Hi. Today we're going to talk about ecology. So we are going to wonder what's ecology? Also to talk about the different levels of organization of an ecosystem, what's the keystone species, the idea of the resilience of our community, and also we are going to talk a little bit about interactions between individuals and species. So let's start with the definition of ecology. To do it, let me introduce you Ellen Swallow. She defined ecology as the science of the conditions of the health and well-being in everyday human life. So she is considered to be the first person to talk about human ecology. Basically, the idea is that humans live in an environment and this environment has some effects in our health. Also, we make some changes in the environment so that finally the consequences are in our health and well-being. So when Ellen Swallow gave these ideas and this definition of ecology, it was in the 19th century and her idea defining ecology as an applied science. An applied science that one of the main object is to change the world instead of only observing it which would be more proved way of doing science in an objective way. So all these things and probably other features made the definition of Ellen Swallow not accepted by the scientific community of that time. So finally, nowadays we have the definition of ecology as the scientific study of the distribution and abundance of organisms, the interactions between them that cause these abundances and distributions and also the relation with the matter and energy. So Haeckel was the first person to define ecology in 1866 and he defined it as the body of knowledge concerning the economy of nature, defining the economy of nature as the dynamic relationship between species and their habitats. So from Haeckel until now with the definition I have given to you, we can see that many other definitions have been through the path over time and Ellen Swallow ones was not accepted. But nowadays, many of the students in ecology take into consideration the relationship between human and environment. The effects that human made to environment and consequences of environment to human's health. So nowadays from my opinion, we are using Ellen Swallow definition. Maybe many ecologists are doing it without knowing that she was the first person to leave that idea. So because nowadays we are doing a lot of studies related to global change and climate change. So this is basically the idea that she was proposing related to human ecology. Well, so if we jump into the next point, the different levels of organization in an ecosystem, we can talk that it is in this order that we find individuals. These individuals are organized in populations, the populations in a species, the species in communities and finally, these communities are organized in an ecosystem. So we can define populations as a set of organisms or individuals that share a time and space, and that they all have some biological properties similar. So they share these biological properties. So it means they are from the same species. Then we have the following level, which are the communities. Communities are a set of organisms of different species coexisting in a time and space. Finally, ecosystems are defined as a community plus the environment. So this means that it considers the living thing but also the abiotic factors, so that the environment that surrounds them. So we have seen what's ecology and we have also have a look to the different levels of organization of ecosystems. Now, I would like to define what does it mean that the community is resilient or a community is resistant and which are the differences. This is an important concept because it is related to the effect of disturbance into a community. So a resilient community is one that returns rapidly to its former structure after this structure has suffered an alteration. Resistant community is one that undergoes relatively little change in the structure in the face of disturbance. Then the next definition is the keystone species. What's the keystone species? To define this, I introduce to you Dr. Mary Eleanor Power. She defined keystone species as species whose impact on the community composition is disproportionately large in front of its abundance. So we have different and examples of keystone species, for example, the wolves or the beaver that transform the landscape, and you can see it in the pictures. So that you will find more information about this keystone species of wolves and beavers in the supplementary materials. Let's start with the last part of this video which is related to the interaction between individuals population and species. Organisms that feed on organic matter, they can be grouped as follows. We can find the decomposers, which are organisms that feed on dead animals or plants. Parasites, which feed from host plants or animals, and then we find the predators which prey on animal or organisms typically killing them, and then finally the grazers, they consume parts of many prey organisms and normally they don't kill them at least immediately. Then we have another group of organisms, which are the primary producers. These are organisms that are called autotroph organisms, and they take the resources from the photosynthetic radiation, water resources, mineral resources, and also nutrients and carbon dioxide. So another type of interaction is the type of interactions related to competition. Basically, we find two different types of competition, the interspecific competition and the intraspecific competition. If we define the interspecific competition, these are individuals of one species that suffered a reduction in the fecundity, growth, or survivorship due to the exploitation of resources or inferences by individuals from another species. Then the definition of intraspecific competition is the same idea but the competition is between individuals of the same species. Finally, the third and last group of interactions between individuals is the mutualism. A mutualistic relationship is one in which organisms of different species interact to their mutual benefit. We can find many different types of mutualistic relationships. For example, a plant that produces fresh fruits and some birds or mammals take them as food. But for the plant, it's also important for its dispersion. We can find also many other examples of other types of mutualistic relationships. So I would like to introduce you Dr. Anna Traveset. She's a scientist that has done a lot of work studying these mutualistic networks and in different types of ecosystems and in different or special temporal places and considering different types of changes in this spatio-temporal conditions. So she has done many work and it hast been published. You can find many information about her and you will find more in the supplementary materials. So here we finish our look into ecology.
