Adaptation: Camouflage & the Rock Pocket Mouse
Watch the 10 minute video on adaptations that produce better fitness in the rock pocket mouse (tied in with homework assignment "Life Imitates Life/Rock Pocket Mouse). This is an example of disruptive selection because one phenotype is favored on the lava flows and the other is favored on the sandstone rocks.
Click here to look at the history of the peppered moth evolution. Darwin felt that because evolution was so slow, it would be difficult to observe. The evolution of the peppered moth, however, occured over a relatively short period and was extensively studied. The website teaches you about that history and allows you to play a game to test the survival rate of differently colored moths. This is an example of disruptive selection, because one phenotype was more fit in one local environment (the sooty forests near industrial cities) while the other phenotype was more fit in the other local environment (unpolluted forests of the country).
Indonesian Mimic Octopus
This octopus not only utilizes color changes, but can change its behavior to mimic a flounder or a poisonous sea snake
Adaptation: Bloodless Ice Fish
Click on this link to watch a short video on the "birth and death" of genes that allowed icefish to adapt to extreme cold. This is an example of directional selection, where the loss of hemoglobin was the favored extreme in the subzero ocean temperatures.
Consequences of adaptations
Sometimes traits will result as a consequence of an adaptation and do no improve fitness. An example is the giraffe, whose long neck appears to be a result of sexual selection, and not necessarily because a longer neck improved availability of food sources high in the trees. Giraffes indeed spend much of their time foraging from the floor of the savannah. Another 'unintended' consequence of neck growth is the length and route of the laryngeal nerve, which is responsible for such things as controlling sounds in the larynx. The brain is only about 2 inches from the larynx, yet the nerve travels down the neck and then makes a U-turn back up to the larynx. As Richard Dawkins argues in the video link, this is not an 'intelligent design'. It simply is a consequence of all necks getting longer and the original design of the nerve following suit. There is no benefit to the length of the nerve. Therefore it is not an adaptation but a consequence of an adaptation (called a spandrel). WARNING for the faint-hearted.... the video shows a dissection of the giraffe's neck. You may wish to listen but not watch.