Metazoan refers to a multicellular organism belonging to the kingdom Animalia. Derived from the Greek terms "meta" meaning beyond or after, and "zoan" meaning animal, metazoans represent a vast and diverse group of animal species characterized by cellular differentiation and specialized tissues and organs.
Metazoans are distinguished from unicellular organisms (e.g., bacteria and protists), as well as colonial organisms composed of multiple individual cells (e.g., sponges and volvox), by their complex structural organization. Metazoan bodies are composed of various specialized cell types, which collaborate and interact to perform specific functions required for survival.
The classification of metazoans is based on embryonic development, body plan, and genetic relatedness. It includes animals ranging from simple, undifferentiated organisms to complex, highly evolved creatures. This classification encompasses creatures as diverse as insects, fish, birds, reptiles, and mammals, including humans.
Metazoans exhibit a variety of reproduction methods, including sexual and asexual modes. They display various modes of feeding, locomotion, sensory perception, and communication. Additionally, their anatomical structures and physiological systems are adapted to specific ecological niches and environmental conditions.
Metazoans have colonized virtually every known habitat on Earth, from terrestrial environments to aquatic ecosystems, including both freshwater and marine habitats. The immense diversity and ecological adaptation of metazoans contribute significantly to the global ecosystem function, including nutrient cycling, pollination, seed dispersal, and predation.
