Timaru Girls’ High School Level 3 Biology External 4 Credits Keywords for AS 91605 – Demonstrate understanding of evolutionary processes leading to speciation. 1. Adaptive radiation The evolution of a number of different species of plant or animal from one ancestral species, eg. Darwin’s Galapagos finches. 2. Allopatric speciation Speciation occurring where organisms are initially capable of actually interbreeding but cannot because they are geographically separated. 3. Allopatry Describes groups of organisms that could potentially interbreed but do not because they are geographically separated. 4. Analogous structures Structures that are superficially similar but have evolved in different ways, eg. the wings of birds, bats and insects. 5. Ancestral type A hypothetical individual possessing the ancestral or primitive characteristics of a group of species. 6. Artificial selection Deliberate selection by humans for desired features in a plant or animal species. 7. Autopolyploidy A type of polyploidy where the multiple sets of chromosomes are all derived from the same species. 8. Cladistics A method of classification in which animals and plants are placed into groups called clades when they share characteristics that are thought to indicate common ancestry. 9. Classification The arrangement of organisms into a series of groups based on physiological, biochemical, and anatomical or other relationships. 10. Cline A gradual variation in the characteristics of a species or population over its geographical range. 11. Convergent evolution The development of superficially similar structures in unrelated organisms, usually because the organisms live in the same kind of environment. 12. Divergent evolution An accumulation of changes in the gene pools of two (or more) populations, leading to the formation of races, sub-species, species etc. 13. Evolution The gradual process by which the present diversity of plants and animals arose from the earliest and most primitive organisms. 14. Geological record Fossils preserved in sedimentary rock layers that can be used to trace the evolutionary history of a species. 15. Homologous structures Structures that have a similar evolutionary history but have developed to suit different functions, eg. wings of a bat, flippers of dolphins and arms of humans have all evolved from paired pectoral fins of an ancestral fish. 16. Hybrid The offspring of a mating where the parents differ in at least one characteristic. The term is usually applied to offspring of widely different parents, eg. different varieties/species. 17. Instant speciation The formation of a new species through autopolyploidy or allopolyploidy. Because the chromosome numbers of the new ‘instant’ species do not match that of the original species they cannot interbreed. 18. Macro-evolution The formation of a completely new species, genera, etc. 19. Micro-evolution The accumulation of (through mutation) of new characteristics in a species. 20. Natural selection The process that brings about new species by eliminating individuals that are less well adapted to their current environment from a population showing variation, allowing mainly individuals with advantageous adaptations to survive and reproduce. 21. Parallel evolution The development of related organisms along similar evolutionary paths due to strong selection pressures acting on all of them in the same way. 22. Phyletic speciation or Sequential speciation Speciation where adaptation by a species to changing environments creates a new species. This occurs because along with adaptations to the environment, barriers to breeding with the ‘original’ species are developed. 23. Phylogeny The evolutionary history of an organism or a group of related organisms. 24. Polymorphism The existence of three or more distinctly different forms within a plant or animal species, eg. the different ‘castes’ found in social insects such as bees or ants. 25. Primitive feature A feature that is assumed to have been present in the evolutionary ancestor of a species of group of species. It may or may not have been simpler, depending on the evolutionary history of the species. 26. Reproductive isolation A barrier to breeding that exists due to differences in mating season or mating organs, eg. flowers flowering at different times of year. 27. Ring species Two apparently distinct species that are connected by a series of intermediate geographical and structural subspecies between which interbreeding can occur. 28. Selection pressure The extent to which organisms possessing a particular characteristic are either eliminated or favoured by environmental demands. 29. Speciation The development of one or more species from an existing species. It occurs when sympatric or allopatric populations diverge so much from the parent population that interbreeding cannot occur. 30. Species A category used in the classification of organisms that consists of a group of organisms that can usually breed together and produce fertile offspring. 31. Sub-species A group of individuals within a species that breed more freely among themselves than with other members of the species and resemble each other in more characteristics. 32. Sympatric speciation Speciation occurring where organisms living within the same area are theoretically capable of interbreeding, but cannot because of difference in behaviour, flowering time etc. 33. Sympatry Describes groups of organisms that live in the same geographical area. 34. The new synthesis Also referred to as ‘neo-Darwinism’. It combines the ideas of Darwin with the discoveries of Mendel and forms the basis of modern evolutionary science. 35. Vestigial organ Any part of an organism that has diminished in size during its evolution because the function it serves has decreased in importance, eg. the appendix in humans.