Which of the following statements regarding protozoa is FALSE?
Protozoa are common in water and soil.
Some protozoan pathogens are transmitted by arthropod vectors.
Nearly all protozoa cause disease.
Protozoa are unicellular eukaryotes.
Most protozoa reproduce asexually
The Correct Answer and Explanation is:
The FALSE statement is:
“Nearly all protozoa cause disease.”
Correct Answer: Nearly all protozoa cause disease
Protozoa are a diverse group of unicellular eukaryotic organisms that are mostly microscopic and motile. They are part of the kingdom Protista and exhibit a wide range of habitats and life cycles. Despite their diversity, only a small fraction of protozoa are pathogenic to humans.
1. Protozoa are common in water and soil – True
Protozoa thrive in moist environments and can be found abundantly in freshwater, marine environments, and soil. They play a crucial ecological role as both predators and prey, helping maintain microbial balance.
2. Some protozoan pathogens are transmitted by arthropod vectors – True
This is a significant characteristic of some disease-causing protozoa. For example:
- Plasmodium species (cause malaria) are transmitted by Anopheles mosquitoes.
- Trypanosoma brucei (African sleeping sickness) is transmitted by tsetse flies.
- Leishmania species are transmitted by sandflies.
These vectors are critical to the life cycle and transmission of these protozoans.
3. Protozoa are unicellular eukaryotes – True
All protozoa are unicellular, meaning each organism consists of a single cell. However, they are eukaryotic, possessing membrane-bound organelles, including a nucleus, mitochondria, and more complex intracellular structures than prokaryotes.
4. Most protozoa reproduce asexually – True
The majority of protozoa reproduce through asexual methods, such as binary fission, multiple fission, or budding. Some species can also reproduce sexually during part of their life cycle, which enhances genetic diversity.
5. Nearly all protozoa cause disease – False
This statement is incorrect and misleading. While protozoa are known for causing diseases such as malaria, amoebiasis, giardiasis, and trypanosomiasis, the vast majority are harmless to humans. Many protozoa contribute positively to ecological systems by recycling nutrients and serving as food for other organisms.
Summary:
Most protozoa are non-pathogenic and essential to ecosystems. The false statement is that “nearly all protozoa cause disease,” as only a small proportion are harmful to humans.
