4.3.1: Introduction to Community Ecology

Unit 4.3.1 - Introduction to Community Ecology

• Please read and watch the following Learning Resources
• Reading the material for understanding, and taking notes during videos, will take approximately 30 minutes.
• Optional Activities are embedded.
• Bolded terms are located at the end of the unit in the Glossary. There is also a Unit Summary at the end of the Unit. 
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Learning Objectives

• Develop an appreciation of the interconnected nature of ecological communities
• Organize species interactions based on their impacts on the species involved

Introduction to Species Interactions

Populations rarely, if ever, live in isolation from populations of other species. In most cases, numerous species share a habitat. The interactions between these populations play a major role in regulating population growth and abundance. All populations occupying the same habitat form a community: multiple populations inhabiting a specific area at the same time. The number of species occupying the same habitat and their relative abundance is known as species diversity. Areas with low diversity, such as the glaciers of Antarctica, still contain a wide variety of living things, whereas the diversity of tropical rainforests is so great that it cannot be counted. Ecology is studied at the community level to understand how species interact with each other and compete for the same resources. Below, some of the interactions in these communities are introduced.

Video

Learn about ecological communities in this 6-minute video.
Question after watching: In BC, old-growth and second-growth forests are often discussed. How would these correspond to the concepts of succession mentioned in this video? Which do you think is likely to have the highest level of biodiversity?

The interactions among populations of different species play a major role in regulating population growth and abundance. A species interaction is an effect that a pair of organisms living together in a community have on each other as seen in Figure \(\PageIndex{1}\). Interactions range from mutualism, which benefits both species involved, to competition (Figure \(\PageIndex{2}\)), which harms both species involved. Interactions can be indirect, through intermediaries such as shared resources or common enemies. All of these interactions can be organized by the effects the species have on each other Figure \(\PageIndex{1}\).

Species interactions may be short-term, like pollination and predation (Figure \(\PageIndex{3}\)), or long-term; both often strongly influence the evolution of the species involved. Short-term interactions are short-lived in terms of the duration of a single interaction: a predator kills and eats a prey; a pollinator transfers pollen from one flower to another; but they are extremely durable in terms of their influence on the evolution of both partners. As a result, the partners coevolve.

Figure \(\PageIndex{1}\): Summary of species interactions, showing how each species is impacted by the interaction. ("-" indicates the species experiences an overall cost from the interaction, "+" indicates the species experiences an overall benefit from the interaction, "0" indicates the species does not experience either a benefit or a cost from the interaction...the interaction is neutral). Produced by N. Gownaris.

Figure \(\PageIndex{2}\): The black walnut secretes a chemical from its roots that harms neighboring plants, an example of competition.

Figure \(\PageIndex{3}\): Predation is a short-term interaction, in which the predator, here an osprey, kills and eats its prey.

Video

This 4-minute overview of species interactions will prepare you for the next sections of this Chapter.
Question after watching: Which of these topics do you think you will need to spend extra time to understand?