Download Zajler: Nature vs

Zajler: Nature vs. Nurture
1
REVIEW OF LITERATURE
Introduction
The use of genetics is a growing and useful area of science. The discovery of the human
Gnome along with new discoveries in evolutionary science has brought us closer to
answering the basic questions of exsistence.
Discussion
Fish
Fish are cold-blooded, mostly marine vertebrates (Bailey, 2001). There are more
than twenty-four thousand known species of fish, more than any other group of vertebrate
species (Resnick, 2002). Fish range in many sizes, as do their habitats (Chinery, 2002).
Anatomy of most fishes is composed of scales covering the body, fins, a head, an
abdomen, a tail, gills, and viscera (Johnson, 2003).
Types of Fish
Wag guppies (Poecilia reticulata). Wag guppies (Poecilia reticulate) are part of
the freshwater-fish (Poecilidae) family (Lerman, 2004). Wild guppies are found along the
Gulf of Mexico and the coasts of Eastern Mexico, Central America and South America
(Smith, 2000). Both genders display yellow, red, black, navy blue, brown and black
coloration; the males display a brighter coloration than the females, although the natural
colors are not as bright as those displayed by guppies sold on domestic and international
markets. The brighter colors are the results of selective breeding (Taylor, 2005).
Although Wag guppies are a freshwater fish, they are able to tolerate an amazing amount
of salinity (Anderson, 2000). Wag guppies are omnivorous, feeding on plant material to
Zajler: Nature vs. Nurture
2
small bugs and decaying organic matter (Friswold, 2000). The males range in size from
two to three centimeters and display brilliantly colored scales. The females are larger,
ranging from three to five centimeters, and are somewhat mono-colored. These
differences allow for easy identification of a mate (Bobick, 2003).
All guppies share the same anatomy, both externally and internally. They all have
the same body structure that consists of a head, abdomen, and tail. The head contains
important senses operated by the brain, such as sight and smell (Chinery, 2002). Guppies,
as well as all fish, have the ability of perception and sensibility of their habitats through
their eyes and nasal septum, otherwise known as nostrils (Ellis, 2001). The body contains
the majority of viscera, as well as the lateral line, which provides stability and sensitivity
to the immediate surroundings (Friswold, 2000). All guppies are covered in an epidermis,
the outermost skin layer that excretes a slime coating for biological protection, and
scales, which protect the guppy from harmful agents in the habitat (Resnick, 2002). All
guppies have the same fins. The caudal fin, which is the tail, provides thrust for
swimming. The fin is divided into the upper and lower lobes, respectively, by the fork of
the tail. The anal fins, located on the underside nearest the caudal fins, provide stability.
The pectoral and pelvic fins, also located on the underside but nearest the gills, assist in
direction, swimming backwards, and speed control (Smith, 2000).
All guppies possess similar organs. The brain controls every function of the body
and has various messages delivered to specific regions of the body via the spinal cord
(Johnson, 2003). The esophagus ingests and directs nourishment to the stomach, where it
is digested. The pyloric ceca, small intestine, colon, pancreas, liver and kidneys aid in
further digestion and excretion of wastes and toxins (Friswold, 2000). The two-
Zajler: Nature vs. Nurture
3
chambered heart pumps blood throughout the closed-circulation system that all fish
possess (Chinery, 2002). The swim bladder controls buoyancy and aids in hearing
(Bailey, 2001). All guppies have complex senses and systems. Guppies possess bones
leading from the swim bladder that amplify and lead vibrations from the water to nerves
within the inner ear where they are heard (Chinery, 2002). Guppies possess muscles in
the cornea and iris that focus the eye, refract the image, and then pull on the lens. The
amount of work done by these muscles depends on the distance the object is from the
eye; darkness also affects how these muscles contract the lens (Bailey, 2001). Guppies
also possess muscles in the nasal septum that contract water inside to receptor cells that
respond to certain substances in the water, generating nerve impulses translated as
smelling (Bobick, 2003). Guppies have taste buds in the oral cavity and the lateral line
that respond to food in the water (Smith, 2000).
Guppies are livebearers, meaning they birth live young (Campbell, 2006). The
reproductive process is sexual, with the male releasing sperm into the water after
courtship and the female absorbing via the gravid spot, a special pore located near the
anus. Female guppies possess the ability to store sperm from a variety of males that can
be used over a prolonged period of time. Gestation ranges from three weeks to a month.
The female births thirty to seventy offspring, with the mother ingesting the weaker
offspring to survive the birthing process. After a few hours, the female is able to be
inseminated again (Davis, 2003).
Grass Pickerel (Esox americanus vermiculatus).Grass pickerel are subspecies of
the freshwater pike family (Fisher, 2002). This variety of pike is commonly referred to
“Peaceful Pike” because of their docile nature
Zajler: Nature vs. Nurture
4
that is so unusual among species of pike. These organisms are among the natural
predators of Wag guppies (Bobick, 2003). Grass pickerel are found along the Eastern and
Southern American Coasts, the Gulf of Mexico, and the Eastern Mexican coast (Chinery,
2002). Grass pickerel are the smallest species of pike, with both genders ranging from ten
to sixteen centimeters (Smith, 2000). Male grass pickerel are distinguished from females
by possessing a metallic green coloration around the body and amber or pale fins. Black,
wandering bars surround the body and the eyes (Bailey, 2001). These organisms are
highly carnivorous, feeding on worms, small invertebrates and fish, crustaceans and
various insects (Chinery, 2002).
All pike share the same external and internal anatomy that contains similar
appendages and structures to those of guppies (Bailey, 2001). The head contains the brain
that regulates important bodily functions as well as important systems, such as sight and
smell; the body contains the viscera needed for digesting food, control of movement, and
excretion of wastes (Smith, 2000). The fins are located in similar places and provide the
same functions as those of guppies (Resnick, 2003).
Pike, however, are egg-layers, although the reproductive process is similar to that
compared to guppies (Fisher, 2002). Females are inseminated by males during the
spawning season usually occurring during spring and the sperm is received by the gravid
spot. Gestation requires at most a week, at which time two thousand to a hundred
thousand eggs are laid and hatched within three weeks (Haas, 2001).
DNA and Genetics
Genetics is the study of heredity among organisms (Campbell, 2005). The basic
units of heredity are deoxyribonucleic molecules, or “DNA” molecules (Campbell,
Zajler: Nature vs. Nurture
5
2004). The molecules contain one of four nitrogenous nucleotides, those being adenine,
guanine, cytosine, and thymine, a phosphate group, and deoxyribose in the form of sugar
(Campbell, 2006). In the nucleus of a cell, DNA molecules are found in a double helix
structure because every DNA molecule binds with its complementary nucleotide located
on the opposite side of the double helix (Hamilton, 2002). DNA molecules store and
transmit genetic information that instructs cells which proteins to produce. These proteins
code for vital functions necessary for life and various behaviors, including mating and
predation (Levine, 2006).
Color and Color Mechanics
Colors are the visible properties derived from the spectrum of light that
corresponds to the spectral sensitivities of the eye (Bobick, 2003). Color categories,
which are the names of the colors, are associated with the materials and physics of the
object, and light absorption and refraction, and how they stimulate the receptors in the
brain (Campbell, 2005). The well-known colors, which are the colors associated with the
rainbow, are those easily processed by the eye because they can be produced with only
one wavelength; on the spectrum of light, these colors measure from four hundred to
seven hundred nanometers (Towle, 2000). The color of any object is influenced by its
physics in its immediate environment and how it is perceived by the eye and the brain.
Other variables also affect color: the viewing angle, immediate surroundings and overall
lighting (Campbell, 2004). Color is transmitted into the brain by wavelengths of light not
being absorbed by the object (Campbell, 2005). In the eye are color-receptor cells that
reduce color to three basic colors: blue, yellow and red. These cells are stimulated to
present the brain the actual color of the object (Levine, 2006). When subjected to
Zajler: Nature vs. Nurture
6
deficient lighting, a structure known as the rod stimulates the cones focus color as either
black or white, which is why during periods of darkness silhouettes of objects can only be
identified (Kowalis, 2005). Once the color has been processed by the eye, the information
is sent by three opponent channels that lead to the ventral stream of the brain. This
portion of the brain processes color (Campbell, 2005). It can only process “pure” color
and not mixtures of colors, such as yellow-blue (Kowalis, 2005). Color mixtures are
psychological and are the result of biased interpreting the processed results from the
ventral system (Bobick, 2003).
Inheritance of Color
On the scales of fish lie special genes collectively known as chromatophores.
These types of genes are broken down into melanophores, xanthophores, and
leucophores. Xanthophores are the dominant forms of chromatophores and are
responsible for the display of dull coloration, such as brown and gray, among all species
of fish. Leucophores are less dominant and control a milky coloration present in red and
orange shades displayed in fish species. Melanophores are the least dominant
chromatophores, controlling all light colorations, such as yellow (Takeuchi, 2005).
Behavior and Ethology
Behavior is the actions an organism performs in response to its environment
(Robinson, 2004). In all animals, behavior is mainly genetic, as it is controlled by the
brain, the endocrine system, and the nervous system (Campbell, 2004). Ethology is the
overall study of animal behavior. This study concerns behavioral patterns such as mating,
emotions, learning, culture defense, and predation, and sexual conduct (Campbell, 2005).
It attempts to define these patterns within the scope of anatomy, evolutionary history, and
Zajler: Nature vs. Nurture
7
neurobiology (Ellis, 2001). Instinct is a popular term in this branch of zoology, as it
implies that all animal behavior is genetic, since the anatomy of certain organism is
suited for a certain type of action. That is, the genome of an organism such as a lion has
allowed for adaptations needed for the organism to successfully hunt, such as keen
eyesight, a powerful physique, claws, and strong mandibles (Adelmann, 2001). Behavior
in the abstract, however, is not limited to just patterns, it also concerns learning. Behavior
is the result of imprinting and mimicking the actions of other, similar organisms
(Campbell, 2006). Behavior is also the result of evolutionary activity, as certain actions
have been refined over generations to be the most beneficial to organisms (Balaban,
2005).
Ethology was established as a branch of science by the research conducted by
Aristotle in his observations of the natural world, Jean- Baptiste Lamarck in his work
Scala Naturae, and Charles Darwin in his work On The Origin Of Species (Campbell,
2005). Later research, specifically Konrad Lorenz and his work with Greylag Geese and
Nikolaas Timbergen and his work with digger wasps (Balaban, 2005).
Predation
Predation is an interaction where one organism, the predator, hunts and consumes another
organism, prey, for nourishment (Campbell, 2005). There are two forms of predation, the
aforementioned, and parasitism, where one organism invades the body of another and
feeds directly of it, eventually killing it (Levine, 2006). Regardless of form, predation is
important in ecology because it prevents any one species from becoming dominant and
upsetting the natural balance of a habitat (Bobick, 2003). This is because predators
occupy various trophic levels in a food chain, thus one species of predators may be
Zajler: Nature vs. Nurture
8
preyed on by others (Balaban, 2005). It is understood that predation occurs to obtain
nourishment. Recent research has shown that a predator will not hunt if hunger is not an
issue, since costs outweigh benefits regarding energy usage (Gahlin, 2002).
Related Studies
John Endler conducted the famous experiment regarding microevolution in
guppies. He set up two aquaria with a predator and various group sizes of Dalmatian
Guppies present (Gahlin, 2002). In one aquarium, the gravel was coarse and did not
match the markings on the guppies’ scales. The other aquarium had fine gravel that did
not match the markings as well (Kowalis, 2003). The Dalmatian guppies were allowed to
breed, and eventually fifteen generations of guppies were bred (Takeuchi, 2005). Endler
noticed that as the generation progressed, the markings on the scales eventually
resembled the markings of the gravel. As this phenomenon occurred, the predators’
chances of successfully hunting prey lessened because of the increased camouflage
natural selection provided the guppies (Wiley, 2002).
In a continuation of his experiment, Endler took half the guppy populations of
both aquaria and switched them, so that each aquarium had an equal amount of guppies
with sporadic and massive markings (Kowalis, 2003). He noticed that the guppies that
had coloration different than the coloration of the environment were more successful in
mating with the opposite gender (Takeuchi, 2005). Endler concluded that color plays an
important factor in camouflage and mate selection (Wiley, 2002).
In another famous experiment, Nikolaas Tinbergen experimented with fixedaction patterns in Stickleback fish (Campbell, 2005). Fixed-action patterns are triggered
by certain stimuli and once the action has initiated, it is executed until completion
Zajler: Nature vs. Nurture
9
(Campbell, 2006). He was inspired to conduct the experiment by observing that a red
truck had passed by an aquarium containing Sticklebacks and the fish had displayed
aggressive behavior (Campbell, 2005). In this experiment, Tinbergen set up two aquaria
that contained both male and female Stickleback fish (Wiley, 2002). When other species
of fish, both male and female, possessing a red belly were introduced to either aquaria,
aggressive behavior was displayed until the those species of fish were removed
(Campbell, 2005). Tinbergen hypothesized that the red belly triggered certain responses
from the male Sticklebacks that were likely displayed to ensure their right to the female
Sticklebacks (Kowalis, 2003). He also hypothesized the male sticklebacks determined
that those species of fish were rival male Sticklebacks (Gahlin, 2002). To test this
hypothesis, Tinbergen introduced various species of fish lacking red anywhere on the
body and observed that no aggressive behavior was displayed (Wiley, 2002). To further
validate his hypothesis, Tinbergen constructed a model that closely resembled a male
Stickleback, and various other models of various shapes and sizes with red bellies
(Campbell, 2005). When aggressive behavior was observed, Tinbergen concluded that
predation and other aggressive behavior was triggered by certain stimuli, and that these
actions, once initiated, are executed to completion (Wiley, 2002).
Conclusion
Researching genetics and fish evolution has helped me to understand the behavior
of the two types of fish in my experiment. I have learned ….