Flower-pollinator relationships

Many flowers have close relationships with one or a few specific pollinating organisms. Many flowers, for example, attract only one specific species of insect, and therefore rely on that insect for successful reproduction. This close relationship is often given as an example of coevolution, as the flower and pollinator are thought to have developed together over a long period of time to match each other's needs. This close relationship compounds the negative effects of extinction. The extinction of either member in such a relationship would mean almost certain extinction of the other member as well. Some endangered plant species are so because of shrinking pollinator populations. In biology, coevolution is "the change of a biological object triggered by the change of a related object."[1] Coevolution can occur at many biological levels: it can be as microscopic as correlated mutations between amino acids in a protein, or as macroscopic as covarying traits between different species in an environment. Each party in a coevolutionary relationship exerts selective pressures on the other, thereby affecting each other's evolution. Coevolution of different species includes the evolution of a host species and its parasites (host–parasite coevolution), and examples of mutualism evolving through time. Evolution in response to abiotic factors, such as climate change, is not coevolution (since climate is not alive and does not undergo biological evolution). Coevolution between pairs of entities (often referred to as pairwise c evolution) exists, such as that between predator and prey, host and symbiont or host and parasite, but many cases are less clearcut: a species may evolve in response to a number of other species, each of which is also evolving in response to a set of species. This situation has been referred to as "diffuse coevolution." There is little evidence of coevolution driving large-scale changes in Earth's history, since abiotic factors such as mass extinction and expansion into ecospace seem to guide the shifts in the abundance of major groups.[2] However, there is evidence for coevolution at the level of populations and species. For example, the concept of coevolution was briefly described by Charles Darwin in On the Origin of Species, and developed in detail in Fertilisation of Orchids.[3][4][5] It is likely that viruses and their hosts may have coevolved in various scenarios.[6] Coevolution is primarily a biological concept, but has been applied by analogy to fields such as computer science, sociology / International Political Economy[7] and astronomy. An endangered species is a population of organisms which is facing a high risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters. The International Union for Conservation of Nature (IUCN) has calculated the percentage of endangered species. Many nations have laws offering protection to conservation reliant species: for example, forbidding hunting, restricting land development or creating preserves.