When there is a process going in a particular direction and then something occurs to make it reverses direction.
the primary subdivision of a taxonomic kingdom, grouping together all classes of organisms that have the same body plan.
a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past adjacent plates.
any cellular organism that has no nuclear membrane, no organelles in the cytoplasm except ribosomes, and has its genetic material in the form of single continuous strands forming coils or loops, characteristic of all organisms in the kingdom Monera, as the bacteria and blue-green algae.
any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product.
The study of the age of rocks by scientists. This is done by scientists looking at the layers of the sedimentary rock.
the process by which collision of the earth's crustal plates results in one plate's being drawn down or overridden by another
a ratio of light reflected from the earths surface to the earths atmosphere. This results in the melting of ice. This keeps the earth cool.
A bacteria which is classified as its own class due to their extreme living conditions (extreme heat).
ubiquitous one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains, comprising the Schizomycota, a phylum of the kingdom Monera (in some classification systems the plant class Schizomycetes), various species of which are involved in fermentation, putrefaction, infectious diseases, or nitrogen fixation.
The rapid diversification of multicellular animal life that took place around the beginning of the Cambrian Period. It resulted in the appearance of almost all modern animal phyla.
any organism having as its fundamental structural unit a cell type that contains specialized organelles in the cytoplasm, a membrane-bound nucleus enclosing genetic material organized into chromosomes, and an elaborate system of division by mitosis or meiosis, characteristic of all life forms except bacteria, blue-green algae, and other primitive microorganisms.
An organism adapted to living in conditions of extreme temperature, pressure, or chemical concentration, as in highly acidic or salty environments.