Apicomplexan life cycle clue — organisms with mammalian and insect hosts and a schizogony stage belong to which protozoan phylum?

Introduction:
Life-cycle signatures are powerful taxonomic clues. Schizogony (multiple fission producing many merozoites) alongside alternation between an insect vector and a mammalian host points to a specific phylum of parasitic protozoa.

Given Data / Assumptions:

• Two-host cycle: insect vector + mammalian host.
• Presence of schizogony as a proliferative stage.

Concept / Approach:
Apicomplexa (e.g., Plasmodium, Toxoplasma) are obligate parasites noted for apical complexes and complex life cycles. Plasmodium alternates between Anopheles mosquitoes and humans; schizogony occurs in human liver and red blood cells.

Step-by-Step Solution:

Verification / Alternative check:
Malaria life-cycle diagrams clearly show schizogony (exoerythrocytic and erythrocytic) and mosquito–human alternation, hallmark Apicomplexa.

Why Other Options Are Wrong:

• Sarcomastigophora: locomotory groups, lacks defining apicomplexan life-cycle traits.
• Microspora: spore-forming intracellular parasites with different biology.
• Myxozoa: parasitic cnidarians, not protozoa.

Common Pitfalls:
Confusing “multiple fission” generically with binary fission; overlooking the vector-borne hallmark of Apicomplexa.

Final Answer:
Apicomplexa