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Behavior: Biological Explanations
Biological explanations of behavior will fall into one of four categories: physiological, functional, ontogenetic, and evolutionary. Normal behavior or commonsense behavior does not fall into any of these categories. For example someone does something, such as eats icecream, that is a "want to". However, those things that are not explained, such as why someone yawns or why a bird flies south for the winter without thinking about it. These things fall into one of the categories listed above.
The Pysiological explanation relates the behavior to an activity of the brain or other organs. It correlates with the mechanics of the body. The chemical reaction that allows hormones to trigger brain activity and the path by which brain activity controls the movement of muscles through contractions would fall into this category.
A functional explanation defines or elaborates why a behavior evolved in the way that it did. Within a small population a gene that spreads by pure accident is called a genetic drift. At times one dominant male, such as an african lion, has a large number of offspring and spreads all of his genes. The larger the population or community the less impact or powerful the genetic drift is. A functional explanation can pinpoint the advantage.
Another example would be a species that can change his color to match his surroundings. The functional explanationt to this would be the species can change colors to hide from his predators.
Ontogenetic explanation describes the development of a behavior or structure. It maps the influences of nutrition, genes, experiences, and the correlations or interactions of these factors in producing behaviors.
In specific species, a young male bird learns songs by listening to the adult males. Being able to develop the song and sing it requires both the genes that make it possible and the chance to hear it early in life when it can be learned. This would be an example of Ontogenetic Explanation.
This explanation looks at a behavior or structure by way of evolutionary history. When a cat becomes frightened it's hairs will stand up on it's body. When a person becomes frightened they get goosebumps. This erection of hairs makes an animal look larger to its predator. This leads to the belief that our ancestors were hairier and thus our goosebumps were at one time a defense mechanism where hairs would stand out just as the cats does.
An exmaple of this type of explanation would be when a species of birds has a song that sounds almost identical to that of another type of bird of a different species. Baird's sandpipers and dunlins are two different types of shorebirds, but both give their calls in distinct pulses, not like any other shorebirds. This relation suggests that the two types of birds evolved from a single ancestor.
We can understand behavior much better when we can combine as many approaches as possible. It's important to understand the body mechanisims that bring about the behavior, how it comes about in the individual, how it has evolved, and to what function it serves. Knowing how each explanation works helps us understand behavior more effectively.
Niko Tinbergen (1973, p. 161)