Species Richness: Definition & Determining Factors

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Ecosystems of Oceans and Freshwater: Biological Diversity and Water

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:07 Definition
  • 1:02 Sampling Considerations
  • 2:13 Taxonomy
  • 3:51 Standardization
  • 4:43 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Laura Enzor

Laura has a Master's degree in Biology and is working on her PhD in Biology. She specializes in teaching Human Physiology at USC.

In this lesson, you'll learn what species richness is and what factors can influence the index of species richness. You'll also discover why it is an important index to measure in terms of conservation.


Species richness, very simply, is a count of the different species in a given ecosystem, region or particular area. You make the assumption that each organism constitutes a single species. Imagine a picture of a lake. How many different species might you see? You might see three different types of organisms: birds, fish and plants. So, in this lake community, the species richness would have a value of three.

One important thing to keep in mind is the difference between species richness and species diversity. Species diversity takes the abundance, or number of individuals, of different species into account, while species richness does not. If we again think about our lake community, you might note that there are four fish and three birds. Therefore, the species diversity would be higher for fish. However, the species richness index would remain the same.

Sampling Considerations

The level of species richness can vary depending on a few variables, one of which is how you sample. For example, an index of species richness would greatly vary if you were counting species in an entire mesic hardwood forest, versus a one-meter-by-one-meter plot in the same forest.

How you sample the environment in question is determined by what you want to gain by a species richness index. If you are more interested in how many different types of trees are in the forest, sampling a small plot won't tell you much. However, if you are interested in what insects live on the forest floor, sampling the entire forest would take years!

You may be asking why we should care about species richness. Why is knowing what species are in a given ecosystem important? Species richness is an important index when thinking about conservation of a given habitat. Areas or habitats with rare species are considered to be a conservation priority. An accurate species richness index can help determine what conservation measures need to be taken to provide a habitat where species can survive and thrive.


Another consideration when determining species richness is taxonomy. Taxonomy is the science of classifying things. In biology, we classify things in a certain order, which is: kingdom, phylum, class, order, family, genus and species. The mnemonic phrase 'King Phillip Crossed Oceans For Good Spices' can help you remember the order.

Let's take a quick look at an example, and classify humans:

  • Our kingdom is Animalia, because we are animals
  • Our phylum is Chordata, which is for chordates, or animals with a backbone
  • Our class is Mammalia, since we are mammals
  • Our order is Primate, since we are evolutionarily considered to be primates
  • Our family is Hominidae, which is a family specifically for humans
  • Our genus is Homo
  • Our species is Homo sapiens

Note that when talking about a specific species, you include both the genus and species name.

So if we can identify specific species in a given environment versus labeling organisms as just a fish, plant or bird, then our species richness index may dramatically change.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account