There are some things that can prevent decay, one if them is ice, an example of that is a frozen mammoth, ice can prevent the body from decaying, another thing is amber, it can trap an insect and prevent it from decaying, lastly there is tar, a substance that covers thing in a black substance that prevents it from decaying.
Variations are beneficial for the survival of the species. Populations of organisms fill well-defined places, or niches, in the ecosystem, using their ability to reproduce.However, if some variations were to be present in a few individuals in these populations, there would be some chance for them to survive.
Cells, tree, digestive system, public transportation system, government systems, school systems, families, dog, forest, pond, prairie, communication systems, towns, insect, solar system, weather systems, bird, correctional system, squirrel, soil, etc.
