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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.
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.
Two-headed farm animals sometimes travel with animal side shows to county fairs. Most notably, The Venice Beach Freakshow supposedly houses the largest collection of two-headed specimens in the world, including over 20 two-headed animals that are alive. Many museums of natural history contain preserved two-headed animals.
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.
Cephalization is a characteristic feature of the bilaterians, a large group containing the majority of animal phyla. [3] These have the ability to move, using muscles, and a body plan with a front end that encounters stimuli first as the animal moves forwards, and accordingly has evolved to contain many of the body's sense organs, able to detect light, chemicals, and gravity.
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
NEW YORK (AP) — Scientists restored some activity within the brains of pigs that had been slaughtered hours before, raising hopes for some medical advances and questions about the definition of ...
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.