What is the relationship between evolution and inheritance?Does it affect evolution?
Yes.... they are intertwined.
Only the most fit (really meaning the "most adaptable" not necessarily the strongest) survive the rigors of life.
And if that life has a lethal, and thus defective gene, that individual never lives long enough to pass on that defective gene....it dies before sexual maturity.
Thus, over the eons that life has lived on this planet, there is a constant mutation or mutations in all living things in all directions. If those mutations are advantageous to life, they survive, as does the individual carrying any of them. If they are hugely disadvantageous, that individual, as mentioned isn't likely to survive.
Since life on this planet has been going on a very long time, mutations are rare. Most of us, and most plants and animals have long ago eliminated those horribly defective genes. This does not mean that mutation are eliminated. Some crop up out of no where. Radiation can do that, or a mistake in replication of the DNA can do that as well.
What you inherited from your parents help you survive.... in fact your genetics are rather finely tuned.
But this does not mean that any of us cannot get a defective gene or an inherited one, that tho it does not kill us, it makes our life less pleasant.
People are born all the time with genetic defects that they get from their parents....being very near sighted for one. Because optometrists can correct that with prescriptive lenses, those people can have as good eye sight as anyone. There are inherited hearing defects, too. Flat feet appear to be inherited, yet each of these are not lethal, just inconvenient.
Modern medicine can correct many inherited defects.
But if it is an inheritable defect, and a rather severe one, many carrying these don't opt for children. Cystic Fibrosis is one. If each parent has a recessive gene for CF but they themselves do not have the disease, the risk looks like this:
CC Cc cC cc.
The parents run a risk each time they opt to conceive of 1 in 4 of a child having the disease. (cc) Two in four of the child being a carrier only (Cc, cC) and a one in four of the child being free of the disease altogether, (CC.
I had a set of parent who opted to have children anyway (I am a science/English/math teacher). The parents had four children in all. Two of them had the disease!! One was in one of my classes. He lived to age 19. He was extremely sickly, spoke to no one----He couldn't.... he'd just start coughing, was an odd blue color..... and spent a few days every month in the hospital getting his lungs cleared out.
Sad for him. He was in my English class, and wrote about it...rather wishing he were dead. One of his stories was about a flying dragon, who came to visit often. His parents, in the story he wrote, kept him in a high block walled prison. The dragon could fly in and out. He couldn't even see over the high wall.
One day he asked the dragon to take him out of this prison his parents had build for him... the dragon was reluctant at first. Then it agreed on a later visit. To him, and to me, the reader, the dragon was escape. The only way he could escape this disease, was to die. He had asked the dragon to help him....................die. In his story, the dragon took him onto his back and flew the both of them out of that prison. I kept that essay for years and years. It was a profound writing for a student only 15.
Helpful? If you need more, or have an additional question, please feel free to write.