Bilaterian
Bilaterian
Bilaterian (/bɪˈlætəriən/), from the Latin bilaterus meaning "two-sided", is a term used in Biology to describe animals that exhibit bilateral symmetry, meaning they have a front and a back end, as well as an upside and downside, and therefore a left and a right side that are mirror images of each other.
Etymology
The term "Bilaterian" is derived from the Latin bilaterus, which means "two-sided". This term is used to describe the bilateral symmetry that these animals exhibit.
Characteristics
Bilaterians are a major group of animals that include humans, most insects, fish, and birds. They are characterized by having a body plan that is symmetric around a central axis, with a distinct head and tail (anterior-posterior axis) and a back and belly (dorsal-ventral axis). This is a step up in complexity from the radial symmetry exhibited by many simpler animals such as jellyfish.
Evolution
The evolution of Bilaterians is a significant event in the history of life on Earth. The first Bilaterians are thought to have appeared in the Ediacaran period, over 600 million years ago. The development of bilateral symmetry is believed to have allowed for more efficient locomotion and has been linked to the development of complex organs and organ systems.
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