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Biology Eleven - Rat Island

A look at how a trapped rat might adapt to an island climate over many generations in order to survive.

Emily Dawson

on 1 October 2012

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Transcript of Biology Eleven - Rat Island

Our climate is an island that has two very distinct sides, and therefore two very distinct varieties of rats. Rat Island Habitat Nose Food Source Eyes Ears Competition Tail Predators A Biology Project by
Jesse Bartsoff and Emily Dawson This all goes back to when a little known ship sank nearby, with an absolute infestation of rats on board. Those rats that survived had certain characteristics - including the much-needed ability to swim - and these changed in accordance to their new environment. This island is cleanly divided into two halves. The southern side is shaded (we're below the equator) and cooled by the ocean breezes. This is the side where large fish-eating birds come to land and lay their eggs on the rocks. Sparse cacti grow here, and are the only consistent food source for rats on this side. The northern side is very hot and humid, with little breeze to cool the air. This creates an environment where the cacti thrive, providing a rich food source. This is where a species of cactus-eating tortoise also dwells. These rats are active during the day, as they do not need to avoid the sun's heat - They are quite comfortable in the shade. Due to the climate, these rats are nocturnal in order to escape the heat of the day. The rats have developed very sensitive whiskers, as well as increased sense of smell, with the ability to seek out food. Northern Side Rats Southern Side Rats The only natural food sources on this side are fish and rare cacti, but once a year they are able to feast upon the eggs of the nesting birds. The rock is sedimentary, and light brown in colour. These rats will have shorter tails than their original ancestors, so as to best avoid the bird's attacks of revenge. These rats have a sense of smell far superior to their ancestors, so as to better find the sparse food sources. Their ability to see has been augmented as well, and they can now detect subtle movements of fish in the water, and tell the difference between a stone and a camouflaged egg. Their claws and teeth will have evolved to break through the shells of the eggs, and to pick apart the fish. These rats have developed shorter fur, to adapt to the tropical climate, and lighter colouring to blend with the rocks. Their tails have also become broader and more powerful, so as to improve the rats' swimming ability,
and therefore, their ability to catch fish. The southern rats' ability to hear and the sensitivity of their whiskers have both remained unchanged. The already adept digestive system has now specialized to oope with small fish bones and egg shell pieces. These rats have also developed the ability to burrow in the rock bed, having developed stonger claws than their ancestors. So they should turn out looking something like this... With teeth providing the ability to pierce through cacti's outer layer, the rat finds food and a form of water. The cacti also function as the rats' home, and their moist burrows provide relief from the scorching days heat. These rats have also developed a more acute sense of hearing, to accommodate for their decreased vision. Their claws and teeth have adapted to penetrate the waxy coating of the cactus, which their digestive system has developed to cope with. This rat has developed darker and longer fur, to cope with the chill and darkness of the night. Nonetheless, these rats have retained their ability to swim, and their longer tails. Thus, our island is one of the rare examples of sympatric speciation. Provided with these facts, the northern rat resembles something like this... So in the end, thanks to natural selection and sympatric speciation, the result is two very different rat populations. That's all folks!
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