What are the two major ideas that have helped direct the study of biology?  What was so important about them?

Scientific theories are much more than general ideas. They are potential explanations for repetitive patterns in the universe, and are often composed of two parts. The first part defines or describes a pattern in the natural world, while the second identifies the mechanism of process for creating that pattern. They must be based on several different cases of observation and experimentation and are general enough to be applicable to different areas of study. The two major concepts that drive biological study are the Cell Theory and the Theory of Natural Selection.

The Cell Theory (Hooke; Virchow) states that all living organisms are made up of cells (the “what” part of a theory) and that all cells are created from preexisting cells (the “how” part of a theory). It disproved the once-popular idea that life was generated spontaneously and determined that all cells are related by a common ancestry. This concept is so important to biology, the study of life, because it essentially defines what it means to live. No biologist can encounter life without encountering cells. The mechanism of cell creation stated in this theory is also vital to understanding evolution.

Galapagos Finches

The Theory of Natural Selection (Darwin; Wallace) builds off of the second part of the Cell Theory to state that all species are related by a common ancestry (“what”) because the characteristics of species can be modified over generations through “natrual selection” (“how”). Natural selection is the process by which populations adapt overtime when individuals with greater fitness survive to reproduce and pass their genetic information on to the next generation. It works under the conditions that individual organisms vary in heritable information and certain genetically produced traits aid survival and reproduction. This becomes important in understanding the dynamic nature of biology. The traits present in populations are constantly changing over time as they adapt to changes in the environment. This is essential in the studies of evolution and the active ecology present today.


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