A glossary of terms used in Railsback's GEOL 1122 lectures

This is a list of terms used in Bruce Railsback's GEOL 1122 lectures at the University of Georgia. The sole purpose of this list is to clarify Railsback's GEOL 1122 lectures. This is not necessarily a list of terms that must be known for an exam. The definitions are not necessarily those found in standard references - anyone wanting definitions found in standard references should look in standard references.

This list is in order of appearance in lecture. You can use your browser's "Find" function to locate a particular word.

To the first half of this glossary.

Biological Evolution - change in Earth's biota through time.

Earth's Biota - all the living things on Earth.

Inheritance of acquired traits - the idea generally associated with Jean Baptiste de Lamarck (1744-1829) that organisms can develop biological characteristics during their lifetimes and then pass those characteristics along to their offspring.

Natural Selection or "Survival of the Fittest" - the idea that individuals best fitted for their environment survive to reproduce and thus to pass along their genetic characteristics to their offspring.

Artificial Selection - human attempts to modify domesticated plants and animals by selective breeding, resulting in the various present breeds of dogs, cattle, horses, and the like.

Chromosomes - bundles of DNA occurring in pairs in all the cells of all organisms.

Asexual reproduction - the generation of a new organism by division of a cell with complete replication of the DNA of the parent cell.

Sexual reproduction - the generation of a new organism wherein two parents each donate half the DNA of the offspring, so that there is not complete replication of the DNA of either parent.

Meiosis - process of cell division required for sexual reproduction.

Mitosis - process of cell division required for asexual reproduction and for growth of organisms generated by sexual reproduction.

Population: All the individuals of one species living within reproducing distance. (a "Gene Pool" in Stanley's usage).

Speciation - the development of new species.

Allopatric speciation - origin of new species as the result of physical separation one one species into at least two populations that then diverge.

Founder effect - development of a population or species with characteristics that by chance were present in an individual or individuals in the small population separated during allopatric speciation.

Sympatric speciation - origin of new species as the result of divergence of a species, without physical separation.

Genetic Drift - change in a species, or development of a new species, as the result of mutation and random change in the gene pool, not caused by environmental or ecological pressures.

Phyletic gradualism - a view of evolution suggesting that species arise and/or diverge slowly and perhaps constantly.

Punctuated equilibrium - a view of evolution suggesting that speciation occurs relatively abruptly, and that species are stable (or in "equilibrium") for relatively long periods of time between abrupt speciation events.

Divergent evolution - one species gives rise to multiple species, or (at a larger scale) one taxonomic group (a genus, a family, or an order) gives rise to several with diffent characteristics.

Convergent evolution - two unrelated species evolve to similar form, usually to exploit similar niches.

Niche - the role of an organism in its environment, which involves its food resources, its territory, and all the other factors that influence its survival.

Ontogeny - the development of an organism, beginning in the embryonic stage.

Phyologeny - the ancestry of a species.

Autotrophs - organisms that produce their own food by photosynthesis or chemosynthesis.

Heterotrophs - organisms that feed on other things to acquire energy and biomass.

Prokaryotes - organisms in which the chromosomes are not isolated in a nucleus in the cell, and with few or no organelles within the cell.

Eukaryotes - organisms in which the chromosomes are isolated in a nucleus of the cell, which also contains organelles like mitochondria or chloroplasts.

Cyanobacteria - photosynthesizing bacteria, also known as "blue-green algae".

Stromatolites - layers or layered mounds of sediment generated by mats of cyanobacteria that trap fine sediments and then overgrow those sediments before generating another mat, which then traps more sediment.

Metazoans - multicellular animals.

Vascular plant - a plant with the capability to transport and distribute water and nutrients via specialized tissues. Non-vascular plants rely on diffusion to transport water and nutrients to the cells.

Spore - a reproductive cell carrying all the DNA of the parent and capable of development into a new organism.

Psilophyte - a rootless leafless seedless vascular plant.

Lycophyte - a seedless vascular plant with stem-less leaves attached directly to the stalk.

Sphenopsid - a segmented or jointed seedless vascular plant.

Fern (Pteridophyte) - a leafy seedless vascular plant.

Gymnosperm - a seed-bearing non-flowering plant, so that the seeds develop without protection and so that fertilization is largely by wind.

Angiosperm - a flowering seed-bearing plants, so that the seeds develop in an ovule and so that fertilization is largely by insects or birds.

Phylum Chordata - organisms having a notochord & gills during development.

Craniata - Chordates with a cranium.

Subphylum Vertebrata - craniates with a backbone or cartilage.

Phylum Echinodermata - marine invertebrates in which plates of Mg-rich calcite from an exoskeleton, commonly with spines of the same mineral.

Crinoids - a class of echinoderms with a holdfast at their base, a stalk, and a cup or "head" with numerous radiating arms.

Protostomes - animals in which the body cavity develops with a mouth that remains the mouth. Includes most non-chordate metazoans.

Deuterostomes - animals in which the body develops with a mouth that becomes the anus after development of a second mouth. Includes echinoderms and chordates.

Spiral cleavage - development of cells in most non-chordates.

Radial cleavage - development of cells in echinoderms and chordates.

Ostracoderms - armored jawless fishes (Late Cambrian - Devonian).

Acanthodians and Placoderms - Jawed (and spiny or armored) fishes (Silurian-Permian).

Cartillaginous Fishes - fishes with cartillaginous, rather than bony, skeletons (sharks and rays). (Devonian-Recent).

Bony Fishes - fishes with bony skeletons (Osteichthyians) (Middle Devonian-Recent).

Ray-finned fishes - fishes in which radiating thin bones support the fins.

Lobe finned fishes - fishes in which fins are supported by stronger non-radiating bones.

Crossopterygians - lobe-finned fishes from which amphibians seem to have diverged.

Amniotes - vertebrates in which the embryo is contained in a membrane (the amnion) that does not allow loss of water. Reptiles, birds, and mammals fall in this category, but amphibians and fish do not.

Amniotic egg - an egg with a membrane (the amnion) that does not allow loss of water.

Pelycosaurs - sail-backed reptiles that appear to have been ancestors of the earliest mammals.

Thecodonts - reptiles that appear to have been ancestors of dinosaurs and other later reptiles.

Ornithischians - bird-hipped dinosaurs.

Saurischians - lizard-hipped dinosaurs.

Endotherms - organisms that control their body temperature at a near-constant level ("warm-blooded" organisms, such as mammals and birds).

Ectotherms - organisms whose body temperature is that of their environment ("cold-blooded" organisms, such as fish, amphibians, and modern reptiles).

Pleisiosaurs - Long-necked streamlined Mesozoic marine reptiles.

Icthyosaurs - Mesozoic marine reptiles with shapes similar to modern dolphins or large fish.

Pterosaurs - flying (or gliding) reptiles not ancestral to birds.

Archaeopteryx - earliest (Jurassic) fossil bird.

Mammals - hairy or furry warm-blooded animals with breast-feeding females.

Cynodonts - a reptile (or mammal?) group with characteristics of both, and apparently ancestral to mammals.

Dentary - 1. one of the jaw bones of reptiles. 2. the jaw bone of mammals.

Marsupials -mammals in which the undeveloped young are held in pouches after birth.

Placental Mammals - mammals in which a placenta nourishes the unborn young in the womb until viability and birth.

Monotremes - Egg-laying milk-secreting warm-blooded verte brates with reptilian skulls.

Multituberculates - Mesozoic to early Tertiary herbivorous rodent-like mammals.

Primates - Promisians, monkeys, apes, and humans: mammals generally characterized by grasping hands, relatively large brains, and stereoscopic vision.

Stereoscopic vision - vision in which the sensory inputs from both eyes are combined into one image by the brain, rather than two separate images.

Anthropoids - monkey-like primates, including ancestors of chimpanzees, old world monkeys, new world monkeys, gorillas, and australopithecines.

Australopithecines - fossil late Tertiary primates; earliest hominids.

Hominids - primates of the the genera Australopithecus and Homo.

Red Shift - An apparent lengthening of the wavelength of light as observed at a point that is getting farther from the source of the light.

Big Bang - The theory that the universe as we know it began with an explosion of matter that resulted in the present expansion of the universe. The expansion is indicated by the red shift observed in light coming from distant galaxies.

Gravitiational lensing - a convergence of light caused by the gravitational field of a celestial object. The significance with regard to the Big Bang theory is that the lensed (more distant) object always has a higher recessional velocity that than the lensing (nearer) object.

Time dilation - the observed slowing of explosions of supernovae in more distant galaxies, presumably because of the faster movement of those galaxies from our point of observation (akin to the red shift, but independent of it).

Un-evolved matter - the hydrogen and helium in the universe, as opposed to the matter in denser elements. A relative term.

Solar Nebula Model - a model of the origin of our solar system in which a whirling cloud of matter (dust & gas) largely condenses into a star (the sun). The outlying parts of the cloud condense and accrete into planets. The Sun eventually condenses to begin thermonulear reactions, causing solar winds that blow gases away from inner planets.

Solar flaring - a star's (and our sun's) intense emission of radiation soon after it begins thermonuclear reactions. These emission can sweep away dust and gases near the star.

Dropstones - sediment released by icebergs as they melt and thus dropped to the sea floor. Such sediment usually consists of much larger particles than the deep-sea sediment into which it is dropped.

Paleobiogeography - the study of the geographic distribution of fossils. This may involve differences in fossils with latitude or with position on different continents or in different ocean basins.

Ooids - small (less than 2 mm in diameter) concretions, usually of CaCO3, and usually found in limestones, such as oolitic limestones.

Albedo - reflection of solar radiation directly back to outer space from the earth's surface. Albedo is greater from land than from water.

Cyclothem - a sequence of sedimentary rocks in which lithologies vary cyclically (i.e., a sequence is repeated to give multiple cycles).

d18O or delta18O - a measure of the abundance of 18O in a sample. Greater values of this parameter indicate higher concentrations of 18O. (The values actually report the difference, in parts per thousand, between the sample and an internationally accepted standard material. That material will be either "Standard Mean Ocean Water" ("SMOW") or a Cretaceous belemnite from the PeeDee Formation in South Carolina ("PDB").)

Foraminifera (or "forams") - small (generally microscopic) protozoans that commonly secrete a test or shell of calcite. Some are planktic (they live in the surface waters of the ocean) and some are benthic (they live on the sea floor).

Equable - equal along a gradient, and thus in climate studies pertaining to a world where climate is the same from equator to poles. The present great change in temperature from equator to poles means that Earth's present climate is not very equable.

Glacier - a mass of flowing ice that exists for more than one year.

Crevasse - an open crack or fissure in the surface of a glacier.

Till - sediment that consists of a broad range of particle sizes and that was deposited by a glacier.

End morraine - a curvilinear mass of till deposited at the downslope or ablating end of a glacier. Also called a Terminal Morraine.

Ground Morraine - a mass of till that exists across a large area and that was deposited under a glacier.

Erratic - a large boulder that is found in an area devoid of other such boulders and that has a lithology inconsistent with the local bedrock or with other local geologic features.

Striations - parallel grooves in flat bedrock surfaces. They are commonly formed by movement of a glacier over the bedrock in question.

Eccentricity - The degree to which a closed loop (e.g., the orbit of a planet) deviates from a circle.

Precession of the equinoxes - the change in the timing of spring and fall on Earth relative to Earth's position in its orbit, due to a wobble in earth's rotation.

Greenhouse gas - a gas that adsorbs radiation reflected from or emitted by the Earth and then releases the adsorbed energy as heat. Carbon dioxide (CO2) and methane (CH4) are good examples.

Acid Rain - rainfall made more acidic than natural rainfall by human input of gases to the atmosphere. The most common such gases are SO2, which oxidizes to make sulfuric acid (H2SO4), and oxides of nitrogen (NOx, where x is 1 or 2), which oxidize to make nitric acid (HNO3).

CFCs (chlorofluorocarbons) - anthropogenic chemicals that react with ozone (O3) in the upper atmosphere, leading to depletion of ozone and resultant enhanced passage of ultraviolet radiation throught the atmosphere.

If you're a GEOL 1122 student and think a term should be added to this list, please send an email message to Bruce Railsback at rlsbk@gly.uga.edu.

If you think any of the above definitions should be improved, email a complete definition to Bruce Railsback at rlsbk@gly.uga.edu.

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