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Ecology : Concepts basic
All living things have a way of living that depends on their structure and physiology and also on the type of environment in which they live, so that physical and biological factors combine to form a great variety of environments in different parts of the biosphere. Thus, the life of a living being is closely adjusted to the physical conditions of its environment and also to the biotic ones, that is, to the life of its fellow beings and of all the other classes of organisms that make up the community of which it is a part. (one)
The more that is learned about any kind of plant or animal, it becomes increasingly clear that each species has undergone adaptations to survive in a particular set of environmental circumstances. Each can demonstrate adaptations to wind, sun, humidity, temperature, salinity, and other aspects of the physical environment, as well as adaptations to specific plants and animals living in the same region. (2)
It deals with the scientific study of the interrelationships between organisms and their environments, and therefore with the physical and biological factors that influence these relationships and are influenced by them. But the relationships between organisms and their environments are nothing but the result of natural selection, from which it follows that all ecological phenomena have an evolutionary explanation.
Throughout the more than 3 billion years of evolution, competition, engendered by reproduction and limited natural resources, has produced different ways of life that have minimized the struggle for food, living space, shelter and shelter. couple. (1)
We can also define the term ecology as the study of the mutual relationships of organisms with their physical and biotic environment. This term is now much more in the public consciousness because human beings are beginning to become aware of some bad ecological practices of humanity in the past and today. It is important that we all know and appreciate the principles of this aspect of biology, so that we can form an intelligent opinion on topics such as contamination with insecticides, detergents, mercury, waste disposal, dams for electric power generation, and their defects on the humanity, about human civilization and about the world we live in.
The Greek word oikos means "house" or "place to live", and ecology (oikos logos) is literally the study of organisms "at home", in their native environment. The term was proposed by the German biologist Ernst Haeckel in 1869, but many of the concepts in ecology predate the term by a century or more. Ecology deals with the biology of groups of organisms and their relationships with the environment. The term autoecology refers to studies of individual organisms, or populations of isolated species, and their relationships with the environment. The contrasting term, synecology, designates studies of groups of associated organisms forming a functional unit of the environment. Groups of organisms can be associated with three levels of organization: populations, communities and ecosystems. In ecological use, a population is a group of individuals of any kind of organism, a group of individuals of a single species. A community in the ecological sense, a biotic community comprises all the populations that occupy a defined physical area. The community, together with the non-living physical environment, comprises an ecosystem. Thus, synecology is interested in the many relationships between communities and ecosystems. The ecologist studies issues such as who lives in the shadow of whom, who eats whom, who plays a role in the spread and dispersal of whom, and how energy flows from one individual to the next in a food chain. The ecologist tries to define and analyze those characteristics of populations other than the characteristics of individuals and the factors that determine the grouping of populations in communities. (2)
Trophic levels and food chains
All plants compete for sunlight, soil minerals and water, but the needs of animals are more diverse and many of them depend on a certain type of food. Plant-eating animals are the primary consumers of all communities; in turn, they serve as food for other animals, secondary consumers that are also consumed by others; thus, various feeding levels or trophic levels can be recognized in a living system. The producers they are autotrophic organisms and especially green plants, which occupy the first trophic level; herbivores or primary consumers occupy the second level, and so on. The death of both plants and animals, as well as the waste products of digestion, give life to the decomposers or blasters, heterotrophs that feed on dead or decomposing organic matter from producers and consumers, which are primarily bacteria and fungi. So the energy originally from the sun passes through a power network. Power networks are typically made up of many interlocking power chains, representing single pathways to the network. Any network or power chain is essentially an energy transfer system. The many chains and their interconnections help prey and predator populations adjust to environmental changes and thus provide some stability to the system.
Biomass and energy
The food web of any community can also be conceived as a pyramid in which each one of the steps is smaller than the previous one, from which it feeds. At the base are the producers, who feed on the minerals in the soil, partly from the activity of decomposing organisms, and then the different levels of primary, secondary, tertiary consumers, etc. Primary consumers are small and plentiful, while the larger prey animals at the top are relatively so rare that they are no longer useful prey for other animals.
Biomass is the total amount of living matter, at a given time, in a given area or at one of its trophic levels, and is expressed in grams of carbon, or in calories, per unit area. Biomass pyramids are very useful to show biomass at a trophic level. The increase in biomass in a given period is called the production of a system or a given area.
The transfer of energy from one trophic level to another is not totally efficient.
Producers spend energy to breathe, and each consumer in the chain spends energy obtaining food, metabolizing it and maintaining their vital activities. This explains why food chains have no more than four or five members: there is not enough energy above the predators at the top of the pyramid to maintain another trophic level.
Ecologists use the term ecosystem to indicate a natural unit of living or inert parts, with mutual interactions to produce a stable system in which the exchange of substances between living and inert plants is circular. An ecosystem can be as large as the ocean or a forest, or one of the cycles of the elements, or as small as an aquarium containing tropical fish, green plants, and snails. To qualify as an ecosystem, the unit must be a stable system, where the exchange of materials follows a circular path.
A classic example of an ecosystem compact enough to be investigated in quantitative detail is a pond or pond. The non-living part of the lake includes water, dissolved oxygen, carbon dioxide, inorganic salts such as sodium, potassium, and calcium phosphates and chlorides, and many organic compounds. Living organisms can be subdivided into producers, consumers and disintegrators according to their role, helping to conserve the ecosystem as a stable whole of mutual interaction. First, there are organisms producers; like green plants that can make organic compounds from simple inorganic substances by photosynthesis. In a lake, there are two types of producers: the larger plants that grow on the shore or float in shallow water, and the microscopic floating plants, mostly algae, that are distributed throughout the liquid, up to the maximum depth reached. by the light. These small plants, which are collectively referred to as phytoplankton, are rarely visible, except in large numbers, in which case they impart a greenish tint to the water. They tend to be far more important as producers of food for the lake than visible plants.
Organisms consumers they are heterotrophs, eg insects and their larvae, crustaceans, fish, and perhaps some freshwater bivalves. The primary consumers are those who ingest plants; the secondary ones, the carnivores that feed on the primary ones, and so on. There could be some tertiary consumers who ate the carnivorous secondary consumers.
The ecosystem is completed with organisms decomposers, bacteria and fungi, which break down the organic compounds of cells from the dead producer and consuming organisms into small organic molecules, which they use as saprophytes, or into inorganic substances that can be used as raw material by green plants. Even the largest and most complete ecosystem can be shown to be made up of the same components: producing, consuming, and disintegrating organisms, and inorganic components.The structuring of an ecosystem consists of the biocenosis or set of living organisms in an ecosystem, and the biotope or environment in which these organisms live.
Habitat and ecological niche
In writing the ecological relationships of organisms, it is useful to distinguish between where an organism lives and what it does as part of its ecosystem. Two fundamental concepts useful for describing the ecological relationships of organisms are habitat and ecological niche.
The habitat of an organism is the place where it lives, its physical area, some specific part of the surface of the earth, air, soil and water. It can be very vast, like the ocean, or large continental areas, or very small, and limited, for example, to the bottom of a rotten log, but it is always a physically well-defined region. Several animals or plants can live in a particular habitat.
On the other hand the ecological niche it is the state or role of an organism in the community or ecosystem. It depends on the structural adaptations of the organism, its physiological responses and its behavior. It can be useful to consider the habitat as the address of an organism (where it lives) and the ecological niche as its profession (what it does biologically). The ecological niche is not a physically demarcated space, but an abstraction that includes all the physical, chemical, physiological and biotic factors that an organism needs to live.
To describe the ecological niche of an organism it is necessary to know what it eats and what eats it, what are its limits of movement and its effects on other organisms and on non-living parts of the environment. One of the important generalizations of ecology is that two species cannot occupy the same ecological niche.
A single species can occupy different niches in different regions, depending on factors such as the food available and the number of competitors. Some organisms, for example animals with different phases in their life cycle, successively occupy different niches.
A tadpole is a primary consumer, feeding on plants, but the adult frog is a secondary consumer, digesting insects and other animals. In contrast, young river turtles are secondary consumers, eating snails, worms, and insects, while adult turtles are primary consumers, feeding on green plants like aquatic celery.
Food and trophic webs
It is estimated that the rate of use of resources in terrestrial ecosystems is a maximum of 10%, so the number of links in a food chain must, by necessity, be short.
However, a field study and a deeper knowledge of the different species will reveal that this trophic chain is only a working hypothesis and that, at most, it expresses a predominant type of relationship between several species of the same ecosystem.
The reality is that each of the links maintains relationships with other species belonging to different chains. It is like an electrical conduction cable, which to the distant observer will seem like a unit, but when we get closer we will see that this cable in turn consists of other smaller conductors, which are not a solid unit either.
Each of these conductors will be made up of small copper filaments and those who conduct electricity are actually the tiny units that we know as electrons, components of the atoms that make up the element copper. But it is necessary to highlight a fundamental difference: in the cable all the successive subunits go in the same direction, but in the food chain each link communicates with others that are often located in different directions. The grass not only feeds the sheep, but also the rabbit and the mouse, which will be preyed upon by an eagle and an owl, respectively. The sheep does not have the wolf as its only enemy, even if it is the main one.
The eagle will try to get hold of its reeds and, if there is a lynx in the territory, it will compete with the wolf, which in case of difficulty will not hesitate to also feed on rabbits. In this way, the original chain has brought to light the existence of other lateral ones and between all have formed a dense tangle of interspecific relationships.
This is what is known by the name of trophic web.The network gives a vision closer to reality than the simple chain. It shows us that each species maintains relationships of different types with other elements of the ecosystem: the plant does not grow in a single field, although in certain soils it thrives with special vigor.
Also, in general, the herbivore does not feed on a single plant species and it is not usually the exclusive component of the carnivore's diet. The food web, contemplating a single but important aspect of the relationships between organisms, shows us how important each link is to form the global set of the ecosystem.
The productivity it is a characteristic of populations that also serves as an important index to define the functioning of any ecosystem. Its study can be done at the species level, when its economic use is of interest, or of an environment in general.
Plants, as autotrophic organisms, have the ability to synthesize their own body mass from the elements and inorganic compounds of the environment, in the presence of water as a vehicle for reactions and with the intervention of sunlight as an energy supply for them.
The result of this activity, that is, plant tissues, constitute primary production. Later, the animals eat the plants and take advantage of these organic compounds to create their own body structure, which in some circumstances will also serve as food for other animals.
That is secondary production. In both cases, the ratio between the amount of nutrients entered and the biomass produced will give us the so-called productivity, which measures the efficiency with which an organism can take advantage of its trophic resources. But the set of organisms and the physical environment in which they live make up the ecosystem, so the productivity applied to all of them will help us to obtain a parameter with which to measure the functioning of said ecosystem and to know the way in which the Energy flows through the various levels of your organization.
Productivity is one of the most used parameters to measure the efficiency of an ecosystem, which is generally calculated as the quotient between an output variable and an input variable. Productivity is developed in two main environments, aquatic and terrestrial communities.
At the unicellular level, both in animal and plant organisms, the relationships between the different individuals present in a given environment are mainly conditioned by physical and chemical factors.
As their habitat is generally water, where they are usually part of plankton, the rapid multiplication of these organisms can sometimes cause an excessive amount of metabolic waste in reduced environments or a total depletion of dissolved oxygen that causes their death. The relationship between each unicellular organism is mediated by the common environment that they share, into which they discharge their metabolites and from which they receive those of other organisms.
In the case of organisms of greater biological entity, of multicellular forms, any relationship between individuals of the same species always has a component of cooperation and another of competition, with one or the other predominating in extreme cases. Thus, in a colony of polyps, cooperation is total, while animals with solitary habits, like most shrews, hardly allow the presence of congeners in their territory outside the reproductive season.
The colony is a type of relationship that implies close functional collaboration and even transfer of one's own individuality. The corals of a reef specialize in various functions: there are individuals with stinging organs that defend the colony, while others are responsible for obtaining food and others for reproduction. This type of association is very frequent also in plants, especially the lower ones. In the higher plants, due to the inability to move, formations arise in which the whole creates suitable conditions for each individual, so there is ecological cooperation, while competition for space occurs, preventing the specimens of Larger seedlings grow from their own seeds.
In the animal kingdom we find societies, such as those of ants or bees, with a strict division of labor. In all these cases, the grouping follows an automatic instinctual tendency. As we move up the zoological scale, we find that, in addition to this mechanical component of grouping, relationships emerge in which the behavior or the ethology of the species play an increasing role. Schools of fish are a prime example. In large colonies of many birds (flamingos, seagulls, penguins, etc.), relationships between individuals are ritualized to prevent harmful competition.
Something similar happens in herds of mammals. Family groups that regulate intraspecific relationships appear among many carnivores and, to a maximum degree among primates, and in this case factors such as the learning of the offspring, the recognition of the individuals themselves and other aspects studied by ethology pass to occupy a foreground.
In this case, the interest in food or space prevails, although in many cases, to achieve some ends, commitments are used that are manifested in associations of the type of symbiosis.
This broad section includes all those direct or indirect relationships between individuals of different species and that are studied in other sections. Among them we have parasitism and predation, necrophagy or the use of other organisms to obtain protection, place to live, food, transport, etc. The importance of these relationships is that they often establish energy flows within trophic networks and therefore contribute to the structuring of the ecosystem. The relationships in which plant organisms intervene are more static than those of animals, but both are the result of the evolution of the environment, on which, in turn, the species act, even modifying it, by virtue of the relationships they maintain. between them.
Populations and their characteristics
Population can be defined as a group of organisms of the same species that occupy a given area. It has characteristics, a function rather of the group as a whole than of each individual, such as population density, frequency of births and deaths, age distribution, rate of dispersal, biotic potential and growth pattern. Although individuals are born and die, the birth and death rates are not characteristic of the individual but of the global population. Modern ecology is especially about communities and populations; the study of community organization is a particularly active field today. Population-community relationships are often more important in determining the existence and survival of organisms in nature than the direct effects of physical factors on the environment.
One of its important attributes is density, that is, the number of individuals that inhabit a unit of surface or volume.
Population density is often difficult to measure based on the number of individuals, but it is calculated by indirect measurements such as insects trapped for an hour in a trap.
The graph in which the number of organisms is inscribed as a function of time is called population growth curve.
Such curves are characteristic of populations, not isolated species, and their similarity between the populations of almost all organisms from bacteria to man is surprising.The birth rate, or birth rate, of a population is simply the number of new individuals produced per unit of time.
The peak birth rate it is the largest number of organisms that could be produced per unit of time under ideal conditions, when there are no limiting factors.
Mortality refers to individuals who die per unit of time. There is a minimal mortality theoretical, which is the number of deaths that would occur under ideal conditions, exclusively due to the physiological alterations that accompany aging.
Arranging in graph the number of survivors of a population against time, we obtain the survival curve. From these curves it is possible to deduce when a particular species is most vulnerable. As mortality is more variable and more affected by environmental factors than by birth rates, these have an enormous influence on the regularization of the number of individuals in a population.
Ecologists use the term biotic potential or reproductive potential to express the exclusive ability of a population to increase the number, when the proportion of ages is stable and the environmental conditions are optimal. When the environment is less than optimal, the rate of population growth is slower, and the difference between the potential capacity of a population to grow and what actually grows is a measure of the resilience of the environment.
Food chains and pyramids
The number of organisms of each species is determined by the speed of energy flow through the biological part of the ecosystem that includes them.
The transfer of food energy from its origin in plants through a succession of organisms, each of which devours the one that precedes it and is eaten in turn by the one that follows it, is called food chain. The number of links in the chain should be limited to no more than four or five, precisely because of the great degradation of energy in each one. The percentage of food energy consumed that is converted to new cellular material is the effective percentage of energy transfer.
The flow of energy in ecosystems, coming from sunlight through photosynthesis in autotrophic producers, and through the tissues of herbivores as primary consumers, and of carnivores as secondary consumers, determines the total weight and number (biomes) of organisms at each level of the ecosystem. This flow of energy decreases markedly in each successive step of nutrition due to heat loss in each energy transformation, which in turn decreases the biomes in each step.
Some animals eat only one kind of food, and therefore are members of a single food chain. Other animals eat many kinds of food and are not only members of different food chains, but they can occupy different positions in different food chains.
An animal can be a primary consumer in one chain, eating green plants, but a secondary or tertiary consumer in other chains, eating herbivorous animals or other carnivores.
Man is the end of various food chains; For example, eat large fish that other small fish ate, which fed on invertebrates that in turn fed on algae. The final magnitude of the human population (or the population of any animal) is limited by the length of our food chain, the percentage of energy transfer efficiency at each link in the chain, and the amount of light energy that falls on Earth. .
Man can do nothing to increase the amount of incident light energy, and very little to increase the percentage of energy transfer efficiency, so he can only increase the energy supply of food, shortening the food chain, that is, consuming primary producers, vegetables and non-animals. In overpopulated countries such as China and India, the natives are mainly vegetarians because the food chain is thus shorter and a given area of land can thus support the largest number of individuals.
A biotic community is the set of populations that live in a defined habitat or area that can be large or small. The interactions of the various types of organisms preserve the structure and function of the community and provide the basis for the ecological regularization of the succession in the community. The concept that animals and plants live together, in a harmonious and orderly arrangement, not randomly scattered on the surface of the Earth, is one of the important principles of ecology.
Although a community can encompass hundreds of thousands of plant and animal species, many are relatively unimportant, so that only some, due to their size and activities, are decisive in the life of the whole. In terrestrial communities, the dominant species are usually plants because they provide food and offer shelter to many other species; As a result, some communities are named for their dominant plants, such as mugwort, oak, pine, and others. Aquatic communities that do not contain large conspicuous plants are generally distinguished by some physical characteristic: fast-flowing community, flat-mud community, and sandy beach community.
In ecological research it is unnecessary to consider all the species present in a community. Typically, a study of the major plants that control the community, the larger populations of animals, and the fundamental energy relationships (food chains) in the system will define the ecological relationships in the community. For example, studying a lake would first investigate the classes, distribution, and abundance of important bearer plants and the physical and chemical factors in the environment that might be limiting. Then, the reproduction rates, mortality rates, age distributions and other population characteristics of the fish important to the fishery would be determined. A study of the classes, distribution and abundance of primary and secondary consumers of the lake, which constitute the food of fishing fish, and the nature of other organisms that compete with these fish for food, would clarify the basic food chains of the lake. Quantitative studies of these would reveal the basic energetic relationships of the system and show how efficiently the incident light energy is being converted into the desired end product, the fish meat. Based on this knowledge, the lake could be intelligently managed to increase fish production.
The ecologist's mission
In both rural and urban areas there are many tasks that the ecologist must carry out at present. Its fundamental mission, from a practical point of view, can be summed up in a single word: prevent. Any irrational action that occurs in the biological environment brings true consequences chain reactions. The ecologist's advice must come before and not after, because once the destructive process of the environment has started, it is very difficult to stop it. The second mission of the ecologist is to conserve, which not only implies avoiding destruction but also favoring, sometimes artificially, populations whose existence is in danger.
Biomes or life zones
El bioma es una zona de vida dentro del globo terrestre o más precisamente un tipo principal de hábitat en el que la vegetación dominante comprende algunos tipos característicos que reflejan las tolerancias del ambiente y a la que se vinculan determinadas comunidades animales.
Es lógico que encontremos biomas acuáticos y continentales. Los primeros podrán subdividirse a su vez en lacustres o palustres (correspondientes a las lagunas y lagos), fluviales (ríos) y marinos (mares y océanos). En tierra firme podemos reconocer biomas específicos al bosque, la tundra, el desierto, la pradera, la estepa y la selva. La biogeografía es una ciencia de síntesis, derivada de la geografía y vinculada estrechamente a la biología, que intenta describir y explicar la distribución de los seres animados en la Tierra. Aunque la comunidad biológica es indivisible, se ha subdividido el campo de esta ciencia en dos grandes ramas: fitogeografía, que trata sobre la distribución de los vegetales, y zoogeografía, de los animales. Decimos que esta disciplina es sintética porque parte de datos analíticos que le brindan otras especialidades, tales como la botánica, la ecología, la zoología, la geografía física, la edafología y la climatología. A partir de este gran cúmulo de información se hace indispensable el rescate, entre los casos particulares, de las leyes básicas de la distribución biológica.
Existen distintos tipos de biomas, tanto terrestres como acuáticos. Entre los biomas terrestres podemos distinguir: la tundra, la taiga, el bosque templado, la pradera, el bosque esclerófilo, el desierto y el bosque tropical lluvioso.
La ecología es la ciencia que estudia a los organismos en su propio hábitat, y las relaciones que mantienen a los seres vivos con su entorno. Actualmente la ecología se encarga de preservar la naturaleza y las especies en extinción.
Los niveles tróficos son aquellos que dividen una cadena alimentaria en: productores, consumidores y descomponedores. Una cadena alimentaria es la transferencia de energía alimenticia a través de una sucesión de organismos que producen, consumen, y a su vez son consumidos por otros.
La biomasa es la cantidad total de materia viviente en un momento dado y en un área determinada.
Un ecosistema es un sistema estable de tipo circular en el cual existe una constante interrelación entre organismos vivos e inertes. Los componentes de un ecosistema son los productores, consumidores y descomponedores. Y su estructuración consta de el biótopo y la biocenosis.
La diferencia entre hábitat y nicho ecológico es que el hábitat es el lugar en donde vive un organismo (domicilio), y el nicho ecológico es el papel que desempeña en él (profesión).
Una red trófica es un conjunto de relaciones interespecíficas que forman parte de la cadena alimentaria o trófica.
Una población es un conjunto de individuos de la misma especie que ocupan un determinado lugar, y comunidad es un conjunto de individuos de distinta especie que ocupan un determinado territorio.
El potencial biótico se refiere a la capacidad de una población de aumentar en número.
Los distintos biomas terrestres son: tundra, taiga, bosque templado, pradera, bosque esclerófilo, desierto y bosque tropical lluvioso.
CULTURAL, S.A. Atlas de la Ecología Editorial THEMA España 1996 112 pp.
VILLEE, C. Biología 7° edición Mc Graw-Hill Interamericana México 1995 875 ppCUERDA, J. Atlas de Biología Editorial THEMA Colombia 1994 93 pp.
COSITORTO, A. Enciclopedia de Ciencias Naturales Medio Ambiente y Ecología Editorial Oriente S.A. España 1995 Tomo 3 313 pp.1.
THÉRON, A ; VALLIN, J. Ecología de las Ciencias Naturales Editorial Hora S.A. España 1987 133 pp.