Question 1

Protist diversification may be linked to changes in interactions with other contemporary protists, as some protists began to consume other protists and not just Bacteria or Archaea.

Accepted Answer

Protist diversification was likely influenced by changes in interactions with other protists, including the emergence of predation on other protists. This allowed for the evolution of new ecological niches and increased competition, leading to further diversification.

Question 2

Which of the following is an important consequence of the evolution of diatoms and coccolithophorids?

Accepted Answer

The evolution of diatoms and coccolithophorids led to the redistribution of silica and calcium carbonate in the oceans. These minerals became a significant source of sediments on the deep seafloor, altering the geological landscape of the ocean. This is a crucial consequence of the evolution of these organisms. Option A is incorrect because while diatoms and coccolithophorids dominate primary productivity in the oceans, it is not their evolution-specific consequence. Option C is partially correct but not the most significant consequence of their evolution. Option D is incorrect.

Question 3

Which of the following organisms is currently one of the MOST important photosynthetic organisms in the oceans?

Accepted Answer

Diatoms are currently one of the most important photosynthetic organisms in the oceans. They are responsible for a significant amount of primary production and play a crucial role in the oceanic food web. They are also able to adapt to changes in environmental conditions, making them a resilient and important species in the oceans.

Question 4

Imagine that your uncle is a scientist who has found himself in possession of a time machine. The two of you travel back to the Paleozoic Era, and are perusing the oceans for microscopic life. What will you find?

Accepted Answer

During the Paleozoic Era, you would find photosynthetic organisms like cyanobacteria and green algae, as well as heterotrophic protists such as radiolarians.

Question 5

A researcher discovers a new microfossil. At first, he is uncertain whether this organism was a bacterium, archaeon, or protist. After careful study, he determines that this organism was a protist. What features were present in this microfossil that lead the researcher to this conclusion?

Accepted Answer

The answer of A researcher discovers a new microfossil. At...

Question 6

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

Accepted Answer

Dinoflagellates, coccolithophorids, and diatoms are all types of planktonic organisms that first appeared in the Mesozoic Era, specifically in the Triassic period.

Question 7

Which of the following statements is TRUE regarding the eukaryotes of 1200 million years ago?

Accepted Answer

At this stage in Earth's history, photosynthetic eukaryotes were present. This is supported by fossil evidence of primitive algae and other photosynthetic organisms dating back to around 1200 million years ago. The other options are either incorrect or unsupported by evidence.

Question 8

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

Accepted Answer

Diatoms first appeared in the Mesozoic Era, and their silica-based skeletons contribute to the accumulation of sediments on the deep seafloor.

Question 9

Which of the following statements is TRUE regarding radiolarians?

Accepted Answer

Radiolarians have shells made of silica, not calcium carbonate, and other protists also have silica shells. Their shells are complex and not just circular. The statement about evolution due to high sulfide levels is speculative and not widely supported.

Question 10

A young paleontologist is extremely excited. In sedimentary rocks dating from 70 million years ago, she has found some new microfossils. The shells of which of the following organisms likely contributed to the accumulation of sediments on the seafloor (and the formation of these sedimentary rocks)?

Accepted Answer

All of the organisms listed are known to contribute to the accumulation of sediments on the seafloor and the formation of sedimentary rocks. Diatoms, radiolarians, foraminiferans, and coccolithophorids are all types of single-celled organisms with hard shells or skeletons made of mineralized materials. When these organisms die, their shells and skeletons sink to the seafloor where they contribute to the accumulation of sediment over time. Therefore, all of the choices are correct.

Question 11

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

Accepted Answer

Cyanobacteria were indeed primary photosynthesizers in the ocean before the Mesozoic Era, but diatoms did not become significant until the Mesozoic.

Question 12

Which is the oldest group of eukaryotes to be recognized in the fossil record?

Accepted Answer

Red algae are the oldest group of eukaryotes to be recognized in the fossil record, with fossils dating back to 1.2 billion years ago. Green algae, diatoms, coccolithophorid algae, and dinoflagellates all have more recent fossil records.

Question 13

It appears that eukaryotic diversity took off around 800 million years ago. Which of the following is thought to be responsible for this?

Accepted Answer

The ability to prey on other protists is thought to have originated or expanded 800 million years ago, setting in place an evolutionary arms race. This likely drove the diversification of eukaryotic organisms. The other choices are either inaccurate or insufficient to fully explain the diversification of eukaryotic diversity.

Quiz 27: Eukaryotic Cells: Origins and Diversity