Final answer:
Animals share several fundamental characteristics that unify them, including being eukaryotic, multicellular, heterotrophic, having specialized tissues, a fixed body plan, sexual reproduction, and various developmental characteristics.
Step-by-step explanation:
Animals share several fundamental characteristics that unify them. They are eukaryotic, multicellular, and heterotrophic organisms that ingest their food. Animals also have specialized tissues, such as nerve, muscle, and connective tissues, which enable them to perform various functions.
Additionally, most animals share a fixed body plan and reproduce sexually. They exhibit a range of developmental characteristics, such as the number of germ tissue layers formed during development and the origin of the mouth and anus. Animals also have the ability to grow and develop, regulate their internal environment, and detect and respond to environmental stimuli.
In conclusion, the fundamental characteristics of animals include being eukaryotic, multicellular, heterotrophic, having specialized tissues, a fixed body plan, sexual reproduction, and various developmental characteristics.