Simple version:
First, the section with the desirable gene must be identified. Assuming that has already happened, the section of DNA must be excised from the original genome using restriction enzymes, which recognize certain DNA sequences and snip DNA at those sites. DNA ligase is used to "glue" these ends back together. The DNA is inserted into a plasmid (also with restriction enzymes), which would usually contain antibiotic-resistance genes (so they survive in an environment containing the antibiotic, which would also help show if the bacteria have been successfully transformed).
Then comes the actual transformation process. The bacteria to be transformed are mixed with calcium chloride (which causes the bacteria to be more receptive to the plasmids) and then mixed with the plasmids. The bacterial cells are subjected to a heat shock (the solution is heated and rapidly cooled, e.g. by placing the mixture in a hot water bath and quickly transferred to ice) so they will take up the plasmid (since the temperature change makes the membrane more permeable). The bacteria are placed on a growth medium containing the antibiotic they're resistant to. Only those successfully transformed would survive.
Most enzymes fall into the protein category
I believe your answer would be ecological succession
Well it really depends on what kind of change there is. For this I'll use a drought as an example. If a drought occurs in an area the plant life and vegetation will start to die off in that area. From there, primary consumers would run out of food. then secondary consumers, and so forth and so on. it'd be like putting a cow in a field of dirt with no food and a large bucket of water. Eventually the cow will die of starvation. Now apply this to all of the animals in that ecosystem.