aquatic: An adjective that refers to water.

behavior: The way something (often a person or other organism) conducts itself or acts towards others.

chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H₂O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

crustaceans: Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.

CT scan: (Also known as a CAT scan). The term is short for computerized axial tomography. It is a special type of X-ray scanning technology that produces cross-sectional views of the inside of a bone or body. A computer can then digitally assemble the images from these slices to create a 3-dimensional reconstruction of internal features.

debris: Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.

digest: (noun: digestion) To break down food into simple compounds that the body can absorb and use for growth. Some sewage-treatment plants harness microbes to digest — or degrade — wastes so that the breakdown products can be recycled for use elsewhere in the environment.

dinosaur: A term that means terrible lizard. These reptiles emerged around 243 million years ago. All descended from egg-laying reptiles known as archosaurs. Their descendants eventually split into two lines. For many decades, they have been distinguished by their hips. Many large dinosaurs died out around 66 million years ago. But some saurischians lived on. They are now the birds we see today (and who have now evolved that so-called “bird-hipped” pelvis).

ecosystem: A group of interacting living organisms — including microorganisms, plants and animals — and their physical environment within a particular climate. Examples include tropical reefs, rainforests, alpine meadows and polar tundra. The term can also be applied to elements that make up some artificial environment, such as a company, classroom or the internet.

element: A building block of some larger structure. (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

environment: The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

extinct: (n. extinction) An adjective that describes a species for which there are no living members.

food web: (also known as a food chain) The network of relationships among organisms sharing an ecosystem. Member organisms depend on others within this network as a source of food.

fossil: Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.

gut: An informal term for the gastrointestinal tract, especially the intestines.

habitat: The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

herbivore: A creature that either exclusively or primarily eats plants.

limb: (in physiology) An arm or leg.

literally: An adjective indicating that the phrase it modifies is precisely true. For instance, to say: "It's so cold that I'm literally dying," means that this person actually expects to soon be dead, the result of getting too cold.

lizard: A type of reptile that typically walks on four legs, has a scaly body and a long tapering tail. Unlike most reptiles, lizards also typically have movable eyelids. Examples of lizards include the tuatara, chameleons, Komodo dragon, and Gila monster.

mammal: An animal distinguished by possessing hair or fur, the secretion of milk by females for the feeding of their young, and (typically) the bearing of live young. They also are warm-blooded (or endothermic).

monitor lizards: A family of muscular, predatory reptiles with scaled bodies, forked-tongues and a good sense of smell. Some are good swimmers, such as the water monitor, which tend to grow to about 1.5 meters (5 feet) long. The biggest monitor, the venomous Komodo dragon, can reach lengths of 3 meters, weigh in at more than 200 pounds, sprint at speeds of 20 kilometers (13 miles) per hour, and eat up to 80 percent of its body weight at a single sitting. At the other end of the spectrum is the Dampier Peninsula monitor, the smallest of these reptiles, which as an adult will span just 23 centimeters (9 inches) and weigh a mere 16 grams (0.6 ounce).

paleontologist: A scientist who specializes in studying fossils, the remains of ancient organisms.

Pangaea: (or Pangea) A supercontinent that existed from about 300 to 200 million years ago. It was composed of all of the major continents seen today, squished together.

Permian: A time in the distant geologic past, about 250 million to 300 million years ago. Many reptiles rose to prominence on land; these were not yet dinosaurs. Many large invertebrates ruled the oceans during this period. But most would die off at the end of the Permian, as it gave way to a new geologic period known as the Triassic.

phosphorus: A highly reactive, nonmetallic element occurring naturally in phosphates. Its scientific symbol is P. It is an important part of many chemicals and structures that are found in cells, such as membranes, and DNA.

predator: (adjective: predatory) A creature that preys on other animals for most or all of its food.

prey: (n.) An organism hunted by another, often for food. (v.) To attack and eat another organism.

reptile: Vertebrate animals belonging to a group known as Reptilia. Most reptiles have skin that is covered with scales or horny plates. Snakes, turtles, lizards and alligators are all reptiles. Once considered their own separate group, birds now belong to this order. With the exception of modern birds, most reptiles are cold-blooded (or ectothermic).

species: A group of similar organisms capable of producing offspring that can survive and reproduce.

synapsids: A subclass of terrestrial vertebrates. Although the earliest ones likely resembled reptiles, taxonomic data suggest they actually were extinct, non-reptile ancestors of today’s mammals (which are also synapsids).

X-ray: A type of radiation analogous to gamma rays, but having somewhat lower energy.