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SUBMIT HOMEWORK ASSIGNMENT
FROM LAST WEEK
2.1 The Organization of Life/ Viruses
2.2 Comparing Bacteria to Archaea
Review
• What are the two types of cell division?
– Mitosis and Meiosis
• What is the difference between the two?
– Mitosis produces 2 identical cells to the parent cell
– Meiosis produces reproductive cells—half the number of
chromosomes as the parent cells
• Why is meiosis important? (Hint: creates one
of the 3 types of bio-)
– Creates genetic diversity
Prokaryotes vs Eukaryotes (Table 2.1)
• Two basic cell types recognized by biologists
Eukaryotes
Membrane bound organelles
Unicellular/ Multicellular
Most are aerobic
Reproduce by mitosis/meiosis
Prokaryotes vs Eukaryotes (Table 2.1)
• Two basic cell types recognized by biologists
Prokaryotes
Circular DNA
No membrane bound organelles
Unicellular
Many are anaerobic
Don’t reproduce by mitosis/meiosis
Viruses
• Neither prokaryotic nor eukaryotic
• Not capable of living independently outside of cells—
use host cell’s machinery for survival and
reproduction
• Dormant outside of the living cells
• No cytoplasm, membrane bound organelles or cell
membranes—not living organisms?
• So how are they able to cause disease in plants and
animals?
• Biologists have a system of classifying viruses, but it
is not part of the classification system of life.
Viruses
• WHAT DO VIRUSES LOOK LIKE?
Capsid: the outer protein layer that surrounds the
genetic material of the virus
Genetic material can be in the form of DNA or RNA
Viruses
• How do they reproduce?
– THEY DON’T! They replicate 
– Require a host cell (either prokaryotic or eukaryotic)
Viruses
• Lytic vs Lysogenic Cycle
– http://www.youtube.com/watch?v=NUrGNd-a76E
1. Lysogeny involves viral DNA integrating with host DNA
– Viral DNA is then referred to as the provirus.
2. Lysis refers to the rupturing of the cell membrane.
3. Lytic Cycle is a part of the Lysogenic Cycle, but not necessarily
the other way around.
• LYTIC CYCLE: new viruses are made, kills host cell
• LYSOGENIC CYCLE: viral DNA is copied during cell
division
Viruses
• In viruses that undergo the lysogenic cycle, effects
on the host may not be immediate.
HERPES SIMPLEX VIRUS (cold sores)
• Appear when the viral cycle destroys cells
• Disappears when the virus is in its provirus stage
• The trigger to switch between one replication
strategy to another depends on the health of the
host cell.
Viruses
HIV (human immunodeficiency virus)
• Only when the infection spreads to more and
more cells do the symptoms of AIDS (acquired
immune deficiency syndrome) eventually appear
• AIDS results in an inability of the body to fight
off infection because HIV has destroyed the
body’s T-cells (white blood cells)
• Death occurs from an accumulation of other
infections and ailments, not from AIDS itself.
Prions
• Non-viral disease causing agents
• Cause several deadly brain diseases
• Like viruses, cause diseases that are not
usually detected for decades after infection
• Only known disease-causing agents that do
not contain DNA/ RNA (and therefore are not
viruses)
Prions
• They are proteins normally found in the body
that are converted into a more harmful form
(isomer)
• Mad Cow Disease is an example of a
prion-caused deadly brain disease.
Viruses and Biotechnology
• Viruses can be useful tools for genetic engineers
who want to make a copy of a certain gene
• Used for their ability to enter host cells and direct
the activity of the host cell’s DNA
1. Insert the gene into the viral DNA/RNA
2. Virus enters host cell and directs the cell to make
multiple copies of the virus
• Each new virus made contains the added gene
that researches want copied
Archaea vs Bacteria
• Both are prokaryotes, so why are they in two
different domains?
• The two groups are more different from each
other than any two groups within the domain
• Example?
• Archaea have an independent evolutionary
history than Bacteria; the two have many
differences in their biochemistry
• Archaea is actually more closely related to Eukaryotes
than Bacteria
Archaea vs Bacteria
• Both are prokaryotes, so why are they in two
different domains?
1. Obtain energy differently
– NO Archaea perform photosynthesis
• Aerobic respiration (requires oxygen)
• Photosynthetic BACTERIA exist however (cyanobacteria)
6CO2 + 6H2O → C6H12O6 + 6O2
Archaea vs Bacteria
• Both are prokaryotes, so why are they in two
different domains?
1. Obtain energy differently
– Some Archaea: methanogenesis
• Form of anaerobic respiration; a process that occurs in
environments that lack oxygen
• One of the final stages of decomposition
• Without methanogenesis, carbon products would
accumulate.
CO2 + 4 H2 → CH4 + 2H2O
CH3COOH → CH4 + CO2
Archaea vs Bacteria
• Both are prokaryotes, so why are they in two
different domains?
2. Live in different habitats
– Archaea are extremophiles
• They are able to live in environments of extreme heat
(Thermophile), acidity (Acidophile), or salt
concentrations (Halophile)
– Most Bacteria are mesophiles
• Habitats of moderate condition; less extreme
Archaea vs Bacteria
• However they both have similar reproduction
strategies
1. Binary Fission (pg. 62)
•
In environmentally favourable conditions
2. Conjugation (of plasmids)
•
In less favourable conditions
• Only bacteria form endospores
Homework
•
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Pg. 55 #3, 5
Pg. 58 #4, 6, 14
Pg. 62 #7, 8, 11, 12
Pg. 66 #5, 8
• Create a chart comparing Viruses,
Bacteria and Archaea .