IngoVals

If I remember correctly one definition of Species is that if it can mate and have a fertile offspring it's the same species. The fertile part is because some species can breed which almost always results in a sterile offspring. What is it the makes a species able to breed with another? Do the still share so many common genes involving breeding while others have changed more? Is there something specific Gene-wise that controls when they can. Why do the offspring become sterile? What are some species that can breed. I remember Mule and Liger and some where the species are more similiar then most breeds of dogs ( wolfs/coyotes, polar bear/grizzly) What are the more stranger ones? Also why can dog breeds look so different and still be the same species while things like gray/ red wolf, black/brown bear, white/black rhino look almost identical but are seperate species? Donkey's and Horses ( and zebras ) are quit different looking, so is the Lion and the Tiger. Many species are closer in appearance so I would think more likely to interbreed. Has anyone thought about the possibility of a human/chimp or human/gorilla possibilities ( I'm just talking wether genetics would allow it, not suggesting anything and certainly not volunteering ).

Hello This is my first post here and I'm looking to get some perspective on my thoughts. I only undestand basics in this field so when I started thinking more about I knew I had to get expert help. My case revolves around the breeding of species, especially when breeding special traits in animals.For example you might breed a dog species to be really big. The tactic is to find a male and a female that are big so their offspring will be big as well. I started wondering why the offspring could however get bigger then it's parents. Let's assume the trait is based on 1 gene and let's give it a value, with bigger values meaning bigger animals ( I know it's not simple like this and that's probably the answer but humor me). If the size is base on the average of the gene values on animal had 7-5 the other 6-6 (so both effective size 6). The offspring could get 7-6 and later mate with sibling and that one has 7-7. But there it's reached the maximum in that family. However if one parent had been 10-2 the maximum would have been much bigger. I know of course that we can't assume value and such. But let's say a superior mate (or equal) has reached the state of having a gene pair where both gene perform the same. At that time it's offspring can't surpass it. So this must work very differently then I think. Is it so that there is a best gene for a given trait ( a one gene trait that is ) in that species and if you could get it to have both in the pair you've reached maximum? Please don't laugh at me for simplifying it so much and help me understand how a trait can get exagerated in a inbred species. Is it just the fact that there are so many genes controlling each trait that there is always room for optimization or some explanation that is far off from what I'm talking about.