What is the spark that powers Evolution?

Cells have a recognizable need to replicate. The answer to the "spark" of evolution likely lies within the mysteries of the cell.

"Life finds a way."

-Sab

The question seems vague. What drives evolution? What causes something to function? Are you asking what makes things evolve, or how did life start? The second we only have a hypothetical framework for, the first is broad but answerable. But in the broadest sense I guess the closest approximation is chemistry drives evolution.

How did life start? Autocatalytic feedback loops of organic compounds. Say you take a group of chemical compounds that attract like chemical compounds, and then when it bunches up together, splits forming two seperate sets of similar groups of compounds. What you have is chemistry replicating imperfectly. When you have replication with variation, then natural selection takes place because those that replicate more successfully will outnumber those that replicate less successfully. What followed would be a complex web of chemistry producing primitive protocells.

What drives evolution? That same chemistry acting today. Your DNA has four letters that form a code, ATCG (Standing for the nitrogenous bases Adenine, Thymine, Cytosine, and Guanine). Groups of three of these letters such as TAC code for particular amino acids (TAC for instance, after going through processes called transcription and translation, produces the amino acid methionine). Strings of amino acids form proteins which make up your cells, and cellular functions. Slightly changing a DNA code can have drastic effects, or barely any effect depending on what it's coding for.

DNA replicates itself before the cell divides, and then passes that copy onto a cell that is produced asexually from the parent cell. Sperm and egg cells develop through a process call meiosis, in which copies of your genetic code are put into special cells to be used for reproduction. An important thing to note is that DNA replication is not perfect. It's very accurate, but not perfect. Sometimes during meiosis the replication does not work perfectly and letters in your DNA code may be changed. This is called mutation, and when this happens in meiosis it means that your sperm or egg will contain these mutations which get passed to the offspring. These offspring will have variations in their body that the parents may not have. That's the fuel for natural selection. And over millions of years these small changes in DNA code add up.

Another important thing to know is what speciation is. Why can a deer mate with a deer but not a moose? They are both fury, four legged, hoofed mammals after all. The answer is genetic difference. Even if you could convince the two to mate, or just take their sperm and egg into a lab and inject one into the other, it wouldn't work. The genetic code would be too vastly different to get the process of cell division started to produce a viable zygote. So if you have a population of a species of say....lizards and they start to spread out over a large area, say hypothetically there is a river and there are lizards on both sides of it. Now lets say there is a slightly different selective pressure on each side of the river. Both populations of lizards would begin to accumulate different mutations, the lizards would gradually begin to look different as they adapted to their circumstances on each side of the river. A million years go by and the river dries up, and now the lizards can intermingle. But now they cannot mate any longer because their genetic differences are too great, and they look so different they aren't even interested in mating anyway. This is called a speciation event, and it was caused by what is know as allopatric speciation, or speciation because the population was divided for an extended period of time. Repeat this for a hundred million years and you've got a bunch of different species that only bear a passing resemblence to the original species.

So what powers evolution? Energy from our sun, plus the stochastic nature of chemistry on a molecular level, the rest is just the law of natural selection wherein those that reproduce more edge out those that reproduce less when there is a limit on the resources provided.

Does this answer your question at all? If not, what is it left that you aren't clear on? I will be glad to elaborate further.

How do the processes that are described as "evolution" know the way to the finished function?