Ecology is the study of how organisms interact with one another and with their environment. Environment can be split into two components; the living portion, termed the biotic component (e.g., organisms), and the nonliving portion, termed the abiotic component (e.g., air, soil, water, etc.). Ecologists organize the biosphere into several levels. A population is a group of individuals of the same species occupying a common geographic area. A community is formed when two or more populations reside in the same geographic location. An ecosystem is comprised of a community and its surrounding abiotic factors. A biome is a collection of ecosystems with similar climates and communities. Energy Flow Food webs describe the flow of energy within an ecosystem by linking together several food chains. Each food chain begins with an organism that uses energy from light or chemical reactions to produce organic compounds from inorganic compounds through photosynthesis or chemosynthesis, called an autotroph (also referred to as a producer). Any organism that can't produce its own organic compounds and must consume other organisms to obtain them is called a heterotroph (also referred to as a consumer). Heterotrophs can be further organized based on what they consume: Herbivore-a heterotroph that only consumes plants Carnivore-a heterotroph that only consumes animals Omnivore-a heterotroph that consumes both plants and animals Detritivore-a heterotroph that consumes detritus (dead and decaying organic matter) Decomposer-a heterotroph that breaks down dead and decaying organic matter using biochemical reactions Note that as opposed to detritivores, decomposers break down dead and decaying organic matter using biochemical reactions without ingesting it. Each "step" in a food chain is called a trophic level. For example, autotrophs comprise the first trophic level of a certain food chain, the heterotrophs that consume those autotrophs make up the second trophic level, and so on. Within each food chain, only about 10% of the amount of energy that is initially available to one trophic level is available to the organisms in the next trophic level. Biogeochemical Cycles A biogeochemical cycle is a description of the pathways a chemical substance takes to recycle itself. Some of the most important biogeochemical cycles are depicted in the table below. Cycle Description Picture Hydrologic Cycle The cyclic movement of water between Earth's hydrosphere, atmosphere, cryosphere, biosphere, and lithosphere. Click on the diagram to the right for a better view of it. Usgs water cycle.jpg Carbon Cycle The cyclic movement of carbon in different chemical forms from the environment to organisms then back to the environment. Ccycle.jpg Nitrogen Cycle The cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment. Ncycle.jpg Phosphorus Cycle The cycle that involves the uptake of phosphorus by organisms. Phosphorus in the environment is mainly found in rocks, but natural weathering processes can make it available to biological systems. Phosphorus is an essential nutrient for plants and animals in the form of the ions PO43- and HPO42- . (phosphate ion, hydrogen phosphate ion, respectively) It is a constituent of DNA-molecules and RNA-molecules, which store energy,(in the form of ATP and ADP) and of fats of cell membranes. (lipids) Pcycle.jpg Community Interactions Table of community interactions Within a community, species will interact in multiple different ways. The term symbiosis is usually defined as the interaction between two or more species. There are many different types of symbiosis which are defined by whether or not the interaction is beneficial, detrimental, or without effect to the species in the interaction, and they are described below; Commensalism-an interaction which is beneficial to one species, but has no effect on the other species Amensalism-an interaction that is detrimental to one species, but has no effect on the other species Antagonism-an interaction that is beneficial to one species, but detrimental to the other species Predation-a form of antagonism in which a predator feeds on its prey, and the prey is killed in the process Parasitism-a form of antagonism in which a parasite feeds on its host, but the host is not usually killed Mutualism-an interaction that is beneficial to both species Competition-an interaction that is detrimental to both species (described in more detail below) In addition, two species that don't have an effect on each other are referred to as neutral. Competition As described above, competition is an interaction that is detrimental to both species. Competition can be described as intraspecific (among individuals of the same species) or interspecific (between different species). Competition occurs when two or more species occupy the same niche. A niche is the conditions in which an organism lives and the way the organism uses those conditions (such as how they utilize a resource), and is sometimes described as the functional role of an organism in a community. According to the competitive exclusion principle, no two species that occupy the same niche can coexist indefinitely; eventually one species will always reign dominant and lead to the eventual extinction of the other. This can be avoided by the organisms undergoing a shift towards different niches. Human Impact: Aquatic Issues, Air Quality Issues, and Climate Change There are many visible human impacts on the environment. However, not all of them are easy to see, and there are many different ways that humans can negatively affect the world around them. Aquatic Environment About 40% of all humans live within 100 km of a coastline, so humans have a large impact on aquatic environments. Dead Zones A "dead zone" occurs when the aquatic environment is very low on dissolved oxygen. This often happens because of an algal bloom. This happens when eutrophication of a body of water (excess input of nutrients) allows algae on the surface of the body of water to proliferate quickly, forming large algal populations. This algae at the surface can reduce the amount of sunlight reaching aquatic plants, which hampers photosynthesis (sometimes completely), resulting in decreased levels of dissolved oxygen. Additionally, as algae from the initial eutrophication begin to die, the dead biomass will be decomposed by aerobic (oxygen-requiring) bacteria, further depleting the water of dissolved oxygen. Many aquatic organisms depend on oxygen to survive, so with low concentrations of oxygen, organisms will die out or leave for other areas with higher oxygen levels. This creates a dead zone with very little aquatic life. The state of having low oxygen levels is known as hypoxia. The state of almost no dissolved oxygen is known as anoxia. Air Quality The release of greenhouse gases into the air affects the quality of the air we breathe, since certain particulates can cause discomfort or even diseases. Acid Rain Also see Ecology#Acid Rain. Acid rain is the effect that occurs when greenhouse gases, primarily sulfur dioxide and nitrous oxides, are dissolved into water droplets in the air. This leads to a high concentration of hydrogen ions in the rain, which in turn results in an acidic solution (pH of usually 5 or 6). Climate Change Please see Ecology#Global Warming and Meteorology/Climate#Greenhouse Gases for more information. Climate Change is defined as the change in weather patterns over an extended period of time. Factors that can determine and affect climate are called forcing mechanisms. Forcing mechanisms can be further classified as either internal or external. In Green Generation, the greatest emphasis is on external forcing mechanisms, primarily human influences. Solutions and Sustainability Sustainability has many different definitions, but most of them refer to a system's ability to be productive over an extended period of time. Such a concept can be difficult to achieve in practice, but there are solutions available to help improve a system's sustainability. Bioremediation Bioremediation is the use of biological organisms to clean up an environment. Generally the term refers to the use of microbes to decontaminate a polluted area, but the term can apply to plants and fungi as well. Renewable Energy Please see Wind Power#Alternative Energy for more information. Renewable energy comes from resources that can be renewed relatively quickly, such as wind or vegetation. The use of renewable energy can prevent ecological damage if a resource is only utilized under a sustainable yield. Resources can be divided into three classifications based on how promptly they are renewed: Perpetual-resource is continuously and instantaneously renewed on a human timescale (e.g., solar energy, wind, etc.) Renewable-although not instantaneously, resource is renewed on a human timescale (e.g., vegetation, etc.) Nonrenewable-resource is in a fixed supply on a human timescale; take a very long time to be renewed (e.g., coal, oil, etc.) Everyday Solutions People can contribute to sustainability by doing some very simple things on an everyday basis. Some everyday solutions include: Buy produce locally Walk or bike rather than drive a personal vehicle Limit use of plastic Recycle materials when needed Use efficient light, water, and insulation fixtures Terrestrial Issues and Population Growth Issues Population Growth People are organisms, and like any organism, they need resources to live. However, humans are unique in that we have built a large, organized civilization with advanced infrastructure, which takes up significantly more resources than other beings whose main concerns are survival and procreation. As the human population continues skyrocketing past 7 billion, there are several ways this can affect the environment Rise in Carbon Emissions - the current human population is based around non-renewable energy sources that release greenhouse gases when burned. Until humans make a commitment to renewable energy sources, the release of gases will only increase with more population. In addition, the greater the population, the faster these resources will run out Destruction of Habitat - As humans continue building, they have to develop undeveloped areas, which destroys the habitats of that area. Deforestation is a common issue (more on deforestation below), and ocean habitats are also affected due to the large concentration of people living along coastlines. Pesticides and Fertilizers - People need food to live, so farmers are key to sustaining the human population. Unfortunately, most farmers use pesticides that can seep into the soil, polluting it, and can run off into nearby waterways, which pollutes the water for ecosystems downstream. Terrestrial Environment Due to the wide variety of environments people live in, there are several different impacts humans have had on terrestrial environments. Deforestation Deforestation is the destruction of forest environments for wood or human development. Deforestation results in a loss of habitat for many species, therefore hurting biodiversity. The loss of photosynthesis results in less buffering of carbon dioxide levels. A method of clearing forests for agriculture called slash-and-burn involves the burning of vegetation and releases a massive amount of carbon into the atmosphere. Deforestation can drive desertification, as described in more detail below. Desertification Desertification is a type of deterioration of land in which a relatively dry region becomes more and more arid. The primary cause of desertification is the removal of vegetation, which may occur as a result of several factors, such as drought and human activities. The removal of vegetation makes soil more susceptible to erosion. After the topsoil is eroded, infertile soil layers are left to harden into caliche, which hinders further plant growth. The removal of vegetation also results in less evapotranspiration, and therefore even drier conditions. Many different countermeasures are used to prevent and combat desertification, such as reforestation. Reforestation of certain plants can help enrich the soil and restore its fertility. Reforestation also occurs in the form of windbreaks and woodlots. Windbreaks are rows of trees planted in a way as to provide shelter from the wind, and can help reduce soil erosion and evapotranspiration. Woodlots are like forests, but are generally distinguished by being too small for full-scale commercial harvesting.
