Author: University of California - Riverside
Source: http://www.sciencedaily.com/releases/2014/01/140110103720.htm
Published: Jan. 10, 2014
Summary:
One of Darwin's ideas while he was on the HMS Beagle on an expedition around the world, was that organisms "evolve to lose structures, functions, and behaviors they no longer needed when environmental circumstances changed." He also noticed that island organisms acted more tame, which he believed was because they adapted to having less predators around them. Researchers from University of California - Riverside, Indiana University, Purdue University - Fort Wayne, and George Washington University concluded that island lizards are, in fact, tamer than mainland lizards. To conclude this, the researchers analyzed the flight initiation distances (the distance between the predator and the prey before the prey starts to flee) of island lizards and mainland lizards from around the world. The results show that the farther the island is from the mainland, the more tame the lizards are, and the flight initiation distance is reduced because there are less to no predators to flee from. Results also show that predator approach speed is important, as well as the size of the prey relative to the predator. If the prey is small, the predator will not attack that individual prey, resulting in a very small to no flight initiation distance.
Connection:
The connection from this article is to the evolution unit. In that unit we learned about natural selection. Natural selection on remote islands will favor animals with reduced flight initiation distances because there is no reason for animals to waste the time and energy on an unneeded escape from predators that are scarce or nonexistent on the island. The lizards will not go through natural selection of large flight initiation distances if that will not be something that helps the lizards survive and reproduce. This study also is important because it proves that Darwin's observation of animals being tamer on islands is true. Though the lizards and other animals are losing their extended flight initiation distance, they are still adapting and changing to better suit themselves in their new environment with few to no predators, rather than like animals living on the mainland who are adapting and changing to better suit themselves living with predators (natural selection).
It seems like this kind of trait would be acquired, like the lizards were never taught what to run away from, but is it, in fact, an instinct that is inherited and passed down as a homologous structure to the next species?
ReplyDeleteDue to the small amount to absence of predators on the islands, the animals go through natural selection to gain the trait of being tame and having a reduced flight initiation distance so they are not wasting the energy on an unneeded escape. The animals mate with other tame animals, and pass on the trait of having a reduced flight initiation distance to their offspring and that happens from generation to generation to create animals that are very tame on the islands. The tameness would not be passed down as a homologous structure though.
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