All organisms die without fail, but species continue to live and show diversity due to -
Reproduction
Every organism has a distinct lifespan. Upon completion of this duration, senescence causes the natural death of an organism. Organisms can avoid extinction by their ability to reproduce. So in a way, reproduction enables the continuity of species, generation after generation.
Reproduction does not create exact copies of the parents but usually creates offsprings that share a lot of traits with their parents. The distribution of traits changes due to modification of the genes that produce the offspring. As the distribution of traits changes over time, favourable traits become more and more common, with the environment favouring the organisms with these traits - a process called natural selection. All this diversity and the process of natural selection occur due to reproduction.