Final answer:
Trypanosoma evades the host immune system by altering its surface proteins with each generation.
Step-by-step explanation:
The parasitic protist that evades the host immune system by altering its surface proteins with each generation is Trypanosoma. Trypanosoma brucei, the parasite responsible for African sleeping sickness, changes its surface glycoproteins with each infectious cycle. By switching to a glycoprotein coating with a different molecular structure, it can continuously replicate and avoid the immune system's specific antibody defense.