Question 1

Which of the following best describes the process of secondary endosymbiosis as it relates to protist evolution?

Accepted Answer

A heterotrophic eukaryote engulfs a photosynthetic eukaryote, which then becomes an organelle.

Question 2

Which structure is unique to the Euglenozoans and helps distinguish them from other protists?

Accepted Answer

A crystalline rod inside their flagella

Question 3

Diatoms play a significant role in the global carbon cycle because:

Accepted Answer

Their dead cells sink to the ocean floor, sequestering CO$$_2.$$

Question 4

Which of the following is an example of an analogous structure between brown algae and land plants?

Accepted Answer

Holdfasts and roots

Question 5

Why do red algae appear dark red or almost black in deep water?

Accepted Answer

They possess the pigment phycoerythrin, which absorbs blue and green light.

Question 6

Which nutrient most commonly limits the growth of photosynthetic protists in freshwater environments?

Accepted Answer

Phosphorus

Question 7

What is the main evolutionary significance of gene transfer from endosymbionts to the host nucleus?

Accepted Answer

It makes the endosymbiont dependent on the host for survival.

Question 8

Which group is considered the closest relatives to land plants?

Accepted Answer

Charophytes

Question 9

A scientist observes a protist with a hairy and a smooth flagellum. To which group does this organism most likely belong?

Accepted Answer

Stramenopiles

Question 10

If global sea surface temperatures (SST) continue to rise, what is the most likely impact on marine photosynthetic protists and the global carbon cycle?

Accepted Answer

Protist biomass will decline, reducing carbon sequestration in the ocean.

Question 11

Which of the following best explains why diatom blooms are considered a controversial method of geoengineering?

Accepted Answer

They only sequester CO$$_2 in $$areas with little ocean circulation, making their effectiveness limited.

Question 12

Which of the following statements about protists is FALSE?

Accepted Answer

All protists are multicellular.

Question 13

Which of the following is a real-world consequence of declining phytoplankton populations due to nutrient limitation?

Accepted Answer

Increased atmospheric CO$$_2$$ levels

Question 14

Which of the following best describes mixotrophy in Euglenids?

Accepted Answer

They can switch between autotrophy and heterotrophy depending on environmental conditions.

Question 15

Which of the following is NOT a member of the SAR clade?

Accepted Answer

Euglenozoans

Question 16

A marine biologist finds an organism with a two-part, glass-like wall made of silicon dioxide. This organism is most likely a:

Accepted Answer

Diatom

Question 17

Which of the following best explains why gene transfer from endosymbionts to the host nucleus was crucial for the evolution of organelles?

Accepted Answer

It allowed the host to express and target proteins back to the organelle.

Question 18

Which of the following is a correct pairing of protist group and a key ecological role?

Accepted Answer

Brown algae – Major marine producer

Question 19

Which of the following statements about green algae is TRUE?

Accepted Answer

Green algae are a paraphyletic group.

Question 20

Which of the following best describes the relationship between photosynthetic protists and aquatic food webs?

Accepted Answer

They form the base of the food chain, supporting all other aquatic life.

Protist Diversity and Evolution: Endosymbiosis, Major Clades, and Ecological Roles

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