# Biology, Answering the Big Questions of Life/Theories

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# Scientific Theories

Scientific theories are overarching explanations of the world that are based on many, many lines of evidence. There are many scientific theories that are important in Biology. Here I will list some of the over arching theories that shape our modern understanding of life, and some lines of evidence for why we believe those theories are true.
    The Cell Theory
    The Endosymbiotic Theory of organelle origin
    The Theory of Natural Selection
    The chromosomal Theory of Inheritance (Gene Theory)
    The Fluid Mosaic Theory of Membrane function
    The Atomic Theory
    The Germ theory of Disease
    Plate tectonics
    Quantum theory
Some theories are primarily introduced to students by way of Natural Laws. Natural laws are theories that are best described as simple statements or equations. These are facts that under certain conditions are almost always true. Some of these natural laws include the following.
    Gas laws, such as Boyle's law
    Gravity
    Mendel's law of genetic inheritance
    The laws of Themodynamics
We use these laws as assumptions in many of our scientific experiments, but they too are based on many experiments and lines of evidence.
In fact, when a textbook lists a fact in passing, there is usually an entire body of experimentation behind it. As you get deeper into science, you will learn more about the background of these theories and natural laws and how we came to believe them. Usually as an introductory student of biology, you are told that these are facts, but remember that most theories do have limitations, and by probing the edges of those theories, we learn more about the world around us.

## Discrediting Theories

For a theory to be discredited, it is not enough to find one example where it does not work. Remember theories are based on several lines of evidence. Most single examples where something does not work results in modification of the theory rather than discrediting it.
To discredit a theory, you must disprove the major assumption or conclusion of the theory. This usually happens by proposing a NEW theory that better explains the phenomena.
Even when a New Theory is proposed, that often is not enough to discredit an older theory which may still help others to understand something in a limited case.
For example NEWTON's Laws of motion were found to be less accurate than EINSTEIN's laws on the motion of Mercury, but on Earth, Newton's laws are more basic and easier to use. Therefore NEWTON's laws of Motion are not said to have been discredited by Einstein. They are refined by it.
An example of a discredited theory is Spontaneous Generation. Spontaneous generation suggested that living organisms such as flies came from inorganic matter such as trash. When Pasteur proved that Cells come only from preexisting cells, it showed that spontaneous generation did not accurately explain what was happening in the world, so that theory was discarded in favor of the cell theory.
Discrediting theories is a necessary part of science. It is by getting rid of the old theories that we get closer to what is real, and so it is not considered a bad thing. Every disproven theory is a step toward greater understanding of the world.

### Examples of Disproved Theories

    Spontaneous Generation
    Lamarkianism
    The Humours theory of health in the body
    Geocentrism
    The Ether theory of the universe

## Biological theories in the Flux

There are many mysteries of science that are not fully understood and so theories are proposed and modified.
For example, although the Theory of Organic Evolution is thought to be explained best by Natural Selection, there are many details about how it works that are currently being researched. For example the Assembly Theory has been proposed to explain why complex systems can suddenly arise in novel situation. If accepted, this would likely become a refinement of Natural selection. [reference - https://www.nature.com/articles/s41586-023-06600-9]
Examples of theories that are not conclusively accepted as proven or disproven. Often these will be called hypotheses in order to show that evidence is still being gather to support them. Even so, they all have large lines of evidence and cannot be discounted without discussion.:
    The Gaia Hypothesis - The earth acts like an organism where large systems work together to provide homeostasis.
    The RNA world theory on the origin of life - The first cells used RNA as both information storage and as enzymes (ribozymes) to reproduce itself.
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