$$6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 1

Which of the following best describes the role of autotrophic protists in aquatic ecosystems?

Accepted Answer

They serve as primary producers, converting light energy into chemical energy via photosynthesis.

Question 2

During photosynthesis, algae convert light energy into which molecule, and what is its chemical formula?

Accepted Answer

Glucose, $$C_6H_{12}O_6$

Question 3

What is a major consequence of dinoflagellate blooms in aquatic ecosystems for human health?

Accepted Answer

Production of neurotoxins that can cause illness in humans.

Question 4

Which process performed by protists is directly responsible for enabling aerobic cellular respiration in most aquatic organisms?

Accepted Answer

Production of oxygen ($$O_2) $$during photosynthesis.

Question 5

How do heterotrophic protists contribute to nutrient cycling in ecosystems?

Accepted Answer

By sequestering nutrients from dead organisms and excreting them, making nutrients available to primary producers.

Question 6

Kelp forests are considered ecosystem engineers because they:

Accepted Answer

Provide essential habitat for many marine species.

Question 7

Which of the following equations represents the overall process of photosynthesis in protists?

Accepted Answer

$$6CO_2 + 6H_2O + 	ext{light energy} ightarrow C_6H_{12}O_6$ + 6O_2$$

Question 8

A sudden increase in nutrients (nitrogen and phosphorus) in a lake leads to a massive algal bloom. What is a likely ecological consequence?

Accepted Answer

Oxygen depletion as bacteria consume dead algae, leading to fish kills.

Question 9

Which of the following best explains how protists contribute to long-term carbon storage in aquatic environments?

Accepted Answer

By burying their cells in sediment, locking up carbon.

Question 10

Why are protists considered keystone species in some aquatic ecosystems?

Accepted Answer

Their presence is essential for maintaining ecosystem structure and function.

Question 11

Which trophic level do autotrophic protists primarily occupy in aquatic food webs?

Accepted Answer

Primary producer

Question 12

A scientist measures the oxygen concentration in a pond before and after a large algal bloom. What change is most likely observed, and why?

Accepted Answer

Oxygen concentration decreases as bacteria decompose dead algae, consuming oxygen.

Question 13

Which of the following is a direct benefit to humans provided by kelp forests?

Accepted Answer

They enable the existence of harvestable species, supporting fisheries.

Question 14

Which pathway best describes the flow of energy through an aquatic ecosystem involving protists?

Accepted Answer

Primary producer $$\rightarrow$$ Primary consumer $$\rightarrow$$ Secondary consumer $$\rightarrow$$ Tertiary consumer

Question 15

Which of the following is NOT a way protists impact human well-being?

Accepted Answer

Increasing atmospheric nitrogen through nitrogen fixation

Question 16

A lake experiences a winter drought, reducing water flow. What effect might this have on protist populations and ecosystem health?

Accepted Answer

Protist populations decrease, reducing primary production and affecting higher trophic levels.

Question 17

Which of the following best describes the dual role of protists as both consumers and decomposers in nutrient cycling?

Accepted Answer

They sequester nutrients from living and dead organisms, then excrete nutrients to make them available to producers.

Question 18

Which of the following scenarios illustrates a negative impact of protists on aquatic biodiversity?

Accepted Answer

A dinoflagellate bloom produces neurotoxins, causing fish and shellfish die-offs.

Question 19

Which of the following is a multi-step process by which protists help regulate atmospheric carbon?

Accepted Answer

Algae absorb $$CO_2$$ during photosynthesis, and when they die, their cells are buried in sediment, locking up carbon.

Importance of Protists in Ecosystems and to Human Well-being

Study Guide - Practice Questions