PSYCH101 Chapter Notes - Chapter 3: Homo Habilis, Homo Erectus, Homo Sapiens

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16 Aug 2016
PSYCH 101- Chapter 3 (Biological Psychology) Notes
What are genes?
- Genes: the basic units of heredity; genes are responsible for guiding the
process of creating the proteins that make up our physical structures and
regulate development and physiological processes throughout the lifespan
What is DNA?
- DNA (deoxyribonucleic acid): a molecule formed in a double-helix shape that
contains 4 nucleotides: adenine, cytosine, guanine, and thymine (A, C, G, T)
What is a genotype?
- Genotype: the genetic makeup of an organismthe unique set of genes that
comprise the individual’s genetic code
What is a phenotype?
- Phenotype: the physical traits of behavioral characteristics that show genetic
variation, such as eye color, the shape and size of facial features, and even
What are chromosomes?
- Chromosomes: structures in the cellular nucleus that are lined with all of the
genes an individual inherits
- Have 23 chromosomes (half from mother and half from father)
What is homozygous?
- Homozygous: 2 corresponding genes at a given location on a pair of
chromosomes are the same
What is heterozygous?
- Heterozygous: when 2 genes differ
What is behavioral genomics?
- Behavioral genomics: the study of DNA and the ways in which specific genes
are related to behavior
-Ex. Human Genome Project
What is behavioral genetics?
- Behavioral genetics: the study of how genes and the environment influence
-Involve comparing people who are of different levels of relatedness
oIe. Parents and their offspring, siblings
What are monozygotic twins?
- Monozygotic twins: come from a single ovum (egg), which makes them
genetically identical (almost 100% genetic similarity)
What are dizygotic twins?
- Dizygotic twins/fraternal twins: come from 2 separate eggs fertilized by 2
different sperm cells that share the same womb; these twins have approx.
50% of their genetics in common
What is heritability?
- Heritability: a statistic, expressed as a number between zero and one, that
represents the degree to which genetic differences between individuals
contribute to individual differences in a behavior/trait found in a population
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-Heritability of 0 means that genes don’t contribute to individual differences
in a trait
-Heritability of 1.0 means that genes account for all individual differences in a
-Estimates change overtime based on our different experiences shows us that
nature vs. nurture interacts to produce behavior
What is epigenetics?
- Epigenetics: the study of changes in gene expression that occur as a result of
experience and that do not alter the genetic code
What is diathesis-stress model?
- Diathesis-stress model: the interaction between a genetic predisposition for a
disorder and life stress
What is natural selection?
- Natural selection: the process by which favorable traits become increasingly
common in a population of interbreeding individuals, while traits that are
unfavorable become less common
What is evolution?
- Evolution: the change in frequency of genes occurring in an interbreeding
population over generations
-Not a continuous process
How do Darwin’s theories of evolution and natural selection relate to human
-Humans are animals too
-Development of traits that improve survival is based on the shuffling of the
genetic material
What is intrasexual selection?
- Intrasexual selection: a situation in which members of the same sex compete
in order to win the opportunity to mate with members of the opposite sex
What is intersexual selection?
- Intersexual selection: a situation in which members of one sex select a mating
partner based on their desirable traits
What is homo habilis?
- Homo habilis (“handy man”): appeared about 2.5 million years ago
-Brain was about 50% larger than its ancestors
-Thrived for about 800 000 years
What is homo erectus?
- Homo erectus (“erect man”): a brain approx.. 1/3 larger than of homo habilis
-Able to adapt to different environmental conditions
What are homo sapiens?
- Homo sapiens (“wise men”): arose in Africa and quickly spread around the
Reasons why the human brain is more powerful than any other on the planet
1. Human brains have more folds and grooves on the outer surface than any
other species
2. The front third of the human brain is more developed than of any other
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3. Humans and a few other species have found a way to “cheat” some of the
biological restrictions on brain and head size
What are neurons?
- Neurons: one of the major types of cells found in the nervous system, that are
responsible for sending and receiving messages throughout the body
-Primary purpose = to “fire”, to receive input from one group of neurons and
then to transmit the information to other neurons
What is the cell body?
- Cell body (Soma): the part of the neuron that contains the nucleus that
houses the cell’s genetic material
What are dendrites?
- Dendrites: small branches radiating from the cell body that receive messages
from other cells and transmit those messages toward the rest of the cell
What is the axon?
- Axon: transports information in the form of electrochemical reactions from
the cell body to the end of the neuron
What are neurotransmitters?
- Neurotransmitters: the chemicals that function as messengers allowing
neurons to communicate with each other
What are sensory neurons?
- Sensory neurons: receive information from the bodily senses and bring it
towards the brain
What are motor neurons?
- Motor neurons: carry messages away from the brain and spinal cord and
towards muscles in order to control their flexion and extension
What are glial cells?
- Glial cells: are specialized cells of the nervous system that are involved in
mounting immune responses in the brain, removing waste, and
synchronizing the activity of billions of neurons hat constitute the nervous
What is myelin?
- Myelin: a fatty sheath that insulates axons from one another resulting in
increased speed and efficiency of neural communication
-Myelin protects the impulses from this decay, thus reducing how often the
impulses need to be regenerated
- Unmyelinated: the neural impulses decays quickly and needs to be
regenerated along the axon
What is resting potential?
- Resting potential: relatively stable state during which the cell is not
transmitting messages
- Resting potential = -70 mV
What is action potential?
- Action potential (AP): a wave of electrical activity that originates at the base
of the axon and rapidly travels down its length
- Threshold potential = -55 mV
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