Final answer:
A human who harbors a protozoan that lives and reproduces inside their red blood cells is an example of a host. Plasmodium falciparum, which causes malaria, is one such parasite that utilizes humans as hosts in its complex life cycle that also involves mosquitoes as vectors.
Step-by-step explanation:
A protozoan that lives and reproduces inside of a human red blood cell makes the human an example of a host.
In biology, a host refers to an organism that harbors a parasite, or a smaller organism inside it.
Parasites such as Plasmodium falciparum, which causes malaria, live and reproduce inside human hosts but have complex life cycles often involving another organism, such as a mosquito, that acts as a vector to spread the disease.
A protozoan can switch between the trophozoite stage, where it is actively feeding and growing, and the cyst stage, an encapsulated form that can survive harsh conditions.
When a protozoan like Plasmodium infects a human, it undergoes asexual reproduction within the liver and red blood cells, leading to symptoms of malaria as the parasites are released into the bloodstream.