Earth Sciences and Ecology



First published on November 7, 2017

Ecology involves the interactions between organisms, such as plants, animals and microbes, and their environment. There are several important concepts in ecology.

Test tubes in a clear rack containing water plants and rocks

Ecology as a science

Environmental Envelope

A particular ecosystem exists within an environmental envelope. Parameters of that envelope include flows into and out of the ecosystem such as sunlight, water and material flows.

The envelope also include conditions within the envelope such as temperature and humidity. On a regional level, the result is the climate type, such as prairie, tropical rain forest or desert. For more information, read about the Köppen climate classification system.


Population, also called stock, is the quantity of a particular organism. It is important because it indicates the magnitude of energy and nutrient flows through an ecological system. It is also a measure of momentum of energy consumption. Population typically refers to the count of a type of organism, such as individual tigers rather than each cell in a tiger’s body. Likewise, each ant in an anthill would comprise a counted individual, even though ants in such a hill are interdependent.

Food Webs

Food webs concern the integration between organisms in terms of what they eat and what eats them. Food chains also indicate the flow of energy and nutrients through a system. Generally, more complex food webs are more stable. In contrast, removing a single element from a simple food web can destabilize and even destroy that web.

Green field of tall then vertical leaves in water.

Green field (Credit: US govt.)

At the base of all food webs is a means of capturing an external energy source, typically being sunlight, but sometimes more exotic sources such as hydrothermal vents. On land, including wetlands, green plants capture sunlight and form most of the base. Forests, grasslands, agricultural crops and even desert cacti form the base. In the oceans, phytoplankton capture sunlight and form most of the base.

Arrows connecting prey with predators, such as a puffin to a fox.

Marine food web in Alaska (Source: US Govt.)

Population Dynamics

Food webs can evolve over time, in cycles and permanently. Predator-prey relations are an example of changes in the components of the food web over time. For example, if the population of predators grows too much, then over predation will occur. Consequently, the population of the prey falls, and can no longer support such a large population of predators. The population of predators falls, resulting on less pressure on the prey population, which then recovers. This cycle can repeat itself many times, as expressed in the Lotka-Volterra Predatory-Prey model (shown below in a systems dynamics process). Such Predator-Prey cycles  occur in human economies as well.

Click on the “Simul…” button to run the below simulation of the relation between a moose and wolf population where wolves prey on moose. Feel free to explore additional settings and options. You can even create your now account on the underlying Insightmaker platform and create your own simulations.

Further Reading


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