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The Biosphere A Thin Layer of Life The biosphere is the thin continuous layer around earth’s surface in which organisms thrive. This layer is about 20 km thick (10 km above sea level to 10 km below sea level) and has two divisions: the terrestrial biosphere (organisms on land) and the aquatic biosphere (organisms in marine or freshwater). The skin of an apple is like the biosphere on earth. Ecosystems The basic unit that living things are found in is called an ecosystem. An ecosystem is the living community and the non-living environment the community lives in a defined place. It has a living part referred to as the biotic part and a non-living part referred to as an abiotic part. An ecosystem can be as small as a decomposing log and as large as a lake or forest. The Biosphere and Other Spheres The biosphere, more recently called the ecosphere, is found in and sustains itself from the other spheres (hydrosphere, lithosphere and atmosphere). Ecosphere The term ecosphere refers to the global ecosystem, the complex web of interactions between all living organisms on our planet and the non-living environments they interact with. It’s a term which suggests that our planet is like a living entity which balances itself to maintain its life support systems. An older term, Gaia, was used to refer to our planet as this entity. Since Gaia was the pagan goddess representing mother earth, many scientists have found the term somewhat new-age religious and have replaced it with the more neutral term, ecosphere, the living planet with systems to maintain itself. Biological Organization: 1 Organisms The basic unit of life is the organism, a single living thing. Biological Organization: 2 Populations A population is all the organisms of one kind in a certain area at a certain time. Biological Organization: 3 Communities A community is all the living things in an area at a certain time. Biological Organization: 4 Ecosystems An ecosystem includes the living community and the non-living environment in an area at a certain time. Biological Organization: 5 Biomes Biomes are large regions (the size of provinces or larger) with similar kinds of vegetation and animals. A kind of biome is a boreal coniferous forest or a desert or a grassland. Ecology Ecology is the study of levels of life organization above the organism. It sometimes is referred to as skin-out biology because it focuses on living relationships outside of an organism like those between organisms of the same kind, different kinds or relationships with nonliving parts of the environment. Skin-out Biology vs Skin-in Biology Any study of the insides of an organism are skin-in Biology while ecological studies are skin-out studies. Food Chains A food chain shows a limited eating relationships of a few organisms. All food chains begin with a producer (green plant) or detritus (wastes or remains or an organism). A consumer is an organism that must eat another organism or detritus. An herbivore eats plants only. A carnivore eats animals only. An omnivore eats both plants and animals. The arrows in a food chain point towards the eater, away from the eaten. Each eating level is referred to as a trophic level. Energy Chains Organisms make and eat food for energy to stay alive. Thus a food chain really shows how energy is passed from the source (the sun) through the organisms in an environment. Detritus Food Chains When a food chain begins with organic wastes or dead remains (detritus), it is called a detritus food chain. Energy is Lost in Food Chains as Heat Since organisms use energy to digest, absorb, and live (giving it off as heat) and since all the organisms at one tropic level are not eaten by the next highest trophic level, the energy passed on to each higher trophic level is about only 10% of what the lower trophic level had. Organisms eating at the highest trophic level have the lowest amount of energy available to them. Why Energy is Lost from Lower to Higher Trophic Levels An organism uses energy to stay alive so this is not passed on. An organism gives off food wastes so the energy in them is not passed on. Finally, not all organisms of a trophic level are eaten so the energy in the survivors is not passed on to the next highest tropic level. Food Webs A food web shows the eating relationships for a large number of different species in a given ecosystem. Single organisms are really part of many interconnected food chains. Food Webs Provide Stability Because of food webs with many interconnecting food chains, an organism can adjust to eating other food sources if some particular food source becomes scarce. This allows the scarce food organism to recover in numbers. Thus a food web helps to bring stability and balance to an environment, helping to keep all organisms alive and thriving. Greater Food Web Complexity Provides Greater Stability The more complex the food webs in an environment, the more stabile the environment will be in terms of providing food for all organisms and keeping their numbers in balance. Unstable Human-made Environments The most common way to grow agricultural crops is to grow them in massive fields which makes it easy to harvest with machines. These environments tend to be unstable because there is little or no food web but rather, one food chain. To maintain a single food chain, humans use chemical pesticides (to kill insect pests) and herbicides (to kill competing weeds Unstable Human-made Environments If agriculture developed food webs rather than food chains, the systems would be much more stable, requiring no chemical poisons. Food Pyramids A food pyramid is a graphical representation of all the organisms in an area for each of the trophic levels in that area. Pyramid of Numbers: Its Inaccuracy Food pyramids of numbers of organisms in each tropic level do not show the true importance of each tropic level because a single individual of one tropic level is given equal importance with a single individual in another tropic level. A single tree is much more significant than a single small aphid yet they count the same in a pyramid of numbers. Pyramids of Biomass: Equate the Biomasses of Different Species A pyramid of biomass equates 1 g of a producer with 1 g of a consumer. Biomass pyramids give a more accurate picture of the relationship between trophic levels but it can also give an inaccurate picture if a herd of bison suddenly eats lots of the grasses which would make the second trophic level (herbivore weight) larger than the first trophic level (grass weight) in the environment at this moment in time. Energy Pyramids : Most Accurately Show Trophic Relationships Energy pyramids measure the energy (kcal) found at each trophic level. This is the most accurate comparison because 1 kcal of producer is equivalent to 1 kcal of consumer (1 kcal in one thing is the same amount of energy as 1 kcal in another thing). Energy pyramids always have the largest values for the lowest trophic levels (producers), tapering to smaller and smaller values (approximately a 90% reduction for each trophic level – each level having approximately 10% of the level below it). Comparison of Food Pyramids A food pyramid best shows the true relationship between trophic levels when it is an energy pyramid. Why are the largest animals herbivores? Large animals (like elephants) are herbivores because, being large, they require large amounts of energy and there is more energy at the herbivore trophic level than the carnivore trophic level. Why do top carnivores have smaller litters than herbivores? Because top carnivores have less energy available due to eating at the top of the energy pyramid, they tend to have smaller litters (typically one or two, depending on food availability) while herbivores eating at lower trophic levels have enough energy to have larger litters (six or more is common for rabbits). Human Diet and Trophic Levels When humans feed as herbivores (vegetarian diet), they have more energy available for their populations. When humans feed as carnivores (meat diet), less energy is available for the entire population since energy has been used by the animals that are eaten. The Energy and Material to Make a Hamburger Meat costs more and uses more energy and materials to produce than grain. Why are the world’s largest populations more vegetarian? India and China have the world’s largest populations. Their diets are more vegetarian than meat-based. Why? There is not enough energy in the domestic animals of these countries to support their large populations but as they eat plants and plant products, there is more energy available to support their large populations. Vegetarians Save Food Energy and Reduce CO2 and CH4 Emissions By consuming plants rather than consuming an animal that eats plants, vegetarians are saving food energy. In addition, vegetarians reduce their carbon footprints (amount of CO2 and CH4 produced to sustain a person over a year) which helps reduce global warming. Polenta – corn dish Vegetarian Diets Are Healthy Vegetarian diets have been shown to have benefits for a person’s circulatory system, improving circulation, reversing problems (see insert on coronary angiogram) and helping to reduce weight. Reasons Why People Choose More Vegetarian Diets The majority of persons who begin to eat more vegetarian do so in order to be more healthy. A second reason is that they are concerned about the way farmed animals are treated or they may feel that they do not want to eat other sentient beings, that can sense and feel. Risks With the Typical North American Diet – Fat and Sugar The typical North American diet which included many sugary and fatty foods (cookies, muffins), many deep-fried foods (fries, chicken, fish, donuts), many sugary drinks (juices, soda pops), many salty and fatty foods (potato chips, munchies) and many meat-based dishes contributes to obesity and many health problems like circulatory diseases (heart attacks), stroke, diabetes, and kidney disease. How well do you understand energy relationships? Imagine yourself in a space ship travelling with just chickens, their eggs and some popcorn seeds to feed the chickens. These items are your only food. As an astronaut aboard this ship, you can choose what to eat and in which order to eat the corn, chickens or eggs. What order of eating these three items would be the best order to sustain you the longest on your space voyage? Energy and Matter Movements in an Ecosystem Energy flows through ecosystems, powering weather, powering living things, turning to heat and then escaping to space. Energy has an overall linear flow, sun to earth systems/living things to space. Matter on earth cycles from one form to another and eventually can come back to its original form, being used again and again. Biogeochemical Cycles A biogeochemical cycle is a pathway that a particular element (nutrient) takes through the biosphere, the lithosphere, hydrosphere and atmosphere. The cycle of a nutrient shows how it is used and passed on from one place on earth to another until eventually is returns to where it began. These cycles involve biological, geological and chemical processes so the terms biogeochemical cycle is used. Carbon Carbon atoms are a fundamental unit in cells of all living things. Carbon is also an essential part of chemical processes that sustain life. Plants are made of carbon Animals are made of carbon: Carbon Storage Carbon is stored in many different locations. Short-term shortage is found in aquatic and terrestrial organisms, and in CO2 in the atmosphere and top layers of the ocean. Longer-term storage is found in middle and lower ocean layers as dissolved CO2, and in coal, oil and gas deposits in land and ocean sediments. (c) McGraw Hill Ryerson 2007 Trapped Carbon Sedimentation traps many long-term stores of carbon. Layers of soil and decomposing organic matter become buried on land and under the oceans. (c) McGraw Hill Ryerson 2007 Trapped Carbon Changes to Fossil Fuels Slowly, under great pressure over many years, coal, oil and gas form. Carbon stores are also known as carbon sinks (c) McGraw Hill Ryerson 2007 Carbon can become Rocks Carbonate rocks (like limestone) are another form that carbon takes when carbon dioxide reacts with water and dissolved minerals like calcium or magnesium. Layers of shells also are deposited in sediments on the ocean floor, forming carbonate rocks like limestone over long periods of time. (c) McGraw Hill Ryerson 2007 Plants Absorb Carbon in the form of Carbon Dioxide Plants perform photosynthesis in which energy from the sun puts together CO2 and H2O to form glucose, a sugar, a carbohydrate. • CO2 + H2O + sunlight C6H12O6 + O2 • Photosynthesis also occurs in cyanobacteria and algae in oceans. (c) McGraw Hill Ryerson 2007 Carbon from plants to animals to the air Cells perform respiration in which they use oxygen to burn glucose and release its energy for them to use. C6H12O6 (from plants) + O2 CO2 (to air) + H2O + energy The energy released is used for growth, repair and other life processes. (c) McGraw Hill Ryerson 2007 Carbon Cycles (Is Used and Reused Over and Over) Carbon moves from air to plants to animals to dead remains in ponds, lakes and oceans to rocks to fossil fuels to cars and factories to the air again. Decomposer Role in Carbon Cycle Decomposers break down the carbon compounds in organic wastes and dead organisms. Carbon is released from decomposition as CO2 gas. Carbon Cycling Through Ocean Currents Ocean Processes: CO2 dissolves in cold, northern waters and sinks. These currents move into the tropics and rise to replace warm surface waters in the tropics which then move towards the north pole. This process is called ocean mixing. (c) McGraw Hill Ryerson 2007 Volcanoes and Fires Cycle Carbon Volcanic eruptions release CO2 from earth rocks. Forest fires also release CO2 from organic matter. (c) McGraw Hill Ryerson 2007 Human Influence on the Carbon Cycle Since the start of the Industrial Revolution (160 years ago), CO2 levels have increased by 30% from the increased burning of fossil fuels. The increase in CO2 levels in the previous 160 000 years was 1% 3%. (c) McGraw Hill Ryerson 2007 Human Influence on the Carbon Cycle Carbon is being removed from long-term storage more quickly than it naturally would as we mine coal and drill for oil and gas. (c) McGraw Hill Ryerson 2007 Human Influence on the Carbon Cycle CO2 is also a greenhouse gas, which traps heat in the atmosphere. (c) McGraw Hill Ryerson 2007 Human Influence on the Carbon Cycle Greenhouse gases allow shorter wavelengths of light energy through but reflect longer wavelengths (infrared). When sunlight energy is absorbed, shorter wavelength light is converted into longer wavelength light which is reflected back by greenhouse gases. (c) McGraw Hill Ryerson 2007 Human Influence on the Carbon Cycle Clearing land for agriculture and urban development reduces plants that can absorb and convert CO2. Farmed land does not remove as much CO2 as natural vegetation does. (c) McGraw Hill Ryerson 2007 The Carbon Cycle The greatest carbon sink (storage form)is in rocks of the earth’s crust. The next largest carbon sink is in deep ocean sediments. The Oxygen Cycle Air is about 21% oxygen gas, O2 . Oxygen gas in the stratosphere reacts with high energy radiation to form ozone, O3 . Oxygen gas is used by respiring organisms to form carbon dioxide gas (CO2 ) and water (H2O) . Oxygen gas also reacts with rocks to weather them, forming oxide compounds. When organisms die, their dead bodies have compounds with oxygen in them and these may be buried in sediments which slowly release oxygen over time in the forms of carbon dioxide, oxygen gas or other compounds. The oxygen cycle is in many places linked with the carbon and nitrogen cycles. The Element Nitrogen Nitrogen is very important in the structure of DNA and proteins. In animals, proteins are vital for all functions, especially muscle function. In plants, nitrogen is important for functions like growth. (c) McGraw Hill Ryerson 2007 Forms of Nitrogen on Earth The largest store of nitrogen is in the atmosphere in the form gaseous N2. Approximately 78% of the Earth’s atmosphere is N2 gas. Nitrogen combines with oxygen to form nitrates (NO3- ) and with hydrogen to form ammonia (NH3) and the ammonium ion (NH4+). It is made into proteins, DNA and RNA by plants and animals. In these various forms, nitrogen is found in oceans and soil. Smaller nitrogen stores are found in terrestrial ecosystems and waterways. (c) McGraw Hill Ryerson 2007 Nitrogen Fixation A group of land plants called legumes can change air N2 into the plant nutrient, nitrate (NO3-). In natural waters, cyanobacteria convert N2 into nitrate. Nitrate is a plant nutrient absorbed from the soil by plant roots. Legumes have special bacteria in their roots that make nitrates from nitrogen gas in the soil. (c) McGraw Hill Ryerson 2007 Nitrogen is cycled through processes involving plants 1. Nitrogen fixation occurs when a legume plant allows itself to become infected with the rhizobium bacteria. The legume plant feeds the rhizobium bacteria and the bacteria makes the legume nitrates from nitrogen gas. The swellings on legume roots where rhizobium bacteria live are called nodules. (c) McGraw Hill Ryerson 2007 Nitrogen is cycled through processes involving plants 1. In nitrogen fixation there is a mutualistic relationship between the Rhizobium bacteria and the legume plant since they both help each other. (c) McGraw Hill Ryerson 2007 Nitrogen is cycled through processes involving plants 1. Different legumes have a common flower structure. They do not require fertilizers like other agricultural crops. Legumes put nitrates back into the soil so they naturally make soil more fertile. Legume plants include beans, peas, clovers, alfalfas, peanuts, broom, lupines, locust trees etc. (c) McGraw Hill Ryerson 2007 Nitrogen is cycled through processes involving plants 1. Nitrification is a process in which special soil bacteria change ammonia and nitrite into nitrate which is then absorbed (uptake) by plants. (c) McGraw Hill Ryerson 2007 Nitrogen Fixation by Lightning • The energy in a lightning flash converts some N2 in air into nitrate which dissolves in and falls with atmospheric rain. (c) McGraw Hill Ryerson 2007 Fires and the loss of nitrates. • Forest and ground fires heat up the soil, converting nitrates back into nitrogen gas, N2 . Volcanoes also convert nitrates in magma into N2 . (c) McGraw Hill Ryerson 2007 The Nitrogen Cycle (continued) • Excess nitrogen dissolves in water, enters the waterways, and washes into lakes and oceans. The nitrogen compounds eventually become trapped in sedimentary rocks, and will not be released again until the rocks weather. See page 81 (c) McGraw Hill Ryerson 2007 Human Impact on the Nitrogen Cycle • Due to human activities, the amount of nitrogen in the ecosystem has doubled in the last 50 years. Burning fossil fuels and treating sewage releases nitrogen oxide (NO) and nitrogen dioxide (NO2). Burning also releases nitrogen compounds that increase acid precipitation in the form of nitric acid (HNO3). (c) McGraw Hill Ryerson 2007 Human Impact on the Nitrogen Cycle • Agricultural practices often use large amounts of nitrogencontaining fertilizers. Fertilizers change to nitrates and these add nitrogen to water run-off from the fields which gets into rivers and streams. (c) McGraw Hill Ryerson 2007 Human Impact on the Nitrogen Cycle: Eutrophication This promotes huge growth in aquatic algae = eutrophication. These algal blooms use up all CO2 and O2 and block sunlight, killing many aquatic organisms. The algal blooms can also produce neurotoxins that poison animals. (c) McGraw Hill Ryerson 2007 The Phosphorus Cycle • Phosphorous is essential for life processes in plants and animals. – Phosphorous is a part of the molecule, ATP, that carries energy in living cells. – Phosphorous promotes root growth, stem strength and seed production. – In animals, phosphorous and calcium are important for strong bones. (c) McGraw Hill Ryerson 2007 The Phosphorus Cycle Phosphorous is not stored in the atmosphere. Instead, it is trapped in phosphates (PO43–, HPO42–, H2PO4–) found in rocks and in the sediments on the ocean floor. (c) McGraw Hill Ryerson 2007 The Phosphorus Cycle • Weathering releases phosphates from rocks. • Weathering is the breakdown of rocks mainly through the action of water and oxygen. – Chemical weathering, via acid precipitation or lichens, releases phosphates. (c) McGraw Hill Ryerson 2007 The Phosphorus Cycle Physical weathering, is where wind, water and freezing release the phosphates. Phosphates are then absorbed by plants, which are then eaten by animals. Weathering doesn’t occur until there is geologic uplift, exposing the rock to chemical and physical weathering. (c) McGraw Hill Ryerson 2007 The Phosphorous Cycle • Humans add excess phosphorous to the environment through mining for fertilizer components. • Humans can also reduce – Extra phosphorous, often with extra potassium, then phosphorous enters the ecosystems faster than methods cansupplies. replenish Slash-and-burning of the natural stores. forests removes phosphorous from trees, and it then is deposited as ash in waterways. See page 85 (c) McGraw Hill Ryerson 2007 Imitating God’s Way: Recycle God has established cycles in nature so that there is no overall build-up of wastes. All living things are created to depend on each other. We are NOT independent or self-sufficient. (c) McGraw Hill Ryerson 2007 Imitating God’s Way: Recycle When a person presumes to dispose or “throw away” wastes, there is no “away”. When too much of a nutrient is piled up somewhere, the overall balance is destroyed. (c) McGraw Hill Ryerson 2007 Imitating God’s Way: Recycle and Don’t Plunder the Planet Humans need to reduce their use of nutrients (reduce what we buy and the wastes we produce) and they need to recycle materials just like God has them recycle in His creation. (c) McGraw Hill Ryerson 2007 End of Presentation A A