BIOL 3463 Study Guide - Fall 2018, Comprehensive Midterm Notes - Zygosity, Zidovudine, Virus
BIOL 3463
MIDTERM EXAM
STUDY GUIDE
Fall 2018
➢ Koch’s postulates:
o You should be able to identify the disease causing pathogen in every person sick with
that disease
o You should be able to culture that pathogen
o Inoculating a healthy individual with that pathogen should result in the same disease
o You should be able to reisolate the pathogen from the newly infected individual
➢ When AIDS patients are initially treated with AZT their CD4+ and macrophage cell count
increased. But over time they began to decrease again
o HIV has a very high mutation rate, often various forms of reverse transcriptase will be
better at ignoring the azide side group
o These mutants will vary with respect to enzyme function
o Some mutants will ignore AZT
o These mutants survive and reproduce better
➢ Transmission rate hypotheses
o If transmission of a disease from an existing host to a new host is frequent, than natural
selection will favor increased virulence
o If transmission of a disease from an existing host to a new host is rare, than natural
selection will favor benign forms
➢ Being virulent or benign are alternative strategies for a virus. Both strategies have costs and
benefits
➢ Mutation in the CCR5 coreceptor prevents gp120 from binding to host cell and thus provides
some resistance to HIV
➢ HIV evolves so quickly and there are many different forms so it is nearly impossible to create
a single effective vaccine
➢ Theory of special creation:
o Species were created independently of one another and they do not change over time.
They were created recently and God was responsible for this act of creation
➢ But, there is evidence of species changing over time
o Soapberry bug: Beak length has changed overtime depending on which food source
was available to them
o European house sparrow: Phenotypes changed quickly once introduced to New York
and population spread across North America
o Introducing shrews to Newfoundland → Shrews don’t tend to follow the island trend.
Species are not fixed, the can change over time.
▪ On an island, smaller animals tend to get bigger, animals the size of rabbits
tend to stay the same and bigger mammals tend to be smaller on an island
➢ Ring species
o Adjacent populations can mate and produce offspring with intermediate phenotypes.
But certain species have large enough differences that have led to reproductive
isolation. Where the ends of the ring overlap, the species cannot interbreed. This
demonstrates that intraspecific variation can lead to separate species incapable of
reproduction.
➢ Homology
o The same genes are turned on for the development of similar bones, but the are turned
on at different times and for different lengths of time
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➢ Darwin concluded: Structures were not created independently, but are related by common
ancestry
➢ Synapomorphy: Shared derived characteristic
➢ Principal of parsimony: The simplest explanation is usually correct. Molecular evidence was
not available to Darwin but has since then been called a frozen accident
o All organisms use the same genetic code because they have all inherited this system
form an ancestor which used this genetic code (frozen accident)
➢ Vestigial structure: A functionless or rudimentary homolog or body part that has an
important function in a closely related species
o Ex. Stubby wings of kiwi, stubs expressed on snakes
➢ Fossil records:
➢ Overall pattern
o In the oldest fossil beds, there were only fish – no evidence of birds or mammals. More
recent fossil beds began to reveal amphibians. Overtime, reptiles and mammals began
to appear in fossil beds.
➢ Law of succession
o Recent fossils from one area are most similar to extinct species from that same area
➢ Kelvin estimated that the earth was between 25-100 million years old by estimating the
starting temperature of the earth, the size of it and calculating how long it would take to cool
down.
o He was missing the contribution of heat from radioactive decay
o Darwin estimated the year to be several billion years old based on rates of
sedimentation
➢ If you date the layers of igneous rock below and above a sedimentary layer containing a
fossil, you can accurately date the fossil.
o K40 has a half life of 1.3 billion years. When K40 turns to Ar40, the Ar40 boils out as a
gas, becomes a liquid and solidifies as it cools. By looking at the ratio of K40 to Ar40,
the igneous rock can be dated
➢ Transitional forms
o Transitional species have characteristics from ancestral populations as well as has
novel traits seen in dependent species
o Ex. Archaeopteryx is not a direct ancestor, but a representative of the transition from
dinosaur to birds
➢ Summary for common ancestry:
o Homologous structures
o Fossil records – overall pattern
o Fossil records – Law of succession
o Fossil records – Transitional forms
o Vestigial organs
➢ Natural selection produces the pattern called decent with modification
➢ Natural selection must hold true if:
o Individuals vary
o Some of this variability is heritable
o More offspring born than can survive
o Survival and reproduction is random
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
When aids patients are initially treated with azt their cd4+ and macrophage cell count increased. Being virulent or benign are alternative strategies for a virus. Mutation in the ccr5 coreceptor prevents gp120 from binding to host cell and thus provides some resistance to hiv. Hiv evolves so quickly and there are many different forms so it is nearly impossible to create a single effective vaccine. Theory of special creation: species were created independently of one another and they do not change over time. They were created recently and god was responsible for this act of creation. But, there is evidence of species changing over time: soapberry bug: beak length has changed overtime depending on which food source was available to them and population spread across north america. Ring species: adjacent populations can mate and produce offspring with intermediate phenotypes. But certain species have large enough differences that have led to reproductive isolation.
