life11e_ch39

How would you build a multicellular animal?

This might seem like a silly question; even bioengineers don’t build animals. But as you begin to study animal form and function, or animal physiology, it is instructive to think of all of the problems animals must solve to survive. For example: they must:

extract energy and nutrients from the environment.
build all of the internal structures they need.
eliminate toxins and metabolic waste products.
sense the environment and respond to it in various ways, including movement.
maintain constant conditions in their internal environments.
reproduce.

Single- and multicellular organisms have evolved to conquer these challenges. In fact, single-celled organisms are remarkably abundant and thrive in widely diverse environments. Multicellular organisms have evolved complex body systems to conquer the same challenges. Given the success of single-celled organisms, why have multicellular animals evolved? How is it advantageous to be multicellular? Multicellularity confers two advantages—large size and the opportunity for cells to specialize.