Cognitive Psychology

The discipline of psychology evolved from the philosophical idea of dualism that maintained the mind and body operated independently of one another to create the human experience (Kowalski, 2011).  Psychology is the study of the mind and behavior through the study of brain functions, physical behaviors, and the environment (Kowalski, 2011). The relentless pursuit of psychologists trying to figure out how and why the mind functions as it does caused the development of cognitive psychology (Galotti, 2014).

Define Cognitive Psychology

Cognitive psychology is the study of higher mental processes concerning how individuals receive, process, and use information (Galotti, 2014). How memory works, the process of thought, and the process of perception are the key ideas of cognitive psychology (Galotti, 2014).  The development of cognitive psychology originated from the thoughts of functionalism and behaviorism in addition to the study of individual differences and the development of cognitive science.


William James founded functionalism originated research on why the mind functions.  He believed that a behavior was a portrayal of the functioning of the mind (Galotti, 2014).  Other functionalists believed that the mind allowed for adaptive behaviors and that habits change through avoidance of triggering stimuli (Galotti, 2014).  The major belief of functionalism was that in order for the study of behavior to be successful, one must study the behavior in the natural state of the environment (Galotti, 2014).Observation allows for the viewing of behavior without interference.  Although the study of functionalism relied solely on observation of the outward behavior, it implied that there was a function to behavior and researchers used this idea to delve into the internal study of behavior through the functions of the brain (Galotti).


Behaviorist’s primary focus is observable behavior than can be justly and scientifically measured without internal events being considered (McLeod, 2007).  John Watson, the founder of behaviorism, believed that individuals learn behavior from environment and behavior is not innate  (McLeod, 2007).. Edward Tolman took a different view on behaviorism with his rat and maze tests.  Tolman believed that the mind had to contain a mental map developed through cognition in order for a rat to memorize the track of the maze to obtain a goal of food (Galotti, 2014).

Freud’s psychodynamic approach criticized behaviorism because the unconscious mind and instincts receive no consideration, rather rejected forcing behavior to be seen solely as an observable study (McLeod, 2007).Biological psychologists criticisms include the absence of genetics being responsible for a behavior in addition to the environment (McLeod, 2007).Cognitive psychologists claim memory, thinking and process all relate to behavior as well (McLeod, 2007).

Study of Individual Differences

Sir Francis Galton took an individual approach to the study of the differences between individual cognitive ability (Galotti, 2014).  Galton was fascinated with the fact that intelligence varied among individuals.  He questioned the assistance of genetics in attaining certain levels of intelligence.  He set out to find the answer he was looking for through developing a series of tests for cognitive ability (Galotti, 2014).  Galton’s efforts assisted future psychologists to develop more cognitive tests, set up statistical analysis to calculate results, and leave a question to ponder:  What is the nature of cognitive abilities?

Cognitive Science

The cognitive revolution found its beginnings with the rejection of behaviorism based on the premise that theorists believed that a behavior could not occur without some mental representation (Galotti, 2014).  The establishment of human factors engineering in which physical and psychological characteristics are taken into account when designing a system for human use marked the beginning (Galotti, 2014).   Human factors engineering caused the development of person-machine systems in which cognitive ability and motivation combine into the equation labeling individuals as limited-capacity processors meaning an individual has limited cognitive ability (Galotti, 2014).

During this time, Noam Chomsky was studying language and realized how an individual attains, comprehends, and produces speech is vital to the understanding of language (Galotti, 2014).  He left the thought to future psychologists:   How is it possible for an individual to learn a large complicating language so easily, quickly, and with perfection?  Between the rules of language and the amount of information, it seemed difficult for such a limited capacity (Galotti, 2014).

During the revolution, localization of function was brought to light declaring that functions were localized to a certain area of the brain.  Research proved this theory to have some truth to it.  Donald Hebb found that some functions were built in a localized area over a period of time, which was later found through testing with kittens that there are some functions that only occur in certain areas of the brain such as visual content (Galotti, 2014).


The development of computers and artificial intelligence is the last leg of the development of cognitive science.  Computers caused the thought that the mind operates like a computer:  It must be fed information (Galotti, 2014).  Researchers began to compare the functions of the mind to the functions of a computerized machine.  A storage center is necessary in order for information to be retained and recalled.  A processing center must be available to change and make inferences based off previously attained information (Galotti, 2014).  Artificial intelligence is being designed based off the kinds of information humans can retain and how they process the information turning a human mind into a machine (Galotti, 2014).  All of this information led scientists to look at the representations of information, known as cognitive science.

Behavioral Observation

Behavioral observation is important in cognitive psychology because it allows researchers to see cognition occur naturally, not forced within the confines of a lab (Galotti, 2014).  Observation allows for testing of theories and hypotheses researchers develop.  Since observing internal mental processes is not possible, an inference can be made about a behavior based on the observation of the behavior.  Additionally, two aspects of behavior can be seen with one eye potentially to find a relationship between the two which allows for inference at the possibility of a change in one of the aspects (Galotti, 2014).  It is also vital to use observation in order to have a comparison for the unseen processes of behavior in order to establish any relationship between the conscious and unconscious aspect of the research (Galotti, 2014).


Cognitive psychology is a fairly new branch that has developed as psychology continues to evolve.  It has taken views from all aspects of psychology and included them to determine what and how does the brain make things happen.  Cognitive psychology opens a door of answers to questions that have been probing researchers for many years.




Galotti, K. M. (2014). Cognitive Psychology: In and Out of the Laboratory, (5th ed.). Retrieved from The University of Phoenix eBook Collection database

McLeod, S. A. (2007). Behaviorist Approach. Retrieved from http://www.simplypsychology.org/behaviorism.html

Kowalski, R., & Westen, D. (2011). Psychology (6th ed.). Hoboken, NJ: Wiley.



Phineas Gage

Cognition refers to the mental processes associated with knowledge, including memory, thinking, and reasoning (Galotti, 2014).  Researchers have spent many years trying to figure out the different levels of explanation for cognitive functioning in the brain, which has proven to be intricate and tedious to define the level of functioning for individual neurons (Galotti, 2014  ).  Researchers believe it is vital to understand the roles of the different areas of the brain in order to understand the role of the brain in cognition.  The accident experienced by Phineas Gage revealed new information about how areas of the brain affect cognitive functioning.

Role of Brain in Cognitive Functioning

Different areas of the brain are responsible for different functions giving reason to know the anatomy of the brain.  The hindbrain is the lowest portion of the brain, located at the rear of the skull and includes the pons, medulla, and the cerebellum (Galotti, 2014  ).  These structures are responsible for the relay of information, life support functions, and coordinating muscular activity (Galotti, 2014  ).  The midbrain, the arousal area,  is found in the central area of the brain and is responsible for the transmission of information within the brain itself (Galotti, 2014 ).

The forebrain, the area most widely studied for cognitive functioning, is the largest area of the brain located at the front of the skull (Galotti, 2014  ).  This area contains the thalamus, responsible for relaying information to the cerebral cortex, and the hypothalamus is responsible for hormone release and maintaining homeostasis within the body.  Also included is the hippocampus, responsible for long-term memory and the amygdala, responsible for the emotional strength of memories (Galotti, 2014  ).  Additionally, this area contains the cerebral cortex responsible for transmitting information throughout the cortex (Galotti, 2014  ).

The cerebral cortex contains a division of four lobes.  The parietal lobe includes the somatosensory cortex responsible for processing sensory information, such as touch and temperature from the body (Galotti, 2014 ).  The occipital lobe is the visual processing area (Galotti, 2014 ).  The temporal lobe aids in processing memory (Galotti, 2014 ).  The frontal lobe contains three sections:  the premotor cortex plans the fine motor movements carried out by the motor cortex.  The third section, the prefrontal cortex is responsible for executive functioning that manages cognitive process in the brain.  These processes include inhibiting undesired behavior and maintain personality (Galotti, 2014  ).

Phineas Gage

Phineas Gage was a railroad construction foreman in Vermont who had suffered an accident that should have left him dead (Grieve, 2010).  A tamping iron about three feet seven inches long, one and a quarter inches in diameter, and weighing about thirteen pounds launched through Gages skull landing about eighty-two feet away from the accident (grieve, 2010).  The accident resulted in an orbitofrontal lobotomy, with no surgical procedure which destroyed his left frontal lobe and left him without a left eye and as a new man in general (McMillan, 2010).

Prior to the accident, Gage was held in high regard as a shrewd, businessman and foreman, with an even temper, quiet, reserved, and energetic (Grieve, 2010).  Post-accident, Gage was socially inept, giving way to conflicts, unfocused on goals, and had a new tendency to use obscene language (Macmillan, 2010).  Phineas Gage became a new man.  Phineas was soon well enough to return to work on the railroad, however, was denied employment because he no longer portrayed a solid, knowledgeable and patient foreman (McMillan, 2010).  Eventually, Gage became a coach driver in Chile, that demonstrates that he was still able to learn a new trade, and he had demonstrated an improvement in his social skills (McMillan, 2010).

This traumatic brain injury suffered by Phineas Gage sparked new theories and research on traumatic brain injuries as well as the control the brain has over a behavior.  Researchers were curious to find out exactly what areas of the brain impact what aspects of life.  Gage survived for twelve years after the accident, but developed severe epilepsy which eventually brought him home to his mother (Grieve, 2010).  He lived with his mother for a brief period, until epilepsy, developed from his injury, took his life in San Fransisco in 1860 (Grieve, 2010).

Brain Support of Cognition

The case of Phineas Gage led to the idea of localization, or the thought that different areas of the brain controlled different functions of the brain (  ).  The tamping iron tore through only the frontal lobes of the brain.  The fact that Gage was able to remain in a “normal,” conscious stature after the accident implied that motor  and muscular functioning, as well as life support functions, were unaffected by the accident.  The fact that there are records of severe behavior and personality changes post-accident led researchers to make the assumptions of localization ( ).

The idea of localization and the idea behavior and personality were functions controlled in the frontal lobes, led to the belief that lobectomies could potentially be a benefit to those suffering from behavior or mental disorders, known as psychosurgery (“The University of Akron,” 2014). Researchers later found that lobectomies were erroneous and caused greater damage than good and that the reenactment of Gage’s injury never proved possible with recovery evident in the future.  What researchers did learn was that the frontal lobes are responsible for higher executive function in areas such as learning, personality, memory, and comprehension of actions (“The University of Akron,” 2014).


The manner in which the brain functions have proven to be difficult in learning.  Through the use of a terrible accident that rightfully should have rendered a man dead, researchers have been able to begin a more in-depth understanding of behavior and how it results from mental processes localized to certain areas of the brain. The case of Phineas Gage opened doors to theories and experiments which have made great strides to conclude that the brain fully supports cognitive functioning localized to a specific area.  Researchers now know which areas to probe and manipulate in the diagnosis and treatment of mental illness and brain injury.



Galotti, K. M. (2014). Cognitive Psychology: In and Out of the Laboratory, (5th ed.). Retrieved from The University of Phoenix eBook Collection database..

Grieve, A. W. (2010). Phineas P gage – ‘the man with the iron bar’. Trauma, 12(3), 171-174. doi:http://dx.doi.org/10.1177/1460408610375648

McMillan, M., & Lena, M.  L., (2010).  Rehabilitating Phineas Gage.  Neuropsychological Rehabilitation.  20(5), 641-658. doi:  10.1080/09602011003760527

The University of Akron. (2014). Retrieved from https://www.uakron.edu/gage/lobotomy.dot



Theory of Acquired Needs

David McClelland developed the theory of acquired-needs (Acquired Needs Theory (2001-2013)).  McClelland idealized that an individual develops personal individualistic needs through life experiences (Acquired, 2001).  Needs that are developed through experience are acquired through the learning process (Tallis, 2009).

According to this theory, an individual falls into one of three categories : Achievement, affiliation, or power (Acquired Needs Theory (2001-2013)).  Those in the achievement category strive to excel by avoiding low risk accomplishments as they are too easily obtained decreasing satisfaction in the individual (Acquired, 2001).  Achievers also avoid high risk accomplishments because obtaining these accomplishments is a matter of chance (Acquired, 2001).

An individual who falls in the affiliation category desires feelings of acceptance and peace inn a group by conforming to the normalities within the group (Acquired, 2001).

Those who fall under the power category are considered goal seekers either personally or institutionally (Acquired Needs Theory (2001-2013)).  Those seeking personal power feel the need to control others which is viewed as a negative desire (Acquired, 2001).  Those seeking institutional power, or social power,  desire to assist others in reaching their personal goals (Acquired, 2001).

Establishing which needs category an individual falls in, McClelland and his colleagues developed the Thematic Apperception Test (Acquired Needs Theory (2001-2013)).  The TAT is a visual response test in which the individual is given a card with a black and white photo on it (Acquired, 2001).  The individual is asked to form a story about the picture on the card (Acquired, 2001).  Based on the individual responses, a rating is given in regards to their needs which are demonstrated through the stories they told (Acquired, 2001).  Additionally, this test is used to establish other types of needs such as emotional, cognitive, and economical (Donovan, 2009).




Incentive Sensitization Theory

Incentive sensitization theory, proposed by Terry Robinson and Kent Berridge in 1993 (Robinson and Berridge, 1993), states that drug craving and desire results from an incentive, but not from pleasure (Deckers, 2010).  Through repetition of drug use, the brain of an addict becomes sensitized to drug stimuli (Deckers, 2010) causing an increase of the probability of repeating use  as well as the seeking and taking behaviors associated with addiction (Robinson, 1993), but not the hedonic value of drugs (Deckers, 2010).  The theory is a model of neuroadaptation in which the nervous system adapts behaviorally and neurochemically (Deckers, 2010).


There are six criteria that must be met inorder for addiction to fall under Incentive sensitization theory.


  1. There must be a common neural system affected by many addictive drugs in which dopamine transmitters are enhanced and engaged (Robinson, 1993).
  2. The nervous system should become hypersensitive, by gradually developing psychological addictive behaviors (Robinson, 1993).
  3. Neuroadaptation caused by the use of drugs last a long period time after use of drugs had stopped (Robinson, 1993)
  4. Neuroadapatations should be susceptible to environmental control allowing addict to be susceptible to relapse of addiction (Robinson, 1993).
  5. Pathological craving should warrant incentive motivational effects of drugs and their stimuli while the neuroadaptations should increase the motivational effects (Robinson, 1993).
  6. An addict should experience the persistence of addictive behavior despite the negative outcomes, but should not enjoy the hedonic effect, but only the incentive effect (Robinson, 1993).







Deckers, L. (2010). Motivation: Biological, psychological, and environmental (3rd ed.). Boston, MA: Allyn & Bacon

Robinson, T. E., & Berridge, K. C. (1993, April). The neural basis of drug craving: an incentive-sensitisation theory of addiction. Brain Research Reviews, 1993(18), 247-291. Retrieved from http://deepblue.lib.umich.edu/bitstream/handle/2027.42/30601/0000238.pdf?sequence=1


Image 1 retrieved from:  http://blogs.plos.org/mindthebrain/files/2012/12/pill-bottle.jpeg

Image 2 retrieved from:  http://focus.psychiatryonline.org/data/Journals/FOCUS/4266/foc0011123340001.jpeg



Motivation and the Brain

A person’s drive to succeed in life surfaces from motivation.  The ability to understand what motivation is and where it derives from means understanding the behaviors that encompass a motivation.  Motivation begins with developing a drive to become successful in any aspect of life.    Motivation derives from internal and external incentives obtained while establishing and working to achieve a certain goal.   Understanding the concept of motivation and its effects on individual behavior, is imperative to define the links between motivation and behavior.


              Psychologists seek to learn the reasons an individual acts in a certain manner by studying motivation (Tauer, 2005).  A motive is the triggering force of action and lays dormant within an individual until the individual establishes a true desire(Deckers, 2010).  Motives are the pushing and pulling forces that lead a person to think, perceive, and display certain behaviors as an effort to obtain personal satisfaction (Hunter, 2012).  Obtaining personal satisfaction means obtaining personal desires and needs, which vary from person to person, allowing for individual motives to vary greatly as well (Hunter, 2012).  Motivation consists of internal and external factors that keep an individual interested and committed to obtaining a goal (Deckers, 2010).  Motivation begins with the development of goal and ends with feelings of accomplishments obtained through the use of ideas, energy, determination, and action, (Deckers, 2010).

Originally, Greek philosophers based explanations of motivation on hedonistic ideas, but overtime evolved into a new philosophical idea that an individual gained the motivation to obtain a goal because of his or her desire to gain a certain incentive (Deckers, 2010).  The idea was brought about by philosopher Arthur Schopenhauer who also claimed that it was not possible for an individual to develop the motivation internally without a positive incentive as a return (Deckers, 2010).  Psychologists also adopted the idea that an incentive was necessary for motivation to occur.

Psychologist Henry Murray also believed that an incentive is necessary for the process of motivation, but his thoughts elaborated to include that an individual’s needs vary just as the levels of dominance and intimacy vary (Hunter, 2012).  Psychologists Atkinson and McClellan also agreed that motivation comes from the receipt of a positive incentive (Deckers, 2010).  These psychologists define a motive as an individual’s internal drive to gain a positive incentive by avoiding negativity that proves the main goal of motivation is to obtain an incentive (Deckers, 2010).  Desired incentives may arise from an array of factors such as intrinsic or extrinsic factors.

Intrinsic Motivation

            Intrinsic motivation includes the internal sources that drive an individual to behave in a certain manner (Tauer, 2005).  These drives vary from individual to individual as well as personality (Tauer, 2005).  An individual motivated internally does not behave in a certain manner in order to receive a material incentive, but rather for the internal incentive that varies among individuals (Deckers, 2010).  Through the use of the five-factor model of personality, psychologists are able to decipher an individual’s unique personality makeup and find the correlation of the individual’s personality and environment to predict an individual’s motivations (Tauer, 2005).  Since genetic factors aid in the development of personality, and personality aids in motivation, it is possible that an individual inherit certain desires and motivations to obtain those desires (Tauer, 2005).  An individual may have been predisposed to addiction which may lead to alcoholism in life (Tauer, 2005).    Internal motivation includes the personal feelings associated with obtaining a set goal on a personal level that allows an individual to feel self-sufficient and confident within themselves driving them toward success (Deckers, 2010).

Extrinsic Motivation

            External motivation refers to the environmental factors that lead an individual to act in a certain manner (Deckers, 2010).   Environmental changes reflect motivational change in an individual (Tauer, 2005).  An individual who is motivated by extrinsic factors behave in a certain way in order to obtain some material incentive (Tauer, 2005).  A Student works hard to obtain good grades in order to receive recognition into college or an individual who works to receive a paycheck are both examples of extrinsic motivation (Tauer, 2005).  Individuals do not behave in certain ways because they passion they have for the effect of the behavior, but to receive incentives such as praise, recognition, or materialistic items such as money (Tauer, 2005).  Motivation is the root of behavior portrayed by an individual (Deckers, 2010).  Motivation develops from the notion that an incentive, positive or negative, is rewarded after obtaining a goal (Deckers, 2010).  The incentive may be personal, social, or materialistic (Deckers, 2010).

Motivation and Behavior

Intrinsic and extrinsic motivation both rely on the operant conditioning theory of B. F. Skinner which claims that behavior arises from motivation through incentives that vary among individuals as the needs of individuals vary (Ryan, 2000).   The theory of learning implies intrinsic motivation derives from internal motives seeking the gain of cognitive knowledge, physical and social development that produce psychological satisfaction (Ryan, 2000).  Additionally, extrinsic motivation derives from an internal desire of psychological satisfaction triggered from the acceptance of an outside incentive (Ryan, 2000).

            Human behavior is a highly complex process that involves the correlation of both intrinsic and extrinsic motivational factors (Tauer, 2005).  In order for a behavior to occur, there must be an internal drive to begin the process (Deckers, 2010).  The internal drive is the initial idea established to begin a behavior (Deckers, 2010) or modification of behavior as in the operant conditioning and learning theories (Ryan, 2000).  The intrinsic motivation causes the behavior to begin; however, it combines with extrinsic motivation in order for success to occur (Deckers, 2010).  A student has a desire to go to college is intrinsic motivation.  In order for the student to obtain the goal, he or she must work towards good grades.  Maintaining good grades also requires motivation which is achieved through external praise and other forms of incentives such as social recognition (Deckers, 2010). Achieving the necessary grades creates personal satisfaction, determination, and a sense of contentment takes place increasing the students drive to continue the behavior (Tauer, 2005).  As motivation continues, the behavior continues until success is achieved, however if the incentives decrease, motivation decreases and achieving success may not occur (Tauer, 2005).


Motivation causes an individual to display a certain behavior in an effort to obtain a desired incentive defined as a goal (Deckers, 2010).  Philosophers and psychologists have come to a mutual acceptance that behavior derives from motivation through an internal or external motivation that seeks to establish psychological satisfaction (Hunter, 2012).  Motivation occurs in several forms from personal emotional satiety to social and physical satiety (Deckers, 2010).  Both intrinsic and extrinsic motivators are necessary to keep a solid flow of motivation within a person who desires to obtain a certain goal (Tauer, 2005).




Deckers, L. (2010). Motivation: Biological, psychological, and environmental (3rd ed.). Boston, MA: Allyn & Bacon


Hunter, M. (2012). HOW MOTIVATION REALLY WORKS: TOWARDS AN EMOTO-MOTIVATION PARADIGM. Economics, Management and Financial Markets, 7(4), 138-196. Retrieved from http://search.proquest.com/docview/1326326749?accountid=458


Ryan, R. M., & Deci, E. L. (2000, January). Intrinsic and Extrinsic Motivations: Classic Definitions and New Directions. Contemporary Educational Psychology, 25(1), 54-67. Retrieved from http://Intrinsic and Extrinsic Motivations: Classic Definitions and New Directions


Tauer, J.  (2005).  Motivation.  In N.  Salkind (Ed.).  Encyclopedia of human development.  (pp. 858-861).  Thousand Oaks, Ca.:  SAGE Publications, Inc.  doi:  http://dx.doi.org.ezproxy.apollolibrary.com/10.4135/9781412952484.n420


Energy vs Motivation

What is the link between mental energy and motivation?  Why is it important to understand this link in regards to the model of mental energy?

Mental energy is the psychological force that causes a person to act in a certain manner.  Motivation is the drive that a person has which causes them to act in a certain manner.  Motivation is the cause of mental energy.  If a person demonstrates the drive to accomplish a goal, the mental energy necessary to follow through also develops.  The model of mental energy is a three-dimensional idea that includes motivation as the driver of mental energy, cognition as the information processor, and mood as the lack or increase of drive.  The model is based on four different theories.  In regards to the model, motivation is vital in all theories.  Content theories define the actual sources of human motivation.  Processed based theories define what forces may induce human motivation.  Decision-making theories define the ways in which humans adopt their intentions.  Sustained-effort theories define the amount of effort exerted to meet their intentions.  Understanding motivation in these four aspects gives an understanding of the amount of energy a person maintains when trying to obtain a goal as well as, coming up with ways to maintain that level of energy throughout the task.


Theory of Evolution

The theory of evolution, developed by Charles Darwin, has been a controversial issue for hundreds of years (John Donovan, 2009).  In the absence of evolution, modern medicine and public health developments would not be possible because the world would have a ton of facts with no connections between them leaving the world vastly diverse and randomly disconnected (Donovan, 2009).

The theory of evolution is based on the premise that all forms of life are related through the sharing of a common ancestry (Donovan, 2009).  Claim is made that apes and human share a common ancestry because of the similarities in the skeletal make-up of the two (Donovan, 2009).  Additionally, claim is made that a  chimpanzee also shares ancestry with apes and 96-98% of human genes are similar to a chimpanzees genes (Donovan, 2009).  This leads evolutionists to believe that humans, chimpanzees and apes all share ancestry with other large primates in history (Donovan, 2009).

Charales Darwqin used the idea of homology to explain the close relations between species (Donovan, 2009).  He explained that the more anatomical and genetic similarities between species meant that the species were more closely related than others (Donovan, 2009).  For instance, a human and ape have definite similarities in skeletal structure giving them a related ancestry (Donovan, 2009).  Moreover, there is also a definite distinction in the facial expressions and ability of faqcial movement linking them even closer in ancestry (Donovan, 2009).

The theory of evolution by natural selection is the idea that evolution resembles branching  in that behavior is a replication of genomes that will survive in a certain environment or will survive long enough to replicate genetic material (Bridgeford, 2009).  Throughout the process of replication, genes evolve  or adapt to be able to survive and environment (Bridgeford, 2009).  Darwin basis his theory off four ideologies:

  1. Each generation of individuals are produced in increasing numbers that can survive an evolving environment (Donovan, 2009).
  2. Variations in genetics exist among species which are heritable to compensate for evolving environments (Donovan, 2009).
  3. Indivuals with heritable traits that have genetically evolved are better adapted to survive in a new environment (Bridgeford, 2009)
  4. When a species can no longer breed successfully with the same species, a new species has evolved within the same ancestr (Bridgeford, 2009).

Evolution provides deep explanation on how so many species exist and why there are these variations in individuals, as a matter of fact, it is found that 98% of human genes are actually bacterias that assist in human survival in environments (Donovan, 2009).



Bridgford, N. (2009). Darwin’s theory of evolution. Young Scientists Journal, 2(7), 48-50. Retrieved from http://search.proquest.com/docview/870490482?accountid=458

John Donovan For, T. R. (2009, Feb 08). THE EVOLUTION OF DARWIN’S THEORY. The Register – Guard Retrieved from http://search.proquest.com/docview/377829581?accountid=458