Ecosystem ecology is the integrated study of living and non-living components of ecosystems and their interactions within an ecosystem framework. This science examines how ecosystems work and relates this to their components such as chemicals, soil and animals. Ecosystem ecology examines physical and biological structures and examines how these ecosystem characteristics interact with each other; this helps us understand how to maintain high quality water and economically viable commodity production. A major focus of ecosystem ecology is on functional processes, ecological mechanisms that maintain the structure and services produced by ecosystems; these include primary productivity and trophic interactions. Studies of ecosystem function have improved human understanding of sustainable production of forage, fiber and provision of water. Functional processes are mediated by regional-to-local level climate and management, thus ecosystem ecology provides a powerful framework for identifying ecological mechanisms that interact with global environmental problems global warming and degradation of surface water.
This example demonstrates several important aspects of ecosystems: Ecosystem boundaries are nebulous and may fluctuate in time Organisms within ecosystems are dependent on ecosystem level biological and physical processes Adjacent ecosystems interact and are interdependent for maintenance of community structure and functional processes that maintain productivity and biodiversityThese characteristics introduce practical problems into natural resource management. Who will manage which ecosystem? Will timber cutting in the forest degrade recreational fishing in the stream? These questions are difficult for land managers to address while the boundary between ecosystems remains unclear. We need better understanding of the interactions and interdependencies of these ecosystems and the processes that maintain them before we can begin to address these questions. Ecosystem ecology is an inherently interdisciplinary field of study. An individual ecosystem is composed of populations of organisms, interacting within communities, contributing to the cycling of nutrients and the flow of energy.
The ecosystem is the principal unit of study in ecosystem ecology. Population and physiological ecology provide many of the underlying biological mechanisms influencing ecosystems and the processes they maintain. Flowing of energy and cycling of matter at the ecosystem level are examined in ecosystem ecology, but, as a whole, this science is defined more by subject matter than by scale. Ecosystem ecology approaches organisms and abiotic pools of energy and nutrients as an integrated system which distinguishes it from associated sciences such as biogeochemistry. Biogeochemistry and hydrology focus on several fundamental ecosystem processes such as biologically mediated chemical cycling of nutrients and physical-biological cycling of water. Ecosystem ecology forms the mechanistic basis for regional or global processes encompassed by landscape-to-regional hydrology, global biogeochemistry, earth system science. Ecosystem ecology is philosophically and rooted in terrestrial ecology; the ecosystem concept has evolved during the last 100 years with important ideas developed by Frederic Clements, a botanist who argued for specific definitions of ecosystems and that physiological processes were responsible for their development and persistence.
Although most of Clements ecosystem definitions have been revised by Henry Gleason and Arthur Tansley, by contemporary ecologists, the idea that physiological processes are fundamental to ecosystem structure and function remains central to ecology. Work by Eugene Odum and Howard T. Odum quantified flows of energy and matter at the ecosystem level, thus documenting the general ideas proposed by Clements and his contemporary Charles Elton. In this model, energy flows through the whole system were dependent on biotic and abiotic interactions of each individual component. Work demonstrated that these interactions and flows applied to nutrient cycles, changed over the course of succession, held powerful controls over ecosystem productivity. Transfers of energy and nutrients are innate to ecological systems regardless of whether they are aquatic or terrestrial. Thus, ecosystem ecology has emerged from important biological studies of plants, terrestrial and marine ecosystems. Ecosystem services are ecologically mediated functional processes essential to sustaining healthy human societies.
Water provision and filtration, production of biomass in forestry and fisheries, removal of greenhouse gases such as carbon dioxide from the atmosphere are examples of ecosystem services essential to public health and economic opportunity. Nutrient cycling is a process fundamental to forest production. However, like most ecosystem processes, nutrient cycling is not an ecosystem characteristic which can be “dialed” to the most desirable level. Maximizing production in degraded systems is an overly simplistic solution to the complex problems of hunger and economic security. For instance, intensive fertilizer use in the midwestern United States has resulted in degraded fisheries in the Gulf of Mexico. Regrettably, a “Green Revolution” of intensive chemical fertilization has been recommended for agriculture in developed and developing countries; these strategies risk alteration of ecosystem processes that may be difficult to restore when applied at broad scales without adequate assessme
A carnivore, meaning "meat eater", is an organism that derives its energy and nutrient requirements from a diet consisting or of animal tissue, whether through predation or scavenging. Animals that depend on animal flesh for their nutrient requirements are called obligate carnivores while those that consume non-animal food are called facultative carnivores. Omnivores consume both animal and non-animal food, apart from the more general definition, there is no defined ratio of plant to animal material that would distinguish a facultative carnivore from an omnivore. A carnivore at the top of the food chain, not preyed upon by other animals, is termed an apex predator. "Carnivore" may refer to the mammalian order Carnivora, but this is somewhat misleading: many, but not all, Carnivora are meat eaters, fewer are true obligate carnivores. For example, while the Arctic polar bear eats meat most species of bears are omnivorous, the giant panda is herbivorous. There are many carnivorous species that are not members of Carnivora.
Outside the animal kingdom, there are several genera containing carnivorous plants and several phyla containing carnivorous fungi. Carnivores are sometimes characterized by their type of prey. For example, animals that eat insects and similar invertebrates are called insectivores, while those that eat fish are called piscivores; the first tetrapods, or land-dwelling vertebrates, were piscivorous amphibians known as labyrinthodonts. They gave rise to insectivorous vertebrates and to predators of other tetrapods. Carnivores may alternatively be classified according to the percentage of meat in their diet; the diet of a hypercarnivore consists of more than 70% meat, that of a mesocarnivore 30–70%, that of a hypocarnivore less than 30%, with the balance consisting of non-animal foods such as fruits, other plant material, or fungi. Obligate or "true" carnivores are those. While obligate carnivores might be able to ingest small amounts of plant matter, they lack the necessary physiology required to digest it.
In fact, some obligate carnivorous mammals will only ingest vegetation for the sole purpose of its use as an emetic, to self-induce vomiting of the vegetation along with the other food it had ingested that upset its stomach. Obligate carnivores include the axolotl, which consumes worms and larvae in its environment, but if necessary will consume algae, as well as all felids which require a diet of animal flesh and organs. Cats have high protein requirements and their metabolisms appear unable to synthesize essential nutrients such as retinol, arginine and arachidonic acid. Characteristics associated with carnivores include strength and keen senses for hunting, as well as teeth and claws for capturing and tearing prey. However, some carnivores do not hunt and are scavengers, lacking the physical characteristics to bring down prey. Carnivores have comparatively short digestive systems, as they are not required to break down the tough cellulose found in plants. Many hunting animals have evolved eyes facing forward.
This is universal among mammalian predators, while most reptile and amphibian predators have eyes facing sideways. Predation predates the rise of recognized carnivores by hundreds of millions of years; the earliest predators were microbial organisms, which grazed on others. Because the fossil record is poor, these first predators could date back anywhere between 1 and over 2.7 Gya. The rise of eukaryotic cells at around 2.7 Gya, the rise of multicellular organisms at about 2 Gya, the rise of mobile predators have all been attributed to early predatory behavior, many early remains show evidence of boreholes or other markings attributed to small predator species. Among more familiar species, the first vertebrate carnivores were fish, amphibians that moved on to land. Early tetrapods were large amphibious piscivores; some scientists assert that Dimetrodon "was the first terrestrial vertebrate to develop the curved, serrated teeth that enable a predator to eat prey much larger than itself." While amphibians continued to feed on fish and insects, reptiles began exploring two new food types: tetrapods and plants.
Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In the Mesozoic, some theropod dinosaurs such as Tyrannosaurus rex were obligate carnivores. Though the theropods were the larger carnivores, several carnivorous mammal groups were present. Most notable are the gobiconodontids, the triconodontid Jugulator, the deltatheroideans and Cimolestes. Many of these, such as Repenomamus and Cimolestes, were among the largest mammals in their faunal assemblages, capable of attacking dinosaurs. In the early-to-mid-Cenozoic, the dominant predator forms were mammals: hyaenodonts, entelodonts, ptolemaiidans and mesonychians, representing a great diversity of eutherian carnivores
A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, petrified wood, coal, DNA remnants; the totality of fossils is known as the fossil record. Paleontology is the study of fossils: their age, method of formation, evolutionary significance. Specimens are considered to be fossils if they are over 10,000 years old; the oldest fossils are around 3.48 billion years old to 4.1 billion years old. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils; the development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host. There are many processes that lead to fossilization, including permineralization and molds, authigenic mineralization and recrystallization, adpression and bioimmuration.
Fossils vary in size from one-micrometre bacteria to dinosaurs and trees, many meters long and weighing many tons. A fossil preserves only a portion of the deceased organism that portion, mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates. Fossils may consist of the marks left behind by the organism while it was alive, such as animal tracks or feces; these types of fossil are called trace ichnofossils, as opposed to body fossils. Some fossils are called chemofossils or biosignatures; the process of fossilization varies according to external conditions. Permineralization is a process of fossilization; the empty spaces within an organism become filled with mineral-rich groundwater. Minerals precipitate from the groundwater; this process can occur in small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce detailed fossils. For permineralization to occur, the organism must become covered by sediment soon after death, otherwise decay commences.
The degree to which the remains are decayed when covered determines the details of the fossil. Some fossils consist only of skeletal teeth; this is a form of diagenesis. In some cases, the original remains of the organism dissolve or are otherwise destroyed; the remaining organism-shaped hole in the rock is called an external mold. If this hole is filled with other minerals, it is a cast. An endocast, or internal mold, is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail or the hollow of a skull; this is a special form of mold formation. If the chemistry is right, the organism can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it. If this happens before significant decay to the organic tissue fine three-dimensional morphological detail can be preserved. Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization.
Replacement occurs. In some cases mineral replacement of the original shell occurs so and at such fine scales that microstructural features are preserved despite the total loss of original material. A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form, as from aragonite to calcite. Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case the fossil consists of original material, albeit in a geochemically altered state; this chemical change is an expression of diagenesis. What remains is a carbonaceous film known as a phytoleim, in which case the fossil is known as a compression. However, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil. In many cases, however and impressions occur together. For instance, when the rock is broken open, the phytoleim will be attached to one part, whereas the counterpart will just be an impression.
For this reason, one term covers the two modes of preservation: adpression. Because of their antiquity, an unexpected exception to the alteration of an organism's tissues by chemical reduction of the complex organic molecules during fossilization has been the discovery of soft tissue in dinosaur fossils, including blood vessels, the isolation of proteins and evidence for DNA fragments. In 2014, Mary Schweitzer and her colleagues reported the presence of iron particles associated with soft tissues recovered from dinosaur fossils. Based on various experiments that studied the interaction of iron in haemoglobin with blood vessel tissue they proposed that solution hypoxia coupled with iron chelation enhances the stability and preservation of soft tissue and provides the basis for an explanation for the unforeseen preservation of fossil soft tissues. However, a older study based on eight taxa ranging in time from the Devonian to the Jurassic found that reasonably well-preserved fibrils that represent collagen were preser
Primary nutritional groups
Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living and reproduction. The sources of energy can be organic or inorganic compounds; the terms aerobic respiration, anaerobic respiration and fermentation do not refer to primary nutritional groups, but reflect the different use of possible electron acceptors in particular organisms, such as O2 in aerobic respiration, or nitrate, sulfate or fumarate in anaerobic respiration, or various metabolic intermediates in fermentation. Because all ATP-generating steps in fermentation involve modifications of metabolic intermediates instead of the use of an electron transport chain fermentation is referred to as substrate-level phosphorylation. Phototrophs: Light is absorbed in photo receptors and transformed into chemical energy. Chemotrophs: Bond energy is released from a chemical compound; the freed energy is stored as potential energy in ATP, lipids or proteins.
The energy is used for life processes as moving and reproduction. Some bacteria can alternate chemotrophy, depending on availability of light. Organotrophs: Organic compounds are used as electron donor. Lithotrophs: Inorganic compounds are used as electron donor; the electrons from reducing equivalents are needed by both phototrophs and chemotrophs, to keep running reduction-oxidation reactions that transfer energy in the anabolic processes of ATP synthesis or biosynthesis. The electron donors are taken up from the environment. Organotrophic organisms are also heterotrophic, using organic compounds as sources of electrons and carbon at the same time. Lithotrophic organisms are also autotrophic, using inorganic sources of electrons and CO2 as inorganic carbon source; some lithotrophic bacteria can utilize diverse sources of electrons, depending on availability of possible donors. The organic or inorganic substances used as electron acceptors needed in the catabolic processes of aerobic or anaerobic respiration and fermentation are not taken into account here.
For example, plants use water as electron donor to biosynthesis. Animals use organic compounds as electron donors being organotrophs. Both use oxygen in respiration as electron acceptor, but this character is not used to define them as lithotrophs. Heterotrophs: Organic compounds are metabolized to get carbon for growth and development. Autotrophs: Carbon dioxide is used as source of carbon. A chemoorganoheterotrophic organism is one that requires organic substrates to get its carbon for growth and development, that produces its energy from the oxidation and reduction of an organic compound; this group of organisms may be further subdivided according to what kind of organic substrate and compound they use. Decomposers are examples of Chemoorganoheterotrophs which obtain carbon and electron reactions from dead organic matter. Herbivores and carnivores are examples of organisms that obtain carbon and electron reactions from living organic matter. Chemoorganotrophs are organisms which oxidize the chemical bonds in organic compounds as their energy source.
Chemoorganotrophs attain the carbon molecules that they need for cellular function from these organic compounds. The organic compounds that they oxidize include sugars and proteins. All animals are chemoheterotrophs, as are fungi and some bacteria; the important differentiation amongst this group is that chemoorganotrophs oxidize only organic compounds while chemolithotrophs instead use inorganic compounds as a source of energy. The following table gives some examples for each nutritional group: Some authors use -hydro- when the source is water; some unicellular, organisms can switch between different metabolic modes, for example between photoautotrophy, photoheterotrophy, chemoheterotrophy in Chroococcales Such mixotrophic organisms may dominate their habitat, due to their capability to use more resources than either photoautotrophic or organoheterotrophic organisms. All sorts of combinations may exist in nature. For example, most cyanobacteria are photoautotrophic, since they use light as an energy source, water as electron donor, CO2 as a carbon source.
Fungi are chemoorganotrophic since they use organic carbon as both an electron donor and carbon source. Eukaryotes are easy to categorise. All animals are heterotrophic. Plants are photoautotrophic; some eukaryotic microorganisms, are not limited to just one nutritional mode. For example, some algae live photoautotrophically in the light, but shift to chemoorganotrophy in the dark. Higher plants retained their ability to respire heterotrophically on the starch at night, synthesised phototrophically during the day. Prokaryotes show a great diversity of nutritional categories. For example, purple sulfur bacteria and cyanobacteria are photoautotrophic whereas purple non-sulfur bacteria are photoorganotrophic; some bacteria are limited to only one nutritional group, whereas others are facultative and switch from one mode to the other, depending on the nutrient sources available
Probability theory is the branch of mathematics concerned with probability. Although there are several different probability interpretations, probability theory treats the concept in a rigorous mathematical manner by expressing it through a set of axioms; these axioms formalise probability in terms of a probability space, which assigns a measure taking values between 0 and 1, termed the probability measure, to a set of outcomes called the sample space. Any specified subset of these outcomes is called an event. Central subjects in probability theory include discrete and continuous random variables, probability distributions, stochastic processes, which provide mathematical abstractions of non-deterministic or uncertain processes or measured quantities that may either be single occurrences or evolve over time in a random fashion. Although it is not possible to predict random events, much can be said about their behavior. Two major results in probability theory describing such behaviour are the law of large numbers and the central limit theorem.
As a mathematical foundation for statistics, probability theory is essential to many human activities that involve quantitative analysis of data. Methods of probability theory apply to descriptions of complex systems given only partial knowledge of their state, as in statistical mechanics. A great discovery of twentieth-century physics was the probabilistic nature of physical phenomena at atomic scales, described in quantum mechanics; the mathematical theory of probability has its roots in attempts to analyze games of chance by Gerolamo Cardano in the sixteenth century, by Pierre de Fermat and Blaise Pascal in the seventeenth century. Christiaan Huygens published a book on the subject in 1657 and in the 19th century, Pierre Laplace completed what is today considered the classic interpretation. Probability theory considered discrete events, its methods were combinatorial. Analytical considerations compelled the incorporation of continuous variables into the theory; this culminated on foundations laid by Andrey Nikolaevich Kolmogorov.
Kolmogorov combined the notion of sample space, introduced by Richard von Mises, measure theory and presented his axiom system for probability theory in 1933. This became the undisputed axiomatic basis for modern probability theory. Most introductions to probability theory treat discrete probability distributions and continuous probability distributions separately; the measure theory-based treatment of probability covers the discrete, continuous, a mix of the two, more. Consider an experiment that can produce a number of outcomes; the set of all outcomes is called the sample space of the experiment. The power set of the sample space is formed by considering all different collections of possible results. For example, rolling an honest die produces one of six possible results. One collection of possible results corresponds to getting an odd number. Thus, the subset is an element of the power set of the sample space of die rolls; these collections are called events. In this case, is the event that the die falls on some odd number.
If the results that occur fall in a given event, that event is said to have occurred. Probability is a way of assigning every "event" a value between zero and one, with the requirement that the event made up of all possible results be assigned a value of one. To qualify as a probability distribution, the assignment of values must satisfy the requirement that if you look at a collection of mutually exclusive events, the probability that any of these events occurs is given by the sum of the probabilities of the events; the probability that any one of the events, or will occur is 5/6. This is the same as saying that the probability of event is 5/6; this event encompasses the possibility of any number except five being rolled. The mutually exclusive event has a probability of 1/6, the event has a probability of 1, that is, absolute certainty; when doing calculations using the outcomes of an experiment, it is necessary that all those elementary events have a number assigned to them. This is done using a random variable.
A random variable is a function that assigns to each elementary event in the sample space a real number. This function is denoted by a capital letter. In the case of a die, the assignment of a number to a certain elementary events can be done using the identity function; this does not always work. For example, when flipping a coin the two possible outcomes are "heads" and "tails". In this example, the random variable X could assign to the outcome "heads" the number "0" and to the outcome "tails" the number "1". Discrete probability theory deals with events. Examples: Throwing dice, experiments with decks of cards, random walk, tossing coins Classical definition: Initially the probability of an event to occur was defined as the number of cases favorable for the event, over the number of total outcomes possible in an equiprobable sample space: see Classical definition of probability. For example, if the event is "occurrence of an number when a die is
In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area and in a particular time known as a biocoenosis. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization". Community ecology or synecology is the study of the interactions between species in communities on many spatial and temporal scales, including the distribution, abundance and interactions between coexisting populations; the primary focus of community ecology is on the interactions between populations as determined by specific genotypic and phenotypic characteristics. Community ecology has its origin in European plant sociology. Modern community ecology examines patterns such as variation in species richness, equitability and food web structure. On a deeper level the meaning and value of the community concept in ecology is up for debate.
Communities have traditionally been understood on a fine scale in terms of local processes constructing an assemblage of species, such as the way climate change is to affect the make-up of grass communities. This local community focus has been criticised. Robert Ricklefs has argued that it is more useful to think of communities on a regional scale, drawing on evolutionary taxonomy and biogeography, where some species or clades evolve and others go extinct. Clements developed a holistic concept of community, as it was a superorganism or discrete unit, with sharp boundaries. Gleason developed the individualistic concept of community, with the abundance of a population of a species changing along complex environmental gradients, but individually, not to other populations. In that view, it is possible that individualistic distribution of species gives rise to discrete communities as well as to continuum. Niches would not overlap. In the neutral theory view of the community, popularized by Hubbell, species are functionally equivalent, the abundance of a population of a species changes by stochastic demographic processes.
Each population would have the same adaptive value, local and regional composition would represent a balance between speciation or dispersal, random extinctions. Species interact in various ways: competition, parasitism, commensalism, etc; the organization of a biological community with respect to ecological interactions is referred to as community structure. Species can compete with each other for finite resources, it is considered to be an important limiting factor of population size and species richness. Many types of competition have been described, but proving the existence of these interactions is a matter of debate. Direct competition has been observed between individuals and species, but there is little evidence that competition has been the driving force in the evolution of large groups. Interference competition: occurs when an individual of one species directly interferes with an individual of another species. Examples include a lion chasing a hyena from a kill, or a plant releasing allelopathic chemicals to impede the growth of a competing species.
Exploitative competition: This occurs via the consumption of resources. When an individual of one species consumes a resource, that resource is no longer available to be consumed by a member of a second species. Exploitative competition is thought to be more common in nature, but care must be taken to distinguish it from apparent competition. Exploitative competition vary from complete symmetric to size symmetric to size-asymmetric; the degree of size asymmetry has major effects on the structure and diversity of ecological communities Apparent competition: occurs when two species share a predator. The populations of both species can be depressed by predation without direct exploitative competition. Predation is hunting another species for food; this is a positive–negative interaction in that the predator species benefits while the prey species is harmed. Some predators kill their prey before eating them. Other predators are parasites. Another example is the feeding on plants of herbivores. Predation may affect the population size of predators and prey and the number of species coexisting in a community.
Mutualism is an interaction between species. Examples include Rhizobium bacteria growing in nodules on the roots of legumes and insects pollinating the flowers of angiosperms. Commensalism is a type of relationship among organisms in which one organism benefits while the other organism is neither benefited nor harmed; the organism that benefited is called the commensal while the other organism, neither benefited nor harmed is called the host. For example, an epiphytic orchid attached to the tree for support benefits the orchid but neither harms nor benefits the tree; the opposite of commensalism is amensalism, an interspecific relationship in which a product of one organism has a negative effect on another organism but