 We've previously talked about ecosystems as networks, through which resources and energy are flowing, as the components within this network form some interdependent system. A primary question of interest then will be how do any two or more elements within the network interact? Do they interact in a constructive or destructive fashion? Do they synchronize their states to work together, thus forming some larger system of organization, or do they remain asynchronous? All patterns of organization within the ecosystem will have to show some synchronization of states or activity between their constituent parts. We get advanced biological organisms because the cells, tissues and organs coordinate their behavior to enable larger processes to take place and in that way access and process new forms of resources. It is only by all of the components to the digestive system working cooperatively that the complex multicellular organism of a mammal can intercept and transform its food, which is then redistributed back to fuel all of the cells that worked cooperatively in enabling that collective process to take place. But of course this is not always the case. All biotic and abiotic elements to an ecosystem have some boundary condition that defines where this synchronization of states begins to drop off and even become counteractive. We can understand this working together or working apart between elements in a system in terms of what is called synergies. The term synergy comes from the words working together, two or more things that interact to create a combined effect that is greater or less than each of their effects in isolation. Synergy is a prevalent phenomena in biological systems that arises from the concerted action of multiple factors producing an amplification or cancellation effect as such we're talking about constructive or destructive relations. All biological creatures occupy some local domain within the network of an ecosystem, wherein they intercept and transform the resources within that network that are available to that functional and spatial domain and we may call this a niche. The idea of a niche is defined in different ways but here we'll define it as the function or position of a species within an ecological community. A species niche includes the physical environment to which it has become adapted as well as its role as a producer and consumer of food resources. By understanding the set of parameters to the creatures functioning both biotic and abiotic such as the temperature range, humidity, soil nutrients etc. we can understand the niche of that creature. The realized niche is where the creature currently exists and the fundamental or potential niche is where it could potentially be found. We can then think of a niche as the unique nexus of interactions an organism has with other entities within the network through which it performs some unique functional role. Biological interactions are the effects that the organisms in a community have on one another. In the natural world no organism exists in absolute isolation but every organism must interact with the environment and other organisms. These interactions may not be direct, individuals may affect each other indirectly through intermediaries such as shared resources, common enemies or their effect on some abiotic element of the system. Interactions between organisms can produce both conflict and cooperation. Within systems theory these interactions can be understood in terms of synergies. A positive synergy is when two entities interact to produce a combined effect greater than the sum of their effects in isolation. A negative synergy what we might call interference is an interaction that generates a combined output that is less than the simple additive combination of inputs in isolation. Between species ecological interactions can be divided according to their synergy into three different types, predation, competition and mutualism. Ecological predation is defined as any interaction between two organisms that results in a flow of energy or resources from one to the other. A key characteristic of predation however is the predator's direct impact on the prey population. Predation describes a biological interaction where a predator organism feeds on another organism called the prey. Through this habitual interaction, prey come to develop defenses against their predator and predators strive to overcome such obstacles as they co-adapt and this co-adaptation between survival of prey and predator is part of the reason that ecosystems exhibit such diversity and complexity. Predators can be carnivores, herbivores or parasitical. Each type of predator can be categorized based on the degree of impact on the prey. Carnivory is lethal to the prey while herbivory and parasitism may or may not be lethal to the prey. Predation is a process of major importance in influencing the distribution, abundance and diversity of species in an ecological community. Predators may increase the biodiversity of a community by preventing a single species from becoming dominant, thus creating a balance of organisms in a particular ecosystem. If there is a low predator density, then prey have less of a need to adapt. However, as predator density increases, it forces prey to evolve and to become more resistant to those predators, thus forcing more species diversity. Such predators are known as keystone species. The introduction or removal of this predator or changes in its population density may have a profound influence, possibly creating dramatic cascading effects on the equilibrium of many other populations in the ecosystem. Predation and consumption can be modeled in terms of cost-benefit analysis within what is called optimal foraging theory. Optimal foraging theory is a model that helps to predict how a creature behaves when it's searching for food. Although obtaining food provides the animal with energy, searching for and capturing the food requires both energy and time. The creature wants to gain the most benefit, that is to say the most amount of food energy for the lowest cost during foraging so that it can maximize its fitness. This theory then helps us to predict the best strategy that a creature can use to achieve its goals. When two or more organisms niches overlap or they strive for the same resource in some fashion, then we may get a biological interaction of competition. We may consider this competition as the between individual or between population negative interaction due to resource constraints. Competition as part of the struggle for existence represents two or more creatures trying to process the same resources within the network. Since the time of Darwin, many biologists believe that the struggle for existence through competition has promoted biological evolution under natural selection. According to the competitive exclusion principle, species less suited to compete for resources should either adapt or die out. According to evolutionary theory, this competition within and between species for resources plays a central role in natural selection. Biologists typically recognize two types of competition, interference and exploitative competition. During interference competition, organisms interact directly by fighting for scarce resources. For example, large aphid insects defend feeding sites on cotton wool leaves by kicking and shoving small aphids from the best sites. In contrast, during exploitive competition, organisms interact indirectly by consuming scarce resources. For example, plants consume nitrogen by absorbing it into their roots, making nitrogen unavailable to nearby plants. Plants that produce many roots typically reduce soil nitrogen to a very low level which eventually kills neighboring plants. Competition creates a dynamic of exclusivity leading to a dominant hierarchy where one component within the system assumes a superior or inferior position in relation to another. With this hierarchy directly correlated to the access of the desired resource, dominant hierarchies arise where members of a social group interact often aggressively to create a ranking system. In social groups, members are likely to compete for access to limited resources and mating opportunities. Rather than fighting each time they meet, relative relations are formed. These repetitive interactions lead to the creation of a social order that is subject to change each time a dominant animal is challenged by a subordinate one. Mutualism is the way two organisms of different species exist in a relation in which each individual benefits from the activity of the other. Similar interactions within a species are known as cooperation. This is what we call a positive synergy. In ecology and biology, positive synergies refer to mutual collaboration and mutual adaptation either between biological organisms or between organisms and their environment. Compared to competition, positive synergies enable organisms to exist and reproduce at the minimum cost. Completely cooperative relations, symbiosis, are quite common. Some examples that we might cite include some species of acacia trees have special structures that provide food and micro habitat for ants that protect the trees from insects that eat their leaves. Another example would be nitrogen fixing bacteria living in the roots of plants such as legumes where they convert atmospheric nitrogen to a form that plants can use while they provide nitrogen to the bacteria. Similar cooperation exists with fungi that assist plant roots to take out phosphorus from the soil. Honey bees distribute pollen that fertilizes flowers while they collect pollen and nectar as food. Macro ecosystems contain thousands of symbiotic relations such as these. A consequence of this co-adaptation is a group of plants, animals and microorganisms from which the community assembly process can form variable and resilient ecosystems. Positive synergies can be very effective in that they enable the division of labor between various creatures and the formation of complex social systems as exemplified by creatures like termites and bees. In these U-social insects, we can see the advanced division of labor such as sterile insects feeding and guarding the small number of organisms in the colony that are able to reproduce. With positive synergies, we can get emergence. A beehive, like other social insect colonies, is a complex system where the individuals are interacting with each other and those local interactions between the individuals creates very complex and sophisticated behavior at the aggregate level. You have individual units that create a large social group and that social group as a whole comes to have its own integrated processes. The interaction between entities within an ecosystem inherently gives rise to co-evolutionary processes. Co-evolution can be defined as the traits of a species evolving as a reaction to the evolution of the traits of another species and vice versa. Co-evolution can occur on all levels from the molecular to the cellular to the individual to populations to the ecosystem level. When the interaction is between pairs of species such as between pathogen and host or predator and its prey, these species can develop matched sets of adaptations. Here the evolution of one species causes adaptations in a second species. These changes in the second species then in turn cause new adaptations in the first species and is this cycle of selection and response that we call co-evolution. An example is the production of tetrodotoxins in the rough skined newt and the evolution of tetrodotoxin resistant in its predator, the common garter snake. In this pair of predator and prey an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of toxin resistance in the snake. The idea of survival of the fittest through competition is a central paradigm within population biology and ecological ecology, which is a very valid way of interpreting the process of evolution and the development of ecosystems. But long-term survival is not just about competition, it is of course also about cooperation. The survival of the cells in our bodies is predicated upon their working together in a cooperative fashion. A good illustration of this is the theory of symbiogenesis. Symbiogenesis theory is an evolutionary theory that expands the origin of eukaryotic cells from prokaryotes. It states that several key organelles of eukaryotes originated as a symbiosis between separate single-celled organisms. According to this theory, mitochondria, plastids and possibly other organelles representing formerly reliving bacteria were taken inside another cell as an endosymbiont about 1.5 billion years ago. Molecular and biochemical evidence suggests that mitochondria developed from proteobacteria and chloroplasts from cyanobacteria. We can see from this that the relationship between species within an ecosystem is typically a product of a long evolutionary process. But when we change these ecosystems rapidly, we can change this balance. For example, there are many cases where insects become pests when displaced from their native ecosystem. Most agricultural pests turn out to be species that live innocuous lives in their native habitat but become troublesome when they invade or are inadvertently introduced into a new region or new agricultural system. In new situations where these evolved feedback loops get broken through rapid anthropogenic alterations, populations can get out of control affecting the homeostasis of the macro ecosystem. In this video we've been looking at the interaction between the elements within an ecosystem in terms of positive and negative synergies. We firstly talked about how all biological creatures occupy some local domain within the network of an ecosystem, wherein they intercept and transform resources but in so doing they must interact with other elements within the system. We also talked about biological interactions as the effect that the organisms in a community have on one another. How we can understand these different interactions in terms of three types, predation, competition and symbiosis, depending on whether there is a net gain or loss to one or both of the creatures through the interaction. We talked about ecological predation as an interaction between two organisms that results in a net flow of energy or resources from one to another. When two or more niches overlap and organisms strive for the same resource then we will get a biological interaction of competition. We discuss mutualism as the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other and through which we can get the emergence of the division of labour and social complexity. Finally we briefly talked about co-evolution, a process whereby creatures develop in response to changes within each other.