Which statement best defines an animal (Kingdom Animalia)?

• A. A multicellular, eukaryotic autotroph that performs photosynthesis and has cellulose cell walls
• B. A eukaryotic decomposer that absorbs nutrients externally and typically has chitin cell walls
• C. A unicellular, prokaryotic organism that reproduces by binary fission and has peptidoglycan cell walls
• D. A multicellular, eukaryotic heterotroph that ingests food and lacks cell walls

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the key characteristics that define organisms in Kingdom Animalia. Animals are multicellular, meaning they are made up of many cells, and eukaryotic, meaning their cells have a nucleus and membrane-bound organelles.
2. Step 2: Recognize that animals are heterotrophs, which means they obtain their food by consuming other organisms rather than producing it themselves through photosynthesis.
3. Step 3: Note that animals ingest their food, meaning they take it into their bodies for digestion, unlike some other organisms that absorb nutrients externally.
4. Step 4: Identify that animals lack cell walls, which distinguishes them from plants (which have cellulose cell walls) and fungi (which have chitin cell walls).
5. Step 5: Use these defining features to evaluate each statement and select the one that correctly describes animals: multicellular, eukaryotic heterotrophs that ingest food and lack cell walls.