SUBMIT HOMEWORK ASSIGNMENT FROM LAST WEEK

2.1 The Organization of Life/ Viruses2.2 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

EukaryotesMembrane bound organellesUnicellular/ MulticellularMost are aerobic Reproduce by mitosis/meiosis

Prokaryotes vs Eukaryotes (Table 2.1)

• Two basic cell types recognized by biologists

ProkaryotesCircular DNANo membrane bound organellesUnicellularMany 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 DNA1. Insert the gene into the viral DNA/RNA2. 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

– NO Archaea perform photosynthesis• Aerobic respiration (requires oxygen)• Photosynthetic BACTERIA exist however (cyanobacteria)

6CO2 + 6H2O → C6H12O6 + 6O2

• Both are prokaryotes, so why are they in two different domains?1. Obtain energy differently

Archaea vs Bacteria

– 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

• Both are prokaryotes, so why are they in two different domains?1. Obtain energy differently

Archaea vs Bacteria

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

• Both are prokaryotes, so why are they in two different domains?

Archaea vs Bacteria

• However they both have similar reproduction strategies1. Binary Fission (pg. 62)• In environmentally favourable conditions

2. Conjugation (of plasmids)• In less favourable conditions

• Only bacteria form endospores

Homework

• 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 .