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| − | The cranium, also known as your brain, is the center of the nervous system in all vertebrate and most invertebrate animals.
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| − | ==The Shape of the cranium==
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| − | The shape and size of the brains of different species vary greatly, and identifying common features is often difficult. Nevertheless, there are a number of principles of brain architecture that apply across a wide range of species. Some parts of brain structure are common to almost the entire range of animals species; others differ "advanced" brains from more simple ones, or distinguish vertebrates from invertebrates.
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| − | ===Invertebrates===
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| − | Groups of invertebrates have complex brains: arthropods (insects, crustaceans, arachnids, and others), and cephalopods (octopuses, squids, and similar mollusks). The brains of arthropods and cephalopods arise from twin parallel nerve cords that extend through the body of the animal. Arthropods have a central brain with three divisions and large optical lobes behind each eye for visual processing. Cephalopods have the largest brains of any invertebrates. The brain of the octopus in particular is highly developed, comparable to the brains of some vertebrates.
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| − | ===Vertebrates===
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| − | The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. Brain size increases with body size but not proportionally. For example, primates have brains 5 to 10 times as large brain as any vertebrate. But Predators tend to have larger brains. When the mammalian brain increases in size, not all parts increase at the same rate. The larger the brain of a species, the bigger the vertebrate is.
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