Chapter 27 Learning curve

Question 1

Which one of the following is a key advantage that eukaryotic cells have over prokaryotic cells?

Answer 1

Eukaryotic cells have a flexible cytoskeleton, which allows them to change shape and gives them the ability to engulf other materials.

Question 2

The only known eukaryotic-bacterial symbioses are the two that explain the development of the chloroplast and mitochondria.

Answer 2

false

Question 3

Which of the following is the best description of a protozoan?

Answer 3

a heterotrophic protist

Question 4

Diatoms appeared during the Mesozoic Era, and the skeletons of these organisms likely contributed to the accumulation of sediments on the seafloor.

Answer 4

true

Question 5

Sexual reproduction gave rise to complex life cycles seen in eukaryotic organisms.

Answer 5

true

Question 6

Which of the following is a hypothesis to explain the origin of the eukaryotic cell?

Answer 6

A eukaryotic cell evolved first, then incorporated a proteobacterial cell that became a mitochondrion.

Question 7

The terms algae and protozoa have significant phylogenetic meaning.

Answer 7

false

Question 8

Which of the following organisms is currently considered one of the primary photosynthetic organisms in the oceans?

Answer 8

diatoms

Question 9

Not all eukaryotes contain a dynamic cytoskeleton―or even a cytoskeleton at all. The smallest eukaryotes actually possess rigid cell walls composed of peptidoglycan, much like bacteria.

Answer 9

false

Question 10

Imagine that a researcher discovers a new type of organelle in single-celled eukaryotes. She suspects this new organelle is the result of endosymbiosis. How could she support this theory?

Answer 10

She could use electron microscopy to determine if any structural similarities exist between this new organelle and prokaryotic cells (i.e., like proteobacteria or cyanobacteria).

She could determine whether this organelle has both an inner and outer membrane.

If this organelle has its own DNA, she could compare its genetic sequence to those of certain prokaryotes.

Question 11

Which of the following is the best description of algae?

Answer 11

a photosynthetic protist

Question 12

Protist diversification may be linked to the action of algae on Earth 800 million years ago. As algae produced oxygen on early Earth and sulfide levels decreased, these events may have paved the way for the diversification of protist life.

Answer 12

true

Question 13

The current theory is that chloroplasts are descendants of symbiotic cyanobacteria that lived within eukaryotic cells. If we look at their respective genomes, however, we see that the cyanobacteria have many more genes than do chloroplasts. Where did these genes go?

Answer 13

Many of them were transported to the nucleus, and others were lost.

Question 14

Some heterotrophic organisms actually contain vestigial chloroplasts.

Answer 14

true

Question 15

During which era did the dinoflagellates, coccolithophorids, and diatoms appear?

Answer 15

Mesozoic Era

Question 16

Eukaryotes have more ways to obtain energy than prokaryotes.

Answer 16

false

Question 17

How does current theory explain the origin of a nucleus in eukaryotic cells?

Answer 17

There is no current theory that explains the origin of the nucleus.

Question 18

To which of the following superkingdoms do slime molds belong?

Answer 18

Amoebozoa

Question 19

Prior to the Mesozoic Era, the primary photosynthesizers in the ocean were the cyanobacteria and the diatoms.

Answer 19

false

Question 20

Which of the following accounts for why eukaryotic cells are typically much larger than prokaryotic cells?

Answer 20

Using molecular motors, eukaryotic cells can transport materials throughout their cytoplasm much faster than prokaryotic cells can, which have to rely on simple diffusion.

Question 21

The genes in chloroplasts more closely match the genes found in cyanobacteria compared to the genes found in the nuclei of photosynthetic eukaryotes.

Answer 21

true

Question 22

Which superkingdom contains members that are responsible for forming red tides?

Answer 22

Alveolata

Question 23

Eukaryotes have the ability to take in nutrients by phagocytosis, whereas prokaryotes do not. Which of the following explains the advantage this brings to eukaryotes?

Answer 23

Eukaryotes are able to exploit other, more complex materials for food that prokaryotes cannot.

Question 24

What structure is found in all members of the superkingdom Stramenopila?

Answer 24

a flagellum with stiff hairs

Question 25

There is no known symbiosis between a heterotrophic host and a photosynthetic partner in mammals.

Answer 25

true

Question 26

The current theory is that chloroplasts are descendants of symbiotic cyanobacteria that lived within eukaryotic cells. If we look at their respective genomes, however, we see that the cyanobacteria have many more genes than do chloroplasts. Where did these genes go?

Answer 26

Many of them were transported to the nucleus, and others were lost.

Question 27

There is no known symbiosis between a heterotrophic host and a photosynthetic partner in mammals.

Answer 27

true

Question 28

Most eukaryotic cells contain mitochondria, but a few single-celled eukaryotic organisms found in oxygen-free environments do not. Which of the following observations led biologists to reject the hypothesis that these mitochondria-free eukaryotes evolved BEFORE the endosymbiotic event that established mitochondria in other eukaryotes?

Answer 28

The nuclear genome of these mitochondria-free eukaryotes contains relics of mitochondrial genes.

Question 29

Which of the following is responsible for the evolutionary success of eukaryotes?

Answer 29

All of the answer options are correct: possessing a dynamic cytoskeleton, having complex patterns of gene regulation, localizing where energy metabolism takes place, possessing a dynamic endomembrane system

Question 30

In eukaryotes that lack mitochondria, what structures take over their function to generate ATP?

Answer 30

chloroplasts or hydrogenosomes

Question 31

To which of the following superkingdoms do diatoms belong?

Answer 31

Stramenopila

Question 32

Chloroplasts and mitochondria in eukaryotes are thought to have originated by __________________, where one organism lives within another.

Answer 32

Endosymbiosis

Question 33

Which of the following statements regarding diatoms is false?

Answer 33

Most diatoms are multicellular eukaryotes.

Question 34

Chloroplasts originated from endosymbiotic cyanobacteria once and only once.

Answer 34

false

Question 35

You have learned that having linear DNA has consequences, the major one being that the DNA gets shortened every time it replicates, something that does not happen with the circular DNA found in prokaryotes. What, then, is the advantage of having linear DNA?

Answer 35

Replication can begin from multiple sites on a linear DNA, allowing for rapid replication and relieving the evolutionary pressure for a streamlined genome.