• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

When One Becomes Two

Extracts from this document...

Introduction

When One Becomes Two How can two organisms look exactly alike, yet be members of different species? This is the question that I was confronted with when studying two rodent populations of the St. Kitt's and Nevis Islands. As an expert in the field of mammalian reproductive strategies, I was hired by the Department of Nature and Island Resources of the West Indies, to investigate a previously undiscovered species of rodent.(1) The rodent population on St. Kitt's was very small and threatened. My goal was to find a way to replenish this population and help to prevent extinction. When I first arrived in the area, I observed that the population of a rodent appearing identical to the St. Kitt's rodent inhabited the island of Nevis.(1) I took note of the fact that the Nevis population was strong and healthy, relatively unaffected by the development threatening the St. Kitt's rodents. In an effort to reestablish the St. Kitt's population, I brought animals from Nevis to St. Kitt's hoping they would mate with each other and increase the population of rodents. Unfortunately, I was unable to observe a single successful reproductive event.(1) ...read more.

Middle

Based on my observations and research, I believe that the microevolutionary changes that occurred in the two populations of rodents were mutation and natural selection. When random mutations occur in gametes, the offspring produced by the gametes will have different characteristics than other offspring. If the mutation is advantageous to the individual, natural selection can occur.(2) Natural selection is dependent upon genetic variation. Because of the variation present in all populations, certain individuals have more advantageous characteristics than other individuals. These advantaged individuals are more likely to survive to reproducing age and to pass on their characteristics to their offspring, while the other individuals not possessing the advantageous characteristic will find it more difficult to obtain the necessities of life, and reproduce. Over several generations, the majority of the population will possess the advantageous trait, and those more possessing it will have died off.(2) In the case of the rodents on the islands, mutations and natural selection created differences in the two species. On the island of St. Kitt's, about 20, 000 years ago, there was a wolf-like predator that preyed on the rodents. ...read more.

Conclusion

The rodents of St. Kitt's were naturally selected by a predator, and their microevolutionary changes accumulated to create a new species, no longer capable of mating with the parent species of Nevis. Once the two populations were recombined, they remained unable to produce viable, fertile offspring because of different reproductive isolations. The rodents populations from the two islands are reproductively isolated behaviourally. Behavioural isolation involves the difference courtship rituals used by animals to attract a mate. The rodents of St. Kitt's have a much shorter courtship ritual than the rodents on Nevis, and the behaviour would be unlikely to attract an individual from the other species. This isolation furthers the blockage of gene flow between the two populations, and keeps the gene pools of the populations separate. In order to understand why the two rodent populations could not mate with each other, I needed to understand microevolution, macroevolution, and reproductive isolations. To summarize, the geographic division or allopatric speciation set up the possibility of the creation a new species, and it was the accumulation of the microevolutionary changes in the populations that eventually led to the development of a unique species, some 15, 000 years later. Once the new species had developed, after recombining with the parent species, they could not successfully mate because of the behavioural reproductive isolation. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Zoology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Zoology essays

  1. The positive correlation shows that the older the molehill the higher the species diversity ...

    5 6 7 35 salad burnett 10 14 10 9 12 11 14 80 pseudosclropodium 2 0 1 3 1 0 0 7 ribwort piontain 0 0 0 0 0 5 7 12 rest harrow 0 0 0 0 4 0 0 4 danylion 0 0 0 0 0 0

  2. This report was commissioned by Sunderland City Council to assess the ecological and educational ...

    In addition Tor-grass (Brachypodium pinnatum) reaches its north-most limit around this region (URL 1). One species, which is particularly rare, is the nationally scarce Blue Moor grass (Sesleria albicans). The grass is characteristic of Magnesian grasslands and is found in very few locations in the UK.

  1. With the aid of examples, discuss the biogeographical consequences of previously separated continents merging.

    The first to do this was Alfred Russell Wallace in 1876 who organised them as follows; Nearctic (North America); Neotropical (South America); Palearctic (Europe and Asia); Ethiopian, sometimes described as Africotropical (African); Australasian (Australia) (J.C. Briggs 1987). This is of course a generalisation as there are highly endemic large islands to be considered like New Zealand, Madagascar and Hawaii.

  2. What is a species? How do new species arise? What is the difference between ...

    The Phenetic species concept places the emphasis on morphological characters when defining species. A species is defined as the smallest groups of organisms that are consistently and persistently distinct and distinguishable from other groups. The problem with this definition is that the criteria are arbitrary and subjective, so there is no definitive identifying feature of a species.

  1. What are the impacts of interspecific hybrids on species conservation?

    Species that result from these types of hybridisation are eligible for protection, as they are the result of the natural course of evolution. The remaining three types of interspecific hybridisation involve situations in which human activities have caused hybridisation. Situations where F1s are primarily detected is classified as type 4 hybridisation.

  2. Due to excessive whaling, many species of whale are near extinction.

    Also, if the whale moratorium is lifted, and commercial whaling begins, then many job opportunities will open up. Seafood is a very high money making industry in Japan, recently one Blue Fin sold for $300,000. Whaling is an industry that employs many Japanese that would otherwise not have jobs.

  1. A Study of the Fishes Caught by Anglers in Downtown Madison, Wisconsin.

    RESULTS A total of 127 anglers were surveyed, and they caught 817 fish altogether on 279 lines (Table 1). More bluegill (745.5) were caught than any other species, and more of them were caught on Lake Mendota than on any other lake.

  2. Compare and Contrast two of the five main approaches in psychology.

    Eventually the cat would panic and begin to scratch all sides of the box, primarily it was an accidental event yet it was rewarded with food and freedom. The idea behind this simple as it may seem, was that the cat would learn from its previous times in the box when it was rewarded.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work