chapter 8 definitions

• Absolute dating


  The process of determining the age of rocks and the fossils they contain on the basis of the physical or chemical properties of materials in the rock
• Adaptation


  An evolved structural, physiological or behavioural characteristic of an organism that increases its chances of survival and reproduction in a particular environment
• Adaptive radiation


  The process by which a species rapidly diversifies into many taxa with differing adaptations; it can be triggered by many factors, such as the emergence of reproductive barriers within a population, changes in the availability of resources, new challenges or new opportunities; it is a type of divergent evolution
• Analogous structure


  Features of organisms that have the same function but not the same structure
• Ancestor


  A species from which other species have evolved
• Biogeography


  The study of the distributions of living things over a geographical area and how those distributions have changed over geologic time
• Bioinformatics


  The digital storage, retrieval, organisation and analysis of a large volume of biological data; bioinformatics has dramatically increased the size, accuracy and scope of data sets, such as those needed for comparative genomics
• Clade


  A group of organisms that includes all the descendants of a common ancestor and the ancestor itself; for example, birds, dinosaurs, crocodiles and their common ancestor form a clade
• Common ancestor


  An ancestor that is shared by different species
• Comparative anatomy


  The study of the similarities and differences in structure between different organisms; a larger number of similar features indicates a more recent common ancestor
• Comparative biochemistry


  Analysis of the similarities and differences in the cellular chemistry of different species; it particularly includes the study of proteins (especially enzymes) and the DNA that encodes them; the results enable evolutionary biologists to obtain a measure of the relatedness between species
• Comparative dating


  The process of determining the age of rocks and their contained fossils relative to one another, allowing an estimation of 'oldest to youngest', without assigning an actual age in years
• Comparative genomics


  A field of biological research in which scientists use a variety of tools to compare the genome sequences of different species; the more similar in sequence the genes and genomes of two species are, the more closely related those species are
• Conserved


  Refers to DNA or protein sequences that have been preserved by natural selection and are still the same or very similar in different species
• Continental drift


  The relative movement of Earth's continental landmasses, which appear to drift over Earth's mantle
• Convergent evolution


  A process whereby unrelated organisms evolve similar adaptations in response to a similarity in their environments
• Divergent evolution


  A process whereby related species evolve new traits over time spent living in different habitats, becoming increasingly different from the common ancestor and from one another, giving rise to new species
• DNA–DNA hybridisation


  A method used to analyse relatedness; similarities in the base-pairing of DNA strands are analysed to show evolutionary links between organisms
• Embryology


  The study of the anatomy of embryos and how they develop over time until the adult stage
• Eon


  A major division of geologic time that is itself divided into eras
• Epoch


  A division of geologic time (periods) that is marked by one or more significant events
• Era


  A division of geologic time (a subdivision of eons) that is itself divided into periods
• Evolution


  The process of cumulative, gradual, inheritable change in a population of organisms that occurs over many generations and a relatively long time
• Fossil


  Preserved remains or traces of an organism
• Genomics


  The study of the genome – how genes interact with one another and the environment, and the resultant proteins produced; knowledge of an organism's entire DNA sequence
• Gradualism


  A theoretical model of evolution that proposes there has been a steady, slow divergence of lineages, irrespective of gaps in the fossil record
• Homologous structure


  Feature that has the same general structure but different functions in different organisms
• Homology


  The existence of shared ancestry between a pair of structures or between genes
• Isotope


  Atoms of an element that have the same number of protons but different numbers of neutrons, and therefore different relative atomic masses
• Molecular homology


  The identification of shared biomolecular elements – generally genes – used to test the closeness of relationships between organisms; it can demonstrate common ancestry
• Molecular phylogeny


  The study of evolutionary relationships using comparative genomics
• Mutation rate


  The number of changes per gene copy in a population over a period of time
• mya


  Millions of years ago
• Niche


  An organism's habitat, way of life, or the way it functions in its environment
• Palaeontology


  The study of life in the past, based on fossil remains
• Period


  A division of an era of geological time that is itself divided into epochs
• Phylogeny


  Evolutionary relationships that exist between species, often expressed in a tree-like diagram
• Principle of superposition


  The principle that states that the oldest rock layer is found in the deepest position, and each consecutive layer above it is relatively younger; it indicates the relative ages of the rock layers and the fossils within them; this principle is fundamental to our interpretation of Earth's history
• Punctuated equilibrium


  A theory of evolution that proposes new organisms evolve quickly after a long period of no change, rather than evolving by gradual change
• Radiometric dating


  Uses the known rates of decay of naturally occurring radioactive isotopes present in a rock or fossil to obtain an absolute date for its age