1.6 A Natural Ecosystem Lakes, rivers, forests, deserts and meadows can be classified as natural ecosystems

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1 1.6 A Natural Ecosystem Lakes, rivers, forests, deserts and meadows can be classified as natural ecosystems A very small ecosystem is called a microecosystem. Science

2 Science

3 Rotting logs can be interesting habitats In each stage of decay, a rotting log hosts plants and animals that either consume it or each other. As they consume the log they slowly create a habitat no longer suitable for themselves. Science

4 The first stage of decomposition begins while the tree is still standing. Insects either bore into it or enter an opening in the bark that may have been created by injury, disease, weather or fire. Science

5 As beetles get under the bark, their tunnels allow air, moisture and fungal spores to enter the tree. Fungi provide food for some bacteria, slugs and insect larvae. Carpenter ants attract woodpeckers. Eventually, the weakened tree falls Science

6 Increased moisture from the damp ground speed up the rate of decay of the bark. Moisture attracts centipedes and scavengers and supports the growth of mosses, ferns etc. Wood-boring insects inhabit the dryer portions of the rotting log. Science

7 As the log collapses, earthworms, fungi and bacteria carry out the remaining decay. The rate of decay is influenced by the temperature, the amount of moisture, the length of the seasons and the succession of organisms Science

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10 Examples of animal life in or on a rotting log: PRIMARY CONSUMERS Bark beetles Click beetles Wood borers Termites Carpenter Ants Fungi Bacteria Science

11 SECONDARY CONSUMERS Centipedes Mites Ants (some species) Spiders Woodpeckers Science

12 SCAVENGERS Earthworms Millipedes Pill Bugs, sow bugs, wood lice Snails Mites Slugs Science

13 Bracket fungi, or shelf fungus, are notable for bearing fruiting bodies (conk) as or in a "bracket": a grouping of individual mushroom caps that lie in a close grouping of separate or interconnected horizontal rows. They are typically tough and sturdy and produce their spores on the tubes of the undersurface Science

14 Understanding Concepts 1 Bracket fungi can grow on the top of the log because its outer covering is hard and protects the interior from drying out. Mould is susceptible to drying out and survives better in a moist microclimate. Science

15 Understanding Concepts 2 The microecosystems under a log and inside a running shoe are similar in that they warm moist and dark Good for moulds, fungi, bacteria etc. Science

16 Understanding Concepts 3 Fallen trees provide nutrients and habitats for decomposers, the materials are recycled for future generations of plants and animals Science

17 1.7 Energy in Ecosystems Energy Flow Through an Ecosystem The vast majority of life on Earth depends on sunlight (insolation) as its source of energy. Science

18 Of all the insolation that reaches the Earth some of it reaches the surface, but only a small amount is used to power photosynthesis (0.023% of the radiation) Science

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20 Trophic Levels Energy from the sun is transferred from one organism to the next through the different levels of food chains. These different levels in food chains are referred to as trophic levels. Science

21 Consider the following simple food chain found here with three trophic levels: Birch Tree-->Moose-->Black Bear Science

22 Notice that energy flow in the food chain always begins with producers. Producers are autotrophs (they make their own food.) Eg; birch trees, berry bushes, moss, lichens and algae. Science

23 The moose is an example of a consumer. Consumers or heterotrophs CAN NOT make their own food. They must get their energy and nutrients from the organisms they eat. Science

24 There are many levels of consumers. The moose is considered a primary consumer because it feeds directly on the plants. A primary consumer is also called an herbivore (plant eater.) Science

25 The black bear is considered a secondary consumer and is called a carnivore. In this example the black bear is also considered the top carnivore since there are no carnivores which feed on it. Science

26 The black bear is at the top of this food chain. The black bear is a carnivore because it is a meat eater when it consumes moose meat. Science

27 Black bears also fit under the category of omnivore (an animal that eats both plants and animals). A wolf, is a strict carnivore (meat eater) as wolves do not have plants as part of their diet. Science

28 Although the black bear is the top carnivore in this example, it is not actually the final consumer. Consider what happens when the black bear or any other member of the food chain dies Science

29 The final consumers in any food chain/web are the decomposers. Decomposers are organisms of decay, that make use of wastes and remains of dead organisms. Science

30 Decomposers are generally bacteria or fungi that break down the materials in the wastes and dead bodies of organisms so they may be recycled. Materials are recycled but the energy that was stored in the food molecules is never recycled. Science

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32 Our simple food chain could therefore be modified as follows Birch Tree-----> Moose------> Black Bear------>Bacteria Science

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34 Whenever energy is transferred from one trophic level to the next within an ecosystem, some of the energy changes form. I.e. not all of the energy produced by the birch tree will reach the moose that eats it. Science

35 When an animal such as a black bear eats the moose, only a small fraction of the energy produced by the birch tree reaches the moose. The further up the food chain you go, the less energy is available. Science

36 In every ecosystem, there is less total energy available to secondary consumers than to primary consumers. Energy is lost on a continuous basis from all living things, usually in the form of heat. Science

37 Of course, when plants and animals die, their bodies decompose and some of the energy goes back into the ecosystem Warning: this movie is a series of pictures as this pig decomposes over 50 days. Science

38 It should be noted that an ecosystem may contain more than three trophic levels. Science

39 #1.Pyramid of Energy The transfer of energy from one trophic level to the next is never 100% efficient since each organism must use some of the energy to keep itself alive. Science

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41 This means that between 80% and 95% of the energy available at one trophic level is never transferred to the next higher level. No wonder there are so few coyotes in the ecosystem compared to the number of birch trees that support them. Science

42 The idea that each higher trophic level has less energy available to it is known as the pyramid of energy. Science

43 In the diagram below, the energy found in the bodies of the organisms is represented by the cube for that level. Science

44 The larger the volume of the level, the greater the energy at that level. Note that energy is measured in Joules (J) Science

45 HUMAN IMPACT ON ECOSYSTEM ENERGY Our ancestors survived by collecting plants and hunting animals; their impact on the ecosystem was small. Science

46 The two important demands on the ecosystem were plant and animals for food and wood for fuel. However, as human populations increased, their need for more energy (food) also increased. Science

47 People started to practice agriculture planting crops and raising animals. lumber for building permanent houses. cleared land for farming food produced allowed the human population to grow. Science

48 Cutting down trees and clearing land will decrease the number of producers in an ecosystem and thus lower the numbers in the lower trophic levels. Less numbers in the lower trophic levels will result in less numbers in the higher trophic levels. Science

49 Food Chains and Food Webs page Science

50 Food Chains One way flow of energy from producers to consumers in an ecosystem Science

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52 Food Chain example Blueberries Caterpillar Owl (producer) (primary (secondary consumer) consumer) Science

53 Most organisms have more than one food supply, so each organism is involved in many food chains Science

54 Food chains interconnect to form a food Web Science

55 What food chains do you see? Science

56 Energy Transfer Energy is reduced as it is transferred from one organism to another in food chains Science

57 The further up the food chain you go, the less energy is available. Science

58 Only 10% of the energy present in a given organism is available for the predator of the organism. Science

59 We represent energy flow in food chains and webs in graphs called pyramids They demonstrate how energy is lost from one trophic level to the next. Science

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61 Human Use for Energy Farming methods have increased food production and medical care has improved the health of humans. Science

62 These changes have allowed human population to grow, placing demands on the ecosystem Science

63 Understanding Concepts 1. Sunlight is the source of energy for photosynthesis on which all life depends. Sunlight also powers the water cycle winds and weather Science

64 Understanding Concepts 2..refers to the position of species on a food chain. Producers are at the first level primary consumers n the second. Science

65 Understanding Concepts 3. A primary consumer eats plants (producers) A secondary consumer eats animals, usually primary consumers Science

66 Understanding Concepts 4 Food Chain Algae->zooplankton-> minnow-> bass Science

67 Understanding Concepts 4. Food Web: Oak squirrel hawk Chestnut bird lynx Grass/ seed bird owl Science

68 Understanding Concepts 5. Arctic ecosystem are more fragile because they have much less biodiversity Science

69 Understanding Concepts 6. The amount of energy taken by humans over the past years has dramatically increased because of the needs of the industry and agriculture. Science

70 1.8 Carbon Cycle Although there are 92 naturally occuring elements, fewer than 20 elements are presently known to occur in the tissues of living things. Only 6 elements make up 99 % of human tissues. Science

71 Carbon, oxygen, hydrogen and nitrogen make up the vast majority of living tissue. These four elements are recycled between : living organisms and the soil, water atmosphere Science

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73 These elements are first used by plants or producers as raw materials and some oxygen is released as a product of photosynthesis. The rest is converted into food and passed through the food web. Science

74 As elements pass through plants, consumers, and finally decomposers, they are returned to the ecosystem in a continuous recycling of materials. If recycling of these materials did not occur, life could not exist. Science

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76 Recycling Through the Atmosphere... Some of these elements (carbon, oxygen, sulfur, nitrogen) are found in gaseous forms and their cycles involve the atmosphere. As a result they have a global nature. Science

77 Not Recycling Through the Atmosphere Other elements generally recycle in a more localized manner since they do not have a gaseous form and do not recycle through the atmosphere. Science

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79 Plants take carbon dioxide and water from their environment. Science

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81 They use the energy from the sun to carry on a process known as photosynthesis which converts carbon dioxide and water into sugar (glucose) and oxygen Science

82 Carbon Cycle and Cellular Respiration The oxygen, produced in photosynthesis, generally passes into the atmosphere. The sugar ( glucose) serves a food for all consumers in the ecosystem. The consumers body cells break down the sugar (glucose) in food in a process known as cellular respiration. Science

83 During respiration, oxygen is taken in from the atmosphere and used to break down the sugar producing energy and carbon dioxide and water. Science

84 Respiration summarized in a chemical equation Sugar (glucose) + Oxygen -> Carbon Dioxide + Water + Energy C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy Science

85 What is the connection between Photosynthesis and Respiration? What's made in Photosynthesis is used in Respiration and What's made in Respiration is used in Photosynthesis. Science

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87 As you can see from the equations, photosynthesis and cellular respiration complement each other the sugar and oxygen produced in photosynthesis is used for respiration. and the carbon dioxide and water produced in respiration is used in photosynthesis Science

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89 During respiration, some of the carbon is released back to the environment as carbon dioxide. Plants undergoing photosynthesis use carbon dioxide and produce oxygen. Cellular respiration uses oxygen and produces carbon dioxide. Science

90 Thus, the carbon is repeatedly cycled through both photosynthesis and cellular respiration. This balance is called the carbon cycle. Science

91 Since the amount of carbon dioxide in the atmosphere is very small( 0.03%), it is essential to life on Earth that the carbon in organisms be returned to the atmosphere when they die. Science

92 Without the carbon cycle, we would quickly run out of carbon dioxide, plants could not trap sunlight, and life on Earth would cease. Science

93 Organic vs. Inorganic Matter on Earth is placed in one of two categories, namely organic or inorganic. Organic substances always contain carbon and hydrogen, and often contain oxygen and nitrogen. Science

94 Organic vs. Inorganic Important chemicals that make up your body such as protein, sugar and fat are all considered organic Science

95 Inorganic matter doesn t contain a combination of carbon and hydrogen. For example, carbon dioxide (CO 2 ), water (H 2 0) and ammonia (NH 3 ) are considered inorganic Science

96 Inorganic Carbon Storage A tremendous amount of inorganic carbon may be absorbed by the oceans, atmosphere, and Earth s crust and stored there. Science

97 1. Atmosphere Storage: The smallest percentage of the total amount of inorganic carbon (about 0.03%) is contained in the carbon dioxide in the air we breathe and is available for photosynthesis. Science

98 2.Ocean Storage: A very large amount of inorganic carbon is found as dissolved carbon dioxide in the oceans. This is available to algae and other water plants for photosynthesis. Science

99 3.Earth's Crust Storage: The largest storage of inorganic carbon is sedimentary rocks, such as limestone, formed from the remains of living things. Science

100 Carbon can be trapped in rocks for millions of years. Events such as volcanic activity and acid rain can break down these rocks releasing carbon dioxide. Science

101 Organic Carbon Storage Organic carbon is also stored- in the bodies of living things. When living things die, their bodies decompose and the carbon is returned to the cycle in inorganic form. Science

102 This normally occurs over a very short period of time. An exception to this is when large amounts of organic carbon is stored for very long periods in bogs. Science

103 Because there is very limited oxygen in bogs, decomposition of plants and animals takes thousands of years. The result is that carbon remains locked away for many years in organic form. Peat is dead plant material Science

104 When peat becomes covered in sediment for long periods of time, it will become coal, a carbon containing fossil fuel. Science

105 Other fossil fuels such as oil and gas contain organic carbon which is trapped in Earth s crust for millions of years Science

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107 Human Activity Carbon dioxide is being produced at a faster rate than nature can recycle it. As a result, the amount of CO 2 in the atmosphere is increasing Also fewer trees results in a reduction of photosynthesis. Science

108 Earth is presently undergoing an enhanced greenhouse effect the atmosphere is gradually heating up. Science

109 If the rise in temperature occurs too fast for organisms to adapt, widespread extinction of plants and animals may result. We are the only species that can do something about the problems we have created Science

110 Understanding Concepts 1. Organic matter always contains carbon and hydrogen and often oxygen and nitrogen. Living things are made of organic matter. Inorganic matter does not have carbon hydrogen combiations Science

111 Understanding Concepts 2. Since organic matter comes from living organisms scientists want to know if organic matter is present. Science

112 Understanding Concepts 3. They are complimentary processes because the raw materials of one are the products of the other and vice versa. Science

113 Understanding Concepts 4. They release carbon from organic matter of dead organisms making it available to be used again by living organisms. Science

114 Understanding Concepts 5. Releases carbon that has been locked in the fuel since they were formed by the death and compression of organic materials from prehistoric plants and animals. Science

115 1.9 Nitrogen Cycle Nitrogen is essential to living things for the production of proteins, and DNA which are used to pass on the hereditary information from parent to offspring. Science

116 Even though the atmosphere is about 78% nitrogen gas, plants and animals are unable to use it directly to make organic nitrogen compounds Science

117 The nitrogen cycle can occur in both land and marine ecosystems but we will focus on land ecosystems. The nitrogen cycle is extremely complex involving many species of bacteria. Science

118 The nitrogen cycle however can be simplified into 5 steps Study the following picture Science

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120 Step #1: Plants change the Nitrogen into... In order for plants to make use of nitrogen it must first be changed into nitrates in the form of nitrate ions (NO 3- ) dissolved in soil water. There are two pathways by which nitrate ions can be produced: Science

121 Pathway 1:Nitrogen Fixation by Lightning: The electrical energy of lightning causes nitrogen gas (N 2 ) to react with oxygen (O 2 ) in the atmosphere to produce nitrate ions (NO 3- ) which reach the soil dissolved in rain. Science

122 Pathway 2:Nitrogen Fixation by Bacteria: Bacteria in the soil can change nitrogen gas (N 2 ) into ammonia (NH 3 ) which then dissolves in water to form ammonium ions (NH 4+ ). Several species of bacteria are involved. Science

123 Step#5:Denitrification.. returning nitrogen back to the atmosphere During this step, nitrites are changed into nitrogen gas (N 2 ) which returns to the atmosphere. This step is essentially the reverse of nitrogen fixation The bacteria which carry out denitrification are anaerobic. Science

124 The term anaerobic means, "in the absence of oxygen." This means that the bacteria can only carry out the process of denitrification in the absence of oxygen, such as when the soil is compacted. Science

125 This action can be reduced by the action of earthworms etc. that burrow into the soil allowing oxygen back into soil environment. The recycling of nitrogen is essentially a series of bacterial processes which are essential for life on Earth. Science

126 Nitrogen is essential to the production of proteins Consumers digest the proteins and DNA into amino acids. These amino acid building blocks are then reassembled to make proteins and DNA of the consumers. Science

127 Human Impact As a result of human activities, many ecosystems have been either destroyed or have had major components such as trophic structure, energy flow or chemical cycling disrupted. Science

128 Acid rain, greenhouse effect, and ozone depletion are of a global scale. Human activities (introduction of exotic species, habitat destruction etc.) are changing the distribution and number of species causing a biodiversity crisis. Science

129 For more on the influence of humans on the Nitrogen Cycle, visit the following web sites: Science

130 Understanding Concepts 1. Nitrogen must be converted into nitrates before organisms can use it. If soil lacks nitogen fixing bacteria, then it has few nitrates for the plants to take in. Science

131 Understanding Concepts 2...by consuming living and dead organic matter that contains nirtrates. Science

132 Understanding Concepts 3. Nitrogen fixing bacteria convert nitrogen to nitrates for the plants, plants provide sugar from photosynthesis for the bacteria Science

133 Understanding Concepts 4. Clover grows in older lawns because of the abundance of denitrifying bacteria. The bacteria in the clover roots benefit the lawn by providing more nitrates Science

134 Understanding Concepts 5. Farmers plant less valuable crops such as clover and alfalfa because they contain nodules with nitrogen fixing bacteria in their roots and increase the nitrate concentration of the soil. Science

135 Understanding Concepts 6. The nitrogen cycle would not be possible without decomposers because nitrogen would be trapped in the bodies of dead organisms. Nitrogen is released during decomposition back to the ecosystem. Science

136 1.10 Should We Interfere with Natural Cycles? Fertilizer Use Plants contain valuable nitrogen. When we eat plants, the contained nitrogen often does not get returned to the ecosystem and thus there is a break in the nitrogen cycle. Science

137 A break in the nitrogen cycle will result in soil lacking nitrogen. Often, in our attempt to restore this nitrogen we may cause other problems by interfering in an otherwise natural cycle. Science

138 The greatest human-driven increases in global nitrogen supplies are linked to activities intended to boost food production. Modern intensive agriculture requires large quantities of nitrogen fertilizer. Science

139 Fertilizers are materials that restore or add nutrients to soil. They are used to increase production from the land and may be natural (manure) or synthetic (chemical). Science

140 Humanity, in turn, requires intensive agriculture to support a growing population. Consequently, the use of nitrogen fertilizer has greatly increased, and the highest rates of application are now found in developing countries with the highest population growth. Science

141 Fertilizers need to be used sparingly There are ways to slow the growth of fertilizer use and the impacts of the nitrogen that is applied to crops. Science

142 Organic Farming Organic food has become one of the fastest growing trends in the food industry. Many supermarkets have an organic food section people are prepared to spend more on such food items for the sake of their own health and environment. Science

143 What's different about Organic Farmer's? use no chemical herbicides or fumigants. use only natural or other organically approved insecticides. provide a safer working environment for field workers. grow strong, healthy plants which are more resistant to disease. Science

144 Organic Farmer's? save water by building healthy soils which retain moisture conserve resources by using composted natural waste products to feed and balance the soil naturally. Science

145 Organic Farmer's? help keep our air, soil and water as well as our food supply, free of toxic chemicals. work with nature to replenish Earth's soil for a sustainable future. Science

146 Organic Fertilizer Advantages... Organic nutrients include such things as manure. (One should avoid using pig, dog or cat manure because of internal parasitic worms which may be transferred to humans.) Bone meal, blood meal, compost, and green manures will also provide nutrients for plants. Science

147 there is less danger of overfertilization by adding organic material to a garden as it provides a slow release of nutrients as it breaks down into an inorganic, water soluble form which the plants can use. the addition of organic material improves soil "workability" and water-holding capacities of sandy soils. Science

148 Disadvantages... if there is an immediate need for nutrients, organic fertilizer cannot supply them in a hurry. information on the exact amount of nutrients in an organic fertilizer such as manure is not available to the user. Science

149 In contrast, when you apply manufactured inorganic fertilizer you know the kinds and amounts of the elements allowing you to meet a plant's nutritional needs Science

150 the possibility of nitrogen depletion is another drawback of organic fertilizers. Because of complex bacterial action, the addition of a large amount of organic material can cause a temporary nitrogen depletion in the soil and therefore in the plants. Science

151 Inorganic Commercial Fertilizer Advantages - The primary advantage of using packaged commercial fertilizer is that nutrients are immediately available to the plants. As well, the exact amounts of a given element can be calculated and given to plants. Science

152 Disadvantages - Commercial fertilizer, especially nitrogen, is easily washed below the level of the plant's root system through the leaching of rain or irrigation. An application which is too heavy or too close to the roots of the plants may cause "burning". Science

153 As well, overly heavy applications of commercial fertilizers can build up toxic concentrations of salts in the soil, thus creating chemical imbalances. If organic materials are readily available and cheap, the expense of the commercial fertilizer should also be considered. Science

154 Whether a gardener chooses to use organic, or inorganic fertilizer's, it's important to follow the instructions. Science

155 Understanding Concepts 1. Because nutrients are taken away in the crop. Science

156 Understanding Concepts 2. They raise the nitrate content thus the nitric acid levels lowering the ph. Decomposers need optimum ph levels, acidic soil may kill bacteria Science

157 Understanding Concepts 2. Excess fertilizers seep into waterways causing the growth of algae. When algae die, population of decomposers increases rapidly depleting oxygen affecting animals Science

158 Understanding Concepts #3 Benefits of fertilizer use: Increases productivity Increases crop yield (lowering costs) Exact formulas; no confusion about content Risks of fertilizer use: Lowers ph Runoff causes algae bloom Reducing oxygen in water Nitrates converted to nitrites which attach to hemoglobin lowering oxygen in blood Science