov/handbook/basics/dna
Mutation
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http://www.cartoonstock.com/directory/g/genetic_mutation.asp
http://www.pbs.org/wgbh/nova/body/epigenetics.html
Natural Selection
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http://www.techapps.net/interactives/pepperMoths.swf
Darwin and Lamarck
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http://davidguilbault.typepad.com/such_is_life_by_david_gui/2009/02/darwins-finches.html
http://galapagosonline.wordpress.com/2011/09/15/charles-darwin-in-galapagos/
http://morriscourse.com/myths_of_evolution/myths_of_evolution.htm
http://www.learner.org/courses/biology/images/archive/fullsize/1678_fs.jpg
Taxonomy
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http://biologicalexceptions.blogspot.com/2012/08/lions-and-tigers-and-ligers-oh-my.html
Punnett Squares
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http://www.bio200.buffalo.edu/labs/heritability.html
http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cross/03t.html
Evolution of Diet
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http://www.webmd.com/digestive-disorders/picture-of-the-appendix
http://www.ironlady2015.com/the-athletes-kitchen/
Evolution and Disease
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http://www.petridish.org/projects/developing-a-treatment-for-sickle-cell-anemia
http://www.umaa.org/
http://textbookofbacteriology.net/tuberculosis.html
Immigration
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http://www.fcps.edu/islandcreekes/ecology/carpenter_ant.htm
http://www.atlanticpestsolutions.net/wp-content/uploads/2011/10/carpenter-ant-damage1.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/f/f5/Howlsnow.jpg/220pxHowlsnow.jpg
Emigration
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http://www.gnutext.com/Anth_Phys/Anth_Phys_2/Evolution.html
http://click4biology.info/c4b/5/images/5.3/Pop-size.gif
Paleoanthropology
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http://www.arthursclipart.org/southafrica/people%20and%20places/early%20man.gif
http://en.wikipedia.org/wiki/Lucy_(Australopithecus)
http://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Ethiopia_in_Africa_(mini_map_-rivers).svg/1084px-Ethiopia_in_Africa_(-mini_map_-rivers).svg.png
Brain
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http://www.brainline.org/content/2009/02/ask-expert-what-neuroplasticity.html
http://www.theamericanbookofthedead.com/2010/09/08/mind-evolution/
Behavior
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http://webspace.ship.edu/cgboer/sociobiology.html
http://en.wikipedia.org/wiki/File:Ethology_diversity.jpg
Genome
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http://www.life.illinois.edu/ib/494/genome.html