Lecture 10: Protists

Question 1

What does “Protist” refer to
Is this a monophyletic group?

Answer 1

most of the eukaryotes, with the exception of plants, animals, fungi (NOT A MONOPHYLETIC GROUP)

Question 2

What are some things that make bacteria and archaea similar

Answer 2

1. The way they divide (binary fision)
2. circular organization of DNA
3. Haploid (one copy of DNA)
4. Unicellular (BESIDES cyanobacteria)

Question 3

What is some evidence of evolution for eukaryotes?

Answer 3

1. nucleus
2. mitosis
3. meiois
4. organelles like mitochondria and chlorplasts
5. linear chromosomes
6. diploidy (2 copies of genes)
7. complex multicellularity

Question 4

How did the prokaryote evolve into a eukaryotic cell

Answer 4

1. The origin of the nucleus
2. the endosymbiotic incorporation of prokaryotic cells to form mitochondria and chloroplasts

Question 5

What are some things that must have occurred to form a nucleus?

Answer 5

1. Eukaryotes package their DNA into chromosomes
2. Eukarotes undergo mitosis
3. Most eukaryotes have a diploid phase of their life cycle

Question 6

Giardia lamblia

Answer 6

A primitive eukaryote that gave insight to the origin of the nucleus. Represents a “missing link” between prokaryotes and eukaryotes. Has 2 nuclei but are both haploid.
Steps may have gone like this:
1. Haploid prokaryote
2. primimative eukaryote with single haploid nucleus
3. primitative eukaryote with two haploid nuclei
4. eukaryote with a single diploid nucleus

Question 7

Oxytricha Trifallax

Answer 7

Has two nuclei calls the micro and macro nucleus. The micro is passed on to the next generation but the macronucleus is where proteins are made.
In the micro, the genetic code is completely scrambled while the macro is not

Question 8

Endosymbiotic theory

What does endo and symbiosis mean

Answer 8

Hypothesizes that some early eukaryotic cells engulfed prokaryotic cells and kept them instead of digesting them
- Endo: within
- symbiosis: a close and prolonged physical relationship between individuals of different species

Question 9

What does the endoysmbiotic theory hypothesize (3 steps)

Answer 9

1. A prokaryote was engulfed by phagocytosis by a primitaive eukaryotic cell
2. The prokaryote was not digested immediately but acted as an endosymbiont that helped cellular metabolism
3. Eventually both the host and the endosymbiont lost the ability to exist on their own because of their mutalistic symbiosis

Question 10

How is it thought for chloroplasts and mitochondria to have arisen?

Answer 10

Mitochondria: endoysmbiosis of an aerobic heterotroph (event occurred once)
Chloroplasts: A eukaryote engulfed a photosynthetic cyanobacterium (multiple occassions)
1st event occurred in the evolutonary branch that leads to plants
2nd event is the engulfment of a eukaryote with a cloroplastr by another eukaryoyte

Question 11

What is the 6 pieces of evidence in favor of the endosymbiotic theory?

Answer 11

1. They are the right size to have come from prokaryotic cells
2. Membranes of both have enzyme and transport systems like those of prokaryotes
3. Organelles divide by a splitting process similar to prokaryotes (fission)
4. Both have circular DNA (like prokaryotes)
5. Both contain machinery for DNA replication and translation suggesting they were once free living
6. Molecular schematics has shown that both their genes are prokaryotic like (more similar than eukaryotic)