Keratin – a group of scleroproteins that form the structural bases of hair, wool, nails, and other epidermal structures in animals
Keystone Species – a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically
Kingdom – a taxonomic category of the highest rank, grouping together all forms of life having certain fundamental characteristics in common
Kleptoparasitism – a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food
Lagomorph – group of mammals characterized by two pairs of continually-growing incisors and fully furred feet
Larva – the stage in the life cycle of an animal during which it is motile and capable of feeding itself that occurs after hatching from the egg and prior to the reorganizations involved in becoming adult
Lateral Line – a system of receptors embedded in special grooves in the skin that is capable of detecting vibrations in the water surrounding the animal
Lek – territory that is held and defended against rivals by males of certain species during the breeding season
Leucism – a condition in which there is partial loss of pigmentation in an animal resulting in white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticle, but not the eyes
Ligament – a sheet or band of tough fibrous tissue connecting bones together
Machairodont – any member of various extinct groups of predatory mammals that were characterized by long, curved, saber-shaped teeth
Mammal – a class of warm-blooded animals characterized by a covering of hair on the skin and, in the female, milk-producing mammary glands for nourishing young
Mandibles – in arthropods, one of the pair of mouth-parts most commonly used used for seizing and cutting food
Marginocephalian – a group of dinosaurs characterized by a bony shelf at the back of the skull
Marsupial – a mammal that raises its young in a pouch
Marsupium – a pouch
Matriarchal – a social group that is led by the dominant female
Megafauna – large or giant animals whose weight is in excess of 44 kg (100 lb) or in excess of 1000 kg (2200 lb). depending on sources used
Melanism – an increased amount of black or nearly black pigmentation
Melon Organ – mass of adipose tissue found in toothed whales that focuses and modulates the animal’s vocalizations and aides in communication and echolocation
Mesocarnivore – a carnivore whose diet is between 25% and 70% vertebrate flesh
Mesozoic – the middle of three eras of geologic time from about 248 to 65 million years ago and characterized by the presence of dinosaurs as the dominant fauna
Metamorphosis – biological process by which an animal physically develops after birth or hatching and involving a conspicuous and relatively abrupt change in the animal’s body structure through cell growth and differentiation
Migration -the movement of animals from one area to another
Mimicry – the similarity of one organism to another that has evolved because the resemblance is selectively favored by the behavior of a shared signal revceiver that can respond to both
Molar – one of the posterior teeth, used for crushing and characterized by the presence of multiple roots and a biting surface formed from patterns of projections and ridges
Mollusk – a class of invertebrates characterized by a soft, unsegmented body usually enclosed in a calcareous shell
Monotreme – the most primitive order of mammals, characterized by the presence of a cloaca and hatching young from eggs
Morph – domesticated reptile displaying skin patterning and/or coloration that has been selectively bred for
Musk – a substance secreted in a glandular sac under the skin of certain animals and possessing a strong odor
Musth – the frenzied state of a male elephant during the mating season
Mutualism – an interaction between members of two species that benefits both
Myotoxin – toxin that causes muscle necrosis and paralysis
Myriapod – a class of arthropods characterized by an elongated, segmented body
Nail – a horny covering on the upper surface of the tip of the digits in primates
Natural Selection – a complex process in which the total environment determines which members of a species survive to reproduce and so pass on their genes to the next generation
Neurotoxin – toxin that affects the functioning of the nervous system
Niche – the functional position of an organism in its environment compromising the habitat in which the organism lives, the periods of time during which it occurs and is active there, and the resources it obtains there
Nocturnal – an animal that is active at night
Olfaction – the sense of smell
Omnivore – an animal that feeds on both plants and animals
Operculum – a bony plate that covers a fish’s gills
Opposable – applied to a digit that can be turned so that its pad makes contact with the pad of each of the other digits on the same limb
Ornithopod – a group pf dinosaurs characterized by three-toed feet, a horny beak, and an elongated pubis
Ossicone – hornlike protuberances on the heads of giraffes and their relatives that are derived from ossified cartilage rather than living bone and covered in skin rather than keratin
Osteoderm – a bony plate embedded in the skin
Osteophagy – the practice of eating bones
Oviparous – reproducing by laying eggs
Ovipositor – specialized egg-laying organ found in most insects
Ovoviviparous -reproducing by having young develop from eggs retained with the mother’s body but separated from it by egg membranes