Hi. In this video, we are going to answer the question, what's biodiversity. So we're going to define this term and we are going to see also concepts like hotspot of biodiversity, which is a biodiversity of the world, and also why is biodiversity important for humans. If we try to define biodiversity and I asked you to imagine what comes into your mind when you think about this word, probably some images like the ones in this slide come into your mind. But defining biodiversity means more things. In fact, biodiversity is a neologism that appeared during the 80's, and it's the synonym for the idea of the biological diversity, which was in the convention of biological diversity by United Nations, was defined as the variability among living organisms including diversity within a species, between a species, and ecosystems. So nowadays, moreover, we have to include in this definition the idea of the genetic diversity. So usually, the term biodiversity is used to talk about diversity of species. But nowadays, we know that this term includes more levels. In fact, it is built out of three intertwined concepts or features. The genetic diversity, the ecosystem diversity, and the species diversity. So it's important to consider these three levels when we talk about biodiversity. Another important concept related to biodiversity is the idea of the hotspots of biodiversity. There has been defined 35 hotspots of biodiversity in the world. It means approximately 2.3 percent of the Earth's surface. These are places on the earth that are both deeply threatened and biologically very rich. So to an area to be considered in this as a hotspot of biodiversity, it's necessary that this area has around 1,500 of endemic plants and also, it must have 30 percent or less of the original natural vegetation. So there are some organizations, you have the names, International Conservation and CEFC, that work for the study and conservation of these areas. So in order to study all these biodiversity, scientists have defined a classification to study these organisms and other living beings. We can start with the idea that the life is divided into different groups that are called domains. The domains in kingdoms, the kingdoms in phylum, classes, orders, and finally, families, genus, and species. So this classification is clear, but how many kingdoms are there? So this is a question that has been done over the time. If you see this slide, from left to the right, you can see how this classification on the number of kingdoms has been changing over the time. In the 18th century, there was the first classification based on two kingdoms, basically, animals and plants. But then, when prokaryotes were discovered, so the microorganisms were discovered and more information has been discovered about them, the number of kingdoms have been changing. So that then we had the classification of three Kingdoms and four kingdoms, and finally, the one based on five Kingdoms. After this classification of the five kingdoms that was accepted by many scientists and it's still being used, appeared a new classification during the 90's based on three domains. In this classification, the microorganisms have more protagonism. Now, I would like to introduce you Lynn Margulis. She was a scientist that made many contributions to biology. I'm sure you will know more about her during this course. Now, I want to talk about her because she was one of the persons that thought that the five kingdom classification was more useful or more recommended than the one based in the three domains, so that she proposed some changes in the five kingdom classification in order to include the new prokaryotes that had been discovered. You can find more information about these ideas of Lynn Margulis and the five kingdom classification in her book called 'The Five kingdoms'. Another woman I would like to introduce is Beatrix Potter. She's well-known by Peter Rabbit collection of books for children and her drawings on the books. But also because she was an important mycologist during the 19th century. So she made many observations and drawing about fungi and made many contributions about these organisms. She also made some experiments related to the germination of spores and she tried to publish it as a research paper in Linnean Society, but it was rejected and it was never published. So if we return to this idea of the classification of biodiversity and if you remember, I told you about these three groups, the three domains of life, you see here how we have the bacteria group, the archaea, and the eucarya. So these prokaryotes have a big protagonism in this classification. So in order to know more about these type of organisms, let's see the following interview.