Question 1

In a recent study, researchers found that carbon dioxide was pumped to the ocean floor after adding a small amount of iron to the water. Which of the following organisms was likely responsible for this result?

Accepted Answer

Diatoms are responsible for this result because they utilize iron as a nutrient to facilitate photosynthesis, which in turn increases their ability to absorb carbon dioxide from the atmosphere. When they die, they sink to the ocean floor, effectively sequestering the carbon.

Question 2

Slime molds and fungi were once included in the same taxonomic group due to some specific similarities in morphology and lifestyle. These two groups are now classified in different taxonomic groups. How would you describe these similarities now that the two groups are classified separately?

Accepted Answer

The similarities between slime molds and fungi that led to their initial grouping are examples of convergent evolution, where unrelated species independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

Question 3

Which of the following results would be most likely if a layer of warm, light water caused by ocean surface warming blocks nutrient upwelling?

Accepted Answer

C) Reduced populations of producers because they have access to fewer nutrients. Nutrient upwelling is crucial for the productivity of marine ecosystems, providing the essential nutrients needed by phytoplankton, the base of the oceanic food web. If a layer of warm, light water blocks this upwelling, the supply of nutrients to surface waters would decrease, leading to reduced populations of producers that rely on these nutrients for photosynthesis.

Question 4

Similar to most amoebozoans, the forams and the radiolarians also have pseudopods, as do some of the white blood cells of animals. If one were to construct a taxon that included all organisms that have cells with pseudopods, what type of evolutionary pattern would the tree show?

Accepted Answer

The tree would show a polyphyletic pattern because the trait of having pseudopods has arisen independently in different lineages (e.g., amoebozoans, forams, radiolarians, and some white blood cells in animals), rather than stemming from a common ancestor that had pseudopods and passed that trait down to all its descendants.

Question 5

A failure in which of the following processes can result in the formation of a supercell that is characteristic of plasmodial slime molds?

Accepted Answer

A supercell in plasmodial slime molds results from repeated nuclear divisions (mitosis) without cytokinesis, leading to a large cell with many nuclei.

Question 6

Green algae and plants are placed in the same phylogenetic group. Which of the following statements presents evidence to support this classification?

Accepted Answer

Similarities in chloroplast structure and pigment composition are key pieces of evidence supporting the classification of green algae and plants in the same phylogenetic group, as both share chlorophyll a and b, which are critical for photosynthesis.

Question 7

Use the following information to answer the question.
Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. In addition, P. bursaria also ingests bacteria.
Which term most accurately describes the nutritional mode of healthy P. bursaria?

Accepted Answer

P. bursaria is considered a mixotroph because it obtains nutrients through photosynthesis via its symbiotic relationship with Chlorella (making it partly autotrophic) and by ingesting bacteria (making it heterotrophic).

Question 8

You have discovered a photosynthetic protist that lives in fairly deep water (for example, 250 m deep).To which of the following groups should this organism be classified?

Accepted Answer

Red algae are known for their ability to live in deeper water due to their pigments, which can absorb and utilize the blue light available at such depths, unlike many other photosynthetic organisms that rely on light available closer to the surface.

Question 9

Many chlorophytes are unicellular, but others are larger and more complex. What does this indicate regarding the evolutionary history of chlorophytes?

Accepted Answer

The presence of both unicellular and more complex forms within chlorophytes suggests that there is extensive genetic variability within the group, allowing for a range of evolutionary adaptations and complexity.

Question 10

Amoebas are polyphyletic. Based on this fact, which of the following statements regarding their evolution is correct?

Accepted Answer

Being polyphyletic means amoebas have evolved from multiple ancestral lines. This complexity necessitates ongoing research to fully understand their origins and evolutionary history.

Question 11

A biologist discovers an alga that is marine, multicellular, and lives at a depth reached only by blue light. Based on this information, to which of the following groups of algae would this organism be classified?

Accepted Answer

Red algae are known for their ability to live at greater depths than most other algae, thanks to their unique pigments that can absorb and utilize blue light, which penetrates deeper into the water.

Question 12

SAR is a highly diverse group of protists defined by DNA similarities determined through whole-genome analysis of various organisms in the group. Which of the following conclusions could be drawn from this information?

Accepted Answer

The SAR group is considered a monophyletic group because it is defined by DNA similarities that indicate the members share a common ancestor, which is a characteristic of monophyletic groups.

Question 13

What do the multiple branching points at the root of the eukaryotic phylogenetic tree indicate about the evolution of eukaryotes?

Accepted Answer

The multiple branching points at the root of the eukaryotic phylogenetic tree indicate that eukaryotes share a common ancestor. This reflects the complexity and diversity of eukaryotic life, suggesting that all eukaryotic organisms diverged from a single ancestral lineage.

Question 14

Which of the following statements correctly describes one difference between green algae and land plants?

Accepted Answer

Green algae can be unicellular or multicellular, whereas land plants are predominantly multicellular. This is a key difference, as land plants have evolved complex multicellular structures to adapt to terrestrial environments. Choices B, C, and D are incorrect because both green algae and land plants have plastids, both can have alternation of generations, and both have cell walls containing cellulose.

Question 15

Living diatoms contain brownish plastids. If global climate change continues to warm surface waters of Earth's oceans, which of the following is the most likely effect on the animals that build coral reefs?

Accepted Answer

Coral reefs rely on a symbiotic relationship with dinoflagellates, which are photosynthetic algae. If the surface waters warm, it can lead to conditions unfavorable for these dinoflagellates, such as being outcompeted for light and nutrients by other organisms like diatoms. This can disrupt the symbiotic relationship, leading to coral bleaching and potentially the death of coral reefs.

Question 16

Researchers have shown that "income levels in countries hard hit by malaria are 33% lower than in countries with similar income that are free of the disease." Which of the following statements is correct regarding this observation?

Accepted Answer

This observation is a correlation between malaria prevalence and lower income levels. Correlation does not imply causation, meaning we cannot confidently conclude that malaria directly causes lower income levels without further experimental evidence.

Question 17

Which of the following types of protists causes the potentially fatal disease dysentery?

Accepted Answer

Entamoeba histolytica is the protist responsible for causing dysentery, a severe form of diarrhea that may include blood. This organism infects the colon through contaminated food or water.

Question 18

Which of the following organisms is a producer?

Accepted Answer

Diatoms are producers because they are photosynthetic algae, capable of converting light energy into chemical energy through the process of photosynthesis, thus producing organic compounds from inorganic substances.

Question 19

You have discovered that some members of an aquatic species of motile, photosynthetic protists have evolved to become parasitic to fish. They gain the ability to live in the fish gut, absorbing nutrients as the fish digests food. Over time, which of the following phenotypic changes would you expect to observe in this population of protists?

Accepted Answer

The answer of You have discovered that some members of...

Question 20

Which of the following groups is matched with a correct anatomical feature?

Accepted Answer

Brown algae are characterized by their unique anatomical features, including a blade, which is a leaf-like structure that assists in photosynthesis. The other options are incorrect matches to the listed groups.

Quiz 28: The Origin and Evolution of Eukaryotes