explain darwin's theory of evolution and his idea of natural selection.?

Question

try to be as in depth as possible

it's not homework! geez! you definitely can't call me lazy. i have worked my butt off all year and i am studying just as hard for this stupid final exam. i am trying to fill in an answer for a review packet so i can make flashcards out of it! i think you shoud think twice before calling me lazy!

Answer 1

The answers already give you pretty much everything, but here's the simple version: Evolution is simply the way a kind of organism changes with time - 'descent with modification'. Sunflowers didn't use to be big, showy, 8 foot-tall plants with giant heads. Wild carrots have small, spindly, stringy roots. Great Danes and Chihuahuas aren't much like the earliest dogs.
Natural selection is one of the forces that drive evolution. Given a variety of traits, some will be more preferable than others, and the organisms with those 'better' traits will tend to produce more kids. The selection may be driven by simple survival (disease resistance, or drought resistance, for instance) or it may be driven by 'sexiness' (bright colors, complicated mating dances, big antlers or tails or manes or other attractive characteristics). It may even be driven by forced breeding (like all those nursery plants, or the kinds of pets, or horses, or pigeons, etc.). The key thing is simply who passes on the most traits, and the genes that produce them. Doesn't matter why. Bob A makes the common mistake of assuming that there is some "best" form of natural selection that humans are somehow perverting by keeping the "weaker" members of the population from dying out. Bullhockey. Selection works in lots of ways, and in the end "fitness" is determined simply by how much any collection of traits helps in producing kids who produce kids of their own. Environments change. Selective pressures change. "Good" traits may become less important under different circumstances next year. "Bad" traits may suddenly become really useful. That's why sex is so important. Keeping a genetic deck full of potentially useful traits that you can shuffle up every generation allows the population to produce some offspring that can hopefully handle any particular varitaion the population may encounter. The life of any particular individual is less important than that some individual(s) survive.

Answer 2

Natural selection is Darwin's theory of evolution. There are 5 "rules" to natural selection:
1. Populations are always over reproducing.
2. Populations are always in competition.
3. Variations of characteristics naturally exist with populations (due to random mutation)
4. Some members of the population will be better selected to compete based on natural variations.
5. Those that compete the best will survive long enough to pass those variations on to the next generation.

Humans, of course, fail at steps 4 and 5. As a species we support the weakest of the species, not the strongest. Corrective lenses, surgery, medicine are all measures that weaken our species.

Answer 3

Well....how about how elegantly simple and logical it is? It is simply that traits are inherited, that there is natural variability in the genetics and traits of any interbreeding population, and that natural selection can then act on those traits to select for one type that is favored over others. One type then leaves more offspring than the other. It is all about leaving offspring. Nothing else really counts (guess why everyone is sex crazy....it is a huge part of our evolutionary makeup...leave offspring!!!).

The second part of the natural selection process, speciation, is only slightly more complicated but still totally logical....that is in order to become so separated that two parts of a population can no longer interbreed (and therefore, by definition, are now separate species....presumably one of them is the "new" species) you have to separate them in time or space or both. Islands are perfect examples. Mountain tops. Anywhere where a population can end up with portions of it's range separated from the other AND with some sort of evironmental selective pressure that favors different characteristics in the two (or more) different places. After awhile (sometimes) the two populations that started out all the same species but ended up on different islands are now separate species, no longer able to interbreed (or no longer effectively overlapping in a way that permits interbreeding). Of course, most of time these random isolations and selection pressures end up wiping out one isolated group or the other. But Darwin's finches are the classic example...one type of finch got out to the Galapagos Islands...and over time they evolved isolated populations on different islands adapted for totally different lifestyles and now a number of different species.

Answer 4

here's an example
u have a population of bugs. u spray them with a poison to kill them. at first it works because most of the bugs were vulnerable to that poison. however there were still a few that had the gene that made them immune. so it was these bugs that kept on producing, and sending that gene to their offspring. meanwhile, all the other bugs are dying. eventually, the population has evolved to be resistant to this poison.

Answer 5

Weaker and retarded animals like the croc on pearls before swine, will starve to death and die. Thus taking that weakness out of the gene pool.

Answer 6

Do your own homework. Or just copy it off wikipedia. Since you can't seem to figure out how to read a book.