BBH 101 PSU Exam 2 Lessons 5-7
Review Questions and Correct Answers
Lesson 5: Prevention and Behavior Change, and Evolution and Genetics ✅=>
Evolution ✅- Charles Darwin embarked on a sea voyage to South America in 1831. He
noticed while visiting the Galapagos Islands that finches that lived on the different
islands appeared to have beaks that were perfectly suited for cracking open the seeds
found on the island they lived on.
- These types of observations led Darwin to his ideas about how organisms change
over time (evolution).
- Darwin hypothesized that as populations grow, they inevitably must reach a point
where there will be more members of the population than the resources in the
environment can support.
- Darwin argued that some organisms are naturally more capable of obtaining resources
than others. Thus, those organisms will be most likely to obtain enough resources to
survive and reproduce, while those that are less capable will die. Because the more
capable organisms can survive and reproduce, their traits will be more likely to be
passed on to the next generation.
- Evolution helps us to understand the ways in which organisms change, and the
pressures that keep certain traits in a population for a long period of time. Evolution
doesn't create species that are constantly changing for the better, it creates a situation
where populations evolve to take advantage of their environments.
- Therefore, evolution doesn't have a goal and doesn't always involve organisms getting
stronger or smarter. Organisms change to take advantage of their environment and, if
they can do that,, they may not evolve for a long time.
Natural Selection and Sexual Selection ✅- Natural selection was the term Darwin used
to describe the process by which organisms with favorable traits were "selected" to
survive and reproduce, while those without such traits were less likely to do so.
- Sexual selection occurs simply because it is found to be attractive to the opposite sex.
This form of selection helps to explain things like peacock's feathers, which don't
promote survival but still are associated with increased reproductive rates.
- Alfred Russel Wallace came up with some of the same ideas Darwin did at around the
same time. Darwin's ideas were more fully formulated, however, and he had gathered
more evidence to support them, so he got the credit.
,- Darwin's ideas were first published in 1859, in a work titled On the Origin of Species by
Means of Natural Selection
Genetics ✅- Darwin's ideas of evolution helped to explain the forces that led to
organisms changing over time, but they didn't explain how traits were passed down from
parent to offspring.
- Then, experiments over the first half of the 20th century pointed scientists to the
hypothesis that heritable information was stored inside an organism's cells, in
deoxyribonucleic acid (DNA).
Chromosomes and Genes ✅- DNA is found in the nuclei of the cells, wrapped up with
proteins in structures called chromosomes. The DNA can be divided into functional
segments, each which acts as a recipe book to produce proteins.
- The functional segments of DNA are known as genes.
- During the reproductive process, each person inherits 23 chromosomes from his or
her mother and 23 chromosomes from his or her father, resulting in 46 chromosomes
(23 pairs) altogether.
- Each collection of 23 chromosomes contains a copy of every gene in the human
genome (all the genetic information of an individual), which are estimated to total
around 20,000 genes.
Alleles ✅Different forms of genes that result in variations in the structure and function
of proteins that result from that gene's expression, or translation into a protein, are
called alleles.
These different alleles can lead to differences in a person's traits and characteristics,
whether they be outwardly observable (e.g. brown eyes vs. blue eyes) or not (e.g.
introvert vs. extrovert).
Phenotype vs. Genotype ✅- Someone's actual genetic makeup, or what alleles they
possess, is known as their genotype.
- The traits and characteristics that result are known as their phenotype.
- Thus, having an allele that encodes for a protein that contributes to blue eyes is part of
one's genotype, while having blue eyes as a characteristic is part of one's phenotype.
Heritability ✅- Nature vs Nurture debates how much genetics contributes to our
appearance, behavior, and characteristics and concerns what proportion of our
characteristics is determined by genes and what proportion is determined by the
environment.
, - The environment refers to anything non-genetic that can influence our healthy
functioning, ranging from social relationships to nutrition to the actual physical
environment.
- Nature vs Nurture is misguided because both genetic makeup and our environment
can cause characteristics.
- Scientists conduct studies to attempt to quantify how much of an influence genetics
has on the appearance of specific traits. These studies attempt to determine heritability,
a term that refers to the amount of variation in a population that can be attributable to
genetics.
- One way that can be measured is through twin studies and adoption studies.
Twin Studies ✅- Identical twins are 100% genetically identical, while fraternal twins are
only about 50% genetically identical.
- Thus, differences between identical twins are likely to be attributable to environmental
factors, not genetics.
- In twin studies, researchers take groups of identical and fraternal twins and examine
traits among them to see if the traits are more commonly shared among identical twins
than among fraternal twins. If they are, it suggests a genetic influence.
Adoption Studies ✅- In adoption studies, researchers examine individuals who were
adopted into new families as a child and compare their phenotypes with that of their
biological parents.
- If an adopted individual is more likely to share a particular trait with his or her biological
parent than his or her adopted parent, it suggests a potentially stronger genetic
influence on the trait.
Gene x Environment Interactions ✅- One reason the nature vs. nurture debate is not
considered to be debate-worthy anymore is that we now know that one's environment
can have a significant effect on how their genotype is translated into phenotype, a
process often called gene expression.
- When genes and the environment interact to produce a certain phenotype, it is often
referred to as a gene x environment interaction.
- One example involves a condition known as phenylketonuria (PKU). In PKU,
individuals are born with a mutation in a gene that encodes for a protein involved in the
break down of an amino acid called phenylalanine.
