BIODIVERSITY ANSWERS 4
Interrestrial ecological communities plants are more common while toppredators are scarce because, in most ecologies, plant communitiescan only be limited by grazers. However, grazers do not cause plantsscarcity because the top predator population consistently put them incheck. Therefore, top predators place too much pressure on thegrazers group leading to a subsequent decline which consequentlyrelieves the plants of the grazer pressure to multiply more sincetheir key resources are mostly nitrogen and water which often areavailable. As a result, if lions and leopards put too much pressureon savanna grassland grazers such as antelopes and giraffes, in thelong run, plant populations will increase due to reduced herbivoresnumber which in turn limits the top predators’ population due todiminished prey supply (Wilson,2010).
Biological-Speciesconcept states that a group of organisms can only be defined as aspecies if free interbreeding among its members can result in themixing of their genes to reproduce a healthy and reproductiveoffspring. However, the concept fails when it comes to the speciationof an asexual organism which reproduce freely without a partner toproduce an offspring. For instance, bacteria are asexual specieshence do not fit in the biological-species concept but theMicrospecies Concept which relies on DNA. Also, some plants such asapple and banana defy the biological-species concept as theyreproduce asexually hence fit the morphological species concepts thatidentify species based on shared morphology.
Adaptiveradiation results when a given species occupy a habitat withunoccupied niches thus specialized adaptations follows rapidly withinthe population as members quickly radiate into the unoccupied niches.Moreover, the process is mainly driven by natural selection andultimately leads to the evolution of new phenotypic traits paving theway for the possible emergence of new species that are fully adaptedto the new ecology. The African cichlid fishes such as Pundamilianyererei and Metriaclima zebra are the latest examples of adaptiveradiation in Lake Victoria and Lake Malawi respectively. The Africancichlids fall among the Neotropical cichlids diverse familycomprising of more than 60 genera and 600 species and exist inCentral and South America as well. Also, in the Galapagos Islands,Darwin’s finches is an example quick diversification within alineage to adapt to a new environment.
Biodiversityrefers to a large variety of life encompassing all its forms ofmanifestations. Therefore, biodiversity incorporates all the levels,forms, and combinations of natural variations as a unifying concept.Further, the main elements of biodiversity variation includeorganismal, nested hierarchies and ecological diversities.Consequently, since life’s varieties can be expressed in multiplemeans, there can be no single supreme biodiversity measure butdifferent measures for particular facets of diversities (Gaston& Spicer, 2004).
Macroevolutiondeals with species evolution that occurs at a grand scale levelleading to new species coming into existence. It involvesevolutionary changes that occur over an extended duration of timefrom a common ancestral origin to give the different speciesvarieties we have today. Macroevolution thus contends that whalescould have descended from land animals or that fish may havedescended from an invertebrate animal. The leading proponents of thetheory are Niles Eldredge and Stephen J. Gould who introduced thePunctuated Equilibrium concept based on the gaps discovered fromfossils (Gaston& Spicer, 2004).On the other hand, Microevolution focuses on small-scale changes thatlead to varieties following modifications in allele frequencieswithin a species population. The major proponent of microevolutionwas Gregor Mendel who believed that small gradual changes occurred inthe gene pool of organisms that occupied a particular habitat.Moreover, unlike macroevolution, microevolution has a greater impacton biodiversity because it posits that variations and the gradualemergence of new species are a consequence of factors such as ongoingnatural selection, random gene mutations, genetic drift, non-randommating and gene flow. A common example of contemporary microevolutionis the development of malarial resistance following sickle cellanemia.
Gaston,K. J., & Spicer, J. I. (2004). Biodiversity:An introduction.Malden, Mass: Blackwell.
Wilson,E. O. (2010). Thediversity of life.Cambridge, Mass: Harvard University Press.