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Windsor Island |
Warwick Archipelago |
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Description |
A small island approximately
five miles off the mainland coast. |
A chain of four variously
sized islands approximately 600 miles northeast of the mainland. |
Habitat |
Wetter, more lush, and
more diverse than the mainland. |
High diversity relative
to the mainland. Individual islands are very different from one another, each boasting
a wide range of habitat types, rainfall, and elevation. |
Niches |
Very few available niches,
due to the large numbers and high diversity of bird species in and around the
pollenpeepers' habitat. |
Many niches available upon
pollenpeepers' arrival, due to the island chain's distance from the mainland. |
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As you begin to investigate the evolution through time of the
pollenpeepers on their new island homes, consider some important factors that drive evolution.
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Habitat:
Habitat strongly directs the path of evolution. Change the habitat, or drop an
organism into a new habitat, and you can expect evolutionary change -- usually
rapid change in a very specific direction. Often, new habitats are ripe with
opportunity because they've not had millions of years to become occupied by a
diverse range of creatures. Niches remain open and free for the taking to any
species able to use them.
Food:
Food is arguably the most important piece of a creature's habitat, driving the
process of evolution, especially when its availability changes. Where food sources
are diverse and plentiful, species can afford to be generalists, eating a wide
variety of foods. A reduction in food availability, however, exerts intense
pressure on a population, which collectively must find new food resources.
Individuals best adapted for utilizing the resources that are available gain an
advantage over others in the population. (Graphic illustrates food availability,
not necessarily food consumption.)
Competition:
Competition may lead to divergence. Populations often diverge physically or
behaviorally in ways that allow them to exploit different resources. This happens
because individuals that differ sufficiently from their competitors in behavior
or morphology can exploit different sets of resources better and thereby survive
and reproduce better than individuals that have more in common with their
competitors. Over generations, coexisting populations diverge in their patterns
of resource, use and competition is reduced.
Predators:
Predators place limitations on their prey by restricting their movements and
forcing populations to evolve defense strategies. When you take away predation
pressures, you eliminate many limitations on how a species can evolve. In the
absence of predators, novel traits can develop freely and persist, if they
offer advantages to their owners. For example, flashy coloration may allow an
individual to be more conspicuous to a potential mate. The result: a more widely
diverse assemblage of organisms in predator-free environments than would
otherwise be possible.
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