The following link is a good place to explore the basics of evolution.
Have you even wondered why people have different skin tones? Why an African has skin pigment that is so much darker than a Scandinavian? The answer is incredibly simple. The human body uses sunlight to process vitamin D. If you live in an area where the sun shines more directly, say, near the equator, then your pigment is darker because the U.V. rays are much stronger and you block out what you don't need. The further away from the equator you get, the less intense the U.V. rays are. Therefore, the human body has evolved and adapted to the environment since our common ancestors left Africa. There is an excellent article about that here.
What about the eye? Many people who argue for intelligent design/creationism (it's the same thing) say that the eye is too perfect to have evolved from natural selection. Our eye is far from perfect. To start, our retina is backwards. Our rods and cones (photoreceptor cells) are aimed away from the light source. Nerve fibers, which must carry signals from the retina to the brain, pass in front of the receptor cells partially impeding the penetration of light to the receptors. There is an excellent article about that here. The following is taken from the previous referenced article:
Another creature to consider is the mole rat. Which theory holds water when the eye of the mole rat is considered? The ancestor of the mole rat presumably used its eyes as it lived above ground and needed them for survival. However, the mole rat has adapted to living underground in complete darkness. Its eyes have become useless--indeed, they have been buried beneath skin and fur and couldn't be used even if the mole rat came into the light. The neurons that were used for sight have been put to better use in the mole rat's brain for other sensory functions. Evolution by natural selection perfectly explains the eyes of a mole rat. A creationist must resort to faith and/or a poor designer.I highly recommend reading the creationist response at the end of the article. That can also be found here. It should also be worth noting that squid have eyes that are evolutionary superior to ours. You might argue that it would take too long for the eye to actually evolve from light sensitive cells. For information on that, please read this link.
Speciation is another strong argument for evolution. Read all about speciation here, http://www.actionbioscience.org/evolution/irwin.html, and here.
Now for the all important argument about the "second law of thermodynamics"
Evolutionary nay sayers often point out that a "theory" is not a "fact". True enough. But what the creationists fail to understand is that a theory is not an idea that may or may not be true; that is a hypothesis. A theory is an idea that best and most completely explains our observations of the world around us. A theory is not meant to be a fact. It is meant to explain facts, and the facts are clear: The Earth is approximately 4.5 billion years old. A scientific law is not, repeat not, a theory that has withstood testing. There is no ladder of certainty in science that goes: hypothesis; theory; law. There are fundamental differences between the concepts. A law is a description of the way the universe works. A theory is an explanation. Newton's Law of Gravitation is called a law because it never tries to explain why gravity works that way; it merely describes the way it works. We know that it's not accurate, but we still call it a law because it meets the actual definition of a scientific law. Similarly, the Laws of Thermodynamics are laws because they merely describe the behavior of thermodynamic systems, not because we are really, really sure about them. Similarly, even though we are pretty sure about relativity, we still call it the Theory of Relativity, because it explains other phenomena. Relativity will never become a law because it is explanatory rather than descriptive. When scientists talk about Evolutionary Theory, they are referring to the mechanisms which produce common descent and speciation, which are acknowledged as facts (true statements about nature i.e. light is both a wave and a particle, Homo sapiens is closely related to apes) in the scientific community. Laws don't always trump theories. Einstein's theory altered Newton's Laws of Motion. It's just that it's what usually happens. Our description is just most often more accurate than our explanation. For a good source about Entropy
Now let's get into the Second Law of Thermodynamics. Here is a blurb that I have taken from this website.
It says that since systems change over time, they are far more likely to change into a state that appears to us to be disordered, this is because their are an almost infinite variety of possible states it could become and most arrangements of atoms/molecules (etc) would appear "disordered" to us. However there is a very small chance that it would form an arrangement that we would consider "ordered", this is very unlikely to happen so in general we say that in closed systems the amount of disorder increase. However it is perfectly possible for the formation of a fairly complex macromolecule (for example) to occur, even if it's "order" increases. Saying that "Entropy" = "Disorder" is a far too simplified version; disorder is an aesthetic quality with which we describe a system. Entropy however, is a physical quantity, it is defined as the measure of the unavailability of energy available for doing work. In other words the proportion of energy not available for Potential energy (i.e. in the form of heat). In order to increase the "order" in a system energy must be put energy in (to create potential energy states and the like), and the "Laws" of thermodynamics state that the state of the waste energy released from this procedure will increase the overall entropy in the greater system. The most commonly used example is a computer storing data. The heat energy from a computer released after it stores information is greater than the energy now in an "ordered" state. Thus the total Entropy increases, even if an ordered structure is formed. You're right, thermodynamics does say that the amount of entropy will increase in a closed system, it is concluded from the principle that the "order" of a system is almost certainly to decrease overtime (like I explained previously). However This planet is not an enclosed system, it radiates energy into space (our planet glows?) and it receives energy from the Sun, a lot of energy. So the entropy in the sun and the rest of the universe may increase but the "order" (or a reduction in entropy) on small areas of this planet may (temporarily at least) increase, without violating the laws of thermodynamics.It would seem better for the educational system of America to continue to let scientists dictate what should be taught in science class. This is scientific data that the community backs itself up with. There is nothing wrong with having the faith that God created the earth, if that's what you believe. There is something very wrong with teaching something that only "faith" can prove in a science class.
(Please add your comments to the main post on Blognonymous. - Kvatch)