1) Evolution is, without going into a ton of detail, the change in allele frequency in populations over time. This means that the distribution of genetic traits (alleles) in a particular group of animals (of the same species) will change as time passes. This is a simple statement with profound implications. This happens by several processes, the most well known and arguably the most prominent one being natural selection. The theory of evolution states that this general mechanism (the change in genetic variability over time) gave rise to all of the diversity of life on earth we see today.
2) I won't give ten of them since that would take forever, but here are a few off the top of my head:
- Human chromosome 2 being an obvious fusion of two great ape chromosomes
- The fact that every gene ever sequenced and used to generate a phylogenetic tree based on homology gives THE SAME phylogenetic tree.
- Retro viral inserts being located at identical points in our DNA to the DNA of close relatives, which slowly diverges as the relatives get more distant.
- The continuous discovery of fossils that just happen to fit into phylogenetic trees matching exactly the trees that come from the aforementioned genes.
The list goes on, mate.
3) This is a very broad question that's not easy to answer without more clarification as to what you're looking for. All species, through natural selection, develop as best they can in their environments, but at the end of the day, some will be more successful than others simply by chance.
The dodo went extinct due to human activity, actually. Before people inhabited its environment, the dodo had no real predators. As a consequence, it was unafraid of just about any other animals. When humans came around, they found them to be easy prey and hunted them extensively. Animals like cats, dogs, etc. that came with the people hunted them too. Sadly, the dodo was quickly decimated.
"Survival of the fittest", formally called natural selection, is by definition "the differential survival of offspring depending on their fitness in their environment" (more or less). For example, that means that a deer that runs fast is less likely to be caught and eaten by lions, and so has a better chance of living to reproduction. Therefore, over time, slower deer are killed off while faster deer reproduce and make more faster deer. The end result is a population of faster deer, which is why deer can run fast :). Of course, real environments are more complex than this, and obviously the lions would be evolving too, perhaps becoming faster themselves, or learning to set traps, etc. but this is the gist of it.
4) If a population of organisms (animals, bacteria, anything) gets separated for some reason and spends long enough time apart, they lose the ability to produce offspring. This is, simply put, because the egg and sperm's receptions become different over time, and if no reproduction occurs, they eventually become different ENOUGH that they can't recognize each other any more (this is a very, very crude description. This is the definition of a new species emerging. Give the two enough time, change their environments around, and they'll end up looking very different. The level of variety in a species depends on a bunch of factors, including, but not limited to:
- How fast the species reproduces. If generation times are shorter, the population evolves faster, making possible more variability.
- How tolerant the environment they're in is to mutants. If the environment is extremely harsh and requires a very specialized organism to live there, then there won't be much variability, since changes tend not to make it. However, in a lenient, more general environment that's not as harsh, more variety is expected since bizarre novelties will survive and pass on their mutant traits.
5) Already addressed.
6) Adaptation is the change in a population's traits in response to a change in the environment. Let's say a bunch of brown mice are living in an environment full of brown rocks. They're all camouflaged and difficult to see, which is good. If, for whatever reason, the rocks were all to become white, the population of mice would, over time, become white as well (because the closer a mouse is to white, the harder it is to see. A brown mouse might be seen before a grey mouse, so the population will turn grey. Then a white one will survive over a grey one. Obviously, this occurs in many many more steps). This is an example of adaptation to a new environment.
These aren't hard questions; they're extremely fundamental, and any college student who understood his/her Biology 1 class can answer them. Take some classes on this rather than issuing bogus challenges on yahoo answers!
Cheers,
Pye