In this post, we will begin by discussing the diversity of genomes and the tree of life. Though we see only a small fraction of the life that exists on planet earth in our daily interactions with our environment, there is a lot more below the surface (both literally and figuratively). Recently, with the use of techniques of molecular analysis and specifically through the analysis of DNA sequences, we have begun to piece together a picture of life on Earth that is closer to the truth, and is not entirely distorted by the perspective we hold that is inherently biased, as large animals living on dry land (Alberts et al. 2014).
When we study the diversity of life, we begin by understanding the many different ways that living organisms obtain their free energy. We can understand this concept most simply, by breaking down organisms into three different categories, and understanding their particular attributes, and what makes them different, per Alberts et al., as follows:
To understand lithotrophic organisms more easily, specifically those that function anaerobically, we can discuss one of the places in which lithotrophic organisms can be found. A dramatic example is the hot hydrothermal vents that can be found on the floor of the Pacific and Atlantic Oceans. New portions of the Earth’s crust form by a gradual upwelling of the Earth’s interior, causing the ocean floor to spread, and in turn forming the place where these hydrothermal vents can be found. Seawater percolates downward and is heated, then driven back upward, carrying along with it a current of chemicals from the hot rocks below. Among these chemicals are H2S, H2, CO, Mn2+, Fe2+, Ni2+, CH2, NH4+, and phosphorus-containing compounds, just to name a few. Some microbes live in the neighborhood of the vent, and other organisms live off of microbes at the vent, which creates an entire ecosystem. This ecosystem is similar in nature to the one that exists in the world of plants and animals and of which we are a part, except in this instance the geochemical energy of light powers the system (Alberts et al. 2014). Below is a redrawing of a figure from the Alberts text, which depicts a hydrothermal vent.
A prospective medical student, looking to help others succeed.