Glossary

Definitions of some of the biological terms used in this thesis are presented below. A number in square brackets after a definition indicates that it is based upon (but may be an abbreviated version of) a definition from one of the following sources: [1] the glossary of [Dawkins 82]; [2] the glossary of [Salthe 85]; [3] the glossary of [Margulis & Sagan 86]; [4] the Encyclopaedia Britannica (http://www.eb.com); [5] the Merriam-Webster Dictionary (http://www.m-w.com); and [6] the web pages of Tom Herbert, Professor of Biology at the University of Miami (http://fig.cox.miami.edu/Faculty/Tom/bil160/06_adaptive.html). Words appearing in bold in the definitions are themselves defined elsewhere in the glossary.

abiotic

Used to refer to that portion of the world not immediately making up part of the biomass of living systems. [2]

adaptive radiation

Evolutionary divergence of members of a sincle phyletic line into a series of rather different niches or adaptive zones. Adaptive radiation is considered to be a rapid process, where adaptation from a recent common ancestor takes place in a short period of time. [6]

adaptive zone

A set of ecological niches that may be occupied by a group of species that exploits the same resources in the same manner. [6]

allele

An alternative form of a genetic locus. [2]

allopatric

Living in another region; said of populations of species which occupy ranges in different places on the earth's surface such that gene flow between them would be restricted or absent. [2]

allosteric

In enzymology, inhibition or activation of an enzyme by a small regulatory molecule that interacts at a site (allosteric site) other than the active site (at which catalytic activity occurs). [4]

biomass

The actual amount of matter included in some living system. [2]

biotic

Referring to living systems, as opposed to abiotic. [2]

Cambrian Period

Earliest time division of the Paleozoic Era, extending from about 540 to 505 million years ago. [4]

Cambrian explosion

The beginning of the Cambrian Period, now thought to date from 540 rather than 570 million years ago, witnessed an unparalleled explosion of life. Many of the major phyla that characterise modern animal life-various researchers recognise between 20 and 35-appear to have evolved at that time, possibly over a period of only a few million years. Many other phyla evolved during this time, the great majority of which became extinct during the following 50 to 100 million years. Ironically, many of the most successful modern phyla (including the chordates, which encompass all vertebrates) are rare elements in Cambrian assemblages; the phyla that contained the most numerically dominant forms were those that became extinct. [4]

coevolution

A long-term process of coming into relation with each other of species or populations by active reciprocal modifications of all the members of the coadapting group. [2]

commensalism

A relation between individuals of two species in which one species obtains food or other benefits from the other without either harming or benefiting the latter. [4]

deme

A local group of organisms in a species that might mate with each other in any given generation. [2]

DNA

Deoxyribonucleic acid. A linear, unbranched nucleotide polymer, containing deoxy-ribose sugars. In biological cells, DNA codes genetic information for the transmission of inherited traits.

dNTP

Deoxynucleotide-triphosphate. The units from which DNA molecules are constructed, each carrying a single nitrogenous base (adenine, guanine, cytosine or thymine).

epistasis

In genetics, the condition whereby the proximity of a gene to others in the genome affects its activity on the phenotype. [2]

eukaryote

One of the two major groups of organisms on Earth, including all animals, plants, protozoa and fungi. Characterised by the possession of a cell nucleus, and other membrane-bound cell organelles. Contrast with prokaryote. [1]

gene

A unit of heredity. Commonly refers to a small section of the genome, but a number of different precise definitions exist.

genome

All the DNA in the cells of an organism. That portion of a cell that physically represents its genotype. [2]

genotype

The particular combination of alleles present at one or more genetic loci in some organism.

gradualism

The doctrine that evolutionary change is gradual and does not go in jumps. [1]

macroevolution

The study of evolutionary changes that take place over a very large time-scale. Contrast to microevolution. Macroevolutionary change is usually recognised as change in gross morphology in a series of fossils. There is some controversy over whether macroevolutionary change is fundamentally just cumulated microevolutionary change, or whether the two are `decoupled' and driven by fundamentally different kinds of process. [1]

metazoan

Any of a group (Metazoa) that comprises all animals having the body composed of cells differentiated into tissues and organs and usually a digestive cavity lined with specialised cells. [5]

microevolution

The study of evolutionary changes within populations. Microevolutionary change is change in gene frequencies in populations. [1]

mRNA

A type of RNA (abbreviation of `messenger RNA'). Carries codes from the DNA in the nucleus to the sites of protein synthesis in the cytoplasm. [4]

mutualism

Association between organisms of two different species in which each is benefited. Mutualistic arrangements are most likely to develop between organisms with widely differing living requirements. The partnership between nitrogen-fixing bacteria and leguminous plants is an example. [4]

niche

The place of an organism within an ecosystem, defined by the ranges of the resources that it utilises. [6]

nucleotide

Any of a class of compounds made of nitrogenous bases and pentose sugars (ribose, deoxy-ribose) with phosphates attached. [3]

ontogeny

The process of individual development. In practice development is often taken to culminate in the production of the adult, but strictly speaking it includes later stages such as senescence. [1]

Paleozoic Era

Major interval of geologic time that began about 540 million years ago with an extraordinary diversification of marine animals during the Cambrian Period and ended about 245 million years ago with the greatest extinction event in Earth history. [4]

parasitism

Relationship between two species of plants or animals in which one benefits at the expense of the other, without killing it. [4]

Phanerozoic Eon

The span of geologic time extending about 540 million years from the beginning of the Paleozoic Era to the present. [4]

phenotype

The manifested attributes of an organism, the joint product of its genes and their environment during ontogeny. [1]

phylogeny

A branching diagram of ancestor-descendant relationships along a temporal axis. [2]

phylum

A group related by a direct line of descent. In taxonomies of biological organisms, the phylum is the basic unit of differentiation within kingdoms.

prokaryote

One of the two major groups of organisms on Earth (contrast eukaryote) including bacteria and blue-green algae. They have no nucleus and no membrane-bounded organelles such as mitochondria; indeed one theory has it that mitochondria and other such organelles in eukaryotic cells are, in origin, symbiotic prokaryotic cells. [1]

protozoan

any member of the subkingdom Protozoa, a collection of single-celled eukaryotic (i.e., possessing a well-defined nucleus) organisms. As such, they are among the simplest of all living organisms. [4]

punctuated equilibrium

The pattern of evolution (very common in invertebrates) whereby species once in existence do not change radically over long periods of time (except perhaps in size) and then are suddenly replaced by other, quite different species. [2]

RNA

Ribonucleic acid. Consists of ribose nucleotides in strands of varying lengths. The structure varies from helical to uncoiled strands.

selfish DNA

A section of DNA on the genome which is not expressed phenotypically.

symbiogenesis

The evolutionary origin of new morphologies and physiologies by symbiosis.

symbiosis

Any of several living arrangements between members of two different species, including mutualism, commensalism, and parasitism. Both positive (beneficial) and negative (unfavourable to harmful) associations are therefore included, and the members are called symbionts. The terms symbiosis and mutualism are sometimes equated and used interchangeably; this practice has resulted in some confusion. [4]

sympatric

Living in the same region. [2]