We have discovered many extrasolar planets similar in size to the Earth that orbit their star in the so-called ”habitable zone”, where the level of radiation can support liquid water on an Earth-like planet's surface. This has led to much interest in whether these planets might actually be habitable, with remotely detectable signs of life. But it is unlikely that any of these worlds are exactly like our own planet. This makes the difficult process of identifying a biosignature even more challenging, as the abiotic signals from even a not-quite-Earth-world could produce a false positive. It is therefore important to understand how the abiotic signatures of a potentially habitable planet might differ from the Earth, so that these processes can be identified correctly. So as we enter the era of being able to observationally probe the atmosphere of rocky exoplanets, what differences are likely and how might they change the planet's evolution and environment? To tackle this question, we took a quantitive look at the impact on a planet's environment due to small changes in the Earth's composition, magnetic field, heat budget and volatile abundance. This work is based on a new collaborative volume entitled "Planetary Diversity: Rocky Planet Processes and Their Observational Signatures” that was published by AAS/IOP in December 2020.