Bio2 Slides Exam 1

What is a character?

defined attribute of a single species

Highlight the main differences between homologous & analogous structures

Homologous

• Common evolutionary history + shared CA

Analgous

• independently acquired structures because of environmental pressures

• No shared CA

• convergent evolution

What is a polytomy in an phylogenetic tree?

2 or more descendant groups with unclear evolutionary relationships

What is the difference between a shared ancestral trait and a shared derived character?

Shared ancestral trait is not unique to clade, it originated in the ancestor. Derived is unique to a clade.

What is a monophyletic group in a phylogenetic tree?

A CA and all of its descendants (the ideal clade)

What is a paraphyletic group in a phylogenetic tree?

The common ancestor and some of its descendants

What is a polyphyletic group in a phylogenetic tree?

Distantly related species not including most recent CA

What is evolution?

changes in allele frequency in populations over time

Are viruses part of the domains of life?

No, they are considered non-living

Are viruses cellular? Also, can they reproduce?

Viruses are non-cellular and cannot reproduce, only replicate

All viruses are obligate intracellular parasites. What does this mean?

They invade susceptible host cells & use the host cells’s resources as well as processes

Do viruses have DNA or RNA?

They can have either DNA or RNA.

Explain the role of a capsid in viruses.

The capsid is the protein coat that surrounds the genetic material, determining the:

• Shape of virus

• plays role in attatchment

What is the capsid made of in viruses?

capsomere (protein subunit)

What is the envelope structure in viruses and do all of them have it?

It is the bilayer membrane outside the capsid obtained from the host cell during budding

not all viruses have it

How does host range or specificy differ between different viruses?

Some have narrow host ranges (even with specific tissues), while other have broad ranges

Explain the mechanism behind the specifity of viruses (why they are particular with what they infect)

They have viral surface proteins that connect to specific host receptor molecules

What does a virulent phage do and what cycle does it use?

• Kills the host at the end of the cycle and utilizes the lytic cycle

SEQ LYTIC CYCLE

1. Attatchment & Injection: virus attatches self to host cell and injects into it

2. The phage DNA remains seperate from the host

3. Replication - The phage replicates its DNA

4. The phage makes its respective proteins

5. Cell lyses and phages exit

What cycles do temperate phages use?

Lysogenic & Lytic cycle

SEQ LYSOGENIC CYCLE

1. Attatchment + injection

2. phage dna intergrates self into host genome

3. host cell divides and DNA is passed onto host daughter cells

What 2 domains of life to prokaryotes belong to?

Archaea & Bacteria (which is what we are focusing on)

Which of these do prokaryotes have: nucleus, organelles, ribosomes?

Ribosomes

In prokaryotes, where is the cell wall located and what is its function?

It surrounds the plasma membrane and maintains cell shape

What are the 3 common prokaryotic cell shapes (and what maintains these shapes?)

1. cocci = spherical

2. bacilli = rod shaped

3. spirilli/spirochetes = spiral
   
   The cell wall maintains the shapes

In prokaryotes (only bacterial prokaryotes) what is the cell wall made of?

Peptidoglycan, which is a polymer made of polypetides and sugars

When it comes to prokaryotic cell structure, what is the function of all these components:

1. Cell Wall

2. Capsule

3. Pili

4. Plasma membrane

5. Cytoplasm

6. Ribosome

7. flagellum

8. plasmids

9. nucleiod

10. Chrosome

1. Cell Wall: Maintains cell shape

2. Capsule: surrounds cell wall + protects against dehydration & phagocytosis

3. Pili: attatchment

4. Plasma membrane: letting things in/out of cell

5. Cytoplasm: cytosol + contents

6. Ribosome: protein synthesis

7. flagellum: locomotion

8. plasmids: small dna circles that have non-essential genes

9. nucleiod: unenclosed area where DNA is stored

10. Chromosome: DNA, always haploid (n)

What are the two stains used in a gram stain?

Crystal violet (purple) & safranin (pink)

If a bacterial cell wall is gram positive, what does that mean?

It means the cell wall has thick peptidoglycan, which traps crystal violet, and stains purple

If a bacterial cell wall is gram negative, what does that mean?

The wall has thin peptidoglycan and can’t trap crystal violet, therefore letting safranin show and staining pink.

CC positive/negative taxis

positive: movement towards the stimulus
negative: movement away from the stimulus

What are the 3 main parts of the bacterial flagellum?

1. The motor: the rings in the cell wall and plasma membrane

2. Hook

3. Filament

SEQ Bacterial flagellum function

H+ pumped out across PM by ETC → Form gradient → Diffuse into cell through motor → Produces force → Hook turns → Filament rotates —→ Now we moving!

SEQ binary fission (the process in which prokaryotes reproduce)

1. The single circular chrosome in the prokaryote cell is replicated

2. The FtsZ proteins then go to middle forming a Ftsz ring, then a septum

3. Cell fully splits, now we have 2 identical cells

What are the two main mechanisms of genetic diversity in prokaryotes?

A. Mutation + Rapid Reproduction

B. Genetic Recombination

SEQ/CC the 3 types of genetic recombination in prokaryotes

1. Transformation: external DNA taken up and integrated into genome

2. Transduction: During phage replication, an error occurs where a fragment of host DNA is packaged into the new phage. The new phage transfers that DNA to another cell, incorporating it into its genome.

3. Conjugation: Genetic info transferred between two living prok cells via a F factor in the form of a plasmid. F+ cell uses pilus to attatch to F- cell, making a mating bridge to transfer plasmid DNA.