ECOSYSTEM STRUCTURE Charilyn d. dela cruz ECOSYSTEM According to E.P.Odum, an American ecologist, an ecosystem is the basic functional unit of organism and their environment interacting with each other and with their own components. An ecosystem includes all organisms that live in a particular place, plus the abiotic environment in which they live - and with which they interact – at that location. STRUCTURE OF AN ECOSYSTEM ❶ The composition of biological community including species, numbers, biomass, life history and distribution in space.. ❷ The quantity and distribution of non living materials like nutrients, water etc. ❸ The range of condition for existence such as temperature, light etc. ❹ The structure of ecosystem is characterized by the organization of the biotic and abiotic components. BIOTIC COMPONENTS ABIOTIC COMPONENTS Inorganic Organic substances substances Carbon cycle Nitrogen cycle Water cycle Lipids Proteins Carbohydrates Climatic factors Edaphic factors Sunlight Precipitation Humidity Wind action Soil topography minerals soil ABIOTIC COMPONENTS A. Climatic Factors Sunlight precipitation humidity wind action Inorganic Substance These includes elements such as carbon, nitrogen, oxygen, etc., used in the synthesis of complex substances and involved in material cycle. Example Carbon Cycle Nitrogen Cycle Oxygen Cycle Phosphorous CARBON, THE BASIS OF ORGANIC COMPOUNDS , CYCLES THROUGH MOST ECOSYSTEM Carbon is a major constituent of the bodies of organisms because carbon atoms help form the framework of all organic compounds. CO2 is the most significant carbon containing compound in the environment of organisms. It makes up 0.03% of the volume of the atmosphere. CO2 is taken up by plants during photosynthesis. Animals eat the photosynthetic organisms and build their own tissues by making use of the carbon atoms in the organic compounds they ingest. Both photosynthetic organism and animals obtain their energy by breaking down some of the organic compounds available to them. CO2 is released by organisms during respiration and decomposition CO2 is also released by automobiles and industries In aquatic ecosystem CO2 reacts spontaneously with the water to form bicarbonate ions (HNO3 -) which act as sources of carbon for photosynthesis by algae and aquatic plants. Methanogens, are microbes that produce methane instead of CO2. Methane that enters the atmosphere is oxidized to CO2 but CH4 that remains isolated from oxygen can persist for great lengths of time. Burning of fossil fuel have created imbalance in the carbon cycle. Carbon that took million of years to accumulate in fossil fuels is being rapidly returned on the atmosphere thus contribute much on global warming. WATER CYCLE Water is so crucial that changes in its supply in an ecosystem can radically alter the nature of an ecosystem. WATER CYCLE PROCESSES Evaporation Condensation Precipitation Run off Percolation & Infiltration Transpiration Completion of cycle • 78 % of the volume of troposphere. • Most complex cycle • N2 gas can’t be used ‘as is’ – it must be “fixed” so that organisms can use it • STEPS TO THE CYCLE Nitrogen fixation Assimilation Ammonification Nitrification Denitrification NITROGEN FIXATION Atmospheric Nitrogen must be processed, or “fixed” for plant use. Some fixation occurs through lightning strikes but most fixation if done by free living or symbiotic bacteria ASSIMILATION Plants get nitrogen from the soil, by absorption of their roots in the form of either nitrate ions or ammonium ions. AMMONIFICATION When a plant or animal dies, or an animal expels waste , initial form of nitrogen is organic. Bacteria or fungi in some cases, convert the organic nitrogen within the remains back into ammonium (NH4+) in the process called ammonification and mineralization. NITRIFICATION The conversion of ammonium to nitrate is performed primarily by soil living bacteria and other nitrifying bacteria. The oxidation of ammonium (NH4+) - is by bacteria Nitrosomonas species The nitrites by nitrobacteria DENITRIFICATION The reduction of nitrates back into the largely inert Nitrogen gas (N2) completing the Nitrogen Cycle Is performed by bacterial species such as pseudomonas and clostridium in anaerobic conditions. They used the nitrate as an electron acceptor in the place of oxygen during respiration. NO3 —NO2 —N2O —N2 ORGANIC SUBTANCES These includes lipids, proteins, carbohydrates Which are formed by biotic components and that are linked with biotic components. They have strong influence on structure behavior and inter relationship of various organisms in an ecosystem. BIOTIC COMPONENTS Producers They are generally chlorophyll bearing autotrophic organisms which prepare organic compounds from inorganic raw materials. Example green plants and photosynthetic bacteria CONSUMERS a. Herbivore c. Omnivores b. Carnivores d. decomposers FUNCTIONS OF AN ECOSYSTEM Ecosystem have functional attributes which keep the component parts running together For example – green leaves prepare food and roots absorb nutrients from the soil. Herbivores feed on part of the plant production and in turn serve as food for carnivores. Decomposers carry out the function of breaking down complex organic materials into simple inorganic product which can be used by the producers. All these functions in an ecosystem occur through delicately balanced and controlled processes. Food Chain, Food Web & Ecological Pyramids Food Chain Flow of energy in an ecosystem is one way process. The sequence of organism through which the energy flows, is known as food chain. Key concepts •In a food chain each organism obtains energy from the one at the level below. •Plants are called producers because they create their own food through photosynthesis •Animals are consumers because they cannot create their own food, they must eat plants or other animals to get the energy that they need. Tropic levels in a food chain Producers Consumers (i) Primary consumers (ii) Secondary consumers (iii) Tertiary consumers (iv) Quaternary consumers Decomposers Types of Food Chain (i) Grazing Food Chain •The consumers utilizing plants as their food , constitute grazing food chain. • This food chain begins from green plants and the primary consumer is herbivore. • Most of the ecosystem in nature follows this type of food chain. Ex: grass => grasshopper => birds => falcon (ii) Detritus food chain •This type of food chain starts from dead organic matter of decaying animals and plant bodies to the micro-organisms and then to detritus feeding organism and to other predators. •The food chain depends mainly on the influx of organic matter produced in another system. •The organism of the food chain includes algae, bacteria, fungi, protozoa, insects, nematodes etc. Detritus Food Chain Significance of Food Chain •The knowledge of food chain helps in understanding the feeding relationship as well as the interaction between organism and ecosystem. •It also help in understanding the mechanism of energy flow and circulation of matter in ecosystem. •It also helps to understand the movement of toxic substance and the problem associated with biological magnification in the ecosystem. Key concepts •A node represents an individual species, or a group of related species or different stages of a single species. • A link connects two nodes. Arrows represent links, and always go from prey to predator. • The lowest tropic level are called basal species. • The highest tropic level are called top predators. •Movement of nutrients is cyclic but of energy is unidirectional and non-cyclic. Types of food web representation TOPOLOGICAL WEBS FLOW WEBS INTERACTION WEB • These food webs simply indicate a feeding relationship. • Bio-energetic webs, or flow webs, include information on the strength of the feeding interaction. • In interaction the arrows show how one group influences another. Different food webs • Soil food web • Aquatic food web • Food web in forest • Food web of grassland • Food web in terrestrial and aquatic ecosystem Aquatic food web Food web in forest Grassland Food Food web of grassland Web Food web in terrestrial and aquatic ecosystem Significance of Food Web •Food webs distinguish levels of producers and consumers by identifying and defining the importance of animal relationships and food sources, beginning with primary producers such as plants, insects and herbivores. •Food webs are important tools in understanding that plants are the foundation of all ecosystems and food chains, sustaining life by providing nourishment and oxygen needed for survival and reproduction. •The food web provide stability to the ecosystem. What are Ecological Pyramids? •Ecological pyramids are graphical representations of the tropic structure ecosystem. •Tropic levels are the feeding positions in a food chain such as primary producers, herbivores, primary carnivore etc. Types of Ecological Pyramid Three types of ecological pyramids can usually be distinguished namely: • Pyramid of numbers • Pyramid of biomass Pyramid of productivity • Pyramid of Numbers •It is the graphic representation of number of individuals per unit area of various tropic levels. •Large number of producers tend to form the base. •Lower numbers of top carnivores occupy the tip Pyramid of Numbers Pyramid of biomass •It is the graphical representation of biomass present per unit area at different tropic levels, with producers at the base and carnivores at the top. •Biomass is calculated as mass of each individual X no. of individual at tropic levels Pyramid of productivity •Pyramid of productivity is a graphical representation of the flow of energy through each tropic level of a food chain over a fixed time period. •The input of solar energy may be indicated by adding an extra to the base. Pyramid of productivity Disturbances in ecosystem Bioaccumulation - When plants / animals take up a chemical from the •environment and do not excrete it,the chemical builds up in the organism over time to a potentially lethal level. Biomagnification Refers to the sequence of processes that results •in higher concentrations of the chemical in organisms at higher levels in the food chain. The concentration of the chemical may not affect lower levels of the food chain but the top levels take in so much it can cause disease or death. • Extinction of species – Due to decrease in population of various species the balance of various tropic levels is disturbed as a result some levels have more accumulation of species while others have very less population.
