Chapter 24, Problem 40A

Summary Introduction

To write:

Microscopic agents that are living and non living.

Introduction:

Microscopic organisms can cause disease. They include bacteria, viruses, protozoa, and fungi. They may be prokaryotic or eukaryotic. Most prokaryotic organisms are unicellular. The microorganisms enter the body through a variety of ways. Contaminated food and water, and vectors are some of the common ways through which the microorganisms enter the body and cause diseases and infections.

Explanation of Solution

Bacteria are prokaryotic microorganisms. They lack membrane bound organelles but is capable of performing life functions. Protozoans are single celled eukaryotes that are either parasitic or free living. Fungi are eukaryotic heterotrophs that are unicellular or multicellular. Unicellular fungi are called yeasts. Among the microscopic disease causing agents, viruses are considered non-living. They are a strand of genetic material within a protein coat. They lack cell organelles, cannot make proteins and are unable to replicate on their own. They need a host cell to replicate. They are some of the smallest known disease-causingstructures. Once a virus attaches itself to a host cell, it goes to the cytoplasm of the host cell and starts to replicate.

Conclusion

Viruses are nonliving microscopic agents. They require a host cell to replicate.