| Term | Definition |
|---|
| notochord | A flexible column of gelatin-like material that provides support in the embryos of all chordates; a common feature of all chordates. |
| nerve cord | A hollow cord under the dorsal surface of chordates; a common feature of all chordates. |
| pharyngeal slits | Slits used for filter feeding in primitive chordates and have been adapted for other functions in more highly evolved chordates; a common feature of all chordates. |
| tail | Section or appendage in chordates that's posterior to the anal opening; a common feature of all chordates. |
| tetrapods | Animals with four feet. |
| flexor | A muscle that brings two bones closer together. |
| extensor | A muscle that opens the appendage back to a straight position. |
| undulation | A side-to-side motion caused by alternating groups of muscles on the vertebrae. |
| lateral line system | Rows of sense organs along the side of a fish's body that detect vibrations in the water. |
| tympanic membrane | A membrane in the ear that detects vibrations in the air (ear drum). |
| echolocation | Emitting and receiving high pitched sounds to locate objects. |
| retina | Tissue on the inner surface of the eye which is lined with millions of light detecting photoreceptor cells. |
| parietal eye | Sensory organ in certain amphibians and reptiles that allows them to distinguish between day and night and between different seasons. |
| cecum | Any one of the cavities attached to intestines which hold bacteria that aid with digestion. |
| mechanical digestion | The process of breaking down food into pieces. |
| chemical digestion | The breaking down of food from a chemical to a more usable chemical by use of enzymes. |
| ruminant | An herbivorous, cud-chewing mammal whose stomach consists of four separate chambers. |
| villi | Projections inside the small intestine that increase the surface area for absorption of nutrients. |
| single-circuit circulatory system | A circulatory system where blood moves through the heart then passes to the rest of the body and back to the heart. |
| atrium | Chamber of the heart that receives deoxygenated blood from the body. |
| ventricle | Chamber of the heart that receives blood from the atrium. |
| pulmonary circuit | Circuit of blood flow that carries blood between the heart and lungs. |
| systemic circuit | Circuit of blood that carries blood between the heart and the rest of the body. |
| ectotherms | Animals (such as lizards, reptiles, or fish) that are unable to maintain their body temperature. |
| endotherms | Animals (such as birds or mammals) that can regulate their body temperature. |
| clade | A biological group (such as species) that includes all descendants of one common ancestor. |
| amniote egg | A shelled egg that surrounds an embryo and embryonic membrane, and which contains a large amount of yolk for nourishing the embryo. |
| spawning | the release of egg and sperm in the water |
| marsupials | Mammals whose immature offspring complete their development in an external pouch. |
| insectivores | Insect-eating mammals that have long narrow snouts and sharp claws for digging. |
| primates | Mammals that include humans, apes, and monkeys. |
| nocturnal | Of, relating to, or occurring in the night; often refers to animals that are active at night and that sleep in the day. |
| diurnal | Of, relating to, or occurring during the day; often refers to animals that are active during the day and which sleep at night. |
| monotremes | Mammals that have hair and mammary glands but reproduce by laying eggs. |
| placental mammals | Mammals that carry their young in the uterus inside a tissue (placenta) that enables nutrients, gases, and wastes to be exchanged between the mother and the embryo. |
| bipedal | Involving two feet. |
| hominids | Members of a biological family which includes humans, extinct species of humanlike creatures and the other great apes. |
| capillaries | Microscopic blood vessels with walls only one cell thick that allow for diffusion of various substances, including fluids, between the blood and tissue fluid. |
| diffusion | The movement of molecules from an area of high concentration to an area of low concentration. |
| oxygenated | Containing oxygen. |
| deoxygenated | Lacking oxygen. |
| cartilage | A translucent somewhat elastic tissue that makes up the skeleton of certain fish, such as sharks and rays. |
| internal fertilization | Egg and sperm unite in the body of the female. |
| external fertilization | Egg and sperm unite outside the body and are deposited in some protected area. |
| chondrichthyes | Fish with cartilaginous skeletons. |
| osteichthyes | Fish with a skeleton made of bone rather than cartilage. |
| agnathans | Jawless fishes. |
| osteocytes | Bone-producing cells. |
| buoyancy | The ability to float when submerged in water. |
| swim bladder | A bag-like structure that contains a mixture of gases from the blood and helps a fish control its buoyancy. |
| metamorphosis | A series of changes from a larval stage to an adult. |
| anapsid | primitive reptile having no opening in the temporal region of the skull |
| diapsid | reptile having a pair of openings in the skull behind each eye |
| diaphragm | A sheet of muscles in mammals that separates the abdominal cavity from the chest cavity and aids in forcing air in and out of the lungs. |
| premolars | Teeth in front of the molars used for shearing food. |
| molars | Teeth toward the back of the jaw used for grinding food. |
| canines | Teeth in front of the premolars that rip and tear food. |
| incisors | Teeth between the canines that are used for cutting. |
| therapsid | A reptile-like ancestor of modern mammals. |
| umbilical cord | A structure with blood vessels that connect the embryo to the placenta. |
| placenta | The structure in the uterus of female mammals that forms the uterine lining and provides for the exchange of nutrients, gases, and metabolic wastes between the mother and the fetus. |
| carnivores | Animals that eat meat. |
| perissodactyls | odd-toed, hoofed mammals |
| artiodactyls | even-toed, hoofed mammals |
| rodents | small, gnawing mammals with continuously growing incisors |
| scandentia | a small order of mammals comprising only the tree shrews |
| edentates | mammals having few or no teeth |
| tubulidentata | an order of mammals consisting of the aardvark |
| chiroptera | an order of flying mammals: bats |
| dermoptera | an order of arboreal gliding mammals: flying lemurs |
| cetaceans | marine mammals: dolphins and whales |
| sirenians | aquatic mammals: sea cows and manatees |
| lagomorphs | mammals with four upper incisor teeth: rabbits, hairs, pikas |
| proboscidea | an order of mammals including elephants and mammoths |
| mammoths | Extinct elephant-like furry mammals in the order Proboscidea. |
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