Lesson 3_Ecosystem and Pathways of Energy PDF

Lesson 3 : Ecosystem and Pathways of Energy GEC 21.1 - ENVIRONMENTAL SCIENCE  The meaning of the word ecology was given by German Biologist Haeckel in 1869. The word ecology is derived from Greek words ‘Oikos’ meaning house, habitat...

Lesson 3 : Ecosystem and Pathways of Energy GEC 21.1 - ENVIRONMENTAL SCIENCE  The meaning of the word ecology was given by German Biologist Haeckel in 1869. The word ecology is derived from Greek words ‘Oikos’ meaning house, habitat or place of living and ‘Logos’ meaning to study. After that…. Danish botanist, Eugenius Warming elaborated the idea of Ecology. Definition Ecology is the study of interactions among organism or group of organisms wit h their environment. The environment consists of both biotic components (living organisms) and abiotic components (non – living organisms).  Ecology is study of interactions between Non-living components in the environment… Light Water Wind Nutrients in soil Heat Solar radiation Atmosphere, etc. AND… Living organisms… Plants Animals Microorganisms in soil, etc.  Ecosystem The term Ecosystem was first proposed by A.G. Tansley in 1935. An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living environment. There are many examples of ecosystems - a pond, a desert, a forest, an estuary, an ocean. Ecosystem is the basic functional unit of Ecology. Definition A group of organisms interacting among themselves and with environment is known as ecosystem. Thus an ecosystem is a community of different species interacting with one another and with their non living environment exchanging energy and matter. Ecology is the study of ecosystems. Example Animals cannot synthesis their food directly but depend on the plants either directly or indirectly.  STRUCTURE OF AN ECOSYSTEM The term structure refers to the various components of an ecosystem. An ecosystem has two major components Biotic (living) components Abiotic (non living) componentsBiotic components Theliving organisms (or) living members in an ecosystemcollectively called biotic components (or) biotic community. Ex: Plants, Animals, Microorganisms  Classification biotic components The members of biotic components of an ecosystem are grouped in to three based on how they get food. Producer (Plants) Consumer (Animals) Decomposers (Micro-organisms) 1.Producers (Autotrophs) Producers synthesise their food themselves through photosynthesis Ex: All green plants, trees. Photosynthesis The green pigment called chlorophyll, present in the leaves of plants, converts CO2 and H2O in the presence of sunlight into carbohydrates. 6CO2 + 6H2O - - - -> C6H12O6 + 6O 2 This process is called photosynthesis V.S.Saravana Mani, Head & AP/ Chemistry, AEC 2. Consumers also called as Heterotrophs: Classification of consumers Consumers are further classified as (i) Primary consumers or Herbivores or Plant eaters: Primary consumers are also called herbivores, they directly depend on the plants for their food. So they are called plant eaters. Examples : Insects, rat, goat, deer, cow etc. (ii) Secondary consumers (primary carnivores) (Meat eaters): Secondary consumers are primary carnivores, they feed on primary consumers. They directly depend on herbivores for their food. the Ex: Frog, cat, snakes, small birds, etc., (iii) Tertiary consumers (Secondary carnivores) (Meat- eaters) Tertiary consumers are secondary carnivores, they feed on secondary consumers. They depend on the primary carnivores for their food. Ex: Hawk, Eagle, Tiger, Lion, etc., Omnivore: Organisms that feed both on plants and animals. Ex: Human, rat, birds. Detritivore: They feed on dead organisms, wastes of living beings and partially decomposed matter. Ex: Termites, earthworm, ants etc. 3. Decomposers Decomposers attack the dead bodies of producers and consumers, and decompose them into simpler compounds. During the decomposition inorganic nutrients are released. The inorganic nutrients together with other organic substances are then utilised by the producers for the synthesis of their own food.  Abiotic (non-living) components The non-living components (physical and chemical) of ecosystem collectively form a community called abiotic components (or) abiotic community. Ex: Climate, soil, water, air, energy etc., 1.Physical components: Include the energy, climate, nutrients and living space that the biological community needs. They are useful for the growth and maintenance of its member. Ex: Air, water, soil, sunlight, etc., 2.Chemical Components: They are the sources of essential nutrients. Organic substances : Protein, lipids, carbohydrates, etc., Inorganic substances: All micro (Al, Co, Zu, Cu) and macro elements (C,H, O, P, N, P,K) and few other elements.  TYPES OF ECOSYSTEM Natural ecosystem: These operate themselves under natural conditions. Based on habitat types, it can be further classified into: 1. Terrestrial ecosystem: This ecosystem is related to land. Ex: Grassland ecosystem, forest ecosystem, desert ecosystem, etc., 2. Aquatic ecosystem: This ecosystem is related to water. I t is further sub classified into two types based on salt content. Fresh water ecosystem (a) Running water ecosystems. Ex: Rivers, Streams… (b) Standing water ecosystems Ex: Pond, lake… Marine ecosystem Ex: Seas and sea shores… 3. Man – made (or) Artificial ecosystems: Artificial ecosystem is operated (or) maintained by man himself.  FUNCTION OF AN ECOSYSTEM The function of an ecosystem is to allow flow of energy and cycling of nutrients. Functions of an ecosystem are of three types. Primary function: The primary function of all ecosystem is manufacture of starch (photosynthesis). Secondary function: The secondary function of all ecosystem is distribution energy in the form of food to all consumers. Tertiary Function: All living systems diet at a particular stage. These dead systems are decomposed to initiate third function of ecosystems namely “cycling”.  The functioning of an ecosystems may be understood by studying the following terms. Energy and material flow. Food chains Food webs Food pyramids  ENERGY FLOW IN THE ECOSYSTEMS Energy is the most essential requirement for all living organisms. Solar energy is the only source to our planet earth. Solar energy is transformed to chemical energy in photosynthesis by the plants (Primary producers). S ome amount of chemical energy is used by the plants for their growth and the remaining is transferred to consumers by the process of eating. Thus the energy enters the ecosystems through photosynthesis and passes through the different tropic levels or feeding levels. The flow of energy in an ecosystem follows the laws of thermodynamics. I law of thermodynamics - “Energy neither can be created nor destroyed, but it can be converted from one from to other”. Energy for an ecosystem comes from the sun. I t is absorbed by plants, it is converted into chemical energy. This chemical energy utilised by consumers transform into heat. I I law of thermodynamics - “Whenever energy is transformed, there is a loss of energy through the release of heat”. Energy is transferred between tropic levels in the form of heat as it moves from one tropic level to another tropic level. The loss of energy takes place through respiration, work, running, hunting etc., Flow of energy and nutrient cycling from abiotic to biotic and vice versa.  FOOD CHAINS Definition “There sequence of eating and being eaten in an ecosystem is known as food chain” (or) “Transfer of food energy from the plants through a series of organisms is known as food chain” A food chain always starts with plant life and ends with animal. When the organisms die, they are all decomposed by microorganism (bacteria and fungi) into nutrients that can again be used by the plants. At each and every level, nearly 80-90% of the potential energy gets lost as heat.  Tropic Levels (T1,T2, T3, T4, T5) (or) Feeding levels The various steps through which food energy passes in an ecosystem is called as tropic levels. The tropic levels are arranged in the following way, The green plants or producers represent first tropic level T1, The herbivores or primary consumers represent second tropic level T2. The carnivores or secondary consumers represent third tropic level T3. The tertiary consumers are fourth tropic level T4. Finally decomposers represent last tropic level T5.  Food chains are classified into two main types Grazing food chain Detritus food chain Grazing food chain: Found in Grassland ecosystems and pond ecosystems. Grazing food chain starts with green plants (primary producers) and goes to decomposer food chain or detritus food chain through herbivores and carnivores. Detritus food chain: Found in Grassland ecosystems and forest ecosystems. Detritus food chain starts with dead organic matter (plants and animals) and goes to decomposer food chain through herbivores and carnivores. The following diagram shows that grazing food chain and detritus food chain are interconnected to each other but are not isolated.  FOOD WEB The interlocking pattern of various food chains in an ecosystem is known as food web. In a food web many food chains are interconnected, where different types of organisms are connected at different tropic levels, so that there are a number of opportunities of eating and being eaten at each tropic level. Grass may be eaten by insects, rats, deer's, etc., these may be eaten by carnivores (snake, fox, tiger). Thus there is a interlocking of various food chains called food webs Difference between food chains and food web: In a linear food chain if one species gets affected (or) becomes extinct, then the species in the subsequent tropic levels are also affected. But, in a food web, if one species gets affected, it doestnot affect other tropic levels so seriously. There are number of options available at each tropic level.  Significance of food chains and food webs Food chains and food webs play a very important role in the ecosystem. Energy flow and nutrient cycling takes place through them. They maintain and regulate the population size of different tropic levels, and thus help in maintaining ecological balance. They have the property of bio-magnification. The non – biodegradable materials keep on passing from one tropic level to another. At each successive tropic level, the concentration keep on increasing. This process is known as bio-magnification.  ECOLOGICAL PYRAMIDS “Graphical representation of structure and function of tropic levels of an ecosystem, starting with producers at the bottom and successive tropic levels forming the apex is known as an ecological pyramid.” In food chain starting from the producers to the consumers, there is a regular decrease in the biomass and number of the organisms. Since energy is lost as heat in each tropic levels, it becomes progressively smaller near the top.  Types of Ecological pyramids Pyramid of numbers. Pyramid of energy. Pyramid of biomass.  I t represents the number of individual organisms present in each tropic levels. Ex: A grassland Ecosystem The producers in the grasslands are grasses, which are in size and large in numbers. So the producers occupy lower tropic level (1St tropic level). The primary consumers (herbivores) are rats, the 2nd tropic level. Since the number of rats are lower Compared to the grasses, the size is small. The secondary consumers (carnivores) are snakes, which occupy the 3rd tropic level. Since the number of snakes are lower when compared to the rats. The tertiary consumers (carnivores) are eagles, which the next tropic level. The number and size of the last level is till smaller. Upright Pyramid A pyramid of biomass is a graphical representation of biomass present in a unit area of various trophic levels. I t shows the relationship between biomass and trophic level quantifying the biomass available in each trophic level.  Pyramid of Biomass I t represents the total amount of biomass (mass or weight of biological material or organism) present in each tropic levels. Ex: A forest ecosystem The above figure shows that there is a decrease in the biomass from the lower tropic level to the higher tropic level. This because the trees (producers) are maximum in the forest, which contribute a huge biomass. The next tropic levels are herbivores (rabbit, deer) and carnivores (snakes, fox). Top of the tropic level contains few tertiary consumers (lion, tiger), the biomass of which is very low. Pyramid of Energy This pyramid indicates not only the amount of energy flow at each level, but more importantly, the actual role the various organisms play in the transfer of energy. An energy pyramid illustrates how much energy is needed as it flows upwards to support the next trophic level. Always there is a huge loss of energy.  FOREST ECOSYSTEM A forest is an area with a high density of trees. A forest ecosystem is one in which tall trees grow that support many animals and birds. The forests are found in undisturbed areas receiving moderate to high rainfall. The forest occupies nearly 3 1 % of the world’s land in India it is only 19% of total land area. Types of forest ecosystem Based upon the climate conditions, forests are classified into Tropical Rain forests. Tropical deciduous forests. Tropical scrub forests. Temperate rain forests. Temperate deciduous forests.  Characteristics of forest ecosystems Forests are characterised by warm temperature and adequate rainfall, which make the generation of number of ponds, lakes etc., The forest maintains climate and rainfall. The forest support many wild animals and protect biodiversity. The soil is rich in organic matter and nutrients which support the growth of trees. Since penetration of light is so poor, the conversion of organic matter into nutrients is very fast. Structure and Function of forest ecosystem I. Abiotic components The abiotic components include basic inorganic & organic compounds present in the soil & atmosphere. In addition minerals, the occurrence of litter is characteristic features of majority of forests. II. Biotic components 1. Producers: In a forest, the producers are mainly trees produce food by photosynthesis. Apart from trees, climbers, epiphytes, shrubs and ground vegetation. Dominant species of trees in forest are Dalbergia, Tectona grandis, Lichens, Fern, Pine, Cedar. 2. Consumers Primary consumers (herbivores): They directly depend on the plants for their food. Ex: Ants, flies, insects, mice, deer, squirrels. Larger animals such as Elephants, Deer, Giraffe etc. Secondary consumers (primary carnivores):They directly depend on the herbivores for their food. Ex: Lizards, snakes, birds, fox. Tertiary consumers :They depend on the primary carnivores for their food. Ex: Animals like tiger, lion, etc., 3. Decomposers They decompose the dead plant and animal matter. Ex: Bacteria and fungi. I t provides numerous environmental services like; Ø Nutrient cycling, Ø Maintaining biodiversity Ø Providing wildlife habitat Ø Affecting rainfall patterns Ø Regulating stream flow Ø Storing water Ø Reducing flooding Ø Preventing soil erosion Ø Reclaiming degraded land & many more…. Apart from environmental values, forest ecosystems have some traditional values as well. Ø Fire Wood & Timber. Ø Fruits. Ø Gums. Ø Herbs & drugs.  GRASSLAND ECOSYSTEM Grassland occupies about 2 0 % of earth’s surface. In addition to grass some trees and shrubs are/also present in grasslands. Limited grazing helps to improve the net primary production of the grasslands. But, overgrazing leads degradation of these grasslands resulting in desertification. Types of grassland ecosystem Depending upon the climate conditions grassland are classified into three types Tropical grasslands Temperate grasslands Polar grasslands  Features of different types of grassland Tropical grasslands They are found near the borders of tropical rain forests. Characterised by high temperature and moderate rainfall (40 to 100 cm). I t is also known as Savanna type. Tall grasses with scattered shrubs and stunted trees and animals like zebras, giraffes, antelopes, etc., are observed here. Temperate grasslands They are usually found in the centres of continents, highly sloped hills. They are characterised by very cold winters and hot summers: Intense grazing and summer fires, do not support shrubs or trees to grow.  Polar grasslands They are found in arctic polar regions. They are characterised by severe cold and strong winds along with ice and snow. In summers several small annual plants grow. There are animals like arctic wolf, weasel, arctic fox, etc., Characteristics of Grassland Ecosystems Grassland ecosystem is a plain land occupied by grasses. Soil is very rich in nutrients and organic matter. Since it has tall grass, it is ideal place for grazing animals. I t is characterised by low or uneven rainfall. Structure and function of the grassland Ecosystems Abiotic components: Nutrients, H, 0, N, P, S, etc., These abiotic components are supplied by C02, H2O, C, Nitrate, phosphates and sulphates. Biotic Components Producers: They produce food. Ex: Grasses, Herbs and shrubs. Consumers:. Primary consumers (herbivores) :They depend on grasses for their food Ex: Insects, cows, buffaloes, deer, sheep, etc., Secondary consumers (carnivores) :They feed on herbivores. Examples: Lizards, birds, Snakes, jackals, fox, etc., Tertiary consumers: They feed on secondary consumers Ex: Hawks, eagle, etc., Decomposers :They decompose the dead organic matter Ex: Fungi and bacteria. Importance: Grasslands are of vital importance for raising livestock for human consumption and for milk and other dairy products Grasslands provided home to many different animals that were hunted and domesticated They are used as grazing area for cattle They Maintain Biodiversity Protects restored habitat for many plants and animals including pheasant, ducks, songbirds and endangered species  DESERT ECOSYSTEMS Introduction Desert occupies about 14% of our world’s land area. I t is characterised by less than 25 cm rainfall. The atmosphere is dry and hence it is a poor insulator. Types of desert ecosystems Based on the climatic conditions, deserts are classified into three types. Tropical deserts. Temperate deserts. Cold deserts.  Features of different types of deserts Tropical desert is an environment of extremes, it is the driest and hottest place on earth. Rainfall is sporadic and in some years no measurable precipitation falls at all. Africa: Sahara desert. Rajasthan: Thar desert. Temperate desert is a barren area of land where little precipitation occurs (less than 10%), characterised by very hot summer and very Winter time. Ex: Atacama, Mojave. Cold deserts have hot summers but extremely cold winters. These are found in high, flat areas, called plateaus. Ex: Gobi desert, Ladakh. Characteristics of Desert ecosystem The desert air is dry and the climate is hot. Annual rainfall is less than 25 cm. The soil is very poor in nutrients and organic matter, Vegetation is poor. Structure and functions of the desert ecosystems I. Abiotic Components Intense solar radiation, lashing winds, and little moisture i.e. less than 10 inches (25 cm) of rainfall. The nutrient cycling is also very low. The characteristic feature of the abiotic component is lack of organic matter in the soil and scarcity of water. Desert Ecosystem II. Biotic Components Producers: In deserts mostly Succulent (e.g., cacti) plants are found available. They have water inside them to stay alive, waxy coating to prevent intense heat, thorn on the outside to protect them from being eaten. Ex: Succulents, Shrubs, bushes, some grasses and few trees. Consumers: These animals dig holes in the ground to live in. They come out at night to find food. Most of the animals can extract water from the seeds they eat. Ex: Locust, scorpions, snakes, camel, elk etc. Decomposers: Desert has poor vegetation with a very low amount of dead organic mater. They are decomposed by few fungi and bacteria. Ex: Fungi and bacteria AQUATIC ECOSYSTEMS The aquatic ecosystem deals with water bodies. The major types of organisms found in aquatic environments are determined by the water’s salinity. Types of aquatic life zone Aquatic life zones are divided into two types. 1. Fresh water life zones Eg. Ponds, streams, lakes, rivers. 2. Salt water life zones Eg. Oceans, estuaries.  FRESH WATER ECOSYSTEM POND ECOSYSTEMS Introduction A pond is a fresh water aquatic ecosystems, where water is stagnant. I t receives enough water during rainy season. I t contains several types of algae, aquatic plants, insects, fishes and birds. Characteristics of pond Pond is temporary, only seasonal. I t is a stagnant fresh water body. Ponds get polluted easily due to limited amount of water. Pond ecosystems are lentic ecosystems – i.e. they involve stagnant or standing water.  Structure and functions of pond ecosystems Abiotic components Ex: Temperature, light, water and organic and inorganic compounds Biotic Components Producers These include green photosynthetic organism. They are of two types. Phytoplankton: These are microscopic marine plants, which freely float on the surface of water. Ex: Floating plants like Nostoc, Anabena, Consmarium. Microphytes are microscopic algae Ex: Floating plants and submerged plants like hydrilla, Jussiaea, wolfia, demna. Consumers Primary consumers (Zooplanktons): These are microscopic animals which freely float on the surface of water. Zooplanktons are found along with phytoplankton. They feed on plants (phytoplankton). Ex: Protozoa, very small fish, ciliates, flagelaltes and protozoans. Secondary consumers (Carnivores):They feed on zooplankton Ex: Insects like water beetles and small fish. Tertiary consumers :They feed on smaller fish Ex: Large fish like game fish. Decomposers: They decompose the dead plant and animal matter and their nutrients are released and reused by the green plants. Ex: Fungi, bacteria and flagellates Importance of pond ecosystems. 1.Biodiversity: Pond ecosystems are very important habitats for so many different types of fish, birds, plants and crustaceans as well as insects such as dragonflies, damsel flies and pond skaters. 2.Ubiquity: Pond ecosystems can be found on every continent on the planet. 3.Abundance: Pond ecosystems are very abundant. Not only can they be found almost everywhere, they can be found plentifully. 4.Source of hydration: A watering hole in a prairie or desert many species of animals will come to pond. Humans can also use these ecosystems as a source of water. 5. Beauty: Pond ecosystems are very beautiful as well. LAKE ECOSYSTEM Lakes are large natural shallow water bodies. Lakes are used for various purposes. Lakes are supplied with water from rainfall, melting snow and streams. Types of lakes Some important types of lake are Oligotrophic lakes : They have low nutrient concentrations Eutrophic lakes : They are overnourished by nutrients like N and P Dystrophic lakes : They have low pH, high humic and content and brown waters. Volcanic lakes : They receive water from magma after volcanic eruption.  Zones of Lake Dependingupon their depth and distance from the shore, likes consists of four distinct zones. Littoral zones: I t is the top layer of the Lake. I t has a shallow water. Limnetic zone: Next to the littoral zone is limnetic zone, where effect penetration of solar. light takes place. Profundal zone: The deep open water, where it is too dark. Benthic zone: This zone is found, at the bottom of the lake.  Characteristics of lake ecosystem Lake is a shallow fresh water body; I t is a permanent water body with large Water resources. I t helps in irrigation and drinking. Structure and function of lake ecosystem I. Abiotic components Temperature, light, proteins and lipids, O 2 CO2 II. Biotic Consumers Producers: They are green plants, may. be submerged, free floating ad amphibious plants. Examples: Phytoplanktons, algae and flagellates.  2. Consumers Primary Consumers (Zooplanktons): They feed on phytopankton Ex: Ciliates, protozoans, etc. Secondary consumers (carnivores) : They feed on zooplankton. Ex Insects and small fishes. Tertiary consumers: They feed on smaller fish Ex: Large fishes like game fish. Decomposers: They decompose the dead plants ad animals Ex: Bacteria, fungi and aclinonrcetes.  RIVER (or) STREAM ECOSYSTEM Introduction The running water of a stream or a river is usually well oxygenated, because it absorb’s oxygen from the air. The number of animals are low in river or stream. Characteristics of River or Stream. I t is a fresh water, and free flowing water systems. Due to mixing of water, dissolved oxygen content is. more. River deposits large amount of nutrients.  Structure and function of River or Stream Ecosystem Abiotic components Examples : River, Light, Temperature, Chemistry, Substrate Biotic Components Producers: Phytoplankton, algae, water grasses, aquatic masses other amphibious plants. Consumers 1.Primary consumers: They feed on phytoplankton. Ex : Water insects, snails, fishes: 2.Secondary consumers: They feed on primary consumers Ex: Birds Decomposers: They decomposes the dead animals and plants. Ex :Bacteria and fungi. V.S.Saravana Mani, Head & AP/ Chemistry, AEC  SALT WATER ECOSYSTEMS. OCEAN (MARINE) ECOSYSTEMS Introduction Oceans cover more than two thirds of the earth’s surface. ocean environment is characterised by its high concentration of salts and minerals. I t supplies huge variety of products and drugs. I t also provides us iron, magnesium, iron, natural gas. Zones of Oceans The oceans have two major life zones. Coastal zone: I t is relatively warm, nutrient rich shallow water. I t has high primary productivity because of high nutrients and sunlight. Open sea: I t is the deeper part of the ocean. I t is vertically divided into three regions. Euphotic zone: I t receives abundant light and shows high photosynthetic activity. Bathyal zone: I t receives dim light and is usually geologically active. Abyssal zone: I t is the dark zone and is very deep (2000 to metres). V.S.Saravana Mani, Head & AP/ Chemistry, AEC Characteristics of Ocean Ecosystem I t occupies a large surface area with saline water. Since ship, submarines can sail in ocean, commercial activities may be earned out. I t is rich in biodiversity. I t moderates the- temperature Structure and function Ecosystems Abiotic components Examples Temperature, light, NaCl, K, Ca, and Mg Salts alkalinity Biotic components 1. Producers : Phytoplanktons (diatoms, unicellular algae, etc., ) and marine plants (sea weeds, chlorophycela, phaeophyceae). 2. Consumers These are heterotrophic macro consumers. They depend on producers for their nutrition. Primary consumers (herbivores) :They feed on producers Ex: Crustaceans, molluscs, fish Secondary consumers (carnivores) : They feed on herbivores Ex: Herring, mackerel, etc., Tertiary Consumers: They are the top consumers. They feed on small Ex: Cod, Haddock, -etc., 3.Decomposers: They decompose the dead organic matter. Ex: Bacteria and some fungi.  ESTUARINE ECOSYSTEM Introduction An estuary is a partially enclosed coastal area at the’ mouth of a river, where sea water mixes with freshwater. I t is strongly affected by tidal action. Estuaries are generally : abundant of nutrients. Estuaries are useful to human beings due to their high food potential. I t is essential to protect the estuaries from pollution. Characteristics of Estuarine ecosystem Estuaries are transition zones, which are strongly affected by tides of the sea. Water characteristics are periodically changed. The living organism in estuarine ecosystems have wide tolerance. Salinity remains highest during the summer and lowest during the winter. Structure and function of Estuarine Ecosystem Abiotic Components Examples :Temperature, pH, sodium and potassium salts and various nutrients. Biotic Components Producers Examples :Marsh grasses, seaweeds ,sea-grasses and phytoplankton. Consumers Examples :Oysters, crabs, seabirds, small fishes Decomposers Examples :Bacterias, fungi and actenomycetous. V.S.Saravana Mani, Head & AP/ Chemistry, AEC Agsalud, Priscilla Signey Laconsay and et.al. (2014). Environmental Science. Jimcyville Publications. Malabon City, Philippines. Cadiz, Arlon P. and Trinidad D. Macasil.(2015). Environmental Science: A Modular Approach. Mindshapers Co, Inc. Cunningham, William P. and Mary Ann Cunningham. (2012). Environmental Science : A Global Concern. 12th Edition. The McGraw-Hill Companies, Inc. Cunningham, William P. and Mary Ann Cunningham. (2013). Principles of Environmental Science : Inquiry and Applications. Seveth Edition. 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