Which kingdom is composed of multicellular organisms lacking cell walls and typically with motile life stages?

• A. Protista
• B. Animalia
• C. Plantae
• D. Fungi

Answer: (B)

Lack of cell walls combined with mobility through life stages is a hallmark of animals. Animal cells don’t have rigid walls, which allows flexible tissue structure and movement via muscles and other tissues. Multicellularity and heterotrophy (ingesting other organisms for food) are also characteristic of animals, helping them move and interact with diverse environments. Plants have cellulose cell walls and are typically non-motile; fungi have chitin walls and are generally non-motile as adults; protists are a diverse group that includes many unicellular organisms. The combination described—multicellular, no cell walls, and typically motile life stages—best fits the animal kingdom.