Question 1

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

Accepted Answer

They act as primary producers, converting light energy into chemical energy stored in biomass via photosynthesis.

Question 2

During photosynthesis, algae absorb carbon dioxide and release oxygen. Which chemical equation best represents this process?

Accepted Answer

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

Question 3

How do heterotrophic protists contribute to nutrient cycling in ecosystems?

Accepted Answer

They consume dead organisms, sequester nutrients in their biomass, and excrete nutrients, making them available to primary producers.

Question 4

A sudden increase in nitrogen and phosphorus in a lake leads to a dinoflagellate bloom. What is a likely consequence for the ecosystem?

Accepted Answer

Oxygen depletion due to increased bacterial decomposition of dead algae, potentially causing fish kills.

Question 5

Which of the following is an example of a protist acting as an ecosystem engineer?

Accepted Answer

Kelp forming underwater forests that provide habitat for many marine species.

Question 6

Why are protists considered keystone species in some aquatic ecosystems?

Accepted Answer

They provide essential habitat and resources that support a wide variety of other organisms.

Question 7

Which of the following best explains how protists benefit human well-being through their role in carbon storage?

Accepted Answer

Algae absorb $$CO_2$$ during photosynthesis, and when their cells are buried in sediment, the carbon is locked up, reducing atmospheric $$CO_2.$$

Question 8

A marine ecosystem experiences a decline in kelp populations. Which of the following is a likely ecological consequence?

Accepted Answer

Loss of habitat for many marine species, leading to decreased biodiversity.

Question 9

Which process performed by protists is directly responsible for enabling aerobic cellular respiration in animals?

Accepted Answer

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

Question 10

In a food web, which of the following correctly describes the flow of energy and nutrients involving protists?

Accepted Answer

Energy flows from primary producers (such as algae) to consumers, while nutrients cycle between organisms and the environment.

Question 11

Which of the following scenarios best illustrates a negative impact of protists on human well-being?

Accepted Answer

Dinoflagellate blooms producing neurotoxins that can cause illness in humans and animals.

Question 12

Which of the following is a multi-step process involving protists that benefits both ecosystems and humans?

Accepted Answer

Algae photosynthesize, absorbing $$CO_2$$ and releasing $$O_2$$; when they die, their carbon-rich cells are buried, storing carbon and reducing greenhouse gases.

Question 13

Which of the following best explains why protists are considered important in nutrient flow pathways?

Accepted Answer

They transfer nutrients from one trophic level to another and make nutrients available to other organisms through excretion and decomposition.

Question 14

A scientist measures a significant drop in dissolved oxygen in a lake following an algal bloom. Which sequence of events best explains this observation?

Accepted Answer

Algae die and decompose, leading to increased bacterial activity that consumes oxygen.

Question 15

Which of the following is NOT a way that protists contribute to human well-being?

Accepted Answer

They act as the primary cause of all infectious diseases in humans.

Importance of Protists in Ecosystems and Human Well-being

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