why is the greatest number of species found in the ecotone
Ecotone Plants in competition extend themselves on one side of the ecotone as far as their ability to maintain themselves allows. Beyond this competitors of the adjacent community take over. As a result, the ecotone represents a shift in dominance. Ecotones are particularly significant for mobile animals, as they can exploit more than one set of habitats within a short distance. The ecotone contains not only species common to the communities on both sides; it may also include a number of highly adaptable species that tend to colonize such transitional areas.[3] The phenomenon of increased variety of plants as well as animals at the community junction is called the edge effect and is essentially due to a locally broader range of suitable environmental conditions or ecological niches.
Evolutionary history of life The evolutionary history of life on Earth traces the processes by which living and fossil organisms evolved since life appeared on the planet, until the present. Earth formed about 4.5 billion years (Ga) ago and there is evidence that life appeared as early as 4.1 Ga.[1][2] The similarities among all present-day organisms indicate the presence of a common ancestor from which all known species have diverged through the process of evolution.[3] More than 99 percent of all species, amounting to over five billion species,[4] that ever lived on Earth are estimated to be extinct.[5][6] Estimates on the number of Earth's current species range from 10 million to 14 million,[7][8] of which about 1.9 million are estimated to have been named[9] and 1.6 million documented in a central database to date.[10] More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.[11]