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The first list shows number of neurons in their entire nervous system. The second list shows the number of neurons in the structure that has been found to be representative of animal intelligence. [1] The human brain contains 86 billion neurons, with 16 billion neurons in the cerebral cortex. [2] [1]
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
Typically, Old World monkeys (paleotropical) are larger than New World monkeys (neotropical); the reasons for this are not entirely understood but several hypotheses have been generated. [3] As a rule, primate brains are "significantly larger" than those of other mammals with similar body sizes. [ 4 ]
The family includes the largest members of the passerine order. The smallest corvid is the dwarf jay (Cyanolyca nanus), at 41 g (1.4 oz) and 21.5 cm (8.5 in). The largest corvids are the common raven (Corvus corax) and the thick-billed raven (Corvus crassirostris), both of which regularly exceed 1,400 grams (3.1 pounds) and 65 cm (26 in).
The sperm whale brain is the largest known of any modern or extinct animal, weighing on average about 7.8 kilograms (17 lb) [61] [62] (with the smallest known weighing 6.4 kilograms (14 lb) and the largest known weighing 9.2 kilograms (20 lb)), [44] [45] more than five times heavier than a human brain, and has a volume of about 8,000 cm 3. [63]
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.
Dolphins have the highest brain-to-body weight ratio of all cetaceans. [11] Monitor lizards, tegus and anoles and some tortoise species have the largest among reptiles. [citation needed] Among birds, the highest brain-to-body ratios are found among parrots, crows, magpies, jays and ravens. Among amphibians, the studies are still limited.
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs .