Algae—A general name for nonflowering plants, which can include single-celled organisms as well as seaweeds. They produce energy via photosynthesis but lack stems, roots, and leaves and are typically aquatic.
Aragonite—A mineral form of calcium carbonate, often forming elongated, needle-like crystals. It is one of the primary forms of calcium carbonate produced by mollusks for their shells.
Calcite—The most common mineral form of calcium carbonate, often forming elongated six-sided pointed crystals. It is one of the primary forms of calcium carbonate produced by corals, foraminifera, and other sea life.
Calcium Carbonate—A chemical compound consisting of calcium, carbon, and oxygen with the chemical symbol CaCO3. Depending on the conditions present, it can take the form of aragonite or calcite, which differ in crystal structure. Corals, mollusks, and other sea life produce it.
Class—A larger biological subdivision of animals, such as insects or mammals. Corals belong to the class Anthozoa, which also includes sea cucumbers and other marine organisms.
Coenosarc—The living tissue that coats a coral skeleton and connects polyps.
Columella—The central rod-like structure within a corallite that supports the septa and enables the polyp to grow upward.
Colonial coral—A coral species that develops as a tightly grouped mass of individual polyps that all contribute to a singular coral skeleton.
Coral—General name for the marine stony external skeletons produced by coral polyps.
Corallite—The cuplike calcium carbonate skeleton of a single coral polyp; many corallites make up a coral colony.
Crystal—A solid body with a repeating atomic structure formed when an element or chemical compound solidifies.
Devonian Period—A period of geologic time occurring between approximately 419 and 359 million years ago, characterized by diverse sea life and the rapid development of life on land.
Eutrophication—Excessive richness of nutrients in a body of water, usually caused by runoff from the land. It typically creates dense plant growth that results in a low-oxygen aquatic environment that suffocates animals.
Extinction event—An event or series of events causing catastrophic die-offs of plants and animals, resulting in numerous species going extinct.
Fossil—Remains of plants or animals that became mineralized and were preserved within rock.
Fossil record—The record of the history of life as preserved within rock layers; the totality of all fossils, which shows us when species lived and when they went extinct.
Fossilization—The process by which remains of plants and animals are turned to minerals within rocks, usually through chemical reactions or slow replacement by minerals.
Genus—A smaller biological subdivision that classifies more-closely related groups of animals, such as specific groups of related corals. Genera are labeled with a capitalized Latin name.
Glacial period—A period of time during an ice age that is characterized by significant southward glacier movement.
Glacier—A slow-moving mass of ice formed by the compaction of snow.
Hexagon—A shape with six sides; something with this shape is referred to as hexagonal.
Hexagonaria percarinata—The specific species of coral preserved in Petoskey stone.
Horn coral—see “Solitary Coral.”
Ice age—A period of time defined by lower-than-average global temperatures and glacier formation and glacial activity.
Invertebrate—Animal without a spine.
Limestone—A common sedimentary rock formed primarily of calcite derived from ancient sea floor sediments, including shells and coral reef material.
Marine—Of or relating to oceans or seas.
Mineral—A naturally occurring chemical compound or native element that solidifies with a definite internal crystal structure.
Photosynthesis—The process by which plants and some other organisms use sunlight to produce food from carbon dioxide and water, generally producing oxygen as waste.
Polyp—A small tube-shaped marine organism, usually with a tentacle-ringed mouth, which may be solitary or live in a colony, and often produces a hard calcium carbonate external skeleton.
Quartz—The most common mineral, quartz consists of silica (silicon dioxide) and forms pointed six-sided crystals that are colorless to white. It is also a constituent of many rocks.
Reef—A stony ridge in a shallow marine environment that is formed by large, intergrown formations of corals and other marine life. Reefs can be large and complex and are vital to the survival of most marine life.
Rock—A massive aggregate of mineral grains.
Rugose coral—An extinct group of both solitary and colonial corals characterized by ridged or wavy external surfaces, resembling wrinkles.
Sedimentary rock—Rock derived from sediments of minerals, animals, or other rocks that have since been cemented and solidified together.
Septa—The individual chambers of a corallite skeleton, typically appearing as ray-like formations stemming from the central columella. Singularly called a septum.
Solitary coral—Coral species that do not live in tightly packed colonies and instead develop as singular tube-like coral structures with a single polyp. Many are known as “horn corals” due to their typical long, tapered, curving, horn-like shape.
Species—A biological subdivision consisting of similar individuals capable of interbreeding or exchanging genes. Every species belongs to a genus, which in turn belongs to a class.
Stony coral—Any species of coral that produces a hard, mineralized skeleton composed of calcium carbonate. Stony corals usually contribute to reefs.
Tessellation—A group of shapes that fit closely together, usually repeating and without gaps or overlaps.
Zooxanthellae—A single-celled organism that lives within coral polyps and produces energy from the polyps’ waste, in turn producing oxygen for the polyp.