Evolution..........?

Question

How exactly does evolution work? The jist is that organisms adapt over many, many years to become better suited for their environment right? What causes the genes of the organisms to change and what causes the entire population of that species to change in the same way?

I'm just trying to learn about it. I can obviously see how a creature would adapt to it's situation during it's lifetime, but doesn't one of Darwin's laws say that that wouldn't pass down to the offspring? Like if a man is little and lifts weights and gets stronger, his son isn't going to be born strong due to that.

Answer 1

Basically what it comes down to is "survival of the fittest"  What happens is over a long period of time, species choose to mate with the best chance of survival.  This will keep happening and eventually, a species will evolve to be faster, or stronger, or more capable to catch prey... that sort of thing.

For example-  A peacock uses their feathers to attract a mate.  So the male peacock with the largest most colorful feathers will find a mate and the others will not.  Eventually over time, the feathers of the peacock will only get bigger and more colorful.    

Answer 2

Genetic mutations are what make the new species. The animals don't adapt to the environment just because the environment is hot doesn't mean that animals will evolve to survive the heat. The have to have the right genetic mutation. If the environment changed too fast or they can't survive in the environment they'll all die.  

Answer 3

Evolution is defined as a change in the frequency of alleles in a population over time. Alleles are versions of genes.

Genes of an individual do not change during their lifetime. Some genes grant a competitive advantage at reproduction, so that organisms with those genes have more offspring. This results in those alleles increasing in frequency in the next generation.

Sometimes mutations occur due to replication errors. This introduces new genes into the gene pool. If the new allele is beneficial, it might become more common  with each generation. New mutations are more likely to be harmful than beneficial.

See references for details. Algebra is necessary to really understand how evolution works.

Answer 4

>"The jist is that organisms adapt over many, many years to become better suited for their environment right?"

Right.

>"What causes the genes of the organisms to change"

That depends on whether you mean an *individual* organism ... or the organism as *species*.  (E.g. when you say "the dog", do you mean an *individual* dog, or the dog *species*.)

What causes the genes of an *individual* organism to be different from its parents are two things: mutations, and (in sexually reproducing species) recombination of genes from both parents.

What causes the overall genes to change in the gene pool of the *species* is natural selection.  Those genes in *individuals* that provide some advantage will spread, while those that provide disadvantage tend to disappear.

>"and what causes the entire population of that species to change in the same way?"

The fact that they share the same gene pool.   As long as there are no barriers to interbreeding, any allele (gene) that provides a significant advantage will eventually spread into the entire population.

>"but doesn't one of Darwin's laws say that that wouldn't pass down to the offspring?"

Yes that's true ... although I've never heard this attributed as one of Darwin's laws.  But yes, one of the key advantages of Darwinism over what's called Lamarckism is that Darwinism *assumes* that an individual only passes down traits to offspring, that it inherited from it's parents.  I.e. it does NOT pass down traits acquired during its lifetime.

The brilliance of Darwin is that he solved the paradox of evolution.   Namely, individuals don't change genetically during their lifetime (they die with the same inherited material as they were born with) ... but somehow the *population* DOES change over time.  How can this be?  Answer:  natural selection.

Answer 5

First off you are correct in what you know from the second paragraph. This was Lamarck's theory of evolution, and Darwin disproved it.

Here is the easiest way to explain it- with an example

You have on species in a defined area (Animal A). Over time, a river forms in the middle going through that area. Animal A is separated onto Side A and Side B. Mutations happen naturally in animals, but the actual mutational phenotypes are random. Say an a few of Animal A on Side B develop a mutation which makes them unaffected by a poisonous plant. Now those select few have more options for food. More food equals less starvation, which results in more of those select few.  Eventually only the ones with the mutation are left on Side B. The mutation becomes so distinct through breeding that the animal becomes a sub species, which may result years later in a new species ==== Animal B

Answer 6

Your second paragraph is absolutely right on!

Here's how populations adapt over many lifespans: Each organism of the same species is slightly different. In sexual reproduction, genes are inherited from two parents so the offspring have different characteristics. A simple example might be one sibling that can run faster than the other. The faster one might be able to escape a predator while the slower one gets caught and eaten and therefore never reproduces. The faster one could live on to produce offspring that inherits the ability to run faster.

Additionally, there can be errors in DNA which cause mutations. Some mutations are favorable and provide better survival capabilities. Most are of no consequence and some are harmful and the organism dies or cannot reproduce.

This is brief and simplified, but hopefully gives you some idea of how adaptations come about - through natural selection of the "fittest" characteristics.

Answer 7

Basically, evolution doesnt work (can you guess i'm a creationist.)

However, the classic old survival of the fittest works wonders.

If there is a short giraffe and a tall giraffe, and all the food is up high, the short giraffe will most likely die sooner and have a lower chance of passing on its genes as it has a harder time getting food. whereas the taller giraffe can reach more food easier, and therefore its life expectancy, and its chances of mating and passing on genes, is extended. If the tall giraffe mates with either an average height or tall giraffe, its children will be taller than average, and so the likely hood of the genetic material for "tall" is increased.