Introduction to Environmental Quality Engineering CE 264 - 2024 PDF

1 INTRODUCTION TO ENVIRONMENTAL QUALITY ENGINEERING CE 264 H.M.K. Essandoh/ M. Appiah-Brempong  Learning outcomes 2  At the end of the course you should be able to:  Explain the basic concepts of the environmen...

1 INTRODUCTION TO ENVIRONMENTAL QUALITY ENGINEERING CE 264 H.M.K. Essandoh/ M. Appiah-Brempong  Learning outcomes 2  At the end of the course you should be able to:  Explain the basic concepts of the environment and the laws of nature  Identify sources of pollution in the environment  Describe the characteristics of water and wastewater  Identify water related diseases and diseases associated with excreta  Classify excreta disposal systems based on water use and point of treatment  Describe various on-site and off-site sanitation systems for handling excreta and how the systems function and their advantages and disadvantages  Explain the physical and chemical characteristics of solid waste  Explain the processes involved managing solid waste  Course content 3  Introduction to the environment: Basic ecological concepts, pollution;  Water Chemistry: Water and wastewater quality parameters.  Basic water microbiology, Public significance of diseases associated with excreta and water related diseases.  Water resources and quality considerations.  Excreta management:  Classification of excreta disposal systems  Handling of human excreta: on-site and off-site systems  Introduction to solid waste management  Introduction 4  A common adage by the naturalist John Muir – ‘Tug on anything at all and you will find it connected to everything else in the universe’.  Eg. the forest behind the college of Engineering laboratories used to harbour a number of trees, shrubs, etc with reptiles like snakes – python, cobras etc, mice, frogs, insects, different species of birds, squirrels, etc.  Since the start of the development of new structures to house the business school certain reptiles like the python have either been killed or chased away.  Introduction 5  In addition small scale farmers have been cultivating vegetables on some portions of the land.  This development has led to increase in population of mice in the forest thereby attracting animals like owls and hawks to the area, a situation which hitherto was not existing.  The water in the stream in the valley is gradually decreasing in volume because of the felling of the trees and exposure of the stream surface to the harsh dry climatic conditions thus increasing the rate of the evaporation.  We need to take care of our environment  Environmental Ethics 6  Ethics is a branch of philosophy that seeks to define what is right and what is wrong  The laws of any nation should match the ethical commitment of those living there.  Not every action that is ethically right can have a law supporting it. E.g.  There is no law that you have to help your elderly neighbour to unload her groceries from the car. But even without a law this must still be the ethically right thing to do.  It is ethically right that after eating snack you do not throw or litter around with the polythene bag that was used to bag your snack.  Environmental Ethics 7  The goal of environmental ethics is not just to convince us to be concerned about the environment but rather to focus on the moral foundation of environmental responsibility and how far this responsibility extends.  Three primary theories have been put forward on moral responsibility regarding the environment. They include:  Anthropocentrism or human centred ethics  Biocentrism or life centred environmental ethics  Ecocentrism  Environmental Ethics 8  Anthropocentrism  The view is that all environmental responsibility is derived from human interest alone.  It assumes that only humans are morally significant and have direct moral standing.  In this view the adage is ‘protect when it benefits humans’.  This view is flawed in the sense that we must ensure that the Earth remains environmentally hospitable for supporting human life and even that it remains a pleasant place for humans to live now and for the future  Environmental Ethics 9  Biocentrism or life centred environmental ethics  According to this theory all forms of life (humans, animals, Plants, microorganisms etc.) have an inherent right to life.  Ecocentrism  This approach / theory maintains that the entire environment deserves direct moral consideration and not consideration that is derived merely from human or animal interests.  In this regard everything existing on the Earth or mother Earth should have the same right to life as any other.  Environmental Ethics  Generally our attitudes or approaches to the environment must evolve 10 around development, preservation and conservation  In order to preserve and conserve our environment, our development should be sustainable.  Sustainable development (SD) is often defined as ‘meeting the needs of current generations without compromising the ability of future generations to meet theirs’.  SD focuses on the promotion of appropriate development to alleviate poverty while still preserving the ecological health of the landscape.  Pillars of sustainable development 11  SD hinges on three pillars namely:  economic development  social development and Social  environmental protection. Equitable Bearable  At times consideration is given to Stnble cultural development as well. Environment Viable Economic  The United Nations Conference on Environment and Development in 1992 in Rio de Janerio, Brazil set  Stnble – Sustainable out a roadmap for sustainable development  Pillars of sustainable development 12 13 Pillars of sustainable development  Social Sustainability 14  For social sustainability social systems, such as a country, family, or organization, should be able to function at a defined level of social well-being and harmony indefinitely.  Wars, endemic poverty, widespread injustice, and low education rate etc. inhibit sustainability  Environmental Sustainability 15  The environment should be able to support a defined level of environmental quality and natural resource extraction rates indefinitely.  This is currently a big problem since the quality of the environment is being degraded by anthropogenic activities and natural resources are running out  Very serious consequences will arise in the future if this is not accorded the needed attention and serious efforts made by all countries to address it  Economic Sustainability 16  For an economy to be sustainable it should be able to support a defined level of economic production indefinitely  MDGs and SDGs 17  Read on the Millenium Development Goals (MDGs) and the Sustainable Development Goals (SDGs)  What are the goals?  What is the relevance of these goals?  How do the MDGs differ from the SDGs?  You will form groups. Each group will make presentations on one MDGs and one SDGs.  Environment 18  The Environment 19  The sum total of external conditions that influence and affect the development and life of an organism.  In addition it is the aggregate of all natural and operational conditions that affects the performance of an equipment or its components and determine the behaviour of a physical system.  The Environment 20 Environmental settings:  Physico-chemical: Water, air, soil, noise, radiations  Biological: terrestrial and aquatic lives  Cultural: history (beliefs), attitudes and practices  Socio-economic: population, economy, infrastructure  The global environment 21  The atmosphere  The hydrosphere  The lithosphere  The biosphere  The atmosphere 22  The atmosphere constitutes the mixture of gases extending outwards from the earth’s surface  Evolved from elements of the earth that were gasified during its formation and metamorphosis  Three types of constituents  Major components  Minor components  Trace components  The atmosphere 23 Major components Minor components trace components Nitrogen (78.08%) Argon (0.9%) Helium (0.005%) Oxygen Carbon dioxide Methane (20.95%) (0.032%) (0.0002%) Water vapour (0.1%) Neon (0.0018%) etc  Structure of Earth’s atmosphere 24 Temperature  The thin film of gas that surrounds the earth varies in 300 structure as the distance Thermosphere increases outward from the surface. 100 Mesopause H (km) Mesosphere  The earth’s atmosphere is Stratopause divided into regions based primarily on considerations of 30 Stratosphere temperature as shown in the figure Tropopause 10 Troposphere 300 600 T (°K)  The atmosphere 25  Structure: the atmosphere may be divided into 4 regions  Troposphere – 0 – 11 km / 15 to -56°C ◼ (nitrogen, oxygen, water vapour, carbon dioxide)  Stratosphere – 11 – 50 km / -56 to -2°C ◼ (ozone)  Mesosphere – 50 – 85 km / -2 to -92°C ◼ (oxygen +, nitric oxide+)  Thermosphere – 85 – 500 km / -92 to 1200°C ◼ (oxygen +, nitric oxide+)  The atmosphere 26  The troposphere  Contains 70 % of the mass of the atmosphere  Density decreases exponentially with increasing altitude  Temperature decreases uniformly with increasing altitude (positive lapse rate)  Energy flows as a result of imbalances in heating and cooling rates between the equator and poles.  Air masses are therefore in constant circulation  The atmosphere 27  The stratosphere  There is increase in temperature with increase in altitude (negative lapse rate)  Has ozone as an important component  Ozone absorbs harmful UV radiation from the sun and balances temperature  The stratosphere serves as a protective shield for life forms on earth  There is slow mixing in the stratosphere. Therefore, pollutants introduced stay for a long time and slowly come down to the troposphere  The atmosphere 28  Mesosphere  Temperature decreases with increase in altitude (positive lapse rate) due to low levels of ultraviolet radiation species, ozone  Thermosphere  Temperature increases with increase in altitude (negative lapse rate)  Oxygen and nitric oxide ionise after absorption of solar radiation in the far ultraviolet region  Structure of Earth’s atmosphere 29  The temperature at the earth’s surface varies from sub-zero °C (i.e. temperatures beneath zero; so it is a term normally used for temperatures in the negative) in the polar regions and high mountains areas to highs of about 70°C in the arid desert regions.  The corresponding air temperatures close to the earth’s surface (within a few metres) are lows of sub-zero and highs of about 50°C.  In very warm areas, the air temperature is typically 10 to 20°C cooler than the hot surface temperatures. Typically, at mid latitudes the temperature falls with increasing altitude in the troposphere.  This is known as positive lapse rate.  Structure of Earth’s atmosphere 30  The decrease continues to an altitude known as the tropopause, above which the temperature increases again in the region known as stratosphere. The height of the troposphere is about 10km above the earth’s surface, while the stratosphere extends a further 20 to 30km.  The lower 0 to 2 km of the troposphere can be further divided into several regions.  This entire region (0 to 2 km) is called the atmospheric boundary layer (ABL).  The ABL is that region where the wind velocity is affected by the shear resistance of the earth’s surface.  The ABL is shallowest over oceans or large inland waterways, where its height is about 500 m.  Structure of Earth’s atmosphere 31  The depth of the ABL may be up to 2 km in urban areas with many tall structures.  In typical rural areas, the ABL depth is about 1 km.  At the earth’s surface, the wind velocity is lowest, and increases gradually (non linearly) to the top of the ABL.  Above the ABL, the wind velocity is approximately constant, being unaffected by the shear resistance of the earth’s surface.  The region of most interest for atmospheric pollution is that within the ABL, though higher regions within the troposphere are of interest to large scale air circulation behaviour and global climate circulation modelling.  A region close to the earth’s surface, called the sub-layer of the ABL, is affected by local roughness and is characterized by high turbulence and strong mixing.  Gas Percentage Nitrogen (N2) 78 Oxygen (O2) 21 32 Argon (Ar) 0.9 Carbon dioxide (CO2) 0.03 Neon (Ne) 0.0018 Helium (He) 0.00052 Average percentage Methane (CH4) 0.00022 chemical composition of air within the ABL Krypton (Kr) 0.0001 Di-nitrogen oxide (N2O) 0.0001 Hydrogen (H2) 5.0 x 10-5 Xenon (Xe) 8.0 x 10-6 Ozone (O3) 2.0 x 10-6 Ammonia (NH3) 6.0 x 10-7 Nitrogen dioxide (NO2) 1.0 x 10-7 Nitrous oxide (NO) 6.0 x 10-8 Sulphur dioxide (SO2) 2.0 x 10-8 Hydrogen sulphide (H2S) 2.0 x 10-8  The hydrosphere 33  World water amounts to about 1.4 billion km3  This is found in oceans, ice caps, lakes, streams, groundwater  Ocean – 97 %  Fresh water –3%  Polar ice caps – 2.3 %  Surface & GW – 0.7 %  Only 1.2 % of all freshwater is surface water (about 0.03%)  The hydrologic cycle helps balance water between air, land, sea, living plants and animals  This occurs through continuous evaporation of water from the seas and oceans, cloud formation and condensation into rainfall  The Earth- lithosphere 34  This is the soil mantle that wraps the core of the earth  Mineral component of the soil comes through weathering of rocks and the organic fraction from plant biomass, bacteria, fungi, earthworms  Three layers can be identified:  Top soil where there is maximum biological productivity and contains the bulk of organic matter. This layer is very important for vegetation cover and agricultural crops  Subsoil which receives organic matter, salts, etc. leached from the top soil  Weathered parent rock from which soil is constituted 35 Light Rays from the Sun in the Tropics Light rays from Sun in Temperate Latitude of Northern and Southern Hemisphere The sun’s rays in the tropics are at right angles whereas it is slanted in the temperate zones.  Soil formation, properties and profile 36  Geologic process  Physical, chemical and biological factors involved in soil formation  Soil texture and structure  Layers in the soil profile  Human activities and impact on soil  Geologic processes 37  Formerly the earth was thought of to be a stable unchanging mass but recent findings and research have shown that activities such as earthquakes, floods, tsunamis, volcanic eruptions and windstorms have been changing the surface of the places we live.  Much of these activities cause large portions of the Earth surface (known as plates) to shift.  The Earth comprises the crust, the mantle, inner and outer core. The crust is the outermost and superficial less dense but thin layer that covers a thick underlying layer called the mantle.  Geologic processes 39  The mantle consist of an inner part and an outer portion that is adjacent to the crust.  The crust together with the outer mantle is referred to as the lithosphere.  The inner mantle portion is a relatively thin layer known as the asthenosphere.  The asthenosphere is capable of plastic flow.  Below the asthenosphere is a solid mass that forms the remaining part of the mantle.  The central core consists primarily of iron and nickel and has a solid centre and liquid outer region.  Plate tectonics 40 ❖ Theory of Plate Tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere ❖ It begins with the idea that the crust (lithosphere) of the earth is made up of seven major plates and several smaller plates  Plate Tectonics 41 The seven major lithospheric plates are:  the Pacific,  the North American,  the South American,  the Eurasian,  the African,  the Antarctic, and  the Australian plates  Plate Tectonics 42  The concept of plate tectonics indicates that the outer surface of the Earth consist of large plates composed of the crust the outer portion of the mantle and that these plates are slowly moving over the surface of the liquid outer mantle.  The movements of the plates on the plastic outer layer of the mantle are independent of each other.  Therefore, some of the plates are pulling apart from one another, while others are colliding.  Where the plates are pulling apart from one another, the liquid mantle moves upward to fill the gap and solidifies.  Thus new crust is formed from the liquid mantle.  Plate Tectonics 43  Approximately half of the Earth surface has been formed in this way for the past 200 million years.  The bottom of the Atlantic and Pacific Oceans and Rift Valley and Red Sea of Africa are areas where this is occurring.  Where plates are pulling apart on one portion of the Earth, they must be colliding elsewhere.  Where plates collide, several other things can happen. Often one of the plates slide under the other and is melted.  Often when this occurs, some of the liquid mantle makes its way to the surface and volcanoes are formed that result in the formation of mountains.  Plate tectonics 45  Volcanic activities add new material to the crust.  When a collision occurs between two plates under the ocean, the volcanoes may eventually reach the surface and form a chain of volcanic islands, such as can be seen in the Caribbean Islands.  Most of these movements are associated with earthquakes.  The movements of the plates are slow and steady sliding movements but tend to occur in small jumps.  These building processes are counteracted by processes that tend to make the elevated surfaces lower.  Gravity provides a force that tends to wear down the high places.  Moving water, ice and wind assist in the process, however their effectiveness is related to the size of the rock particles.  Weathering of rocks 46  Mechanical weathering results from physical forces that reduce the size or rock particles without changing the chemical nature of the rock.  Common causes of mechanical weathering are changes in temperature that tend to result in fractures in rock, the freezing of water into ice that expands and tends to split larger pieces of rock into smaller ones, and the actions of plants and animals.  Because rock does not expand evenly, heating a large rock can cause it to fracture so that pieces of the rock flake off.  These pieces can be further reduced in size by other processes, such as the repeated freezing of water and thawing of ice.  Water that has seeped into rock cracks and crevices expands as it freezes, causing the cracks to widen.  Weathering of rocks 47  Subsequent thawing allows more water to fill the widened cracks, which are enlarged further by another period of freezing.  Alternating freezing and thawing breaks large rock pieces into smaller ones.  Other activities that bring about the breaking of rocks include the following:  The roots of plants growing  Wind and moving water  Activities of organism like worms and rats burrowing  Chemical weathering  Chemical weathering 49  The chemical alteration of rock eg. when rocks are exposed to the atmosphere they may undergo oxidation or hydrolysis by combining with atmospheric oxygen and/or water (acid rain), in so doing get chemically changed into different compounds.  A combination of physical, chemical and biological events acting over time is responsible for the formation of soil.  Land and soil 50  Land is the part of the world not covered by the oceans.  Soil is the thin covering over the land consisting of a mixture of minerals, organic material, living organisms, air and water that together support the growth of plant life.  The proportions of the soil components vary with different types of soils, but a typical ‘good’ agricultural soil is about 45% mineral, 25% air, 25% water and 5% organic matter.  This combination provides good drainage, aeration and organic matter.  The organic material resulting from the decay of plant and animal remains is known as humus  Land and soil 51  Humus accumulates on the surface and ultimately becomes mixed with the top layers of mineral particles.  This material contains nutrients that are taken up by plants from the soil.  Humus also increases the water holding capacity and the acidity of the soil so that inorganic nutrients which are more soluble under acidic conditions, become available to plants.  Humus also tends to stick other soil particles together and helps to create a loose, crumbly soil that allows water to soak in and permits air to be incorporated into the soil.  Compact soils have few pore spaces, so they are poorly aerated and water has difficulty penetrating, so it runs off.  Soil properties 52  Soil properties include soil texture, structure, moisture, biotic content and chemical composition.  Soil texture is determined by the size of the mineral particles within the soil.  The largest soil particles are gravel, which consists of fragments larger than 2.0 millimeters in diameter.  Particles between 0.05 and 2 mm are classified as sand.  Silt particles range from 0.002 to 0.05mm in diameter and the smallest particles are clay particles, which are less than 0.002 mm in diameter.  Clay particles tend to be flat and are easily packed together to form layers that greatly reduce the movement of water through them.  Such soils are poorly aerated and do not drain well.  Clay soils in turn stay moist for longer periods of time and do not easily lose minerals to percolating water.  Soil properties 53  An ideal soil for agriculture use is a loam, which combines the good aeration and drainage properties of large particles with the nutrient – retention and water holding ability of clay particles.  Soil structure refers to the way various soil particles clump together. The particles in sandy soils do not attach to one another; therefore, sandy soils have a granular structure.  The particles in clay soils tend to stick to one another to form large aggregates.  Other soils that have a mixture of particle sizes tend to form smaller aggregates.  A good soil is friable, which means that it crumbles easily.  The soil structure and its moisture content determine how friable a soil is.  Soil profile 54  The soil profile is a series of horizontal layers in the soil that differ in chemical composition, physical properties, particle size and amount of organic matter.  Each recognizable layer is known as a horizon.  Several systems exist for describing and classifying the horizons in soils.  The uppermost layer of the soil contains more nutrients and organic matter than do the deeper layers.  The top layer is known as the A-horizon and consist of small mineral particles mixed with organic matter. It’s usually dark in color because of the high content of organic matter.  If there is a layer of litter (undecomposed or partially decomposed organic matter) on the surface, it is known as the O- horizon.  Forest soils typically have an O- horizon.  Many agricultural soils do not, since the soil is worked to incorporate surface crop residue.  Soil profile 55  As the organic matter decomposes, it becomes incorporated into the A horizon.  The thickness of the A horizon may vary from less than 1 cm on steep mountain slopes to over 1 meter deep.  Most of the living organisms and nutrients are found in the A – horizon.  As water moves down through the A – horizon, it carries dissolved organic matter and minerals to lower layers in a process called leaching.  Below the A-horizon is a lighter coloured layer known as the B – horizon.  Soil profile 56  The B-horizon, often called the subsoil contains less organic material and fewer organisms than the A – horizon.  However it contains accumulations of nutrients that were leached from higher levels.  B – horizon is a valuable source of nutrients for plants and it normally supports a well developed root system.  The area below the B-horizon is known as the C-horizon and it consists of weathered parent material.  The chemical composition of the minerals of the C- horizon helps to determine the pH of the soil.  The characteristics of the parent material in the C- horizon may also influence the soil’s rate of water absorption and retention.  Environmental Engineering 59  Environmental engineering can be defined as the branch of engineering that is concerned with  protecting the environment from the potentially deleterious effects of human activity,  protecting human populations from the effects of adverse environmental factors and  improving environmental quality for human health and well-being  Environmental Engineering 60  Basically it is the application of theories of science and material forces to confront ecological and socio-economic problems so as to reduce pollution, contamination and deterioration of the surroundings in which humans live.  Environmental Engineering therefore involves control of water, soil and atmospheric pollution and the social and environmental impact of planned projects.  Basic ecological concepts 61  Forests, grasslands, oceans, lakes, rivers, mountains, deserts, estuaries support life  Wide variations exist in the structural composition and functions of these various life supporting systems  They are however all alike with regards to consisting of living entities interacting with their surroundings and exchanging matter and energy  Ecology studies  how these different life supporting systems differ from each other with respect to the different types of flora and fauna they support,  how they derive energy and nutrients to live together  how they influence each other and regulate their stability  Basic ecological concepts 62  Ecology is the study of the relationship between living organisms and with their environment. It deals with the study of organisms in their natural home, interacting with their surroundings. It is often defined as the study of ecosystems  Population is a group of plant or animal of the same species living in a given locality at a given time.  Community is a group of plant and animal populations living and interacting in a given locality  Ecosystem is a self-sustaining and self-regulating community of living organisms living together and interacting with their environment  Basic ecological concepts 63  Environment is an aggregate of all the external conditions (both physical and biological) that tends to affect organisms  Ecosystem is a self-sustaining and self-regulating community of living organisms living together and interacting with their environment  The biosphere 64  The biosphere is a thin shell encapsulating the earth  It is made up of the atmosphere and lithosphere adjacent to the surface of the earth and the hydrosphere (about 600m above earth’s surface and 10 000m BSL)  Life forms of earth live in the biosphere  Life sustaining materials in gaseous, solid and liquid form are cycled through the biosphere  The biosphere 65  Life sustaining resources (air, water, food) are withdrawn from the biosphere  Waste products in gaseous, liquid and solid form are discharged into the biosphere  The sustaining and assimilative capacity of the biosphere though great is not infinite  Basic ecological concepts 66  Ecosphere/Biosphere: The sum total of all the ecosystems in the world  Ecological niche: The position of a species within an ecosystem, describing both the range of conditions necessary for persistence of the species, and its ecological role and function in the ecosystem  Habitat is a place where where a population of organisms lives, where it finds its food, mate etc.  Within each ecosystem are habitats  Habitat and niche 67  The habitat of an organism is the space that the organism inhabits, the place where it lives.  The Niche of an organism is the functional role it has in the ecosystem  An organism’s niche includes all the ways it affects other organisms with which it interacts as well as how it modifies its physical surroundings.  In addition the niche includes all of the resources the organism uses  Limiting factors 68  Organisms interact with their surroundings in many ways.  Certain factors may be critical for the existence of a particular species.  A shortage or absence of a particular factor can restrict the success of the species.  Such factors are known as limiting factors.  Limiting factor 69  The factors could be biotic or abiotic. E.g.  Many plants are limited by scarcity of water, light, specific soil nutrients such as nitrogen, phosphorus etc.  Climatic factors such as temperature range, humidity, periods of drought or length of winter are often limiting factors.  It is impossible to understand an organism apart from its environment. THE ECOSYSTEM  Ecosystems 71  Ecosystems are self regulating and normally have a continuous input of energy to retain its stability.  It is an integrated unit consisting of interacting plants and animals and microorganisms whose survival depends on the maintenance and regulation of their biotic and abiotic structures and functions  An ecosystem may be a unit or a system composed of sub- units directly or indirectly linked with each other  Basic ecological concepts-ecosystems 72  The ecosystem functions through the operation of some natural laws.  It operates through the recycling of matter in accordance with the law of conservation of matter and the one-way energy flow in accordance with the first and second law of energy.  Ecosystems 73  Ecosystems do not only include the community of organisms but also organisms and their abiotic environment, which involves the movement of energy and materials through the communities.  Ecosystems have no definite boundaries  Forests, a lake with its biota (Flora and fauna) are also ecosystems  Ecosystems 74  Ecosystems are self regulating and normally have a continuous input of energy to retain its stability.  The only significant source of energy for most ecosystems is sunlight.  Ecosystems would not be possible were it not for the flow of energy into them.  Life on earth is sustained by the flow of energy through ecosystems  Ecosystems 75  Producers in an ecosystem are the only entities that can trap the sun’s energy through the process of photosynthesis and make it available to the ecosystem  The sun is the primary source of energy because all biological life is dependent on the green plants that use the sunlight as a source of energy  Sunlight using organisms are therefore called primary producers  Primary producers obtain their carbon from inorganic sources such as carbon dioxide or bicarbonate  Structure of the Ecosystem 76 The ecosystem has two major components: i. The living or biotic part ii. The non-living (abiotic)  The structure of the ecosystem is directly related to energy transfer and matter recycling.  The plants, animals and microorganisms present in an ecosystem form the biotic component  They have different nutritional behaviour and status in ecosystems and are therefore classified accordingly as producers or consumers depending on how they get their food  Structure of the Ecosystem 77 ❖ Living (biotic) portion i. Producers (Plants or autotrophs): These are plants ranging from tiny floating phytoplankton (algae, diatom etc.) in water ecosystems to giant trees ii. Macroconsumers (animals or heterotrophs): Organisms that cannot manufacture their own food and must consume the preformed food compounds found in plants and animals iii. Decomposers (micro consumers or saprotrophs): Tiny organisms such as bacteria that break down the bodies and complex compounds in dead animals and plants into smaller substances 78 Structure of the Ecosystem ❖ Non biotic portion ❖ The physical and chemical components of an ecosystem constitute its abiotic structure. ❖ It includes energy, climatic factors, edaphic (soil) factors, geographical factors, nutrients, toxic substances i. Energy : Solar energy drives the entire ecosystem by helping to create climate to recycle essential chemicals and to support plant life. Sunlight and shade, intensity of solar flux, duration of sun hours have a strong influence on the ecosystem 79 Structure of the Ecosystem ❖ Non biotic portion i. Other physical factors: temperature light wind humidity current rainfall Latitude and altitude Soil type etc. also have a strong influence on the ecosystem 80 Structure of the Ecosystem iii. Chemical factors:  Water  Oxygen  Carbon  Nitrogen  Phosphorus  Potassium  Hydrogen, etc.  Essential minerals and substances (proteins, carbohydrates, lipids, vitamins and other complex chemicals necessary for life)  The critical inorganic and organic chemicals found in air, water and soil must be recycled again several times through the ecosphere  ROLES OF ORGANISMS IN AN ECOSYSTEM 81 Producers  They are mainly green plants  They use simple inorganic substances in their environment  Sunlight  Water  Carbon dioxide  Chlorophyll  To produce / make complex organic molecules through the process of photosynthesis  Producers are are also known as photo autotrophs  ROLES OF ORGANISMS IN AN ECOSYSTEM 82 Producers  There are some microorganisms which can also produce organic matter to some extent through oxidation of certain chemicals in the absence of sunlight  These are known as chemosynthetic organisms or chemoautotrophs  Sulphur bacteria for eg. in deep oceans can utilise heat generated by the decay of radioactive elements present in the earth’s core and released in the ocean’s depths to convert dissolved hydrogen sulphide and carbon dioxide into organic compounds  Consumers: 83  They are organisms that require organic matter as a source of food and obtain such by feeding on other organisms.  They consume the organic matter to provide themselves with energy and the organic molecules necessary to build their own bodies.  They break down the organic matter to simple inorganic molecules. 84 Consumers  Based upon the way they obtain their food and the kinds of things they eat consumers can be classified as either  Primary, secondary or tertiary consumers  Primary consumers (herbivores) are animals that eat producers (plants and phytoplanktons) as a source of food. Eg. rabbits, insects, humans  Secondary consumers (carnivores) are animals that feed on herbivores eg. frogs  Tertiary consumers (tertiary carnivores) feed on other carnivores eg. snakes, big fish etc  Consumers 85  Omnivores  Animals that eat both plants and other animals. Eg. rats, humans, many birds, fox, etc  Detritivores (detritus feeders or saprotrophs)  These feed on dead organisms, wastes of living organisms, cast-offs and partially decomposed matter  Egs. Ants, earthworms, crabs, vulture etc 86 Consumers  Decomposers  Organisms that use non-living organic matter as a source of energy and raw materials to build their bodies.  They derive their nutrient by breaking down the complex organic molecules into simpler organic compounds and ultimately into inorganic nutrients  Whenever an organism sheds a part of itself, excretes waste products or dies, it provides a source of food for decomposers.  Decomposers are extremely important in breaking down organic matter  Examples of decomposers are various bacteria and fungi 87 Basic Components of the Ecosystem  Ecosystems 88  Ecosystems of the world are studied on the basis of their principal habitats  Among the environmental segments the lithosphere and the hydrosphere are the major habitats for a wide variety of flora and fauna  Ecosystems may be a:  Land-based ecosystem  Marine ecosystem  Freshwater ecosystem  Wetland ecosystem  Mangroves (forest between land and sea)  Ecosystems 89  Land-based (terrestrial)ecosystems  These depend largely on the climate and soil  Higher plants and animals have evolved on land  These include seed plants, insects, warm-blooded animals, etc.  The major terrestrial communities consist of herbaceous plants, shrubs, grass and woody trees, numerous insects, anthropods, birds, etc.  Marine ecosystems  The oceans offer habitat to numerous plants, animals such as zoo-plankton, shrimps, oysters, fishes, reptiles, birds, mammals such as whales and seals  Marine water has high salt content (about 3.5% by weight) and poor fertility compared to fresh water  Ecosystems 90  Freshwater ecosystems  Freshwater bodies such as ponds, lakes, rivers, springs are rich in nutrients and provide good habitat for phytoplankton, zoo-plankton, aquatic plants and fishes  Wetland ecosystems  These are lands where water stands 2.5-300 cm for most part of the year  They harbour a wide variety of plants, animals, fishes and micro-organisms  Mangroves  Forestcommunities in tidal zones  They are a habitat for wild animals and interesting plant species  The Tropical environments 91  Tropical forest of standing trees  Savannah grasslands and woodlots  Deserts  Tropical forests are the most important forest type of the world due to its value for services such as  carbon sequestration  biodiversity  soil and water conservation  source of valuable commercial timber  The Amazonian basin forest is the largest area under tropical forests followed by the Congo basin.  Tropical ecosystem 92 Af: no dry season; Am: short dry season; Aw: winter dry season  Tropical ecosystems 93  Tropical climates are found around the equator between Latitude 25 degrees south and 24degrees North and have temperatures of 18 degrees or higher  The tropics have the characteristics of small temperature changes and long summers.  Due to the high temperature and abundant rainfall, some plants can grow throughout the year.  High temperature and humidity is the most suitable environment for epiphytes to grow.  Tropical ecosystems 94  Tropical ecosystems are ecologically rich, and the tropics are considered an exclusive reservoir of much of the world's biodiversity  Plants of all sizes can vegetate under tropical climates.  Vegetation grows in layers: shrubs under tall trees, and bushes under shrubs.  Almost every inch of space is being well used.  Tropical plants are rich in resources. Examples include coffee, cocoa and oil palm.  Tropical ecosystems have a very high species diversity index and support several plant and animal species hence the prevalence of several diseases  Uses of the Tropical Ecosystems 95  Tropical crops  Sequesters of carbon dioxide  Medicinal use  Soil conservation  Timber  Fuel  Tourism  Transpiration  Clothes and Food  Biological diversity  Odour absorbing plants 96 How the ecosystem functions  Every ecosystem performs under natural conditions in a systematic way  It receives energy from the sun  This energy is passed on through various biotic components  All life depends on this flow of energy  Besides energy various nutrients and water are required for life processes  These are exchanged by the biotic components within themselves and with their abiotic components within or outside the ecosystem  The biotic components also regulate themselves in a very systematic way and have mechanisms to absorb some degree of environmental stress  How an ecosystem functions 97  The major functional attributes of an ecosystem are  Food chain, food webs and trophic structure  Energy flow  Cycling of nutrients (biogeochemical cycles)  Primary and secondary production  Ecosystem development and regulation  Producers and consumers in an ecosystem are arranged in a definite manner and their interactions along with population size are expressed together as trophic structure  Food chains and food webs 98  A Food Chain is a series of organisms occupying different trophic levels through which energy passes as a result of one organism consuming another.  It describes the complex relationships between organisms in an ecosystem  All organisms whether living or dead are potential food for some other organisms  There is therefore essentially no waste in the functioning of a natural ecosystem  There are two major types of food chains  Grazing food chain  Detritus food chain  Both food chains occur together in natural ecosystems but the grazing food chain predominates  Food chains and food webs 99  Food Chain:- a series of organisms occupying different trophic levels through which energy passes as a result of one organism consuming another.  Some food chains rely on a constant supply of small pieces of dead organic material coming from situations where photosynthesis is taking place.  The small bits of non-living organic materials are called detritus.  The floor of a forest can be a perfect example of a detritus food chain.  Food chains and food webs 100  The forest floor receives fallen leaves that serve as detritus food chain.  Initially the leaves will be colonized by bacteria and fungi.  If an earthworm is eaten by a bird, it becomes part of a larger food chain that includes material from both a detritus food chain and a photosynthesis – driven food chain.  When several food chains overlap and intersect, they make up a food web  Food chains and food webs 101  A grazing food chain starts with green plants (primary producers) and culminates in carnivores.  A caterpillar eats a plant leaf, a sparrow eats the caterpillar, a cat or a hawk eats the sparrow  When all these living organisms die they are consumed by microorganisms such as bacteria and fungi (decomposers)  The decomposers break down the organic matter and convert it into simple inorganic substances that can be used once again by the plants  Food chains and food webs 102  Some food chains rely on a constant supply of small pieces of dead organic material coming from situations where photosynthesis is taking place.  The small bits of non-living organic materials are called detritus. The floor of a forest can be a perfect example of a detritus food chain.  A detritus food chain starts with dead organic matter which the detritivores consume  Initially the leaves will be colonized by bacteria and fungi.  Partially decomposed organic matter and even the decomposers are consumed by detritivores and their predators  Grazing food chains 103 Grassland ecosystem Grass Grass Frog Snake Hawk hopper Pond ecosystem Phyto Water fleas Small fish Tuna fish planktons Each organism is assigned a feeding level or trophic level depending on its nutritional status. Food chains Decomposers consume the dead matter of all these trophic levels 104  Detritus food chains 105 Mangrove ecosystem Small Large Leaf litter Algae Crabs carnivorous carnivorous fish fish Forest ecosystem Dead organic matter Fungi Bacteria 106 Figure 4: A typical food chain  Food chains and food webs 107  Food chains in ecosystems are rarely found to operate as isolated linear sequences  Rather they are found to be interconnected and usually form a complex network of several linkages  When several food chains overlap and intersect, they make up a food web  If an earthworm is eaten by a bird, it becomes part of a larger food chain that includes material from both a detritus food chain and a photosynthesis – driven food chain. 108  Food chains and food webs 109  Thus a food web is a network of food chains where different types of organisms are connected at different trophic levels so that there are a number of options of eating and being eaten at each trophic level  In a tropical region the ecosystems are much more complex than in the Antarctic regions  This is because tropical regions have a rich species diversity  As such the food webs are much more complex 110  FOOD CHAINS / FOOD WEBS 111  As one goes up the food chain the amount of biomass present reduces  This is because much of the food consumed by an organism higher on the trophic level is either lost as undigested waste or burned up by the organism’s metabolic activity to produce heat  Very little is converted into body tissue that can be eaten by organisms higher up the food web  Just about 10% of the energy is transferred to the next trophic level  Significance of food chains and food webs 112  Food chains and food webs play a significant role in the ecosystem because the two most important functions of energy flow and nutrient recycling take place through them  Food chains also help in maintaining and regulating the population size of different animals and thus help maintain the ecological balance  Food chains show a unique property of biological magnification (biomagnification) of some chemicals  Several pesticides, heavy metals and other chemicals which are non- biodegradable in nature pass on from one trophic level to the next  At each successive successive trophic level they increase in concentration  Trophic Levels and energy flow in Ecosystems 113  In ecosystems there is always the transfer of energy.  Each step in the flow of energy through an ecosystem is known as a trophic level.  As energy flows through an ecosystem, it passes through several trophic levels.  Producers normally constitute the first trophic level  Herbivores, the second trophic level.  Carnivores that eat herbivores are the third trophic level  Carnivores that eat other carnivores occupy the fourth trophic level.  Trophic levels and energy flow in Ecosystems 114  Omnivores, parasites and scavengers occupy different trophic levels depending upon what they happen to be eating at the time  The transfer of energy occurs in accordance with the second law of thermodynamics.  Each trophic level contains a certain amount of energy.  Each time useful energy is lost, usually as heat to the surroundings.  Therefore, in most ecosystems higher trophic levels contain less energy and fewer organisms  Trophic Levels 115  Each step in the flow of energy through an ecosystem (i.e. each food level) is known as a trophic level.  Producers normally constitute the first trophic level  Herbivores occupy the second trophic level.  Carnivores that eat herbivores are the third trophic level  Carnivores that eat other carnivores as occupants of the fourth trophic level.  Omnivores, parasites and scavengers occupy different trophic levels depending upon what they happen to be eating at the time.  Trophic levels and energy flow in Ecosystems 116  It is normally difficult to actually measure the amount of energy contained in each trophic level.  One of the ways to estimate the amount of energy is to quantify the biomass.  The biomass is the weight of living material in a trophic level.  For a simple ecosystem it is often easy to collect and weigh all the producers, herbivores and carnivores.  The weights often show the same 90% loss from one trophic level to the next as happens with the amount of energy  Energy principles and laws of Energy 117  The ecosystem functions through the operation of some natural laws.  There is close interaction between the biotic and abiotic components for the maintenance of life processes  This interaction is conducted by energy flow in the system and cycling of materials  Flow of energy through an ecosystem takes place through the food chain  This energy flow keeps the ecosystem going  Energy principles and laws of Energy 118  The ecosystem operates through the cycling of matter in accordance with the law of conservation of matter and the one- way (unidirectional) energy flow in accordance with the first and second laws of energy  Matter is anything that has mass and occupies space  Energy is what is used by all living things to move matter around and to change matter from one form to the another  Work is done when energy changes from one form to the other  The Laws of matter and energy 119  The 3 major laws operating in ecosystems are:  The Law of Conservation of Matter  The 1st Law of Energy or Thermodynamics  The 2nd Law of Energy or Thermodynamics  The Laws of matter and energy 120  The Law of Conservation of Matter  Inany ordinary physical or chemical change, matter is neither created nor destroyed but merely changed from one form into the other  The 1st Law of Energy or Thermodynamics  Inany ordinary physical or chemical change, energy is neither created nor destroyed but merely changed from one form into the other.  The 2nd Law of Energy or Thermodynamics  Energy dissipates as it is used or in other words, it gets converted from a more concentrated to a dispersed form.  The Law of the conservation of matter 121  The law states “In any ordinary physical or chemical change, matter is neither created nor destroyed but merely changed from one form into another”.  This means that whatever we think we have thrown away still exists with us in one form or the other  1st and 2nd Laws of Energy 122 1. 1st law  This law states that in any physical or chemical change energy is neither created nor destroyed but merely changed from one form to the other  This means we need energy to get energy  The solar energy captured by green plants (producers) gets converted into biochemical energy of plants and the latter into that of consumers  1st and 2nd Laws of Energy 123 2. 2nd law  This law states that energy dissipates as it is used. It gets converted from a more concentrated to dispersed form  As energy flows through the food chain there occurs dissipation of energy at every trophic level  The loss of energy takes place through respiration, locomotion, running, hunting, etc.  1st and 2nd Laws of Energy 124 2. 2nd law The quality of energy is degraded into a low quality of energy which is mostly in the form of heat  This energy cannot be used to do useful work and is called entropy  The entropy of the universe is thus increasing  Normally the quality of the energy available for useful work will always be lower in quality than the initial energy.  At every level there is about 90% loss of energy.  Only 10% energy is transferred from one trophic lever to the next 125 Energy flow Energy from sun (1000J) We can recycle matter but for all Not absorbed practical purposes we cannot Absorbed (240J) (760J) recycle energy. Production (12J) Heat release (228J) Building new cell Maintenance (7J) tissue (5J) New cell tissue (0.5J) Maintenance (4.5J) New cell tissue Maintenance (0.45J) (0.05J) New cell tissue (0.005J) The rest for maintenance  1st and 2nd Laws of Energy 126  All machines and living things that manipulate energy release heat.  Organized matter tends to become more disordered unless an external source of energy is available to maintain the ordered arrangement.  The chemical reaction that causes rust, for example, releases heat.  Ultimately, orderly arrangements of matter, such as clothing, automobiles, or living organisms, become disordered.  There is therefore an increase in entropy.  1st and 2nd Laws of Energy 127  Eventually, non living objects wear out and living things die and decompose.  This process of becoming more disordered coincides with the constant flow of energy towards a dilute form of heat.  This dissipated, low quality heat has little value to us, since we are unable to use it.  1st and 2nd Laws of Energy 128  It is important to understand that energy that is of low quality from our point of view may still have significance to the world in which we live.  For example the distribution of heat energy in the ocean tends to moderate the temperature of the coastal climates.  High usage of resources particularly petroleum products leads to increase in atmospheric temperature because the petroleum is reduced into low quality energy in the form of heat anytime it is used  1st and 2nd Laws of Energy 129  It is important to recognize that we can sometimes figure new ways to convert low quality energy to high quality energy. Eg. Low quality wind energy to high quality electricity.  An unfortunate consequence of energy conversion is pollution.  The heat lost from most energy conversions is a pollutant.  The wear of the brakes used to stop cars results in pollution.  The emissions from power plants pollute  Trophic Levels and energy flow in Ecosystems 130  In ecosystems there is always the transfer of energy.  The transfer occurs in accordance with the second law of thermodynamics.  As energy flows through an ecosystem it passes through several levels known as trophic levels.  Each trophic level contains a certain amount of energy.  The percentage of useful energy from one trophic level to another is called ecological efficiency or food chain efficiency  Trophic Levels and energy flow in Ecosystems 131  Each time useful energy is lost, usually as heat to the surroundings.  Therefore, in most ecosystems higher trophic levels contain less energy and fewer organisms  It is normally difficult to actually measure the amount of energy contained in each trophic level.  One of the ways to estimate the amount of energy is to quantify the biomass.  Trophic levels and energy flow in Ecosystems 132  The biomass is the weight of living material in a trophic level.  For a simple ecosystem it is often easy to collect and weigh all the producers, herbivores and carnivores.  The weights often show the same 90% loss from one trophic level to the next as happens with the amount of energy  Ecological pyramids 133  An ecological pyramid is a graphic representation of the trophic structure and function of an ecosystem starting with producers at the base and successive trophic levels forming the apex  There are 3 types of ecological pyramids  Pyramid of numbers  Pyramid of biomass  Pyramid of energy  All the pyramids show the effects of the second law of thermodynamics on the flow of energy through systems  Ecological pyramids 134  Pyramid of numbers  This represents the number of individual organisms at each trophic level  The number of organisms in each level is counted  The pyramid may be upright or inverted depending on the type of ecosystem and food chain  E.g. Grassland ecosystems and pond ecosystems show upright pyramids  This basis for comparison of ecosystems is not reliable in most cases  The pyramid of biomass seems to solve the ambiguity in the pyramid of numbers 135 Pyramid of numbers - Grassland  Producers in the grassland are grasses which are small in size but Hawks, other very large in number Top birds carnivores  The producers therefore form a broad base Frogs, birds Carnivores  The herbivores are insects which are smaller in number Herbivores  The tertiary consumers are hawks Insects and are also less in number  The apex therefor becomes Grasses Producers narrower, giving an upright pyramid 136 Pyramid of numbers  137 Pyramid of numbers: Forest  Big trees are the producers in a forest ecosystem. These are less in number, forming a narrow base  A large number of herbivores including insects, birds and several species of animals feed on the Top Lion, tiger leaves, fruits, flowers, bark etc of the trees carnivores  These thus form a broader middle level Snakes, foxes,  Secondary consumers such as foxes, snakes and Carnivores lizards lizards feeding on the herbivores are fewer in number than the herbivores Herbivores Insects, birds  The top carnivores such as lions, tigers etc. are even much smaller in number Producers  The pyramid is therefore narrow at the ends and Trees broader in the middle  Pyramid of numbers: Parasitic food chain 138  Producers such as a few big trees Fleas, harbour fruit eating birds Hyper parasites microbes  These birds act like herbivores, which are larger in number than the Parasites Lice, bugs trees  A much higher number of lice, bugs Herbivores Birds etc grow as parasites on these birds  A greater number of Producers Trees hyperparasites such as fleas and microbes feed on them  An inverted pyramid thus results 139 Pyramid of numbers Grassland Forest Hawks, other Top birds carnivores Top Lion, tiger carnivores Snakes, foxes, Frogs, birds Carnivores Carnivores lizards Herbivores Herbivores Insects Insects, birds Grasses Producers Producers Trees  Ecological pyramids 140  Pyramid of biomass  Thisis based on the total biomass (dry matter) at each trophic level in a food chain  The pyramid can either be upright or inverted  Pyramid of biomass in a forest is upright in contrast to its pyramid of numbers. ◼ This is because the producers, which are trees accumulate a huge biomass while the consumers’ total biomass feeding on them declines at higher trophic levels, resulting in a broad base and narrow top  Pond ecosystems also show an inverted pyramid of biomass  Ecological pyramids 141  Biomass measurements are based on dry weights of the organisms  Comparing food webs in fresh weights could be deceptive  It is usually expressed in g/m2 or in metric tons per hectare 142 Pyramid of biomass - Grassland Snakes, frogs, birds carnivores Squirrels, rabbits, Insects Herbivores Grasses, Producers herbs  Pyramid of biomass: pond 143  The total biomass of producers Tertiary carnivores Big fish (phytoplankton) is much less compared to herbivores Carnivores Small fish (zooplankton, insects), carnivores (small fish) and tertiary carnivores (big fish) Herbivores Insects  The pyramid therefore takes an inverted shape with a narrow base Producers and broad apex Phytoplankton  Ecological pyramids 144  Pyramid of energy  The amount of energy present at each trophic level is considered for this type of pyramid  Pyramid of energy gives the best representation of the trophic relationships and is always upright  At each successive level there is a huge loss of energy (90%) in the form of heat, respiration etc.  There is therefore a sharp decline in energy level of each successive trophic level as we move up from producers to top carnivores. 145 Pyramid of energy Top carnivores Carnivores Herbivores Producers  Limiting factors 146  Every organism’s survival depends on chemical and physical factors  Chemical factors may include  Carbon dioxide  Oxygen  Nitrogen etc.  Physical factors include  Temperature  Light  Precipitation and  Humidity  Organisms are affected by a combined action of these factors  Limiting factors 147  A shortage, excess or absence of these factors can affect its number or distribution.  Such factors are known as limiting factors.  A limiting resource is the nutrient or substance that is in shortest supply in relation to organisms’ demand for it  Too much or too little of any single factor may destroy an organism or limit its numbers and distribution  The limiting factor principle & law 148  This principle deals with the degree of availability of factors, the distribution and the abundance of an organism  Determined by whether the levels of one or more limiting factors fall above or below the levels required by the organism  The law states that the existence, abundance, or distribution of an organism can be determined by whether the level of one or more limiting factors falls above or below the levels required by the organism  Kinds of organism interactions 149  Predation  This is a kind of interaction where one organism – the predator, kills and eats another (known as prey).  To succeed many predators employ several strategies including strength, speed and snares to overpower their prey.  Obviously for the prey to survive, they need to and do breed more else they become extinct.  Normally the prey that is healthier, quicker and better adapted is likely to survive.  Kinds of organism interactions 150  Competition  In this kind of interaction two organisms strive to obtain the same limited resource.  Two kinds of competition exist – Intraspecific and Interspecific competition.  Competition among members of the same species is intraspecific while competition between members of different species is referred to as interspecific competition.  Kinds of organism interactions 151  Competition among members of the same spp. is a major force in shaping the evolution of a species.  When resources are limited, less well-adapted individuals are more likely to die or be denied mating privileges.  Because the most successful organisms are likely to have larger numbers of offspring, each succeeding generation will contain more of the genetic characteristics that are favourable for survival of the species in that particular environment.  Kinds of organism interactions 152  Since individuals of the same species have similar needs, competition among them is usually very intense.  A slight advantage on the part of the individual may mean the difference between survival and death.  Kinds of organism interactions 153  Competitive Exclusion Principle  This is the concept that no two species can occupy the same ecological niche in the same place at the same time.  The more similar two species are, the more intense will be the competition between them.  If one of the two is better adapted to live in the area than the other, the less fit species must evolve into a slightly different niche, migrate to a different geographic area or become extinct.  Kinds of organism interactions 154  Symbiosis is a close long lasting physical relationship between two different species where at least one of them derives some sort of benefits from the contact / interaction.  Three types of symbiotic relationships exist:  Parasitism,  Commensalism  Mutualism.  Kinds of organism interactions 155  Parasitism A relationship in which one organism known as the parasite lives in or on another organism known as the host from which it derives some form of benefit e.g. Nourishment.  Parasites are normally smaller than the host. The host generally is harmed, it is generally not killed immediately.  Two kinds of parasites occur – endoparasites and ectoparasites  Kinds of organism interactions 156  Commensalism A relationship between two organisms in which one organism benefits while the other is not affected.  Many commensal relationships are rather opportunistic and may not involve a long-term physical contact.  Kinds of organism interactions 157  Mutualism  A relationship that benefits both species involved.  In most mutualistic relationships the relationship is obligatory; the species cannot live without each other.  In others the species can exist separately but are more successful when they are involved in a mutualistic relationship. E.g. Many kinds of plants such as legumes (beans, peanuts, clover etc) have bacteria that live in their roots in little nodules.  The roots form nodules when they are infected with certain kinds of bacteria.  The bacteria do not cause disease but provide the plants with nitrogen-containing molecules that the plant can use for growth.  Similarly, many kinds of fungi form an association with the roots of plants. The root-fungus associations are called mycorrhizae.  Roles of organisms in ecosystems 158  Producers: are organisms that are able to use simple inorganic substances in their environment together with sunlight to produce / make complex organic molecules.  Consumers: are organisms that require organic matter as a source of food.  They consume the organic matter to provide themselves with energy and the organic molecules necessary to build their own bodies.  They break down the organic matter to simple inorganic molecules through the process of respiration.  Roles of organisms in ecosystems 159  Decomposers:- organisms that use non-living organic matter as a source of energy and raw materials to build their bodies.  Whenever an organism sheds a part of itself, excretes waste products or dies, it provides a source of food for decomposers.  Decomposers are extremely important in recycling matter by converting organic matter to inorganic material.  Scavengers:- these animals eat carcasses.  Roles of organisms in ecosystems 160  Based upon the way they obtain their food and the kinds of things they eat, consumers can be classified as either primary consumers or secondary consumers  Primary consumers (herbivores) are animals that eat producers (plants and phytoplanktons) as a source of food.  Secondary consumers (carnivore) are animals that eat other animals  Omnivores : Animals that eat both plants and other animals  Materials flow in the ecosystem 161  There are dynamic relations between the living forms and their physical environment  These relations exist as biogeochemical cycles which involve continuous circulation of essential elements and compounds necessary for life.  The biogeochemical cycles for matter recycling in the ecosystem are natural cycles  The cycle describes the convention and movement of materials by biochemical forces through the ecosphere  A biogeochemical cycle is therefore a pathway by which conserved matter moves through biotic and abiotic components of the ecosystem through the law of conservation of matter  Materials flow in the ecosystem 162  These elements and compounds cycle from the environment to organisms and back to the environment i.e.  Materials cycle in the ecosystem through biotic and abiotic components (through the atmosphere, lithosphere, hydrosphere and biosphere)  The nutrients move through the food chain ultimately ending up in detritus  Initial decomposition of detritus by microorganisms  Nitrogeneous matter → ammonia  Carbonaceous matter → carbon dioxide  Sulphurous matter → hydrogen sulphide  Materials flow in the ecosystem 163  There is further decomposition of these products until final stabilised or fully oxidised products are formed (NO3-, CO2, SO42-, PO43-)  CO2 is used as a source of carbon by plants  NO3-, SO42-, PO43- are used as nutrients or for formation of new plant tissues  Biogeochemical cycles therefore involve the transport and transformation of substances through the earth’s system  The natural cycles and ecosystems function in a balanced manner which stabilises biosphere and sustains the life processes on earth  Materials flow 164  Main elements cycling are:  Carbon  Nitrogen  Sulphur  Hydrogen  Phosphorus  Oxygen  These are the basic elements of which all living organisms are composed  Biogeochemical cycles 165  There are three main types of biogeochemical cycles in nature  Gaseous Cycles: e.g. N, C and O2 cycles  Hydrological cycle: water  Sedimentary cycle eg. Ca, P, S, Fe  Hydrological Cycle 166  This cycle helps in exchange of water between air, land, sea, living plants and animals.  It involves  Massive evaporation of water from the ocean  Cloud formation  Rainfall which gives us our supply and reserves of fresh water  Depending on the temperature, it may be rain, snow or hail 167  The hydrologic (water) cycle 168  Water travels on the surface of the earth, underground and in the atmosphere in a cycle – the hydrologic or water Cycle.  Clouds provide precipitation in the form of rain, snow and hail.  Water runs on the surface. Part is used by the vegetation; part flows to the water bodies or infiltrates the soil to form the Invisible phenomena underground water bodies. Evaporation, absorption, water vapour and transport by winds –  Surface water bodies evaporate under the sun energy required for process effect of the sun into gaseous form in the Visible phenomena – atmosphere. condensation, precipitation,  Water vapour condenses in contact with snow, runoff, infiltration, superficial and underground cold air masses, which then creates clouds flow. and comes down as rain.  The carbon cycle 169  Carbon is by far one of the most important elements on earth  Carbon is found in:  All living organisms: It is the building block of all organic substances and therefore the building block of life  The atmosphere, mainly as carbon dioxide and bicarbonate  Soil humus  Fossil fuels  Rocks and soils, mainly as carbonate minerals in limestone or dolomite, or in shales  The carbon cycle 170  The largest reservoir of carbon is the ocean, containing about 85% of the world’s carbon  Carbon is found in the form of dissolved carbon dioxide gas, carbonate and bicarbonate ions  Photosynthesis is the major driving force for the carbon cycle  Green plants take up carbon dioxide as a raw material for photosynthesis through which carbohydrates and other organic substances are produced 6CO + 6H O + 2800kJenergy ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→C H O + 6O 2 2 chlorophyll 6 12 6 2  The carbon cycle 171  The carbon cycle 172  The carbon cycle 173  Formed organic matter then moves through the food chain and is ultimately returned to the atmosphere as carbon dioxide by microorganisms  Respiration by all organisms produces carbon dioxide which is used up by green plants  Stored carbon dioxide in fossil fuels are released by combustion processes  Carbon dioxide is also released by  Fires  Diffusion from oceans  Weathering of rocks  Precipitation of carbonate minerals  The Nitrogen Cycle 174  Nitrogen is the most abundant gas in the atmosphere (78%)  It is an essential constituent of protein, DNA, RNA, chlorophyll  It is cycled through the ecosystem in combined form such as oxides, or reduced form such as ammonia, amino acids, proteins  Atmospheric nitrogen must be fixed or converted into a usable form by:  High energy fixation  Biological fixation  Nitrogen cycle 175  High energy fixation: A small amount of atmospheric nitrogen is fixed by lightening  High energy combines N and H2O resulting in NH3 and NO3  These are then carried to the earth as precipitation  Biological fixation  Responsiblefor 90 % of the nitrogen fixation  Atmospheric nitrogen (N2) is split and combined with hydrogen atoms to form ammonia (NH3)  The Nitrogen Cycle 176  Many kinds of microorganisms fix nitrogen by reducing it to ammonium compounds.  nitrogen fixing bacteria in soils fix nitrogen  all leguminous plants fix nitrogen in the root nodules that contain bacteria  Plants convert fixed nitrogen into proteins and other forms of nitrogen.  When animals feed on plants the proteins are transferred.  The Nitrogen Cycle 177  Some photosynthetic microorganisms also fix atmospheric nitrogen gas by converting it to organic nitrogen  In lakes nitrogen fixing microorganisms are photosynthetic bacteria (cyanobacteria or blue green algae)  Lichens and the aquatic fern Azolla also fix nitrogen in association with some cynobacteria  Upon death of plants and animals, decomposers break down large organic nitrogen molecules into ammonium salts, which are soluble in water. 178 The nitrogen cycle Nitrogen fixing bacteria in soil and root noodles of leguminous plants eg. Clover, peas, beans  The Nitrogen Cycle 179  NH3 in the soil, is combined with H+ ions to form ammonium ion or is converted to NO3 by nitrifying bacteria in a 2-step process (nitrification)  Nitrosomonas  4𝑁𝐻4+ + 6𝑂2 → 4𝑁𝑂2− + 8𝐻 + + 4𝐻2 𝑂  Nitrobacter  4𝑁𝑂2− + 2𝑂2 → 4𝑁𝑂3−  Overall reaction  𝑁𝐻4+ + 2𝑂2 → 𝑁𝑂3− + 2𝐻 + + 𝐻2 𝑂  The Nitrogen Cycle 180  Nitrogen is returned to the atmospheric reservoir by denitrifying bacteria (denitrification)  2𝑁𝑂3− + 𝑜𝑟𝑔𝑎𝑛𝑖𝑐 𝑐𝑎𝑟𝑏𝑜𝑛 → 𝑁2 + 𝐶𝑂2 + 𝐻2 𝑂  The Nitrogen Cycle 181  In lakes nitrogen is usually in the form of nitrate and comes from external sources; inflowing streams or groundwater  When taken up by algae and other phytoplankton it is chemically reduced to amino compounds and incorporated into organic compounds  When dead algae undergo decomposition the organic nitrogen is released to the water as ammonia  The Nitrogen Cycle 182  This ammonia and that from other sources such as industrial wastes and agricultural runoff is oxidised to nitrate by nitrifying bacteria  Nitrogen therefore cycles from nitrate to organic nitrogen, to ammonia and back to nitrate if the water is aerobic  Under anoxic conditions eg in anaerobic sediments, when algal decomposition has depleted the oxygen nitrate is reduced by bacteria to nitrogen gas (denitrification) PHOSPHORUS CYCLE  Reading assignment 184  Read further on the following natural cycles  Geologic cycle  Hydrologic cycle  Carbon cycle  Nitrogen cycle  Sulphur cycle  Phosphate cycle  Oxygen cycle  Environmental crisis 185  The laws of energy give keys to understanding the environmental crisis currently challenging the world.  Environmental problems we are confronted with include  Global warming  Ozone layer depletion  Air pollution  Floods  Polluted water supply  Waste disposal  Land degradation  Desertification  Destruction of rainforest  Rapid population growth etc  Ozone 186  The proliferation of ozone is one of the most widespread environmental problems and one of the most difficult to manage.  Just about every major urban area of the country exceeds the health protective limits for ozone established by the various EPA.  Ozone is a colorless gas with a pungent odor, and the chief component of smog.  Chemically it is a form of oxygen with three oxygen atoms instead of the two normally found in oxygen.  It is very reactive.  Ozone levels high enough to cause health problems for people are also high enough to damage crops and vegetation.  Ozone can also damage the lungs of man, building materials and cultural treasures (monuments).  Ozone 187  Ozone could exist in the troposphere or the stratosphere.  Ozone is produced in the atmosphere (troposphere) when sunlight triggers certain chemical reactions.  The precursors, or chemicals that are initially needed for this reaction to take place include volatile organic compounds (VOCs) and nitrogen oxides (NOx).  VOCs are released into the air when petroleum products are combusted, handled or processed.  NOx are also produced by combustion.  Sunlight provides energy to fuel the reactions between the VOCs and the NOx and naturally occurring atmospheric gases, resulting in the production of ozone and eventual generation of smog.  Ozone 188  Recent findings indicate that some pollutants especially ozone are more harmful in lower concentrations than previously thought because they could cause life long, permanent health damage.  Ozone is the most serious threat to vegetation.  It attacks leaves causing them to yellow, develop dead spots and drop early.  It can reduce plant’s growth, fruit yield and increase susceptibility to insect attack and interferes with photosynthesis.  Ozone 189  The ozone layer in the stratosphere filters out some of the UV light from the sun.  Destruction of the ozone layer allows more of the sun’s UV rays to penetrate to us.  Increased UV can lead to greater incidence of skin cancer, cataracts, reduction in populations of certain fish larvae and plankton.  It also reduces the useful life of outdoor paints and plastics.  Chlorofluoro-carbons (CFC) are compounds that consist of Cl, F and C and used as coolants for refrigerators, air conditioners, propellants for aerosol sprays agents for producing plastic foam and cleansers for electrical parts.  CFCs do not degrade easily in the first layer of the atmosphere (troposphere) and so rise into the stratosphere.  CFCs are broken down by UV light in the stratosphere.  The chlorine atoms released react with the ozone layer to convert it into two molecules of oxygen and chloride.  OZONE UV F Cl F Cl C → C + O3 → O2 + Cl-O → Cl F Cl F O + Cl-O → O2 + Cl  Ozone 191  The Halons are also industrially produced group of chemicals that contain bromine.  Halons destroy ozone in a manner similar to chlorine.  Halons are used primarily in fire extinguishing foam.  Green house gases and global warming 192  Green house effect is a natural phenomenon caused predominantly by water vapour, NO2, O3, CO2 and CH4 (methane) and other gases in the atmosphere.  Their effect on the earth is comparable to that of the glass in a green house.  Greenhouse gases greatly affect the temperature of the Earth  Without them, the earth's surface would be on average about 33 °C (59 °F) colder than at present.  Global warming 193  Visible light passes through the atmosphere to the earth’s surface.  When the light is absorbed by the earth, it is converted to heat.  Some heat escapes, CO2 and other gases in the troposphere trap the rest, warming the earth.  This allows the earth to maintain a warm temperature and support life.  If there is no green house effect, the earth will be much colder.  In recent years, activities of man have generated a lot of CO2 and many people have become concerned about human activity causing the earth to become too warm.  It is important to recognize that there is a great deal of disagreement among scientists about whether global warming is actually occurring.  Causes of global warming 194  Certain types of air pollutants may be producing long-term and perhaps irreversible changes to the global atmosphere.  Industrial growth since the mid-nineteenth century has released large amounts of CO2 into the troposphere.  Burning fossil fuels such as coal, oil and natural gas also release large amounts of CO2.  Clearing of rain forests by burning the wood contributes CO2 and other green house gases to the atmosphere.  Clearing of forests also means less CO2 is removed from the air by plants.  Effects of global warming 195  Recent studies and computer models indicate that by increasing the amount of CO2 in the atmosphere, we may have initiated a warming trend that may raise, average global temperature between 2°F (-16.7°C) to 8°F (-13.3°C) by the year 2050.  Global warming may change weather patterns and regional climates  Natural important agricultural areas could become less productive  Natural ecosystems would also be affected.  Leads to rising sea levels of one foot in the next 30 to 40 years and two to seven feet by the year 2100.  This can inundate 50 to 80% of the US, coastal wetlands, erode all recreational beaches and increase salinity of estuaries and groundwater.  Acid rain 196  Acid rain is mainly attributable to the strong mineral acids –Sulphuric and nitric acids that are derived from oxidation of SO2 and NOx respectively.  Pollutant emission of the strong acids - nitric and sulphuric a