How do you classify an organism as an animal?

📌 CONCEPT: An animal is classified as an organism that belongs to the kingdom Animalia, characterized by the presence of multicellularity, heterotrophic nutrition, and the absence of cell walls in plant cells and chloroplasts.

📐 RULE / FORMULA: The classification of an organism as an animal is based on the presence of certain key features such as the presence of a nervous system, muscles, and sensory organs, and the absence of cell walls and chloroplasts.

💡 WORKED EXAMPLE: For example, humans (Homo sapiens) are classified as animals because they are multicellular, heterotrophic, and have a complex nervous system and sensory organs. They also do not have cell walls or chloroplasts, which are characteristic features of plants.

⚠️ COMMON MISTAKE: Students often confuse animals with other organisms that are also multicellular and heterotrophic, but lack the presence of a nervous system or sensory organs.