algae: Single-celled organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.
Arctic: A region that falls within the Arctic Circle. The edge of that circle is defined as the northernmost point at which the sun is visible on the northern winter solstice and the southernmost point at which the midnight sun can be seen on the northern summer solstice. The high Arctic is that most northerly third of this region. It’s a region dominated by snow cover much of the year.
bdelloid: A class of rotifers (Bdelloidea) that exist solely as females. To reproduce, they clone themselves through a process known as parthenogenesis.
biologist: A scientist involved in the study of living things.
carbon dating: Short for radioactive-carbon dating or carbon-14 dating. A way to measure the age of organic materials — ones containing carbon. Carbon 14, a weakly radioactive isotope, forms in Earth’s upper atmosphere as cosmic rays hit nitrogen atoms. This carbon joins with oxygen to form carbon dioxide, which living organisms take up and incorporate in their tissues. When those organisms die, they stop exchanging carbon with the environment and the share of the C14 isotope starts to fall at a constant rate (one set by the law of radioactive decay). By measuring the share of carbon-14 to carbon-12 in the organism’s remains, scientists can determine how long ago it died.
climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
clone: (in biology) An organism that has exactly the same genes as another, like identical twins. Often a clone, particularly among plants, has been created using the cell of an existing organism. Clone also is the term for making offspring that are genetically identical to some “parent” organism.
core: A long, tube-like sample drilled down into ice, soil or rock. Cores allow scientists to examine layers of sediment, dissolved chemicals, rock and fossils to see how the environment at one location changed through hundreds to thousands of years or more.
decay: (for radioactive materials) The process whereby a radioactive isotope — which means a physically unstable form of some element — sheds energy and subatomic particles. In time, this shedding will transform the unstable element into a slightly different but stable element. For instance, uranium-238 (which is a radioactive, or unstable, isotope) decays to radium-222 (also a radioactive isotope), which decays to radon-222 (also radioactive), which decays to polonium-210 (also radioactive), which decays to lead-206 — which is stable. No further decay occurs. The rates of decay from one isotope to another can range from timeframes of less than a second to billions of years.
embryo: The early stages of a developing organism, or animal with a backbone, consisting only one or a few cells. As an adjective, the term would be embryonic — and could be used to refer to the early stages or life of a system or technology.
microscope: An instrument used to view objects, like bacteria, or the single cells of plants or animals, that are too small to be visible to the unaided eye.
millennium: (plural: millennia) A unit of time equal to 1,000 years.
multicellular: Having or consisting of many cells. This includes all animals and plants, and many types of fungus.
organ: (in biology) Various parts of an organism that perform one or more particular functions. For instance, an ovary is an organ that makes eggs, the brain is an organ that makes sense of nerve signals and a plant’s roots are organs that take in nutrients and moisture.
organism: Any living thing, from elephants and plants to bacteria and other types of single-celled life.
parthenogenesis: An unusual form of reproduction where animals sometimes produce healthy offspring from an unfertilized egg.
permafrost: Soil that remains frozen for at least two consecutive years. Such conditions typically occur in polar climates, where average annual temperatures remain close to or below freezing.
radioactive: An adjective that describes unstable elements, such as certain forms (isotopes) of uranium and plutonium. Such elements are said to be unstable because their nucleus sheds energy that is carried away by photons and/or and often one or more subatomic particles. This emission of energy is by a process known as radioactive decay.
radiocarbon dating: Short for radioactive-carbon dating or simply carbon dating. A way to measure the age of organic materials — ones containing carbon. Carbon-14, a weakly radioactive isotope, forms in Earth’s upper atmosphere as cosmic rays hit nitrogen atoms. This carbon joins with oxygen to form carbon dioxide, which living organisms take up and incorporate in their tissues. When those organisms die, they stop exchanging carbon with the environment and the share of the C14 isotope starts to fall at a constant rate (one set by the law of radioactive decay). By measuring the share of C14 in the organism’s remains, scientists can determine how long ago it died.
ratio: The relationship between two numbers or amounts. When written out, the numbers usually are separated by a colon, such as a 50:50. That would mean that for every 50 units of one thing (on the left) there would also be 50 units of another thing (represented by the number on the right).
rotifer: Any of the tiny (usually microscopic) invertebrate animals belonging to the class Rotifera. Most live in freshwater. They tend to have disk-type structures with powerful hairlike cilia that work like oars to move through water.
sediment: Material (such as stones and sand) deposited by water, wind or glaciers.
suspended animation: A temporary shutdown of most or all living functions without causing death. Examples can include a stored seed, hibernating animal or permafrost-trapped rotifer.
tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
unicellular: An adjective for organisms that possess a single cell, such as an amoeba or bacterium.