Book cover for Biology

Biology

Sylvia S. Mader, Michael Windelspecht

ISBN #9780078024269

12th Edition

687 Questions

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153,501 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This chapter explores the evolution and diversity of protists, focusing on their acquisition of key organelles via endosymbiosis, and their classification into six distinct supergroups. It emphasizes the adaptability of protists through various nutritional modes and reproductive strategies, as well as their significant ecological roles ranging from producers to pathogens. Understanding these elements not only sheds light on evolutionary biology but also informs ecological and human health-related studies.

Learning Objectives

1

Explain the remarkable diversity in form, function, and metabolism among protists.

2

Describe how key organelles such as mitochondria and chloroplasts were acquired through endosymbiosis.

3

Differentiate among the six supergroups of protists and recognize their distinct evolutionary lineages.

4

Analyze the various nutritional modes and reproductive strategies employed by protists.

5

Evaluate the ecological roles of protists as producers, decomposers, and pathogens.

Key Concepts

CONCEPT

DEFINITION

Protists

The simplest eukaryotes that display a remarkable diversity in form, function, and metabolism.

Endosymbiosis

A symbiotic relationship in which one organism lives inside another; this process led to the acquisition of key organelles like mitochondria and chloroplasts in protists.

Mitochondria

Organelles known as the powerhouse of the cell, responsible for energy production, acquired by protists through endosymbiosis.

Chloroplast

Organelles responsible for photosynthesis, acquired by some protists through endosymbiosis.

Supergroups

Major evolutionary lineages into which protists are classified; the chapter identifies six such supergroups including Archaeplastida, Chromalveolata, Excavata, Amoebozoa, Opisthokonta, and Rhizaria.

Example Problems

Example 1

Mitochondria in protists originated from a. cyanobacteria. b. chloroplasts. c. anaerobic bacteria. d. aerobic bacteria. e. eukaryotic cells.

Example 2

Through what process did eukaryotic cells gain chloroplasts and mitochondria? a. engulfment b. endosymbiosis c. endocytosis d. phagocytosis e. transformation

Example 3

What feature of protists allow them to survive harsh environmental conditions? a. vegetative cells b. plankton c. cysts d. plastids e. vacuoles

Example 4

Which of these is a green alga? a. Volvox b. Gelidium c. Euglena d. Paramecium e. Plasmodium

Example 5

In Chlamydomonas, the adult vegetative cell a. is haploid. b. survives harsh environments. c. produces zygospores. d. is dormant. e. is ciliated
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Step-by-Step Explanations

QUESTION

How did protists acquire key organelles such as mitochondria and chloroplasts through endosymbiosis?

STEP-BY-STEP ANSWER:

Step 1: Understand that endosymbiosis is a process where one organism lives inside another, forming a mutually beneficial relationship.
Step 2: Recognize that ancestral protists engulfed other prokaryotic cells, which then became integrated as organelles.
Step 3: Identify that the engulfed bacteria evolved into mitochondria for energy production and, in photosynthetic lineages, evolved into chloroplasts for capturing sunlight.
Step 4: Conclude that this process was essential for the evolution and diversification of protists, enabling them to adapt to various ecological roles.
Final Answer: Protists acquired mitochondria and chloroplasts through the process of endosymbiosis, where engulfed prokaryotic cells evolved into these vital organelles.

Endosymbiosis in Protists

QUESTION

What criteria are used to classify protists into six supergroups?

STEP-BY-STEP ANSWER:

Step 1: Note that protist classification is based on both evolutionary history and morphological characteristics.
Step 2: Understand that molecular data, such as DNA sequencing, helps distinguish the different evolutionary lineages.
Step 3: Recognize the importance of characteristics like nutritional modes and reproductive strategies in classification.
Step 4: Identify that the six supergroups reflect major differences in cell structure and genetic heritage.
Final Answer: Protists are classified into six supergroups based on evolutionary lineage, molecular data, and differences in nutritional and reproductive strategies.

Classification of Protists

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Common Mistakes

  • Believing that all protists are similar in form and function, when in fact they exhibit vast diversity.
  • Confusing protist endosymbiosis with simple predation or phagocytosis.
  • Overlooking the significance of molecular data in classifying protists into evolutionary supergroups.
  • Assuming that protists only play beneficial roles; some can be harmful pathogens.