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Not all animals have neurons; Trichoplax and sponges lack nerve cells altogether. Neurons may be packed to form structures such as the brain of vertebrates or the neural ganglions of insects. The number of neurons and their relative abundance in different parts of the brain is a determinant of neural function and, consequently, of behavior.
Brain power. If you had to guess which animal was packing 32 brains, you'd probably guess wrong. The answer is leeches, which have a brain in each of their 32 body segments.
Sperm whales (Physeter macrocephalus) have the largest known brain mass of any extant animal, averaging 7.8 kg in mature males. [4] Orcas (Orcinus orca) have the second largest known brain mass of any extant animal. (5.4-6.8 kg) [5] Bottlenose dolphins (Tursiops truncatus) have an absolute brain mass
All leech species, however, have 32 segments, called somites, (34 if two head segments, which have different organization, are counted). [30] [31] Of these segments, the first five are designated as the head and include the anterior brain, several ocelli (eyespots) dorsally and the sucker ventrally.
Animal ability to process and respond to stimuli is correlated with brain size. Small-brain animals tend to show simple behaviors that are less dependent on learning than those of large-brained animals. Vertebrates, particularly mammals, have larger brains and complex behavior that changes with experience.
Cephalopods have large, well-developed brains, [8] [9] [10] and their brain-to-body mass ratio is the largest among the invertebrates, falling between that of endothermic and ectothermic vertebrates. [11] The nervous system of cephalopods is the most complex of all invertebrates.
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals.It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for special senses such as vision, hearing and olfaction.
What I would really like to know is the neuron content of a Sperm Whale's brain, as it has the largest of all animal brains (9kg/20lbs). Although not the largest relative to its body size, which might be another interesting cross-reference, with both contributing to an article on how they relate to animal intelligence. -- 123.226.95.231 ( talk ...