EC: Community Interactions Lesson
Community
Is there a vacant lot, abandoned house, or field somewhere in your hometown that has been left undisturbed over a period of time? Are there subdivisions and shopping malls being added to where forests used to be?
Think back to how it has changed over the last months or years. Perhaps it started with bare soil or some grass, and eventually, you noticed taller grasses, bushes, or even some saplings beginning to grow.
You will learn about these changes, as well as relationships between organisms, within a community.
Community Involvement
What is a Community?
A community consists of all the interacting populations (different species) that live in a defined area. Community interactions, such as competition, predation, and various forms of symbiosis, can powerfully affect an ecosystem. A community is defined by biotic factors or living things.
Symbiosis is any close association between two species that share some sort of relationship. The three types of symbiosis are mutualism, commensalism, and parasitism. Click through the slides below to learn more about each type.
Succession
At the beginning of the lesson, we discussed how vacant areas have changed over time. This is called succession.
Type of Succession |
Description |
Starting Material |
Possible Causes (Disturbances) |
---|---|---|---|
Primary Succession | Population of an area that was previously bare of life or soil. Begins with pioneer species that can colonize bare rock, usually lichen. Lichens are a mutualistic partnership between a fungus and an algae and are capable of photosynthesis and enzymatically breaking down rock or other dead organic matter. May end with a climax community. | barren land/rock, no soil or life |
|
Secondary Succession | Re-population of an area after its destruction due to natural or man-made causes. Begins with some amount of soil. Pioneer species are plant species that can tolerate low light and low nutrients. May end with a climax community. | soil and/or other organisms |
|
Stages of Secondary Succession
In succession, we usually focus on the producers (or plants) first because they will influence the environment the most to provide habitats for animals.
The volcanic eruptions and lava flows that built the islands of Hawaii are a good example of primary succession. Take a look at the pictures below and read more about this change over time.
Initially, a volcano erupts spreading lava. Over time, lava weather and soil formation begin. Spores are blown into the area that develops into lichens. Eventually, enough soil forms to hold windblown seeds and moisture so that grasses and weeds can grow. From this point changes continue similar to secondary succession.
Biodiversity
Biodiversity is the measure of the variety of life in a community or ecosystem. The most biodiverse areas of the planet tend to be around the equator, where there are warmer temperatures and higher primary productivity. Extinction (death of the last individual of a species) can be caused by loss of habitat, as well as other factors (over-hunting, pollution and competition with invasive species). Invasive species are those organisms that are introduces to a non-native area and usually outcompete native species for resources.
Why is biodiversity important? It is important because each organism on Earth is part of links in a giant chain. This chain of millions of species provides us with food, air, clothing, and more. Imagine a world without pollinators (to give us fruits/vegetables), producers (for oxygen), or bacteria (to fix nitrogen so we can make proteins from our food chain). These are just a few examples of why biodiversity preserves the delicate balance on Earth.
Challenge and Before You Go
Practice Time! Use the knowledge you learned from the lesson to complete the practice activities below.
Before You Go - You Need To Know
The following key points are from the explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.
- What is symbiosis and what are the three types of symbiotic relationships?
- Symbiosis is a relationship between two organisms. The three types are mutualism (both benefit), commensalism (one benefits, one is neutral), and parasitism (one benefits, one is harmed)
- What is succession?
- Changes in an environment over time.
- What are the two types of succession?
- Primary succession is where there is no previous life and begins with bare rock.
- Secondary succession is where a climax community (stable community) is disturbed and succession begins again. A fire or earthquake can cause secondary succession to occur
IMAGES CREATED BY GAVS (freepik)