Death is an essential feature of life. Indeed, implicitly this is an essential feature of the theory of evolution. A necessary component of the revolutionary process is that individuals eventually die so that their offspring can propagate new combinations of genes that eventually lead to adaptation by natural selection of new traits and new variations leading to the diversity of species. We must all die so that the new can blossom, explore, adapt, and evolve.
West, G. (2017). Scale: The Universal Laws of Life, Growth, and Death in Organisms, Cities, and Companies. Penguin Books.
Natural selection is what we call the combined effects on creatures of inherited variation, having lots of offspring, environmental change in the passage of time. Over the generations, these forces will shape organisms to fit their environment, because only those individuals best adapted to their surroundings will live long enough to reproduce and spread their "favored" traits to the next generation. This, in essence, is Darwin's theory of evolution by natural selection.
Battey, N. and Fellowes, M. (2017). 30-Second Biology. Ivy Press.