For this essay’s purposes, the most important ecological understanding is that the Sun provides all of earthly life’s energy, either (all except nuclear-powered electric lights driving photosynthesis in greenhouses, as that energy came from dead stars). Today’s hydrocarbon energy that powers our industrial world comes from captured sunlight. Exciting electrons with photon energy, then stripping off electrons and protons and using their electric potential to power biochemical reactions, is what makes Earth’s ecosystems possible. Too little energy, and reactions will not happen (such as ice ages, enzyme poisoning, the darkness of night, food shortages, and lack of key nutrients that support biological reactions), and too much (such as , ionizing radiation, temperatures too high for enzyme activity), and life is damaged or destroyed. The journey of life on Earth has primarily been about adapting to varying energy conditions and finding levels where life can survive. For the many hypotheses about those ancient events and what really happened, the answers are always primarily in energy terms, such as how it was obtained, how it was preserved, and how it was used. For life scientists, that is always the framework, and they devote themselves to discovering how the energy game was played.
The critical feature of earliest life had to be a way to reproduce itself, and is common to all cellular life today. The DNA that exists today was almost certainly not a feature of the first life. The most accepted hypothesis is that . The mechanism today is that DNA makes RNA, and RNA makes proteins. DNA, RNA, proteins, sugars, and fats are the most important molecules in life forms, and very early on, protein “learned” the most important trick of all, which was an energy innovation: facilitate biological reactions. If we think about at the molecular level, it is the energy that crashes molecules into each other, and if they are crashed into each other fast enough and hard enough, the reaction becomes more likely. But that is an incredibly inefficient way to do it. It is like putting a key in a room with a lock in a door and shaking up the room in the hope that the key will insert itself into the lock during one of its collisions with the room’s walls. Proteins make the process far easier, and those proteins are called enzymes.
Telomerase is a reverse transcriptase, meaning an enzyme that makes DNAfrom an RNA template (the reverse of normal transcription which uses DNA as thetemplate for making RNA).