How did multicellular life evolve? Algae, yeast and protists like slime moulds give some hints

Single-celled organisms that cluster and cooperate provide tantalising insights into the origins of multicellularity, suggesting this step may not be so rare after all

Why are slime molds categorized in the protista kingdom? - Quora

Slime Mold Life Cycle, Examples & Facts - Lesson

Amoebozoa - an overview

Single Cells Evolve Large Multicellular Forms in Just Two Years

Protist, Life Cycle, Characteristics & Reproduction

Organisms with aggregative multicellularity.

Slime molds as a valuable source of antimicrobial agents, AMB Express

Examples of Multicellular Protists - Lesson

Single Cells Evolve Large Multicellular Forms in Just Two Years

Groups of Protists Biology for Majors II

Slime Molds (U.S. National Park Service)