A: Organisms are giant machines, and they require a lot of energy. All day, every day, most organisms spend their time concerned with the consumption and excretion of biological material. And since they constantly reproduce, they are introducing more of these consumers into the environment.
Birth brings about mutations, which brings about change and leads us down the path of evolution. Without birth, nothing would evolve. And without death, we would completely engulf the planet in just a few generations.
And so, the meaning of death is to bring balance to the ecosystem by ensuring that future organisms have a chance to evolve.