Abiotic and Biotic Factors
The video below shows examples of how scientists use sampling techniques to count deer.
Interactions Among Organisms
Organisms can also benefit from each other. Symbiosis is a relationship between two species that exist closely together where at least one of the species benefits from the relationship. There are three different types of symbiosis- commensalism, mutualism, and parasitism. Commensalism is a relationship between species where one is helped and the other is neither helped nor harmed. Mutualism is a relationship between two species where both species benefit. Parasitism is a relationship between two species where one species benefits and the other is harmed.
Movement of Energy in an Ecosystems
Organisms can also be defined by their energy role, or how they move energy in an ecosystem. The three main energy roles include producers, consumers, and decomposers. The source of all energy in an ecosystem can be traced back to the sun. However, not all organisms can use energy directly from the sun. Producers are organisms that use the sun's energy and transforms it into a useable form that all organisms can use through the process of photosynthesis. Consumers feed directly or indirectly on producers in order to gain energy. Scavengers are a special type of consumer that only eat dead animals. Decomposers are organisms that break down dead organic matter. They return nutrients to the ecosystem to be used again by plants. If there were no decomposers, the plants would take nutrients out of the ecosystem and it would never be returned. Eventually there would be no more nutrients left, the plants would die. If the plants all died, animals would soon follow!
These interactions can be traced through a complex diagram called a food web. Food webs show all possible connections within an ecosystem to follow the flow of energy.