|Life science||Regulations and Behavior 8F3.00||Unifying concepts of science||Change 2.5 a|
CONTENT STANDARDS: Life science
CONTENT TOPIC: Regulations and Behavior
CONCEPT: Organism's response to environmental changes.
CONTENT OBJECTIVE: 8F3.00 To understand how organisms change their internal environment to keep up with changes in the external environment
INSTRUCTIONAL OBJECTIVES: The learner will
TN COMPONENT OF SCIENCE: Unifying concepts of science TN GOAL:
BENCHMARK: New information can modify existing scientific knowledge
BENCHMARK: Selective breeding has resulted in new varieties of plants and domestic animals. Various changes occur as an organism progresses through its life cycle.
Generally speaking, organisms will react to a stimulus in a way that will increase its chances for survival. Homeostasis is defined as the ability of an organism to maintain internal equilibrium by adjusting its physiological processes to preserve the conditions necessary for life.
Most organisms can produce more offspring than are able to survive. Those organisms inheriting the characteristics necessary for survival are favored by being allowed to live and possibly reproduce, thus passing these characteristics along through future generations. This process is known as natural selection. Often, natural selection is referred to as "survival of the fittest."
In the early 1850s, the peppered moth, Biston betularia, was present in the English countryside. This moth was mostly light-colored. The light-colored moth could land on trees and not be seen by its predators. However, as the industrial revolution progressed, the tree trunks began to darken due to the pollution in the country. Now, the light-colored moths stood out and were easily eaten by their predators. As the light-colored months diminished in numbers, the moth population as a whole became darker. The offspring of this new population were also of the dark coloration. The moths were now much closer in coloration to their surroundings and it was much easier for them to go unnoticed by their predators. The change in coloration provided a measure of protection not possessed by the original population as the degree of pollution increased.
In the last few years, pollution control has resulted in much lighter tree trunks once again. As was predicted, the light-colored moths have become more common once again.
2. homeostasis-a process by which an organism responds to environmental stimulli in order to preserve conditions necessary for life.
3. Natural selection-a process whereby an organism which survives will reproduce and cause changes in the environment.
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