Biotic Interactions PDF

Biotic Interactions Ecology is the study of the house. The study of interactions between living organism, including humans. Image on the left has more corals as it is just starting its journey and is full of young corals forming biotic interaction...

Biotic Interactions Ecology is the study of the house. The study of interactions between living organism, including humans. Image on the left has more corals as it is just starting its journey and is full of young corals forming biotic interactions. What “reset” the coral is a storm, which is not an abiotic factor but can influence both the abiotic and biotic. However, they are caused by abiotic and biotic factors. Abiotic factors play a significant role in shaping an ecosystem, but the disturbance itself encompasses a broader concept. Individual ecology - survival and reproduction of the organism itself Population ecology - Population of the same species, how do they work and interact with each other. Biotic Interactions 1  Community ecology - Interactions among different populations. Overlaps with biogeography, evolutionary biology and natural history. Abiotic factors Non-living physical and chemical components of an environment that influence the living organisms within it. Temperature - dangerous as organisms need time to adapt Light Oxygen - at the surface, there are exchanges with the atmosphere. Oxygen Minimum layer (OML): the consumption by bacteria of organic debris. Oxygen deep waters are formed in the polar regions. Tides and waves Soil richness Currents Depth Pressure - affects different organisms in different ways Biotic factors Biotic Interactions 2  These are intraspecific (same species) and interspecific (different species) interactions. Mutualism ++ A positive interaction in which both species reciprocally benefit from a partnership. A beneficial but not mandatory association between two species i.e. clownfish in anemones. Symbiosis is a kind of mutualism, a mandatory association resulting in mutual benefits. The evolution of one must match the evolution of the other. It is the most advanced form of association between species i.e. corals and zooxanthellae. Commensalism +0 A relationship where one organism gains some benefit whilst the other is unaffected i.e. sharks and remora. Inqilism is when an animal that lives in the nest or burrow of another. Phoresy is when an animal is transported by another with no benefit or harm for the host. Biotic Interactions 3  Competition - - Rivalry between organisms for access to resources such as food, light, space, shelter and nutrients. It is of little importance for two different species to use the same food source when the resource is abundant, but as this food becomes limiting, resource partitioning can limit adverse impacts. More than one disturbance may hit because it is a dynamic system and it is meant to happen. Competition happens throughout the timeline unless you come to equilibrium Natural coral recovery despite negative population growth - competition is the main driver of coral mortality Ecological Niches The position of a species within an ecosystem, describing both the range of conditions necessary for persistence of the species, and its ecological role in the ecosystem. Every species occupies a niche (multidimensional space), related to the type of food it eats, where it lives, where it reproduces and its relationship with other species. Biotic Interactions 4  Principle of Gause: No two species can exploit the environment in exactly the same way, occupy the same ecological niche, and coexist - one will be excluded. When two ecologically equivalent species coexist it means that they have realised a differentiation of niches, at least on one resource. The reduced breadth of this resource in the presence of another potentially competing species is the realised niche. Habitat differentiation Coexistence is possible thanks to a food niche differentiation, both in barren areas and in vegetated assemblages. Paracentrotus lividus selectively graze on erect microalgae whereas Arbacia lixula is a scraper, feeding on mostly encrusting corallinales. Succession Interspecific interactions that drive changes in communities. 1. Primary succession - Colonisation of new surface by mature ecosystems. It involves the gradual establishment of biotic communities in lifeless areas. 2. Secondary succession - recolonisation after disturbance by previous ecosystems. The development of communities and ecosystems with different species step by step in a place already containing sediments or bottom. Biotic Interactions 5  Disturbance is any relatively discrete event in time that disrupts an ecosystem, community, or population structure, and changes the resources, substrate availability, or physical environment (Crisafulli et al., 2015). It leads to an environment with more diversity. The chronological replacement of species in a nevvolving community over ecological time (Karlson, 1999). Facilitation Species that modify the environment and make it difficult for others but make it easy for their own species Tolerance All species are able to colonise but vary in tolerance to competition from later successional species. Later species can tolerate less resources and will make up the bulk of the community Inhibit Species that colonise an area but environmental conditions make it less suitable for both early and late species but is more suited to later species that may be more resilient. Extrinsic perturbations oppose the successional process. Organisms are differential prioritised depending on their tolerance to disturbance, the new environment and successive events that may occur. Biotic Interactions 6  Intermediate Disturbance Hypothesis Very low level of disturbance: few species are well-adapted to stable environment Intermediate level of disturbance: opportunities for a wide range of species Very high level of disturbance: reduced number of species because of rapid changes in the environment Dynamic Equilibrium Model (DEM) Biotic Interactions 7  The productivity of an ecosystem affects the relationship between disturbance and biodiversity High species diversity at low disturbance regime when resource availability and growth rate are low (dotted line) High species diversity at high disturbance regime when resource availability and growth rate are high (broken line) Amensalism -0 An interaction in which one species is inhibited or destroyed and the other is unaffected. Achieved through a physical or chemical interaction. Predation -+ Mode of life in which food is primarily obtained by the killing and consuming of animals, including primary producers 10% law of transfer from one trophic level to the next (Lindeman, 1942) Biotic Interactions 8  Lotka-Voltera equations: predator prey models. However, it only works in very simple systems and “make believe” models Indirect effects of predator-prey interaction Overfishing and extirpation (local extinction) of highly valued vertebrate apex predators often trigger herbivore population increases, leading to widespread kelp deforestation. Parasitism -+ Interaction of which one of the actors (the parasite) takes advantage, by feeding, sheltering or reproducing, at the expense of a host without killing it, at least in the short term. Could also be considered a type of predation One of the most successful modes of life on Earth 29,000 species of marine fish so far, but around 100,000 fish parasite species (Rhode 2002) Specialists which infect a particular species or generalists which infect many Ectoparasite -outside the host Endoparasite - in the host Altruism +0 In zoology, a behaviour that benefits another at its own expense i.e. octopus protecting its eggs Biotic Interactions 9