Which of the following statements regarding protozoa is FALSE?
A) Protozoa are unicellular eukaryotes.
B) Nearly all protozoa cause disease.
C) Most protozoa reproduce asexually.
D) Protozoa are common in water and soil.
The Correct Answer and Explanation is:
The FALSE statement is:
B) Nearly all protozoa cause disease.
Explanation:
Protozoa are a diverse group of unicellular eukaryotic organisms, which means they have a defined nucleus and organelles, distinguishing them from prokaryotes like bacteria. Here’s why the other statements are true and why option B is false:
A) Protozoa are unicellular eukaryotes.
This is correct. Protozoa are single-celled organisms that belong to the domain Eukarya. They have membrane-bound nuclei and other organelles such as mitochondria, unlike bacteria which are prokaryotes. Their unicellular nature allows them to carry out all life processes within one cell, such as movement, feeding, and reproduction.
C) Most protozoa reproduce asexually.
This is also true. Protozoa typically reproduce asexually through processes like binary fission (splitting into two), budding, or schizogony (multiple fission). However, many protozoa also have sexual reproduction stages, especially in their complex life cycles, but asexual reproduction predominates.
D) Protozoa are common in water and soil.
This statement is true as well. Protozoa are widely distributed in aquatic and terrestrial environments. They thrive in freshwater, marine habitats, and moist soil where they feed on bacteria, algae, and organic debris, playing a vital role in nutrient cycling and ecosystem functioning.
Why is statement B false?
While some protozoa are pathogenic and can cause diseases in humans and animals—such as Plasmodium (malaria), Giardia (giardiasis), Entamoeba histolytica (amoebic dysentery), and Trypanosoma (sleeping sickness)—the majority of protozoa do not cause disease. Most protozoa are harmless or even beneficial in ecosystems, acting as important members of microbial food webs by consuming bacteria and organic matter, thus helping to recycle nutrients. Only a relatively small number of protozoan species are medically significant pathogens.
Summary:
- Protozoa = unicellular eukaryotes (true)
- Most reproduce asexually (true)
- Common in water and soil (true)
- Nearly all cause disease (false) — most are harmless and ecologically important, only some are pathogenic.
Hence, option B is the false statement.
