Hi learners. Welcome to my course, Ecology from cells to Gaia. We will start to define what is ecology. As the great Russian biologist Dobzhansky said, "Nothing in biology makes sense except in the light of evolution." But at the same time, very little in evolution makes sense except in the light of ecology. Ecology provides the stage direction through which the evolutionary play is performed. Ecologists and evolutionary biologist needs a thorough understanding of each other's disciplines to make sense of the key patterns and processes. Ecology in a certain sense is a science that attempts to describe and explain patterns and processes that occur in the biosphere. So it also attempts to make predictions about the future events based on the past history and current circumstances. Ecology is also environmentalism. Even if we always say that ecology is not environmentalism, but environmentalism is a social cultural movement dedicated to protecting and preserving the environment, which must be based on the ecological science. So ecology is the base of environmentalists. As for Rachel Carson's book Silent Spring, remember it was the beginning on the environmental movement. And this means that if scientists provide good ecology, environmentalist argue with ecologists and vice versa. But we don't have to forget that the first ecologists have been and are indigenous people. In 1945, Aldo Leopold started to be a kind of first civilized person to talk about ecology. And you can see him in the different pictures. He is in this one, in the Forest Service Crew in 1911 in Arizona, when he started to wonder about the natural environment and its protection. Other founders of ecology were Ernst Haeckel, for instance, Frederic Clements. They started to think about how the nature works and how ecology is organized. That's why we recognize now the ecological organization. Ecology deals with five levels of ecological organization. The first level is the basic level, that is about individual organisms. The second level is about population, so individuals of the same species. The third regards communities, a greater or lesser number or populations. The fourth is ecosystem, where the community are packed together with the same physical environment, and the fifth is planet Earth, which is also called biosphere. We recognize in ecology, an ecological succession, so every environment follows a kind of common pattern. Ecologists also work on a variety of time scales. In fact ecological succession, for example, may be studied doing the decomposition of animal dunk, weeks or during the period of climate change since the last ice age, so millennia. So you see two different, very different time scales. The normal period of our research program, usually three or five years may often miss important patterns that occur on long time scales, meaning ecological studies involve careful observation and monitoring in the natural environment of the changing of abundances, and or one or more species over time or through space or both. Establishing the causes of patterns observed, often requires many productive field experiments. Ecology is also a science of dependency, because everything is a kind of relationship between science and probabilistic science can be defined as the science that can be based also on statistical grounds. Many definitions of ecology have been proposed, and probably the first one was that of Haeckel in 1870, and he said that by ecology we mean "the body of knowledge concerning the economy of nature, the investigation of the total relations of the animals both to its organic and inorganic environment." Then Tansley in 1904 said that ecology "is those relationships of plants with their surroundings and with one another, which depends directly upon differences on habitat among plants." So you see two different definitions for animals and for plants in the past. Then Elton in 1927, said that ecology "is the new name for a very old subject. It simply means scientific natural history." More modern definitions are those of Andrew Wharton in 1961. He said that ecology "is the scientific study of the distribution and abundance of organisms" and Krebs in 1972 and then again in 2008 said that "ecology is the scientific study of the interaction that determines the distribution of and abundance of organisms." A more modern definition is that provided by Townsend and other authors in 2003 when they said that "ecology is the scientific study of the distribution and abundance of organisms, and the interaction that determines the distribution and their abundance." So as you see, the definition moved from the animal concept to the plant, to a general environment and to the interaction of the organisms that live in the environment. So with the biotic and abiotic system. So there was more integration during time, and nowadays we see that ecology is a science of the world system. So I have a question for you. Please search your library for a variety of definitions of ecology. Which one is the most appropriate and why? Ecology is also the science of diversity. Life is represented on earth by the diversity of species. And early interest in this diversity mainly existed among explorers and collectors. And the idea that diversity has arisen by evolution, from the earliest ancestors over geological time, was not seriously discussed until the first half of the nineteenth century. At that time, Charles Darwin and Alfred Russell Wallace, strongly influenced by having read Malthus' book, independently proposed that natural selection constituted a force that would drive a process of evolution. We can see natural selection in action within species, in the variation within species over their geographical range, and even over very short distances where we can detect powerful selective forces in action, and recognize ecologically specialized races within species. Natural selection does not normally lead to the original species, unless it's coupled with the reproductive isolation of population from each other. This process is called speciation. Changing climate, particularly during the Ice Age or Pleistocene, bear a lot of the responsibility for the present patterns of distribution of plants and animals. On a longer time scale, many distributions make sense only once we realize that while major evolutionary developments where occurring, populations were being split and separated, and land areas were moving across climatic zones. But biodiversity to many hypotheses have been suggested. Derivate hypothesis by Paul Ehrlich asserts that each species lost like a rivet in an airplane wing can decrease ecosystem function, the working of the whole airplane, although the decreasing rate is slow, more species are eliminated. In this hypothesis, any loss of biodiversity is clearly noticeable. The second hypothesis is called passenger and crew hypothesis by Brian Walker. It's also known as the redundancy hypothesis and suggests that species are like pilots and passengers in an airplane and not rivets. The best way to conserve all species in the ecosystem, is to ensure the continued functioning of that ecosystem, and this strategy in turn calls for special attention to be paid to functional groups that are represented by only one or two species such as pilots, that is functionally groups in which there is little or no redundancy. I'd like to recommend you to follow my course on total biological diversity theories, majors and data sampling techniques, free available on Coursera to explore more about biodiversity and evolution. Thanks for your attention. See you at the next lecture.
