1. What is biodiversity?

1. What is biodiversity?

Biodiversity is a major topic right now, not just because of the threats it faces, but also because we now understand better than ever just how little we in fact know about it.

In the video, we learn about the definitions of biodiversity and the scale of diversity in different groups of organisms.

Read more in scientific articles

Read more in scientific articles where researchers have tried to estimate the number of species we still don’t know about.

  1. How many species are there on Earth and in the ocean?
    Original article
    Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G. B. & Worm, B. 2011: How many species are there on Earth and in the ocean? PLoS Biology 9(8): e1001127. DOI: 10.1371/journal.pbio.1001127.

  2. How many tons of each organism group are there on Earth?
    Original article
    Bar-On, Y. M., Phillips, R. & Milo, R. 2018. The biomass distribution on Earth. PNAS 115(25): 6506-6511. DOI: 10.1073/pnas.1711842115

  3. A study that counted the number of arthropod species in one rainforest.
    Original articleArticle on ResearchGate
    Basset, Y., ym. 2012: Arthropod diversity in a tropical forest. Science 338(6113): 1481-1484. DOI: 10.1126/science.1226727.

Find out

How many species are there? Why can we still not answer this question precisely? Find out for yourself. When we talk about biodiversity, we usually mean the number of species. Yet diversity of habitats and the genetic diversity within species are also important dimensions of biodiversity.

How long do you have to look to find all the species?

Look at Figure 1 in the  Mora et al. article, where the horizontal axis represents time and the vertical axis the number of species groups known at the particular point in time. The lines in the graphs curve, because the longer we have already spent finding out the number of species groups, the more slowly we find new species. In principle if you look long enough, you will eventually find all the species groups. As the line curves and becomes more and more horizontal, you can make a good estimate of the eventual number species you would find.

Try this yourselves in groups of 3-8 people:
  • Decide what you will count: plant species, bird species or different types of rubbish. Decide the limits of your small search area. With a little creativity you can do this in the classroom, for instance by counting different coloured pens in the students’ desks.
  • Choose one person as the timer. They will need a watch, a pen and a piece of graph paper.
  • Choose one person as the classifier, who will need pen and paper.
  • The others begin searching the area. Stay within hearing distance of each other. The searchers shout out what they find to the classifier, who classifies the observations as they see fit and keeps a tally of the different species / rubbish types / colours.
  • Every five minutes the timer asks the classifier how many species have been found so far, and records the answer.
  • At the end, after for instance half an hour, draw the timer’s list as a graph like the ones in the article. Start by finding the largest, i.e. the final tally, round it up and set the top end of the vertical axis to that number. Draw the observations as dots on the graph, and connect the dots with a line.

Does your line curve? Does it curve enough for you to estimate, what the actual number of species in the area might be?

How did the classification go – did you disagree? Biologists sometimes disagree a great deal about how to classify individuals into different species.

Project ideas in biodiversity

1. How can we know what we do not know?

Search the internet for different estimates of how many species are still to be found on Earth. How were the estimates made? How can we know what we do not know?

2. Genetic diversity within species

While species number are talked about the most, genetic diversity within species is also important. Go to the grocery store and photograph different kinds of tomatoes, chilies, apples etc., and to the park to photograph different dog breeds or different coloured pigeons. Make photo collages. Make another trip to a natural environment, and make a separate collage of the genetic diversity you find there. Examples are harder to find in nature, but try something like measuring the flowers on individual plants. When the season is changing, you can find differences in when individual trees come into leaf or turn yellow. If you have snails in your garden, their shells can have a lot of variety. Take a look at the diversity you find in species bred by humans and species found in nature. Why is it harder to find variation in nature? What do you think could be useful about having lots of variation between individuals within a species?