How Natural Selection Drives Evolution - Essay Example

A fine example of natural selection is provided by the finches that were observed by Darwin during his expedition to the Galapagos islands. He found 13 species of finches and each species exhibited variation in beak size and shape. While explaining the concept of natural selection in these finches Darwin rightly observed that all the variations already existed among the finches and that each type of variation was selected based on their adaptability to a particular type of environment.

Birds with beaks suited to eat cacti survived better in arid climates and reproduced to produce offspring with similar beaks. Birds with different beak sizes and shapes that were suited to eat nectar and hard seeds were naturally adapted to that particular environment and reproduced. Thus the process of natural selection chose organisms that were better suited to survive in a particular environment due to the inherent anatomical variations and allowed them to reproduce and contribute to the process of evolution (O’Neil). 2. Explain energy flow in an ecosystem.

Include examples An ecosystem comprises the living and non-living components within a given environment such as a pond, grassland, or forest. The flow of energy is an integral part of the ecosystem which is necessary to facilitate the normal functioning of the ecosystem. The energy that enters the ecosystem transforms at different stages based on the processes involved in the system. Energy enters an ecosystem from the sun as light energy which is trapped by plants which are referred to as the primary producers.

The energy then flows through the various trophic levels as primary producers are consumed by herbivores which are in turn consumed by carnivores and in each level it is transformed into chemical energy through various cellular processes such as photosynthesis and respiration. Waste products are produced at each level and organisms such as scavengers, detritivores, and decomposers feed on these waste products microbes are the ultimate decomposers. The energy is liberated as heat energy during every process which is lost to the ecosystem and this energy cannot be recycled.

The flow of energy through the food chain decreases at every stage beginning with the primary producers. The herbivores will have less energy available compared to the primary producers and so on. This gives rise to the energy pyramid (The concept of the Ecosystem). 3. How can different species arise in a population Speciation or the process by which new species arise from a single species is a natural phenomenon that occurs during the process of evolution. New species arise from an already existing species when a population of the species undergoes geographical isolation.

As a result of this separation, changes occur in allele frequency due to reduced gene flow between the two populations. Speciation of the formation of a new species will occur if these changes result in physical or behavioral changes that prevent the interbreeding between the parent and the newly formed population. Thus for the formation of a new species both geographical and reproductive isolation should occur which results in changes in gene flow and prevent the interbreeding between two closely related populations.