Final answer:
An animal cell is the eukaryotic cell without a cell wall, found in multicellular organisms of the kingdom Animalia, capable of performing specialized functions due to its flexibility in shape.
Step-by-step explanation:
An animal cell is defined as the smallest independently functioning unit of a multicellular organism in the kingdom Animalia. All animal cells are eukaryotic cells, which means they have a nucleus and other membrane-bound organelles. Animal cells differ from plant and fungal cells in that they do not have a rigid cell wall, providing them with the flexibility to adopt various shapes and become specialized for different functions, such as transmitting nerve impulses in the case of nerve cells. Their structure includes cytoplasm encased by a plasma membrane, and they contain essential genetic material in the form of DNA.
Despite the vast diversity in size and function across different animal cell types, they all share a common structure, including cytoplasm, a plasma membrane, and genetic material. The absence of a cell wall in animal cells allows them to form connections and tissues that can adapt and respond to the environment efficiently, contributing to the complexity of multicellular organisms.