Реферат: Finch In A Pinch Essay Research Paper
Finch In A Pinch Essay, Research Paper
As scientists, we have come to this island to observe the evolution of finches when forced into an unfamiliar habitat with a changing food supply.
We believe our finch, Pherous robustus, will have a good chance at survival because its beak will allow for the finch to grasp many different seed shapes and sizes.
During our first 5 years, corn grew well on the island. Our finch population steadily increased during this time period. Our finch was very well adapted to eating the corn because it was very easy for our finch to pick up.
During the next five years there was a drought and only block plants grew. Our finch population steadily decreased during this time period because our finches could not pick up the seeds. They were much too large for their medium sized beaks. Our finches were not well adapted to the block plant seeds.
During the 10 – 15 years, the block plants died out and the pony bead plants took over. The pony bead seeds were very tiny, however our finch was versatile enough to handle the seeds. During this time period our finch population grew slightly because the seeds could be picked up, but with more difficulty than the corn.
During the final generations of our finches the drought ended and all types of foods could be grown again. In this type of environment, our finch population steadily increased because the corn and the pony beads were both present as well as the harder to pick up blocks.
Our hypothesis was correct for the most part, however we thought our bird would be more versatile than it really was. Our finches had a very hard time picking up the block seeds because of their very large size. Our finch was very well adapted to picking up seeds smaller than its head. The corn was the ideal seed for our finches but the pony beads were edible when the conditions changed.
Population Per Year
Specie 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Pherous robustus 153 157 167 170 172 164 155 149 146 141 140 140 140 137 136 139 143 146 149 152
Tweezeris bentails 149 146 146 146 145 151 150 157 162 166 161 172 172 174 172 169 164 172 177 178
Plierous normalis 154 158 166 183 181 187 188 193 196 202 202 205 205 206 211 215 220 230 240 247
Tweeseris pointus 155 156 165 172 178 177 180 181 181 179 184 192 192 193 200 202 204 201 208 212
Tosserus saladis 143 141 142 138 136 154 164 177 191 203 195 179 179 168 157 156 164 163 165 163
All of the finches studied in this experiment originated on the same island. On this island there was diversified food success, allowing natural selection to take place and create separate species to fill different niches on the island. When the natural disaster occurred the finches were forced to migrate to another island where the conditions were not as favorable. The finches that were once separated by clines and food sources are now competing for survival.
The adaptations that the finches evolved on the original island made some finches more successful at food acquisition on the new island. Due to allopatric speciation the isolated population began to deviate form the parent population because of the founder effect and is was less likely to gene flow. The isolated finch population began to diverge genetically under the pressure of different selective forces. The linage is then spread through cladogenesis.
As the food sources changed, different finches in the same species were more successful. Therefore through stabilizing selection the extreme individuals were eliminated by the changing food sources. Because the separate species were able to fill several niches in the environment, polymorphism allows the finches to coexist despite their phenotypic differences.
Once the finches arrived on the island, some finches were better adapted than others. For instance, when there was corn available on the island, tosserus saladus had a hard time picking up the tiny corn with such a large beak. Tweezeris bentalis also had a hard time with the corn because of its beak been too thin. However, Phorous robustus, Plierous normalis, and Tweezeris pointus were well adapted to pick up the corns.
Once the corn died out, the blocks took over. When this happened the finches with the larger beaks strived. Tosserus saladus and Plierous normalis were the best adapted for these conditions. Tweeseris bentalis and Tweezeris pointius could pick up the blocks with some difficulty so they suffered very little loss. Pherous robustus could barely pick up the blocks, therefore suffering the greatest loss.
After the blocks died out, pony bead seeds grew on the island. These very tiny seeds caused some difficulty for the birds studied. All finches, with the exception of Tosserus saladis, increased slight to moderately.
In the final generation of finches studied, all previous types of food was available. In this case all birds thrived, for they had the choice to eat whichever food they were best adapted to eat.