Nervous system
Nervous systems are found in most multicellular animals, but vary greatly in complexity. The only multicellular animals that have no nervous system at all are sponges, placozoans, and mesozoans, which have very simple body plans. The nervous systems of the radially symmetric organisms ctenophores (comb jellies) and cnidarians (which include anemones, hydras, corals and jellyfish) consist of a diffuse nerve net. All other animal species, with the exception of a few types of worm, have a nervous system containing a brain, a central cord (or two cords running in parallel), and nerves radiating from the brain and central cord. The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in African elephants.
Sea turtle
Sea turtles' limbs and brains have evolved to adapt to their diets. One of the main things sea turtles consume is jellyfish and the use of their limbs to hold, swipe, and forage their food has helped them eat more efficiently. Originally sea turtles' limbs have evolved for locomotion but now they have evolved to aid them in the ability to get food. In addition to the evolution of limbs, sea turtles' brains have also evolved. The frontal cortex of a sea turtle's brain was not very developed. This underdevelopment caused the sea turtles to not be able to learn from their surroundings.