This complexity and diversity has developed over the course of millions of years, millions of interactions, both successful and failed. The two main factors for diversity are time and imperfection.
Imperfection stems from how our DNA replicates. DNA replication is the process that governs all life. The happy problem with this process is that it’s never 100% efficient. There are mistakes that happen during the DNA replication, that create some small changes in the new strand of DNA. Extrapolating it to a larger scale, these mistakes cause variations in the organism, variations that make it different from other organisms.
Give these variations some time, and add to it certain environmental disturbances, and you get the formation of a species. Speciation is the creation of a new species from an existing species. This, is the process of evolution as proposed by Charles Darwin.
Evolution is the single phenomenon of nature that has created and maintained the diversity of life on Earth. This diversity exists at all possible levels in the ecosystem:
This is the diversity of genes that is present within organisms of the same species. That is why you and me look different. That is why your friend has a different color of eyes. That is why your brother/sister probably get more pimples than you. That is why no two dogs never look the same. Each organism is different (unless they are clones). The examples are endless. This diversity is a direct result of the imperfection in the DNA replication.
This is the diversity of different organisms present on Earth. We have humans, cats, dogs, tigers, owls, pigeons, Banyan trees and millions of other known and unknown species. Each plays a crucial, if not large, role in the functioning of this planet.
Different species grow and adapt to conditions that are specific to a particular environment. That brings us an ecosystem. On Earth, we have various ecosystems as well. Grassland, tropical forests, oceans, lakes are all examples of ecosystems on Earth.
All of this diversity is structured, and it is supposed to interact in a certain way for it to work properly. That’s how life on Earth started, and continued to flourish. As the most dominant species on Earth, we are fortunate enough to study it and appreciate it.