Download Chapter 3: Evolution, Heredity, and Behavior I. The Development of

Chapter 3: Evolution, Heredity, and Behavior
I. The Development of Evolutionary Science
A. This section deals with how the evolutionary theory came to be
B. The Voyage of the Beagle
1. Charles Darwin had very few scholarly interests in life. However after meeting Fitz Roy, a naval officer,
Darwin set sail on the HMS Beagle as an unpaid naturalist from 1831-1836
2. During his time on the Beagle, Darwin studied many different species. However, he did not develop his theory
for evolution for a while because he interpreted diversity to be consistent with essentialism which was the belief
that all living things belong to fixed classes which have unchanging characteristics with essential different
qualities
C. The Origin of Species
1. Upon returning to England in 1836, Darwin began to review his collection and compare similarities and
differences of the creatures he had found.
2. He was also very interested with the concept of artificial selection, the procedure that mates organisms to
produce offspring with specific characteristics
a. He hypothesized that if artificial selection could create a change in a population of organisms nature
must use a similar mechanism
3. It was another year and a half before Darwin finally came up with his theory of natural selection
4. He realized that over time, less favorable characteristics would tend to die out while more favorable ones
prevailed
5. Darwin waited for another 20 years or so to publish his work. During that time, he gathered evidence and
scientific data to prove his theory
6. Darwin published his theory in the book, The Origin of Species in 1859
7. Alfred Wallace was another scientist who came up with the theory and did not get it in time
D. Discovering the Mechanisms of Heredity
1. Darwin’s theory effectively explained that less desirable traits would eventually disappear while more desirable
traits in a population appear. However, it did not explain how these traits were passed on
2. The key to finally solving this theory was done through the work of Gregor Mendel
3. Mendel was a monk who cross bred pea plants and set the basis for how traits are inherited. His conclusions:
a. “Factors” that were passed to descendants were unchanged
b. Each parent passed one “factor” to its offspring
c. A “factor” is also passed on even if it is not expressed in the offspring
d. These factors that Mendel continues to mention are known as genes which are the unit of heredity
4. Mendel published his work 7 years after Darwin published his works. Scientists then combined the two theories
into one (called the modern synthesis) in the early 1900’s
E. The Three Components of Evolution through Natural Selection
1. Variation-members of a species differ from one another. It is crucial that there is variation so that if the
environment changes, some if not, most of the population will survive
2. Selection-provides direction to the process. Selection favors some individuals over others because of the traits
that they possess
3. Retention-favored variations are retained through heredity. If the population does not retain the variability
from the gene pool, evolution of a species will not occur
4. Selectionism-explanation of complex outcomes as the cumulative effect of the three-component process
identified by Darwin
F. Natural Selection and Behavior
1. The reason that natural selection even occurs is because it serves a function to the organism. The function
determines the behavior of the organism
G. Acceptance of Evolution through Natural Selection
1. Although evolution through natural selection is generally accepted throughout the world many people do not
believe it for various reasons
II. Evolution of Humans
A. Human Origins
1. Methods of Studying Human evolution
a. Fossils-remains of an animal or plant found in the Earth. We can determine what our ancestors did
based on the types of tools they made as well as any biological evidence found in their bones
b. DNA-a molecule resembling a twisted ladder whose sides are connected by rungs of pairs of
nucleotides. We can use DNA to find the genetic makeup of an individual
c. Stone implements
d. Bipedalism-habitually walking upright on two legs. We can order human evolution in time by looking
at the differences in skeleton and compare them to the modern human being
e. Carbon Dating-The method to determine the age at which an organism has lived by measuring the
amount of radioactive carbon. The decay of carbon can be measured for about 60,000 years
i. Carbon dating is not the most reliable method of finding the time of a fossil because it can be
affected by factors such as amount of C14 in the atmosphere
B. The Course of Human Evolution
1. Humans did not evolve from chimpanzees
2. Genetic tests support a common ancestor chimps and humans
3. We share about 99% of our DNA involved with protein production with chimpanzees. However 98% of our
DNA is not used for protein production. Much of our DNA is regulatory genes (genes that govern genes that
code for proteins) which determine how much and when a protein should be administered in the body
4. The earliest hominids belonged to the genus Australopithecus about 6 million years ago
a. The advantage of being bipedal is that animals now have limbs that are free from locomotion
5. About 2 million years ago, hominids had evolved sufficiently to be classified in a new genus, Homo (human)
a. With the arrival of this new genus, brain size increased as well as bipedal locomotion
6. Three types of humans left Africa
a. Standing man-Homo erectus-becomes extinct about 400,000 years ago
b. Neanderthal-Homo neanderthalis-becomes extinct about 300,000 years ago
c. Thinking Man-Homo sapiens- evolved about 200,000 years ago
III. Heredity, Genetics, and Evolution
A. Genetics-the study of hereditary structures of organisms (genes)
1. Heredity-the sum of the traits inherited from one’s parents
B. Basic Principles of Genetics
1. DNA is the genetic blueprint of life
a. It is composed of strands of sugar phosphate backbones and connected by pairs of four nucleotides
b. James Watson and Francis Crick discovered the structure of DNA in 1953
2. Structure of DNA
a. DNA is a molecule that is shaped like a twisted ladder (also known as a double helix)
b. Sugar-phosphate backbones form the side of the ladder while the nucleotides form the rungs
c. The sequence of nucleotides directs the synthesis of a protein molecule
d. Protein synthesis is guided by RNA
e. Genome-the total set of genetic material in a species
C. Genes
1. Genes are instructions to code for protein synthesis. Proteins are a chain of amino acids
2. There are no genes for behavior. Genes code for protein-based physical structures that affect behavior
3. Enzymes-proteins that regulate processes that occur within cells; organic catalysts
D. Chromosomes and Meiosis
1. Genes are located on chromosomes, paired rod-like structures in the nucleus of a cell
2. Mitochondrial played an important role in human evolution
3. 23 pairs of chromosomes
4. Autosomes-chromosomes with corresponding genes
5. Sex chromosomes-X or Y chromosomes that contain genes affecting sexual development (XX girl) (XY boy)
6. Sexual Reproduction
a. Occurs with union of sperm and ovum (germ cells)
b. Germ cells contain only one chromosome from the 23 pairs of chromosomes
c. They are produced in a process called meiosis-
d. During meiosis, corresponding portions of paired chromosomes may be interchanged (crossing over)
e. Identical twins occur when a single ovum divides into two independent cells after it has been fertilized
f. The sex of the offspring is determined by the sperm cell which carries either an X or Y chromosome
E. Dominant and Recessive Traits
1. Allele-alternative forms of the same gene for a trait
2. Dominant allele-trait that is exhibited when only one allele is present; as found in heterozygous cells
3. Recessive alleles-the opposite of dominant allele
4. Phenotype-the organism’s appearance according to genes
5. Genotype-the genetic makeup of an organism
6. Behavioral characteristics are affected by more than one gene which is known as polygenic control
7. Mendelian Traits-only depend on one gene
8. Traits are also affected by the environment
F. Importance of Genetic Diversity
1. Sexual reproduction increases genetic diversity
G. Sex Linked Traits
1. Sex-linked traits-traits affected by genes located on the sex chromosomes
2. Males tend to express more recessive genes because they lack the second X chromosome
3. Hemophilia (page 72)
H. Mutations and Chromosomal Aberrations
1. Mutations-alterations in the nucleotides within a single gene
a. They can be beneficial but most of the time they are not
b. They can occur spontaneously, or may be created as a result of environmental factors (high radiation)
2. Chromosomal Aberration-displacement or deletion of genes with chromosomes or a change in the number of
chromosomes
a. Deletion of chromosomal material or the failure in separation of chromosomes during meiosis and
tends to cause severe implications on the offspring
I. Genetic Disorders
1. Down’s Syndrome-chromosomal aberration consisting of an extra 21st chromosome
a. It is caused by the failure to separate chromosomes by the mother
2. Huntington’s Disease-genetic disorder caused by a dominant lethal gene that produces progressive mental and
physical deterioration after adulthood
a. Certain portions of the brain deteriorate at around of 30 to 40
b. It can be passed unrecognized from parent to child
3. Phenylketonuria (PKU)-genetic disorder caused by recessive genes that impair ability to break down
pheynlalaine. As a result, it accumulates in the blood until the point that it becomes toxic to the brain tissue
a. Infants who have the disease cannot break down certain amino acids which would cause impairment of
brain development
4. Cri du cat syndrome is caused because of a certain genetic alteration which causes various deficiencies in
multiple phenotypes
III. Heredity and Human Behavior
A. It is difficult to assess how much genetics plays a role in behavior due to genetic factors
B. Heritability-variation in a trait due to genetic factors, varies from 0.0 to 1.0
1. The measure reflects the variation of a trait in a population
C. Experimental Procedures for Studying Genetic Influences
1. Artificial Selection
a. Involves selective breeding within a population of organisms
b. Different must be tested on the subjects to determine if genes really do play a role on certain behavior
c. Artificial selection may improve traits in one aspect but deteriorate traits in other aspects which would
then interfere with the experiment
2. Molecular Genetics-the study of genetics at the level of the DNA molecules
a. Knockout mutations-prevent certain gene expression in an organism
i. We can determine how that gene affects a certain behavior
b. Genetic Marker-a known nucleotide sequence that occurs at a particular location on a chromosome
i. We can determine if this certain gene changes over time due to artificially selected groups and
insinuate if this gene has anything to do with the behavior of an organism
D. Correlation Methods for Studying Effects of Genes
1. Concordance Research-studies the similarity between twins
a. Two individuals are said to be concordant for a trait if both express that same trait
b. Concordance tells us how much environment affects a genes expression. The lower the concordance
the higher that environment plays a role
2. Segregation Analysis-correlational method to identify sections of chromosomes that are the same for
individuals expressing a common trait
a. Researchers identify if a certain genetic sequence is associated with a behavioral trait
III. Evolution and Human Behavior
A. Evolutionary psychology-branch of psychology studying how human behavior is affected by evolution
B. Sociobiology-the study of genetic influences on social behavior
1. People in this field study behaviors to determine the adaptiveness of a given social behavior
2. Reproductive Strategies-evolutionary effects on systems of mating and rearing offspring. There are many
different types of reproductive strategies found in nature
a. Monogamy-mating of one female with one male
b. Polygyny-mating strategy of one male with more than one female
c. Polyandry-involves one female mating with more than one male
d. Polygynandry-involves several females mating with several males
e. The reason for the different types of reproductive strategies is because each species has its own type of
parental investment (resources that parents expend in procreating and nurturing offspring)
f. Those reproductive strategies that are more selective (monogamy) tend to have a high parental
investment
3. Sexual Selection-preference for traits that are differently expressed the two sexes, for example, body size
a. Competition for mates leads to natural selection of traits that are particular of a certain sex such as
appearance, body size, and behavioral patterns
b. Many reasons that sexually reproducing organisms select particular mates is for their health and fitness
to reproduce. If these traits are heritable then they favor survival
c. However there are exceptions to this rule. In more impoverished countries men tend to find overweight
women more attractive because overweight tend to have more food because of increased wealth
d. A woman can only produce so many offspring in her lifetime because she produces only one or a few
ova periodically. Males produce numerous sperm at relatively frequent intervals. The cost of reproduction
is more to the female than to the male in polygynous species. The female spends much of her metabolic
resources during the gestation period as well as afterwards nurturing and caring for the child
e. Females in polygynous species invest especially heavily in their offspring because the male is shared
with other females
f. In monogamy, both parents contribute to the survival of the offspring. The parents share the duties in
raising the offspring
g. By sharing the responsibilities, monogamy ensure the chance that the offspring will survive and
reproduce
3. Altruism-behavior benefiting another organism at apparent cost to the individual who executes the action
a. Self-sacrifice
b. It goes against the concept of natural selection and “survival of the fittest”
c. The reason for the existence of altruistic behavior is that the survival of the genes (not the individual)
d. One theory states that natural selection does not favor reproductive success but rather inclusive fitness
which is the total reproductive success of those with whom the individual has genes in common e.g.
siblings
e. Altruistic behavior becomes stronger as the relationship to the individual is closer. (You are more likely
to risk your life, time, energy, or money for a family member than a friend). This is an example of kin
selection, selection that favors altruistic acts toward individuals with whom one has genes in common
f. Reciprocal Altruism-altruism in which one individual benefits another when it is likely that the other
will return the benefit at a later time
C. Evolutionary Psychology
1. When trying to understand human behavior on reproductive fitness, it is very hard to experiment and determine
the reason for a given behavior. Evolutionary psychology applies evolutionary thinking to the full range of human
behavior
2. Evaluating Evolutionary Psychology
a. Evolutionary psychology is a controversial branch of psychology
b. Many people believe that human behavior is too complex to be understood by natural selection alone
c. Another objection is that evolutionary psychology is based on simplistic analogies between of
nonhuman animals and humans
d. Another criticism of selectionism is that the complete sequence of events in the evolutionary process is
not known. And that it undermines our uniqueness, and even our worth, as a species
3. Culture-socially transmitted knowledge, customs and behavior of a group of people
a. Culture, along with natural selection is a method in which one generation can affect the generation of
the next
b. All culture have universal commonalities (religion, living in groups)