8: Species Interactions in Communities
- Page ID
- 103355
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Community ecology is an expanding and rich subfield of ecology. Ecologists investigate the factors that influence biodiversity, community structure, and the distribution and abundance of species. These factors include interactions with the abiotic world and the diverse array of interactions that occur between species. In this chapter we will explore the varied ways in which species interact with one another and the consequences of these interactions.
- Define and classify species interactions based on their outcomes: positive (+), negative (-), or neutral (0)
- Define and provide examples of exploitative interactions.
- Provide examples of defense mechanisms against predation and herbivory.
- Distinguish between intra-specific and inter-specific interactions.
- Explain the competitive exclusion principle and the possible outcomes of inter-specific competition.
- Explain evolutionary arms races between predators/prey, and herbivores/plants and the resulting adaptations of each group.
- Provide examples of mutualisms.
- 8.1: A summary of Interactions
- Populations rarely, if ever, live in isolation from populations of other species. All populations occupying the same habitat form a community (populations of multiple species inhabiting a specific area at the same time). The interactions among populations of different species play a major role in regulating population growth and abundance. Interactions between organisms can result in positive (+), negative (-), or neutral (0) outcomes for the individuals involved.
- 8.2: Exploitative Interactions
- Exploitative interactions, also known as enemy–victim interactions, is an interaction where one organism (the enemy) is the consumer of another organism (the victim) such as predator–prey interactions, host–pathogen interactions, and herbivory. Because of the interactions the victim experiences a strong fitness cost while the enemy benefits. Exploitative interactions can have significant biological effects. For example predators or parasites may cause declines, or even the extinction, of their
- 8.3: Competition
- Competition occurs between organisms on the same trophic level that share resources. When two species have the same role in a community, competitive exclusion will occur, resulting in the local extinction of one species.
- 8.4: Commensalism and Mutualism
- Commensalism occurs when one species benefits, and the other is unharmed. In contrast, both species in a mutualism benefit.
- 8.5: Symbiosis
- There are many cases in which two species live in close association for long periods. Such associations are called symbiotic. In symbiosis, at least one member of the pair benefits from the relationship. The other member may be injured (parasitism), relatively unaffected (commensalism) or may also benefit (mutualism).