Palaeos:		Glossary
Life		Glossary

Life

A.

Autotroph: an organism which makes its own food from inorganic materials. using sunlight or chemical reactions for energy. Wikipedia glossary, MAK

B.

Benthic: Used to describe aquatic organisms that are bottom dwelling. (USGS Paleontology glossary)

Big Five: five mass extinctions identified by Jack Sepkoski and David M. Raup in a paper published in 1982. These are:

• Ordovician–Silurian extinction event (End Ordovician or O-S) – 440–450 Ma at the Ordovician-Silurian transition. Two events occurred that killed off 27% of all families and 57% of all genera. Together they are ranked by many scientists as the second largest of the five major extinctions in Earth's history in terms of percentage of genera that went extinct.
• Late Devonian extinction – 360–375 Ma near the Devonian-Carboniferous transition. At the end of the Frasnian Age in the later part(s) of the Devonian Period, a prolonged series of extinctions eliminated about 19% of all families, 50% of all genera and 70% of all species. This extinction event lasted perhaps as long as 20 MY, and there is evidence for a series of extinction pulses within this period.
• Permian–Triassic extinction event (End Permian) – 251 Ma at the Permian-Triassic transition. Earth's largest extinction killed 57% of all families and 83% of all genera[5] (53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species) including insects. The evidence of plants is less clear, but new taxa became dominant after the extinction.[8] The "Great Dying" had enormous evolutionary significance: on land, it ended the primacy of mammal-like reptiles. The recovery of vertebrates took 30 million years, but the vacant niches created the opportunity for archosaurs to become ascendant. In the seas, the percentage of animals that were sessile dropped from 67% to 50%. The whole late Permian was a difficult time for at least marine life, even before the "Great Dying".
• Triassic–Jurassic extinction event (End Triassic) – 205 Ma at the Triassic-Jurassic transition. About 23% of all families and 48% of all genera (20% of marine families and 55% of marine genera) went extinct.[5] Most non-dinosaurian archosaurs, most therapsids, and most of the large amphibians were eliminated, leaving dinosaurs with little terrestrial competition. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments. The Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia (e.g., Koolasuchus).
• Cretaceous–Tertiary extinction event (End Cretaceous or K-T extinction) – 65.5 Ma at the Cretaceous.Maastrichtian-Paleogene. Danian transition interval. The K–T event is now called the Cretaceous–Paleogene (or K–Pg) extinction event by many researchers. About 17% of all families, 50% of all genera and 75% of species became extinct. In the seas it reduced the percentage of sessile animals to about 33%. The boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds emerged as dominant land vertebrates in the age of new life.

More recently it has been argued on statistical evidence that the "Big Five" represent the largest (or some of the largest) of a relatively smooth continuum of extinction events. See also sixth extinction. (Wikipedia)

Bauplän: The concept of a body plan, Bauplän (pl. Baupläne), is critical to understanding the most fundamental evolutionary radiations. What is a body plan? This is a difficult question to define, and it is usually answered with examples: the insect body plan, the jellyfish body plan, or whale body plan. Loosely defined, a body plan is primarily morphological, involving the shared structural homologies of upper taxa. For example, the vertebrate bauplän might be described as comprising a "cephalised, sensate, bilaterally symmetrical, motile, coelomate gnathostome having a segmented endoskeleton, a dorsal hollow nerve chord, and a ventral gut" (Ostrom 1992, p. 119). Body plans, or baupläne, affect development at its most basic level, thus developmental constraints strongly influence the range of body plans possible. Even in simple animals, axes of symmetry are so fundamental that significant internal co-adaptation is required for viable body plan mutations to occur. (Chris Clowes 2002)

Belief: The position of affirming the truth of a proposition. Belief, if asserted as true in a debate, bears a burden of proof (as does disbelief). See also: unbelief. (W.J. Hudson)

Bilateral symmetry: Symmetry in only one plane, called the sagittal plane, that divides an organism into roughly mirror image halves (note that in nature and biology, symmetry is approximate. For example, plant leaves, while considered symmetric, will rarely match up exactly when folded in half). Thus there is approximate reflection symmetry. Often the two halves can meaningfully be referred to as the right and left halves, e.g. in the case of an animal with a main direction of motion in the plane of symmetry. Contrast radial symmetry. (Wikipedia)

Biocenose: see Community.

Biocentrism : Centered on life as a whole, rejecting the idea that man is the summit of creation, or has greater moral worth or ontological value than other species. Contrast anthropocentrism. (MAK, Wikipedia glossary)

Biochemistry: Chemical reactions that occur within or are associated with living organisms. (UCMP Understanding Evolution Glossary)

Biodiversity: In biology, the degree of variety of the Earth's animal, plant, and microbial lineages within a given ecosystem, biome, or an entire planet. Used to describe species richness, ecosystem complexity, and genetic variation. Different measures of biological diversity (biodiversity) include number of species, number of lineages, variation in morphology, or variation in genetic characteristics. In terrestrial habitats, tropical regions are typically rich whereas polar regions support fewer species. Biodiversity is also a measure of the health of ecosystems. Greater biodiversity implies greater health. The term biological diversity was used first by wildlife scientist and conservationist Raymond F. Dasmann in the 1968 lay book A Different Kind of Country advocating conservation. The term was widely adopted only after more than a decade, when in the 1980s it came into common usage in science and environmental policy. Global biodiversity has fluctuated through time (see following diagram), being diminished by mass extinctions (including the current anthropogenic extinction) and after several million years following such dips, increasing through evolutionary radiation (from UCMP Understanding Evolution Glossary, Allaby 1998, and Wikipedia, A Glossary of Terms Related to Basic Ecology)

From Wikipedia. This image shows the biodiversity during the Phanerozoic. Note that this is a result of changes in both the rate of extinctions and the rate of new originations. The Dresbachian extinction event in particular is obscured by nearly immediate replacement with new genera. Colour code:

• grey = total known genera from Sepkowski's catalogue (cited by Rohde & Muller)
• green = "well-defined genera", i.e. known genera excluding those represented by "single occurrences" and those whose dates are uncertain.
• red = trend for "well-defined genera". Derived by fitting a third-order polynomial to the data.
• yellow = the "Big Five" mass extinctions.
• blue = other extinction events.

Reference: Rohde, R.A., and Muller, R.A. (2005). "Cycles in fossil biodiversity". Nature 434: 208-210. pdf.
(this version of diagram by Albert Mestre)

Biogenetic law: see recapitulation.

Biogeochemistry: effect of biota on global chemistry, and the cycles of matter and energy that transport the Earth's chemical components in time and space. Wikipedia glossary

Biogeochemical cycle: the pathway through which a chemical, element, or molecule moves through the atmosphere, hydrosphere, lithosphere, and biosphere. Wikipedia glossary

Biogeography: the study of the distribution of organisms and species, past and present, and of diverse processes that underlie their distribution patterns. The patterns of species distribution at this level can usually be explained through a combination of historical factors such as speciation, extinction, continental drift, glaciation (and associated variations in sea level, river routes, and so on), and river capture, in combination with the area and isolation of landmasses (geographic constraints) and available energy supplies. Wikipedia

Bioluminescence: The production of light by living organisms. (USGS Paleontology glossary)

Biomass: the sum of all living living organisms in an area; a measure of the quantity of living matter in a given unit area or volume. Wikipedia glossary

Biome: The total complex of biotic communities occupying and characterizing a particular area or zone, classified according to its climate and type of vegetation. More Wikipedia glossary

Biophilia: The term "biophilia" literally means "love of life." coined by psychologist Erich Fromm to describe a psychological orientation of being attracted to all that is alive and vital. Edward O. Wilson introduced and popularized the hypothesis in his book entitled Biophilia. He proposed the possibility that the deep affiliations humans have with nature are rooted in our biology. Unlike phobias, which are the aversions and fears that people have of things in the natural world, philias are the attractions and positive feelings that people have toward certain habitats, activities, and objects in their natural surroundings. (Wikipedia)

Biota: The plants and animals of a specific region or period, or the total aggregation of organisms in the biosphere (Allaby 1998); the total collection of organisms of a geographic region or a time period. (A Glossary of Terms Related to Basic Ecology) More

Biotic factors: The living environmental influences that affect organisms, such as predators, competitors, prey. Wikipedia glossary

Biosphere: life as a planetary phenomenon, the global ecosystem, the totality of life on Earth, or on other planets in the universe. See also Gaia hypothesis.

C.

Cambrian explosion, Cambrian radiation: The abrupt appearance of a diverse and highly derived fauna in the brief Tommotian and Atdabanian Stages of the Early Cambrian is widely known as the 'Cambrian Explosion,' one of the most, if not the most, dramatic evolutionary radiations in the history of life. Although that particular phrase only came into common usage in the early to mid 1970s, the event itself has long been recognized as a phenomenon demanding some accommodation from evolutionary theory. As early as 1859, Charles Darwin drew attention to the matter in Origin of Species, and it is probable he had considered the matter for many years prior to that.

The paleontological evidence does not, generally corroborate molecular clock studies (contrary to the almost bizarre view expressed in Ayala et al. 1998). Bruce Runnegar (1982, p. 397) notes: "Few of the known late Precambrian animals have been closely related to Cambrian organisms, and none of the associated or coeval trace fossils has been thought to have been produced by the animals observed more directly. … What the trace fossil record does tell us, is that there were few large, mobile, bottom-dwelling animals before the end of the [Vendian]." (Chris Clowes 2002-2003)

The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, centers on three key points: whether there really was a mass diversification of complex organisms over a relatively short period of time during the early Cambrian; what might have caused such rapid change; and what it would imply about the origin and evolution of animals. Interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures left in Cambrian rocks.

The "Cambrian explosion" can be viewed as two waves of metazoan expansion into empty niches: first, a co-evolutionary rise in diversity as animals explored niches on the Ediacaran sea floor, followed by a second expansion in the early Cambrian as they became established in the water column. The rate of diversification seen in the Cambrian phase of the explosion is unparalleled among marine animals: it affected all metazoan clades of which Cambrian fossils have been found. Later radiations, such as those of fish in the Silurian and Devonian periods, involved fewer taxa, mainly with very similar body plans. Although the recovery from the Permian-Triassic extinction started with about as few animal species as the Cambrian explosion, the recovery produced far fewer significantly new types of animals.

Whatever triggered the early Cambrian diversification opened up an exceptionally wide range of previously-unavailable ecological niches. When these were all occupied, there was little room for such wide-ranging diversifications to occur again, because there was strong competition in all niches and incumbents usually had the advantage. If there had continued to be a wide range of empty niches, clades would be able to continue diversifying and become disparate enough for us to recognise them as different phyla; when niches are filled, lineages will continue to resemble one another long after they diverge, as there is limited opportunity for them to change their life-styles and forms.

There were two similar explosions in the evolution of land plants: after a cryptic history beginning about 450 million years ago, land plants underwent a uniquely rapid adaptive radiation during the Devonian period, about 400 million years ago. Furthermore, Angiosperms (flowering plants) originated and rapidly diversified during the Cretaceous period. (Wikipedia)

Further reading (giving two diametrically opposite perspectives): Wonderful Life by Stephen J. Gould; The Crucible of Creation by Simon Conway Morris

Community: Any grouping of populations of different organisms that live together in a particular environment (Allaby 1998), including plants, animals, micro-organisms. Each population is the result of procreations between individuals of same species and cohabitation in a given place and for a given time. When a population consists of an insufficient number of individuals, that population is threatened with extinction; the extinction of a species can approach when all biocenoses composed of individuals of the species are in decline. In small populations, consanguinity (inbreeding) can result in reduced genetic diversity that can further weaken the biocenose. Biotic ecological factors also influence biocenose viability; these factors are considered as either intraspecific and interspecific relations. (Wikipedia, A Glossary of Terms Related to Basic Ecology)

D.

E.

Ecological species concept: A definition of a species as a set of organisms adapted to a particular, discrete set of resources (or "niche") in the environment. Compare with biological species concept, cladistic species concept, phenetic species concept, and recognition species concept. See other species definitions. (Fossil Mall glossary)

Ecology: The study of the interactions of organisms with their environment and with each other. (Wikipedia glossary)

Ecomorphology or Ecological Morphology is the science of the relationship between morphological and ecological variation, for example by measuring the performance of traits (i.e. sprint speed, bite force, etc.) associated behaviors, and fitness outcomes of the relationships. See also Functional Morphology. (Wikipedia

Ecosystem: A discrete unit, or community of organisms and their physical environment (living and non-living parts), that interact to form a stable system (Allaby 1998). (A Glossary of Terms Related to Basic Ecology)

Ectotherm: ("outer warmth") colloquially, "cold blooded"; an animal that regulates body temperature through external means; e.g. basking in the sun to become warmer, or sitting in the shade to become cooler. Includes most invertebrates, most fish, and all amphibians and reptiles (apart from endothermic pterosaurs and some or perhaps all dinosaurs). Poikilothermy (body temperature varies considerably) is similar. The Permian sail backed pelycosaurs such as Dimetrodon were classic ectotherms which used their sails as temperature regulation devices. (MAK)

Endemic, Endemism: Present within or limited to a particular geographic or local area. A species or taxonomic group that is restricted a to particular area because of such factors as isolation or response to soil or climatic conditions; this species is said to be endemic to the place and would be native. Compare with Cosmopolitan (Allaby 1998) (A Glossary of Terms Related to Basic Ecology)

Endotherm: ("outer warmth") colloquially, "warm blooded"; an animal that regulates and maintains a constant body temperature and can generate internal heat for maximal metabolic efficiency, regardless of external (environmental, ambient) temperature. Homeothermy (body temperature remains more or less the same) is similar. Thermoregulation includes cooling through panting or sweating (evaporation) and warming through shivering. Birds, mammals, some fish (tuna), some insects (bees) and quite likely feathered bird-like dinosaurs are all examples of endothermy. (MAK)

Endosymbiosis: A relationship in which one organism lives inside another, to the mutual benefit of both (these are called endosymbionts). Examples are nitrogen-fixing bacteria (called rhizobia) which live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects. It is generally accepted that early in the evolutionary history of Eukarya, eukaryote cells engulfed bacteria, forming a symbiotic relationship, which became so mutually interdependent, that they behaved as a single organism; these include mitochondria and chloroplasts. (from Wikipedia and UCMP Understanding Evolution Glossary)

Eubacteria: the majority of extant bacteria; one of the three domains of life on Earth, prokaryotes that are metabolically and morphologically distinct from Archaea. Woese et al 1990 replaced "Eubacteria" with "Bacteria " as the taxon name; in order to avoid ambiguity we have avoided following this course. More

Eukarya, Eukaryote: an organism whose cells contain complex structures enclosed within membranes (called organelles), and in which genetic material is contained within a nucleus, in contrast to prokaryotes. Cell division in eukaryotes is also distinct, involving separating the duplicated chromosomes by means of microtubules. There are two types of division processes. In mitosis, one cell divides to produce two genetically identical cells. In meiosis, which is required in sexual reproduction, one diploid cell (having two instances of each chromosome, one from each parent) undergoes recombination of each pair of parental chromosomes, and then two stages of cell division, resulting in four haploid cells (gametes). Each gamete has just one complement of chromosomes, each a unique mix of the corresponding pair of parental chromosomes. Lynn Margulis argues that some of these structures, for example mitochondria and chloroplasts, were originally distinct organisms, and that the eukaryote cell itself is the result of endosymbiosis between several different types of prokaryote organisms, an event or events of great evolutionary significance. In Carl Woese's molecular phylogeny-based classification, the third domain of life on Earth. Woese rejects the prokaryote-eukaryote distinction. Relative to prokaryotes, eukaryotes represent only a small proportion of life on Earth, Steven Jay Gould refers to this when arguing for nondirectionality. (MAK, incorporates material from Wikipedia) More

Evolutionary biology: sub-field of biology concerned with evolution

From Wikipedia. The structure of evolutionary biology and its relationship to other biological disciplines. The history and causes of evolution (center) are the subject of the various subdisciplines of evolutionary biology (inner ring), which grade into one another and, as shown by the arrows, are related both to one another and to other disciplines (outer ring). The areas of the segments in the diagram convey an impression of the historical contributions of the subdisciplines to the literature of evolutionary biology. (Diagram and text by Andrew Colvin)

Extant : A species or taxon that is still in existence, recent, living, surviving now. The opposite of extinct.

Extinct: A species or taxon that has died out and hence is no longer found on Earth. Extinction may be recent, the result of human activity, or it may have occurred millions of years ago. The opposite of extant. When extinction occurs simultaneously across many taxa it is known as a mass extinction.

Extremophile: an organism that favours extreme conditions (relative to what is optimal to most life on Earth), such as very high or very low temperature, or lack of oxygen. Most life in the universe would almost certainly be extremophile.

F.

Fauna: The animal life of a region or geological period (Allaby 1998). (A Glossary of Terms Related to Basic Ecology)

Fish: A rather taxonomically meaningless assemblage of vertebrates defined only by their non-tetrapod nature. The traditional term is disliked by cladists because it does not constitute a natural clade.

Flora: Plant or bacterial life forms of a region or geological period Allaby 1998 (A Glossary of Terms Related to Basic Ecology)

Food chain: a group of organisms interrelated by the fact that each member of the group feeds upon on the one below it. (Wikipedia glossary)

Food web: a set of interconnected food chains by which energy and materials circulate within an ecosystem. (Wikipedia glossary)

Fungi: Moulds and mushrooms. Not quite animals and not quite plants (though phylogenetically more closely related to the former than the latter). One of the three kingdoms of multicellular life in the Whittaker-Margulis classification scheme. Fungi

G.

Gaia hypothesis: The theory, formulated by the environmentalist James Lovelock and co-developed by the microbiologist Lynn Margulis in the 1970s, that all life on Earth, as well as their inorganic surroundings form a single and self-regulating complex system, maintaining the conditions for life in the planet. The scientific investigation of this hypothesis focuses in the observation of how the biosphere and the evolution of life forms contribute to the stability of global temperature, ocean salinity, oxygen in the atmosphere and other factors of habitability. Remains a controversial topic in some areas of the scientific community, although basically accepted in fields like geophysiology and Earth system science. (from Wikipedia)

Generalist: Jack of all trades, master of none. Highly adaptable, but not able to compete well with more advanced organisms in specialised roles. Tends to be cosmopolitan, generally morphologically primitive. Like R-selected species, good at surviving unstable environments and situations. (MAK)

Gigantotherm: ("giant warmth") an animal that maintains a constant body temperature through simply being so large that it takes a long time for its temperature to rise or fall. Gigantothermy is a form of Homeothermy (having a constant body temperature); it may be arrived at either through ectothermic (giant cold-blooded animal) or endothermic (giant warm-blooded animal) means. Dinosaurs are classic examples of gigantothermy. (MAK)

Guild: Group of organisms having a similar morphology, and exploiting the same food resources, living the same life-style and in the same environment, but which are not necessary related. Because no two types of organisms can occupy the same ecological niche (one will inevitably outcompete the other, and push it aside), comparable guilds have to be separated by geographical or chronological distance. A good example of the same guild is the modern crocodile and the phytosaurian thecodont (Parasuchia) of the late Triassic. Both are astonishingly similar in size, appearance, and life-style, and indeed modern crocodiles only appeared after the phytosaurs had become extinct. But they are only distantly related (both are archosaurian reptiles, but their common ancestor lived millions of years before the first phytosaur appeared). (MAK)

Gymnosperm: "naked seeds", after the unenclosed condition of their seeds (called ovules in their unfertilized state). Their naked condition stands in contrast to the seeds or ovules of flowering plants (angiosperms) which are enclosed during pollination. Includes conifers, cycads, Ginkgo, Gnetales, and extinct groups such as "seed ferns". (Wikipedia)

H.

Habitat: 1. The place, including physical and biotic conditions, where a plant or an animal usually occurs (Allaby 1998). 2. The physical conditions that surround a species, or species population, or assemblage of species, or community (Clements and Shelford, 1939). (A Glossary of Terms Related to Basic Ecology)

Hierarchy: Biological organisation, or the hierarchy of life, is the hierarchy of complex biological structures and systems that define life using a reductionistic approach. Each level represents an increase in organisational complexity, with each "object" being primarily composed of the previous level's basic unit. The basic principle behind the organisation is the concept of emergence: the properties and functions found at a hierarchical level are not present and irrelevant at the lower levels. The usual scheme, from the lowest level (below) to the highest level (top), is as follows (note: the following modifies the table taken from Wikipedia by differentiating organisms and communities and so on):

Each level can also be broken down into its own hierarchy, and specific types of these biological objects can have their own hierarchical scheme. For example, genomes can be further subdivided into a hierarchy of genes (Wikipedia). The hierarchy can also extend beyond the biosphere to the cosmos as a whole; such arrangements being common in Transpersonal Psychology and the New Age/New Paradigm/New Consciousness movement. Philosopher and author Arthur Koestler, in association with (more) suggested a holarchy, a hierarchy of "holons", in which each part is the whole of those unites below it. This idea was adapted by New Age/New Consciousness philosopher Ken Wilber who applied it in an evolutionary context.

Homeostasis: the property by which a system, especially a living organism, regulates its internal environment so as to maintain a stable, constant condition. According to James Lovelock, the planet Earth as a whole is homeostatic system (Gaia Hypothesis). (MAK, Wikipedia glossary)

I.

J.

K.

K-selected species: species that produce fewer but stronger offspring and dedicate more care to their upbringing. K-selected species are better suited for, and better able to compete with strong competitors in a crowded environment. (Wikipedia glossary)

Keystone species: keystone species is a species that has a disproportionate effect on its environment relative to its abundance. Such species affect many other organisms in an ecosystem and help to determine the types and numbers of various others species in a community. (Wikipedia glossary)

L.

M.

Mass extinction: Event involving higher extinction rates than the usual degree of background extinction. See Big Five for diagram of extinction rates, and synopsis of five major extinctions.

Megafauna: animal life, generally specifically applied to terrestrial vertebrate, of exceptionally large size. Dinosaurs and large mammals such as proboscideans (mastodons, elephants, etc), rhinos, and so on are classic examples. Because they are so striking and charismatic, megafauna often feature in nature documentaries, books and artwork on the history of life, and so on.

Metazoa: a multicellular animal, whose cells are organized into tissues and organs. One of the three kingdoms of multicellular life in the Whittaker-Margulis classification scheme. They are rather anthropocentrically divided into Vertebrates and Invertebrates. More

Mimicry: imitative behavior, one species resembling one another, and gaining advantages as a result. For example harmless flies that have the same colouration as bees and wasps. Because predators know that wasps sting they tend to avoid anything that looks like them. See Batesian mimicry and Müllerian mimicry. Wikipedia glossary

Morphospace: a representation of the possible shape, structure, or form of an organism, usually with two or three variables plotted on a grid or diagram. More technically, an n-dimensional space, which each of the n axes corresponds to a variable which describes a particular aspect or character of the organism's morphology. The location in that space represents the specific morphology. So in the diagram at the right, the three axes or dimensions of morphospace each represent a particular variable in shell coiling (here translation rate, expansion rate, and distance of generating curve from coiling axis); together they can describe every possible spiral shaped shell. Adaptive radiation spreads out in morphospace along one or several dimensions. Note that in this diagram only a small proportion of possible morphospaces are occupied, most are impractical for adaptive or anatomic reasons. (MAK, AK's Rambling Thoughts, Mark Ridley; diagram from Raup 1966 via Mark Ridley - Evolution - A-Z morphospace)

Müllerian mimicry: A form of mutually beneficial mimicry in which two or more poisonous species resemble each another.Contrast with Batesian mimicry

Multicellular organism: an organism consisting of a hierarchical assemblage of cells, or in complex multicellular organisms, systems (for example circulatory, digestive, or reproductive) themselves collections of organs; these are, in turn, collections of tissues, which are themselves made of cells. (from Wikipedia)

Mutualism: In ecological and biological science today, mutualism is synonymous with the original scientific and current colloquial term symbiosis, an interaction between individuals of two different species where both benefit. (MAK)

N.

Nekton: Used to describe aquatic organisms that swim, as opposed to plankton which drift. (USGS Paleontology glossary)

Niche: In ecology, the role the species plays in the functioning of the ecosystem: the "functional status of an organism in its community" (Charles Elton, in Odum, 1959). The part of the environment occupied by a particular species along with the resources it uses and produces. A species' niche includes such factors as energy consumed, time of consumption, space occupied, temperature required, mode of reproduction, and behavior. (UCMP Understanding Evolution Glossary)

Nitrogen cycle: a continuous cycle by which nitrogen from the atmosphere and compounded nitrogen keeps getting exchanged through the soil into substances that can be taken up and used by green plants, what is left returns to the air as a result of denitrification. Wikipedia glossary

Nitrogen fixation: A chemical process by which nitrogen in the atmosphere is assimilated into organic compounds. Only certain bacteria are able to fix atmospheric nitrogen, which then becomes available to other organisms through the food chains. (PBS evolution Glossary)

Nucleotide: the building block of DNA and RNA; consists of a sugar and phosphate backbone with a base attached. (PBS evolution Glossary)

Nucleus: a membrane-enclosed central region of the eukaryotic cell, which contains the genetic material.

O.

Oxygen crisis: being a crisis for the earlier mentioned Archaea (one of the three domains of life), in that photosynthetic blue-green algae totally transformed the Earth by changing the atmosphere from reducing to oxygenating, thus paving the way for eukaryote life.

P.

Paleobiogeography: The branch of paleontology that deals with the geographic distribution of plants and animals in past geologic time, especially with regard to ecology, climate, and evolution.

Paleoecology: the study of the relationships between species in fossil assemblages.

Paleoenvironment: Environment in the geologic past. (USGS Paleontology glossary)

Paleoclimate: The climate of a given period of time in the geologic past. (USGS Paleontology glossary)

Parthenogenesis: Development from an egg cell that has not been fertilized. The term for a certain form of asexual reproduction that is found in some lizards, insects (notably among aphids), and certain other organisms. (PBS evolution Glossary)

Pelagic: Referring to open water marine habitats free of direct influence of the shore or ocean bottom. Pelagic organisms are generally free-swimming (nektonic) or floating (planktonic). (USGS Paleontology glossary)

Phanerozoic: the most recent, and current, of the four eons of the geological timescale, the time of diverse and complex life, complex ecosystems, and an oxygen-rich atmosphere. Divided into Paleozoic, Mesozoic, and Cenozoic. The Phanerozoic begins with the start of the Cambrian period, and continues to today. More

Population: A group of potentially inter-breeding individuals of the same species found in the same place at the same time (Booth et al. 2003). A group of organisms, typically a single species, and typically isolated from other members of its species in some manner. (W.J. Hudson)

Pheromone: chemical substance produced by some organisms and emitted into the environment to communicate with others of the same species.. (PBS evolution Glossary)

Philosophy of biology: subfield of philosophy of science, which deals with epistemological, metaphysical, and ethical issues in the biological and biomedical sciences. Although philosophers of science and philosophers generally have long been interested in biology (e.g., Aristotle, Descartes, and even Kant), philosophy of biology only emerged as an independent field of philosophy in the 1960s and 1970s. Philosophers of science then began paying increasing attention to biology, from the rise of Neodarwinism in the 1930s and 1940s to the discovery of the structure of DNA in 1953 to more recent advances in genetic engineering. Other key ideas include the reduction of all life processes to biochemical reactions, and the incorporation of psychology into a broader neuroscience. (Wikipedia)

Phosphorus cycle: the biogeochemical cycle that describes the movement of phosphorus through the environment. (Wikipedia - Glossary of ecology)

Pioneer species: species that first inhabit an environment which was previously unoccupied. (Wikipedia - Glossary of ecology)

Plankton: Aquatic organisms that drift, or swim weakly. Hence Planktonic describing aquatic organisms that float. (USGS Paleontology glossary)

Plant: traditionally and taxonomically meaninglessly used to include all photosynthetic organisms and fungi. In the Whittaker-Margulis scheme one of the three kingdoms of multicellular life, include the land plants and (in later classifications) green algae. more

Predation: the interaction among populations when one organism kills and consumes another one. (Wikipedia glossary)

Primary producer: an autotroph that obtains energy directly from the nonliving environment through photosynthesis or less commonly through chemosynthesis. (Wikipedia glossary)

Primary production: production of organic compounds from carbon through photosynthesis. This effects all life on Earth either directly or indirectly. (Wikipedia glossary)

Prokaryote: also Bacteria, Monera (the terminology differs) are organisms that lack a cell nucleus (pro before, karyon kernel), or other membrane-bound organelles. They include the simplest and oldest forms of life, such as the various types of bacteria and blue-green algae, which don't have a distinct cellular nucleus or other intra-cellular membranes, in contrast to eukaryotes. But they are also very metabolically diverse, and able to survive extreme conditions (which make them good candidates for extraterrestrial life; i.e. if there is life elsewhere in the cosmos, of which the answer must surely be that, the vast majority of it, just like on Earth, will quite likely be prokaryote, or else something equivalent). The prokaryote-eukaryote distinction is rejected by Carl Woese, who, using molecular phylogeny proposes instead three domains of life, two of which - the Bacteria and Archaea, are prokaryote. More

Protozoa: originally "protist" or wastebasket taxon for animal-like (motile, heterotrophic) unicellular eukaryotes; Cavalier-Smith's system one of the six kingdoms of life, including the first eukaryotes, flagellate, and amoeboid forms.

Q.

R.

R-selection, R-selected species: A species that produces a large number of off-spring, each of which receives little care (quantity rather than quality). R-selected species are better suited for variable or unpredictable environments. (Wikipedia glossary)

Resource partitioning: when two or more species share, and compete for a resource in different ways in order for both species to coexist. (Wikipedia - Glossary of ecology)

Rhizaria: corresponds mostly to the old class Rhizopoda (which is invalid due to being polyphyletic), protozoa or protists that have pseudopodia. (MAK)

S.

Sixth extinction: the on-going anthropogenic mass-extinction, so called because it is comparable in impact to the preceding big five. The term was coined or popularised by Richard Leakey and Roger Lewin in their 1996 book The Sixth Extinction: Patterns of Life and the Future of Humankind. In his book The Future of Life (2002), E.O. Wilson calculated that, if the current rate of human disruption of the biosphere continues, one-half of Earth's higher lifeforms will be extinct by 2100. (MAK, Wikipedia)

Snowball Earth: hypothesis that the Earth's surface became entirely or nearly entirely frozen one or more times during the Precambrian. The most recent snowball was about or earlier than 650 million years ago (Neoproterozoic era, during the appropriately named Cryogenian period). Evidence includes glacial deposits found at what at the time were tropical paleolatitudes, It is not known whether the Earth was a full snowball, or a "slushball" with a thin equatorial band of open (or seasonally open) water. (MAK, Wikipedia)

Social behavior: behavior of an individual towards society and members of the same species as a whole. Wikipedia - Glossary of ecology

Subtropical: Bordering on the tropics or nearly tropical. (USGS Paleontology glossary)

Suspension feeder - aquatic or marine organisms which capture food suspended in the water column. Suspension feeders that use a filter to capture food (e.g. brachiopods, crinoids, etc.) are called filter feeders. Suspension feeders were more predominant in Paleozoic ecosystems, where they often would form tiers. (MAK, University of Arizona Geosciences 308 Paleontology glossary)

Superorganism: an organism consisting of many (sometimes thousand, in some cases even millions) individuals working together as a single functional somatic or social unit, e.g. a jellyfish (where individual organisms fulfill the role of different organs) or an ant colony (where the superorganism is more dispersed in space, but also more intelligent). (MAK)

T.

Terrestrial: organisms living mostly or entirely on dry land, in contrast to aquatic or marine; land habitats as distinction from aquatic habitats.

Thermoregulation: the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. This process is one aspect of homeostasis: a dynamic state of stability between an animal's internal environment and its external environment. See also ectotherm, endotherm, gigantothermy. (from Wikipedia)

Tree of Life: poetic term for an evolutionary tree that (ideally) includes all life on Earth. The earliest tree-like diagram was the Tree of Porphyry which classified categories in a branching series. Beginning in the 19th century branching diagrams were used by the French botanist Augustin Augier in 1801, the French evolutionist Jean-Baptiste Lamarck (1744-1829), who produced the first branching tree of animals in his Philosophie Zoologique (1809) based on the Great Chain of Being, and the American geologist Edward Hitchcock (1763–1864), who in 1840 published the first Tree of Life based on paleontology. Charles Darwin also drew abstract trees; Darwin's being the first evolutionary tree of life. It was Ernst Haeckel however who enthusiastically constructed several Trees of Life. Shown on the right is a famous illustration published in The Evolution of Man (1879), which shows a Great Chain of Being model with Homo sapiens at the top. Although this would seem an anthropocentric step backwards in relation to his earlier but more contemporary-looking three-kingdom model, it should be remembered that for Haeckel, as for many 19th century evolutionists, humans were considered the pinnacle of evolution. Teilhard de Chardin serves as a 20th century example. Since then a number of sophisticated trees have been drawn. In evolutionary systematics, trees were generally spindle diagrams that mapped geologic time (vertical axis) against taxonomic diversity (horizontal width) and emphasised monophyletic sensu Haeckel taxa (i.e. both monophyletic (sensu Hennig) and paraphyletic groups). Sometimes width did not reflect diversity but was simply artistic license. For an example of such a tree see the diagram at evolutionary systematics. Supplanting evolutionary systematics in the 1980s, phylogenetic systematics placed great emphasise on tree diagrams, called cladograms, which are based either on gross morphology, molecular phylogeny, or both. Some of these diagrams can be incredibly detailed. (Wikipedia, MAK). Tree of Life also refers to a valuable reference website (albeit still very incomplete, although some taxa, e.g. Agnatha, Ankylosauria, are well represented) with an interactive presentation of the full "tree of life". Detailed references are supplied on each page about particular organisms. It is not entirely up to date with latest ideas; for example, the tree of Eutheria fails to reflect the recent classification into Laurasiatheria, Afrotheria, Euarchontoglires, and Xenarthra. Link. (EvoWiki)

U.

Unicellular Organism: a living system consisting of only a single cell. May be simple, as with bacteria, or complex, as with protists. In the case of protists, different parts of the cell takes on the functions that organs and other systems fulfill in multicellular (many-celled) organisms. (MAK)

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W.

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Y.

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