ECOSYSTEM
Definition: The living community of plants and animals in any area together with the nonliving components of the environment soil, air, and water constitute the ecosystem
Ecosystems include all the living things (plants, animals, and organisms) and non-living things in a given area.
The interaction of living organisms and nonliving environments (sun, soil, and air) produces a stable self-sustained system which is called the ecosystem.
An ecosystem can be defined as a natural self-supported system in which there is proper interaction between living organisms and their nonliving environment.
Ecosystems may be natural ecosystems like forests, lakes, deserts, grasslands, ponds, etc., while examples of man-made ecosystems are aquariums, crop fields, etc.
The Structural Components
Abiotic Component
The major abiotic parts of an ecosystem typically include soil, atmosphere, solar energy (heat and light from the sun), and water. Each of these plays an important role in maintaining the balance in the ecosystem as discussed here:
(i) The soil: Soil is a critical part of an ecosystem. It provides important nutrients and anchors the plants. It absorbs and holds the water for plants and animals and is home to numerous (many) living organisms.
(ii) The atmosphere: It provides water, oxygen, and CO2, for plants and animals in an ecosystem.
(iii) solar energy: The heat and light from the sun i.e. solar energy plays an important role in an ecosystem. While heat contributes to the hydrologic cycle (through evaporation of water) and warmth (state of being warm), light is crucial for photosynthesis.
(iv) The water: Without water, there would be no life. In addition to being an important part of cells, water is also used by plants to carry and distribute the nutrients they need to survive.
Biotic Component
The biotic component comprising living organisms in an ecosystem can be divided into three categories such as;
(i) Producers (ii) Consumers & (iii) Decomposers.
These are the functional groups of an ecosystem and are known as Trophic categories. Together, these groups produce food, pass it along the food chain, and return the end products as starting materials to the abiotic component of the ecosystem.
(i) Producers (autotrophs):
Most producers are green plants and algae, which directly utilize light energy to convert CO, and water to the simplest carbohydrates called glucose and release oxygen as a byproduct. This process is called Photosynthesis.
The producers produce the complex molecules from glucose and mineral nutrients such as Nitrogen, Phosphorus, Potassium and Sulfur which are absorbed from the soil or water. Such complex molecules are essential (necessary) to sustain (support or keep going) life. Hence, producers are also known as autotrophic (self nourishing) organisms.
Interestingly, some bacteria are able to use the energy in some inorganic chemicals to form organic matter from CO, and water. This process is called chemosynthesis. Such organisms are also producers.
All other organisms in an ecosystem get the energy and nutrients they need by feeding on producers. Thus, producers are the building blocks of every ecosystem.
(ii) Consumers:
Organisms feeding on producers are consumers. Consumers are Heterotrophic (nourish on others) organisms which include microscopic bacteria to blue whales
To understand ecosystem structure, consumers are divided into various subgroups according to their food source (figure 2.6) as,
Herbivores are animals that feed directly on plants or algae. e.g. COW
Carnivorous animals that feed on other animals, birds that feed on insects are carnivores, and so are hawks that feed on birds.
Omnivores are animals that feed both on plants and animals, e.g. humans.
(iii) Decomposers and Detritivores:
Photosynthetic bacteria and fungi, including mushrooms, are Decomposers that carry out decomposition. Decomposition is a process of breaking down dead organic matter, including animal waste into stable end products.
Detritivores are organisms that feed on the decomposing particles of organic matter (detritus). Earthworms and some beetles, termites, and maggots (warm like fly larvae) are all terrestrial (land-based) Detritivores.
This category of organisms performs a very valuable service by releasing inorganic substances that are taken up by producers once again and thus helps in completing the nutrient cycle. The biotic components of an ecosystem along with energy flow
Functions Component of Ecosystem
Food chain
Food Web
Biogeochemical Cycles
1. Food Chain
The sequence (connected in series) of food utilization starting with biomass produced (synthesized combination of parts) by photosynthetic producers is called the food chain. In a food chain each organism eats smaller organisms and is eaten up by the larger one. At the base of the chain there is always a green plant or other autotroph (the producer or first trophic level)
One of the simplest examples of the food chain is the one in which biomass is produced by unicellular algae in a lake and consumed by small aquatic organisms, which are eaten by small fish which are eaten, in turn, by large fish. Finally, an eagle, at the top of the food chain, may consume the large fish
The Trophic Levels:
The trophic level refers to the level of consumption in a food chain.
As shown by the example, (algae eagle) there are several levels of consumption in a food chain called trophic levels. The food chain consists of four trophic levels, namely,
Producers-First Level
Primary consumers (herbivores)-Second Level
Secondary consumers-Third Level
Tertiary consumers-Fourth Level
(sometimes called top carnivores)
How have humans affected the food chain ?
Historically humans have been affecting the food chain either by harming or by removing the link in the food chain.
For example, when we spray pesticides to kill the mosquitoes, we put the food chain in danger. Breaking one link in the chain means all of the organisms above the link are in threat of extinction (no longer existing). Similarly by hunting animals, nearly to extinction, everything above the animal in the food chain is put in danger. A chain reaction in the food chain can be risky. Since the food chain provides energy that all living things must have, in order to survive, it is (imperative) necessary that we protect it.
2. The Food Web
An ecosystem consists of many food chains which are interconnected. The food web is a complex network of interconnected food chains (each starting from the same point) as shown in Fig. 2.9 In this example, grass is eaten by three different consumers (grasshopper, rabbit and mouse) each starting a food chain of its own.
The food web shows how eaters, the eaten, and the decomposed are connected to one another. It is a map of life's interdependence. The food web provides more than one alternatives of food to most of the organisms in an ecosystem and therefore increases their chance of survival
3. BioGeoChemical Cycles
All organisms are made up of basic elements such as carbon, nitrogen. phosphorous, sulfur, oxygen and hydrogen. These elements are continuously cycled between air, water, soil, rock and living organisms ie the four spheres (atmosphere, hydrosphere, lithosphere and biosphere) Biogeochemical cycles (life earth chemical cycles), are the pathways describing the movement of these basic elements through the four spheres of environment. These cycles driven directly or indirectly by incoming solar energy and gravity are
Water or Hydrologic cycle
Oxygen cycle
Carbon cycle
Phosphorus cycle
Nitrogen cycle
Sulfur cycle
The Earth's chemical cycles connect past, present and future forms of life. Some of the carbon atoms in your skin may have once been part of a leaf, a dinosaur's skin or a layer of lime rock. Your grandparents or hunter gatherer who lived 25,000 years ago may have inhaled some of oxygen molecules you just inhaled
The Water Cycle (Video is linked)
The hydrologic cycle, also known as the water cycle, collects, purifies, and circulates the earth's finite water supply. When it rains, the water runs along the ground and flows into rivers or falls directly into the sea. A part of the rainwater that falls on land percolates into the ground, thus recharging groundwater aquifers. Water is drawn up from the ground by plants along with nutrients from the sod. The water then transpires from the leaves as water vapor and returns to the atmosphere. As it is lighter than air, water vapor rises and forms clouds. The winds blow the clouds for long distances and when the clouds rise higher, the vapor condenses and changes into droplets, which fall on the land as rain. Part of this rain gets locked in glaciers. Thus, the processes of evaporation from water bodies, transpiration from plant leaves, condensation of water vapor, precipitation, and percolation form an endless cycle that replenishes streams, lakes, and wetlands. Furthermore, the above-mentioned natural processes of the water cycle also remove impurities in water.
The Human Interference With The Hydrologic Cycle:
The human activities interfere with the hydrologic cycle in four ways:
i.Withdrawal of large quantities of fresh water from streams, lakes, rivers and underground sources.
ii. Removal of the vegetative cover of the land and its conversion to concrete jungle. This increases the surface run off and reduces the infiltration that recharges the ground water reservoirs.
iii. Modification of water quality after the use due to addition of pollutants. i.e. pollution of water resources.
iv. Speeding up the hydrologic cycle due to warmer climate caused by greenhouse gases released due to human activities.
The Oxygen Cycle (Video is Linked)
Just as water moves from the sky to the earth and back in the hydrologic cycle, oxygen is also cycled through the environment. Plants mark the beginning of the oxygen cycle. Plants can use the energy of sunlight to convert carbon dioxide and water into carbohydrates and oxygen in a process called 'photosynthesis’.
This means that plants breathe in carbon dioxide and breathe out oxygen.
Animals form the other half of the oxygen cycle. They breathe in oxygen which is used to break down carbohydrates into energy in a process called 'respiration'
Carbon dioxide produced during respiration is breathed out by animals into the air. So oxygen is created in plants and used up by animals. During that time, plants use some oxygen to break down carbohydrates, just as animals do. During night time they. absorb oxygen from the atmosphere for respiration and give off carbon dioxide. Just as animals do. This oxygen is cycled in the atmosphere through the process of photosynthesis and respiration of a very large surface area. Even though plants produce approximately ten times as much oxygen during the day as they consume at night, the nighttime consumption of oxygen by plants can create low oxygen conditions in some water habitats.
Oxygen in water is cycled through the processes of (i) Dissolution from air & (ii) Consumption of organisms, for respiration and oxidation of organic substances.
The Carbon Cycle (Video is Linked)
The carbon found in organic compounds is included in both the abiotic and biotic parts of the ecosystem. Carbon is a building block of both plant and animal tissues. The carbon cycle is based on carbon dioxide gas (CO₂). In terrestrial ecosystems, CO is removed from the atmosphere and in aquatic ecosystems, CO, is removed from water. In the presence of sunlight, plants take up carbon dioxide from the atmosphere through their leaves. The plants combine carbon dioxide with water, which is absorbed by their roots from the soil. In the presence of sunlight, they are able to form carbohydrates that contain carbon. This process is known as photosynthesis. Plants use this complex mechanism for their growth and development. In this process, plants release oxygen into the atmosphere on which animals depend for their respiration. Furthermore, herbivores feed on plant material, which is used by them for energy and for growth. (Both plants and animals release carbon dioxide during respiration. They also return fixed carbon to the soil in the waste they excrete. When plants and animals die, they return their carbon to the soil, thus completing the carbon cycle. Plants play a very important role in regulating and monitoring the percentage of oxygen and carbon dioxide in the earth's atmosphere. Equally, oceans play a crucial role in the carbon cycle. Some CO is removed by marine species during photosynthesis, some stays dissolved in seawater (making it a major carbon storage sink), and finally some of the CO, reacts with sea water to form carbonate and bicarbonate ions Cold sea water can hold more carbon than warm sea water, just like cold soft drinks hold their fizz longer than warm soft drinks. As the temperature of the oceans rises, it becomes less able to absorb CO, and thus more CO is released into the atmosphere.
The carbon cycle ensures that CO is at acceptable levels. This in turn moderates the temperature for life to exist. If the carbon cycle removes too much carbon, the atmosphere will become cool and if too much carbon is added to the atmosphere, the atmosphere will get warmer. Current climate models show an increased concentration of CO, in the atmosphere. The resulting climate change phenomenon is at the forefront of the environmental problems faced by the world today.
The Human Interference With Carbon Cycle :
The human activities affect the carbon cycle, mainly through
(i) Combustion of fossil fuels adding large amounts of CO₂ to the atmosphere.
(ii) Clearing trees and other plants absorbing CO, through photosynthesis faster than they can grow back.
The result has been a gradual build up of CO, in the atmosphere causing an 'enhanced greenhouse effect' that heats the lower atmosphere (troposphere) and the earth's surface.
The Nitrogen Cycle (Video is Linked)
Nitrogen in its gaseous form (N₂) constitutes 78% of the volume of the atmosphere (troposphere). Nitrogen is a crucial component of proteins, many vitamins and the nucleic acids DNA and RNA. However, it cannot be used directly as a nutrient by most forms of life (e.g. multicellular plants or animals).
Nitrogen (N₂) gas is converted into the usable form by two natural processes. Trace the flows and paths in this diagram.The Nitrogen is cycled via three processes namely
Biological nitrogen fixation
Ammonification
Denitrification
Biological Nitrogen Fixation : The process known as biological nitrogen fixation is carried out by certain type of bacteria in aquatic systems, in the soil, and in the roots of some plants. The gaseous Nitrogen (N_{2}) is biologically converted (fixed) to ammonia (NH_{1}) which can be used by plants. The excess ammonia undergoes 'nitrification' where it is converted by specialized aerobic bacteria to 'nitrite ( NO_{2} ) ions and then to 'nitrate ( N O 1^) ions', which are easily used by plants as a nutrient. Plants assimilate (NH_{2}) ammonia, ammonium ( NH_{4} +), and nitrate (NO_{3}) ions to produce nitrogen-containing organic molecules such as DNA, amino acids, and proteins. Animals get their nitrogen by eating plants.
Fixation also occurs due to lightning where N_{2} and O_{2} are converted to nitrogen oxide (NO).
Ammonification:
The nitrogen-rich organic compounds are returned in the form of wastes and dead bodies. Specialized bacteria convert this detritus into simpler nitrogen-containing inorganic compounds such as ammonia and ammonium ions. This process is known as ammonification.
Denitrification:
Ultimately, nitrogen leaves the soil through a process called 'Denitrification'. The denitrifying bacteria convert ammonia and NH_{4} + ions back into nitrogen gas and nitrous oxide (N, O) gas. These gases enter into the atmosphere to begin the cycle again.
The Human Interference With The Nitrogen Cycle:
Human activities like the manufacture and use of industrial fertilizers, fossil fuel combustions and large-scale production of nitrogen-fixing crops, have greatly influenced the nitrogen cycle, particularly during the last hundred years.
The human intervention is summarized in the following steps:
1. Release of large amounts of NO due to fuel burning
2. Release of NO (nitrous oxide) due to anaerobic conversion of dung (livestock wastes) and application of commercial inorganic fertilizers.
3. Release of large amount of nitrogen from soil and plants due to deforestation
The release of nitrogen causes significant impacts such as (1) acid rains (it) acidification of the lake (n) corrosion of metals (iv) deterioration of building materials
The Phosphorus Cycle (Video is Linked)
Very little phosphorus enters the Earth's atmosphere; it is usually found as part of a phosphate ion in terrestrial rocks or as deposits in ocean-bottom sediments. Over time, weathering of rocks brings phosphates into the soil which is then absorbed by plants. Thus, the phosphorus cycle is completed in both land and water. However, most soil contains very little phosphate. It is therefore mined from the earth and added to soil as a fertilizer. Once utilized by plants, it enters the food chain animals may consume these plants. After death, plant and animal decay allows phosphate to return to the soil. Runoff from rain carries phosphorus back to the ocean or deposits it on rocks, thus completing the phosphorus cycle. Human activities such as phosphate rock mining for commercial fertilizers and detergents have a significant impact in altering the phosphate cycle. Runoff of excess phosphate from the soil pollutes aquatic ecosystems by overloading them with nutrients, which in turn minimizes the amount of oxygen available and causes toxic algal blooms.
The Sulphur Cycle (Video is Linked)
Sulphur enters the earth's atmosphere in the form of hydrogen sulphide (H,S) and sulphur dioxide (SO₂). H₂S and SO, are both emitted from active volcanoes. Additionally, H.S is released from organic matter that decomposes anaerobically (without oxygen) found in swamps and tidal flats. Other sources of sulphur are sulphate salts that can be found buried under ocean sediments and in underground rocks and minerals. Humans influence the sulphur cycle by burning coal and oil, both containing sulphur, refining sulphur containing petrol and finally through the release of sulphur dioxide by smelting for the extraction of copper, lead and zinc.
Environmental Degradation
Definition:
Environmental degradation refers to the deterioration of the natural environment due to human activities, resulting in the loss of biodiversity, depletion of resources, and disruption of ecosystems.
Causes:
Pollution: Contamination of air, water, and soil from industrial activities, waste, and chemicals.
Deforestation: Clearing of forests for agriculture, urban development, and logging, leading to habitat loss and soil erosion.
Overexploitation: Excessive use of natural resources such as water, minerals, and fossil fuels, causing depletion and ecosystem imbalance.
Climate Change: Alteration of global climate patterns due to greenhouse gas emissions, affecting weather, sea levels, and ecosystems.
Effects:
Loss of Biodiversity: Extinction of species and loss of habitats, reducing ecosystem resilience and function.
Soil Erosion: Loss of fertile topsoil due to deforestation, agriculture, and construction, affecting agriculture and water quality.
Water Scarcity: Depletion of freshwater resources due to overuse and pollution, impacting drinking water and agriculture.
Health Impacts: Increased incidence of respiratory and waterborne diseases due to pollution and degraded environments.
Consequences:
Ecosystem Collapse: Disruption of food chains and ecological balance, leading to the collapse of ecosystems and loss of services they provide.
Economic Loss: Decreased productivity in agriculture, fisheries, and tourism due to environmental damage and resource depletion.
Social Impact: Displacement of communities, loss of livelihoods, and increased conflicts over resources.
