In this lesson, we'll be talking about community structure, which has 4 key components. The first two are species richness and relative abundance. Species richness is just the number of different species in a community. Are there 5 different types of organisms living here, or are there 10? Relative abundance looks at how many individuals there are of a particular species relative to others in the community. So, there are 3 types of species in the community, but one only has 10 individuals, and the others both have 100. That's the idea behind relative abundance. Now, these two concepts are sometimes merged into this idea of species diversity, which is just a measure that takes into account both richness and relative abundance. And you can see an example of a chart that displays species diversity here, which is really just showing the change in species diversity in North America. Here we have what it used to be, what it is now, and what the difference between those two states is, more or less.

Now, the other key components of community structure are the interactions between all the species of the community and the physical aspects of the community, like the size of the area, the altitude where the community exists, and the type of vegetation present. And you can see some other aspects in this image here behind my head. Now, without going into too much detail, this idea of species diversity is really important because species diversity actually leads to greater biomass production and greater resistance to invasive species. So, species diversity essentially helps bolster ecosystems. Now with that, let's go ahead and flip the page.