A sample of textbook editing and writing:
“…These symbiotic relationships can be found in all aspects of life on earth. For example, bacteria in the stomachs of termites help breakdown the cellulose in wood or algae and moss growing together in the form of lichens. While there are degrees of this symbiosis, i.e. commensalism and mutualism, neither of the two species is harmed.
However, not all examples of interactions are quite as beneficial. Some may only benefit one species and not the other. While some may seriously harm or even kill the one species while aiding the other. This is often seen in nature in the form of parasitory, predatory or herbivory – the interaction between herbivores and the plants they eat – actions. In all three cases one organism gains nutrients and is sustained while the other organism is harmed or killed. For example, a gray wolf hunts and kills an elk. The same elk previously grazed on meadow grass and may have been infected with the parasitory liver fluke (Fascioloides magna)…
… organisms are thought of as individuals – a single shark, a giant sequoia, or a lone wolf. These individuals can give in-depth insight into all the individuals of a single species that live together in the same place and time, or its population. However, researching populations as a whole can give in-depth insight into an ecosystem and the effect that these population have on it. Biologist and various organizations monitor these populations for several reasons including concerns over endangerment, overpopulation, the introduction of an invasive species – non-native species that adversely affect native ecosystems – and the reintroduction of species like you learned about in the chapter opener.
Because of these different population dynamics, many organism populations are monitored frequently and as precisely as possible. There are several key data points that researches collect to give the most accurate population information possible. These data points include a population’s distribution, size, and density. Other key data points the composition of a population: male vs. female, mature vs. young, even specific physical characteristics such as mottling discoloration (piebaldism) in whitetail deer (Odocoileus virginianus).
Governmental agencies such as Fish and wildlife and private conservation groups like Nature Canada monitor populations of animals for several reasons. One such species that is monitored is the whitetail deer. Previously there were concerns about the diminishing size of the whitetail deer throughout North America (Figure 1). However, close monitoring and implementation of regulation based on this monitoring have greatly increased the whitetail deer population. As this population has exploded, coupled with a loss of habitat, the whitetail deer population is monitored for other reasons. Today these populations are monitored with control in mind. As the population has expanded fears of overcrowding, starvation, destruction of farms, and dangers to motorists have opened up hunting seasons and culling practices…”