Community Ecology

Video Transcription

Hi. I'm Jensen Morgan. We're going to talk about some great concepts in environmental science. Today's topic is community ecology. So let's get started.

We're going to talk about important properties of community ecology, different types of species interactions, and our key term for today-- "ecological succession."

"Community ecology" is the study of interactions between multiple species in a given time and area. Community ecologists study four main properties-- species abundance or number and relative abundance of each species in a community, species composition or which species exist in a community, species distribution or the way species are distributed relative to each other, and species interactions or how species impact each other.

Let's put these to use and look at a fictional forest community. Let's say this community spans one square mile in the year 2015. A community ecologist would observe and record the different species in the forest community, such as squirrels, birds, trees, and shrub species. This is species composition.

They would then measure species abundance and calculate the abundance of each species in relation to each other. They might discover that there is a large population of squirrels, a large population of nut-bearing trees, but a low number of swallow bird species. Then the ecologists would observe the species distribution and perhaps discover that there is a sparse but even distribution of oak trees, but that the population of a specific shrub seems to live in only one small portion of a community. Finally, the ecologist would study the different types of relationships that the species are having, such as competition between different bird species or symbiotic relationships between microorganisms and tree roots.

Let's delve a little deeper into types of interactions species can have. We're going to talk about three types of interactions. However, there are more. In terms of interaction outcomes, there are also three possible endings for an interaction-- positive, negative, or neutral.

Our first type is competition-- when species compete for food or resources. This is always a negative outcome for each species. An example would be two bird species competing for available materials to build their nests or food for their young.

Predation is when one species preys or consumes another. This is positive for the predator and negative for the prey. Predation includes carnivores eating other species, herbivores consuming plants, or species that lay eggs on or in another species. An example would be an eagle catching and eating a snake-- good for the eagle, bad for the snake.

Symbiosis is when both species benefit from their interaction. It is positive on both sides. Symbiosis is much more common in nature than people realize.

Many species, including humans, rely on symbiotic relationships to help digest their food. Humans have bacteria in their digestive tract, which allows them to digest their food better. Another example is cows, who also have a symbiotic digestive relationship with bacteria.

And finally, our key term for today-- "ecological succession"-- is the process of the creation of a new community either on barren land or on highly-disrupted environments. Within succession, there are two different types-- primary and secondary succession. Primary succession is when species begin inhabiting and establishing themselves in an environment that has never been inhabited before. An example would be like land created from an oceanic volcano-- as in this photo here-- being inhabited by pioneer species, like moss and algae, and eventually by shrubs, trees, and animals.

Secondary succession is when a disturbance damages communities or organisms in an already-established community enough that there is a vacuum where new species can move in and establish themselves. This is the most common form of succession. An example would be a forest fire-- like this one here, burning a large swath of forest. Over time, new species would move in and begin growing-- modifying the environment. Other disturbances that can cause secondary succession are floods, fires, volcanoes, droughts, overgrazing, and human activity, such as deforestation and over-harvesting.

Now, let's have a recap. We talked about important properties of community ecology, different types of species interactions, and our key term for today-- "ecological succession"-- which is the process of the creation of a new community either on barren land or on highly-disrupted environments.

Well, that's all for this tutorial. I hope these concepts have been helpful, and I look forward to next time. Bye.