BIO 181 FINAL STUDY GUIDE, Latest complete guide (fall 2019/2020)
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Course
BIO 181 (BIO181)
Institution
Georgetown University
BIO 181 FINAL STUDY GUIDE Lecture #1: 1. How did the four macromolecules appear on early earth? Components of “Primitive Soup” Carbohydrates, Lipids, Nucleic Acids, Proteins (four macromolecules of life) We don’t have a clear answer but there are numerous hypotheses. 2. List and explain t...
BIO 181 FINAL STUDY GUIDE
Lecture #1:
1. How did the four macromolecules appear on early earth?
Components of “Primitive Soup” Carbohydrates, Lipids, Nucleic Acids, Proteins (four
macromolecules of life) We don’t have a clear answer but there are numerous
hypotheses.
2. List and explain the basis/background for the four main theories of how life
originated on early earth. Are there any challenges these theories have to overcome?
a) Oparin-Haldane Hypothesis (tested by Miller-Urey)
a. Mimicked atmosphere of primitive Earth
i. Reducing atmosphere w/ oceans and lightening (1924 thought that
atmosphere was reducing but in 1980 found out that atmosphere is
neutral)
b. Demonstrated abiotic synthesis of organic compounds
c. Results: found 17-20 of amino acids
b) Meteorite Hypothesis
a. Meteorites that fall to Earth today will often contain amino acids,
carbohydrates, and nucleotide bases
b. Results: found L and D bases, which are often produced by animals
c) Iron-Sulfur World Theory
a. Simulated hydrothermal vents using CO (carbon monoxide) and KCN
(potassium cyanide) produced amino acids
b. Theory: life originated at hydrothermal vents
c. Challenges: it is very hot, possibly too hot for cells
d. The fourth theory (RNA World) derived from this theory we are still
missing lipids
i. Potential explanation: lipids formed from minerals underneath vents
d) RNA World
a. RNA was the precursor to DNA (both enzyme and genetic storage material)
b. RNA monomers have been produced spontaneously from simple molecules
3. What does organismal evolution look like across time? (list major evolutionary
events and when they happened)
Adaptation to the environment over billions years. Coming to deal successfully with
changes in: oxygen levels, carbon dioxide levels, temperature extremes (hot and cold),
ocean chemistry (pH, salinity, toxic chemicals), water availability, light intensity and
spectral qualities, UV radiation.
Characteristics of the First Cell:
Prokaryotes
Anaerobic as there was no oxygen in the atmosphere
First came the common ancestor, then 3.8 billion years ago the prokaryotes
evolved into two groups: Bacteria and Archaea
, Common ancestor of all species living today speciated into bacteria then further
speciated into archaea and eukarya
EXTINCTIONS:
There have been five mass extinctions, but diversity has increased
End-Permian-Triassic Mass Extinction: 252 million years ago
1. Drop in Sea Level (changed habitat of fauna)
2. Several Volcanic Eruptions (released CO2 which was toxic,
trapped heat, decreased O)
3. Floods, Sea Levels increased
ii. Who survived? Only bottom-dwellers who could tolerate low O,
“suffocation” when there is high CO2 and low O
End-Triassic Mass Extinctions – 200 million years ago
Rising CO2, falling pH, falling O2 (which is same story as above!)
4. Describe the main characteristics of prokaryotic cells.
Simple, single celled organism
Lacks a nucleus and membrane-bound organelles
Not divided up on inside by membrane walls, instead consist of single open space
Majority of its DNA is found in the nucleoid (central region of cell) and typically consists
of a single large loop called a circular chromosome
0.1-5.0 micrometers and much smaller than eukaryotic cells
“The life force” by Service (2013) questions:
1. In 1967, Colin Pittendrigh predicted that functional protocells would be created
within a decade. Why hasn’t this happened?
2. In the early 1990’s Szostak moved away from research on telomeres into the world
of RNA catalysts, why was his discoveries in this field so important to our
understanding about how primitive life on earth started?
3. What are some challenges the Szortak lab still has to overcome to explain early life
on earth?
Need Mg2+ to copy template, without it too slow, but it was ripping it apart
Kurihara et al. (2015) questions:
This is a challenging paper with a lot of field-specific jargon, so let’s try to focus on the
big-picture findings of this paper!
1. What was the general goal of this study?
To examine/study/prove that the primitive soup “protocell” was a DNA-based cell, not
RNA like previously thought.
2. What are the four phases in the self-proliferative cycle of a lab-generated giant
vesicle?
Ingestion Phase, Replication Phase, Maturity Phase, Division Phase
3. What kinds of environmental parameters are needed to stimulate these protocells to
divide?
“The mother of mass extinctions” by Erwin (1996) questions:
, 1. How much diversity was destroyed after the “mother of all extinctions”? What may
be some advantages for plant and animal diversity after an extinction event?
2. How long did this extinction last? Was it fast or slow?
3. What percentage of invertebrates disappeared? How did this percentage compare to
other extinctions? Which animal groups were hit the hardest? Why?
4. How was plant diversity affected during this time?
5. What do we think caused this mass extinction? What is the order of events that the
author thinks brought on this mass extinction?
Lecture #2:
1. Please describe the process of endosymbiosis. What is the evidence to support this
evolutionary change?
Earliest evidence of eukaryotic cells: 2.7 billion years ago
How we got mitochondria and chloroplasts, which produce energy for the cell.
(Dictionary definition: symbiosis in which one of the symbiotic organisms lives inside
the other). It has to do with the evolution of a eukaryotic cell, as does
compartmentalization (how we gained endoplasmic reticulum and nuclear envelope).
Cyanobacteria started producing Oxygen, which was not a good thing for many
organisms
Process: Essentially a protobacteria was engulfed by a eukaryotic cell
FIRST ENDOSYMBIOTIC EVENT Mitochondria
1) A symbiotic relationship developed between an ancestral aerobic heterotrophic
bacterial prokaryote (not an Archaea) and a eukaryotic cell.
a. The bacteria could deal with Oxygen and provide ATP for the cell
2) The energy-producing aerobic prokaryote took up residence inside the engulfing
eukaryotic cell but was not destroyed
3) The energy-producing aerobic prokaryote eventually became the mitochondrion.
4) Eventually, some of the genes from the mitochondrion were transferred to the
nucleus. However, other genes remained becoming the mitochondrial DNA (Humans
inherit only their mother’s mitochondrial DNA since only the nucleus of a sperm
fertilizes the human egg.
SECOND ENDOSYMBIOTIC EVENT Chloroplast
1) Developed between ancestral autotrophic prokaryote (not an archaea) and a
eukaryotic cell
2) The autotrophic prokaryote eventually became the chloroplast
3) Eventually some of the genes from the chloroplast were relocated to the nucleus
but other genes remained in the chloroplast
4) Occurred after the endosymbiotic event of the mitochondrion as all
photosynthetic eukaryotic cell have mitochondria
Evidence: the fact that Eukaryotic cells are more closely related to Bacteria than
Archaea means they must have a common ancestor
, - Both Mitochondria and Chloroplast have ribosomes but more closely
resemble bacterial ribosomes
- Sizes match
- Both mitochondria and chloroplasts carry out protein synthesis like bacteria
- Both have own DNA but more similar to bacterial DNA (circular)
2. What is a protist? Be specific and detailed
- All eukaryotes are protists except fungi, animals, and land plants.
- Informal name of mostly unicellular organisms
- Most nutritionally diverse
- Can be photoautotrophs, heterotrophs, or mixotrophs
3. What are three reasons we should care about studying protists?
1) Protists play key roles in ecological communities
a. Protists are found in diverse aquatic environments
b. Protists often play the role of symbiont or producer
2) They can cause many dangerous human and non-human diseases
3) They are at the bottom of the food chain, so if the population of protists decreases for
any reasons, the rest of the food chain is affected.
4. Describe some of the structural and functional diversity in protists.
Heterotrophs: absorb organic materials or ingest
Photoautotrophs: have chloroplasts, get food from light
Mixotrophs: combine photosynthesis and organic materials
5. Describe how protists move.
Three Options:
a. Amoeboid motion via pseudopodia (false foot), which is the ancestor movement
to muscular movement
b. Swimming via flagella (1-2)
i. Requires ATP
c. Swimming via cilia (short, wave-like) (muscular)
6. Why are dinoflagellates ecologically important? Be specific and detailed.
Have two flagella and each cell is reinforced by cellulose plates
Cause red tide
Very bad
Algal bloom blocks oxygen from entering ocean, suffocating wildlife
Releases saxotoxin, which is poisonous
Shellfish filter red tide so we need to be careful what we eat
Apicomplexans:
- Parasites of animals and cause some serious human diseases Malaria
- Spread through their host as infectious cells called sporozoites
- Apical and lets it through
7. Why is Plasmodium medically relevant? Describe its life cycle and effects on host.
Plasmodium is the protist that causes Malaria in humans, which is a two-host cycle.
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