Lecture 10: Protists

Question 1

What term classifies the majority of eukaryotes?

Answer 1

Protists refer to eukaryotes that are not animals, plant, or fungi. It is a paraphyletic group.

Question 2

What makes eukaryotes different from prokaryotes? (7)

Answer 2

1. a nucleus
2. mitosis
3. meiosis
4. organelles like mitochondria and chloroplast
5. linear chromosomes
6. diploidy
7. complex multicllurity

Question 3

How did the prokaryotic cell evolve into the eukaryotic cell?

Answer 3

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

Question 4

What 3 things had to happen in order for prokaryotes to form a nucleus?

Answer 4

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

Question 5

What is Giardia lamblia and what inferences can we make about the evolution of nuclei based on it?

Answer 5

Giardia lamblia is a primitive eukaryote that has two haploid nuclei.
This suggests that the nuclear envelope formed in these steps:
1. Haploid prokaryote
2. Primitive eukaryote with single haploid nucleus
3. primitive eukaryote with two haploid nuclei
4. Eukaryote with single diploid nucleus

Question 6

What is a symbiosis?

Answer 6

A close and prolonged physical relationship between individuals of two different species.

Question 7

What are the hypotheses of the endosymbiotic theory?

Answer 7

1. A prokaryote was engulfed by phagocytosis by a primitive eukaryotic cell
2. The prokaryote was not digested immediately but acted as an endosymbiont that helped cellular metabolism
3. Eventually both the host and endosymbiont lost the abilitiy to exist ont ehri own because of the mutualistic symbiosis

Question 8

What is the evidence in favor of the formation of mitochondria an dchloroplast via the endosymbiotic theory? (6)

Answer 8

1. Chloroplast and mitochondria are similar to prokaryotes in size
2. Chloroplast and mitochondria have membranes with enzyme and transport systems similar to prokaryotes
3. They divide by fission, similar to prokaryotes, and not mitosis
4. They have circular DNA
5. They have machiner for DNA replication and translation
6. Their genes are “prokaryotic like”

Question 9

What does it mean to be paraphyletic and how does this relate to protists?

Answer 9

Paraphyletic refers to a group of organisms descended from a common ancestor, but the group does not contain all of the descendants from that common ancestor. Protists are paraphyletic.

Question 10

What are the foraminifera?

Answer 10

Single-celled organisms with calcium carbonate shells. Most of the ~4,000 foram species live in the ocean and about 40% are planktonic. The rest live on the bottom of the ocean, where the sediment is made mostly of their shells.

Question 11

What are Euglenids? Name two types.

Answer 11

Trypanosoma cruzi causes Chagas’ disease and infects people through an insect. Trichonyma is a protist that lives in termite guts and helps termites digest wood.

Question 12

What are apicomplexans? Plasmodium falcipurum?

Answer 12

Apicomplexans are parasitic protozoa. Plasmodium falcipurum is a type of apicomplexan that causes malaria, a major cause of disease.

Question 13

What are dinoflagellates? What is a red tide?

Answer 13

Dinoflagellates are mostly unicellular algae and roughly half of which are autotrophs. They are often covered by hard shells made of cellulose and silicate and often have two flagella to propel them through water.

Dinoflagellates serve as a food source for many fish and animals in marine and fresh-water environments.
When dinoflagellates proliferate a lot, a “red tide” ensues. Though usually harmless, these tides can occasionally produce a toxic substance that kills many other species.

Question 14

What are algae? What are the three types?

Answer 14

Algae are the ‘plant-like’ protists. Most algae are autotrophic and multicellular.
- Algae is responsible for fixing half of the world’s carbon and thereby liberating oxygen
- The three types of algae are brown, green, and red.
- Kelp is a type of brown algae that can be used in gunpowder or everyday products
- Green algae are very similar to plants in that they undergo photosynthesis. They can be multicellular or unicellular and the aquatic kind are primarily found in fresh-water environments.

Question 15

Define these terms

• Alternation of generations
• Sporophyte
• Spores
• Gametophyte
• Zygote
• Embryo

Answer 15

• Alternation of generations: the alternation between multicellular haploid and diploid stages
• Sporophyte: The dominant diploid form that produces spores by meiosis
• Spores: are haploid and divide mitotically to generate a gametophyte
• Gametophyte: Developed from spores, the haploid phase of the life-cycle. Produces sperm and egg
• Zygote: The result of syngamy or fertilization. Now has two copies of genes and is diploid
• Embryo: formed from zygote and becomes sporophyte