Problem 9 - Biology Today and Tomorrow with Physiology

Question

The________ are parasitic eukaryotes that live in other cells. a. viruses b. apicomplexans c. euglenoids d. slime molds e. both a and b f. all are correct

Step-by-Step Solution

Answer

Option B: Apicomplexans are parasitic eukaryotes.

Step 1: Understand the Options

Read each option carefully to understand what organisms they refer to. This will help you determine which ones are parasitic eukaryotes that live in other cells.

Step 2: Analyze Option A - Viruses

Viruses are indeed parasites that require a host cell to replicate, but they are not classified as eukaryotes. Thus, they do not fit the criteria of parasitic eukaryotes.

Step 3: Analyze Option B - Apicomplexans

Apicomplexans are indeed parasitic eukaryotes. They are known to live inside host cells and include organisms like Plasmodium, the causative agent of malaria.

Step 4: Analyze Option C - Euglenoids

Euglenoids are not generally parasitic. They are mostly free-living protists that can photosynthesize and do not typically live in other cells.

Step 5: Analyze Option D - Slime Molds

Slime molds are not parasitic eukaryotes. They live independently in moist, decaying wood or soil, and their lifestyle does not involve living inside other cells as parasites.

Step 6: Evaluate the Combination Options

Option E suggests both a and b are correct, but viruses are not eukaryotes. Therefore, E is incorrect. Option F suggests all are correct, which is also incorrect based on the individual analyses.

Key Concepts

Apicomplexans

Apicomplexans are a group of parasitic eukaryotes, known for their ability to live inside other cells, specifically within host cells. These organisms are a subgroup of protozoa, which are a diverse group of single-celled eukaryotic microorganisms. Apicomplexans are characterized by an intricate structure known as the "apical complex" that helps them invade host cells.

One of the most well-known examples of apicomplexans is *Plasmodium*, the parasite responsible for malaria. Apicomplexans target host cells in two main ways:

• They can invade and multiply within the host cell, often causing the cell to burst and release new parasites.
• They use the host's resources for growth and replication, sometimes altering the host cell's function to suit their needs.

Understanding apicomplexans is important for developing treatments and preventative measures against diseases like malaria. In addition to *Plasmodium*, other members include *Toxoplasma gondii*, which causes toxoplasmosis, and *Cryptosporidium*, known for causing gastrointestinal illnesses.

Host Cells

Host cells are the cells that become invaded and inhabited by pathogens, such as viruses, bacteria, or parasitic eukaryotes like apicomplexans. The interaction between the host cell and the invading organism is crucial for the survival of the parasite as well as the progression of the infection.

During invasion, apicomplexans attach to the host cell, at times using their apical complex, and penetrate the cell membrane. Once inside, they can manipulate the host cell's machinery to replicate and grow. This manipulation may lead to a variety of effects on the host cell, such as:

• Disruption of normal cellular functions.
• Use of the host cell's nutrients for parasitic growth.
• Eventual death of the host cell as the parasite multiplies.

Host cells play a key role in the lifecycle of parasitic eukaryotes, underscoring the need for careful study to understand how infections can be controlled.

Protozoa

Protozoa are a broad category of single-celled eukaryotic organisms, noted for their diversity and adaptability. While most are free-living, some have evolved to adopt parasitic lifestyles, such as apicomplexans. Protozoa can be found in a variety of environments, from aquatic to terrestrial habitats.

Despite being single-celled, protozoa display complex life processes that often mimic those of more advanced multicellular organisms. They can perform essential functions such as:

• Reproduction through asexual or, in some cases, sexual means.
• Nutrient acquisition through processes like phagocytosis or absorption.
• Adaptation to various environmental conditions.

Understanding protozoa and their varied lifestyles, especially the parasitic forms, helps in studying diseases they may cause, as well as their roles in environmental ecosystems. This knowledge aids in efforts to control protozoan-related infections and in harnessing beneficial attributes they may possess.