Chapter Two: Cycles of Matter (pages 32-65)

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1 Biology 20 Chapter 2.1_keyed Chapter Two: Cycles of Matter (pages 32-65) 2.1 The Role of Water in the Cycles of Matter (pages 34 40) Due to its ability to form hydrogen bonds, water has several unique properties. Water is: an excellent carrier of dissolved minerals and other materials. an effective medium for transferring energy. a universal solvent. Water has: has a lower density when it is a solid a relatively high boiling point and melting point. special adhesive and cohesive properties. a high heat capacity. Water is an excellent carrier of dissolved minerals and other materials: As water moves from place to place it carries a variety of other substances. for example: water in the soil may contain nitrogen and phosphorus or toxins like methylmercury. Water is an effective medium for transferring energy: Water vapour that evaporates at the equator rises and moves towards the poles, releasing heat as it expands and cools. Liquid water transfers heat in ocean currents from warm regions to cooler regions. The warm air over the water can moderate the temperature over nearby land. Water is a universal solvent: A water molecule consists of two hydrogen atoms that are covalently bonded to one oxygen atom. The hydrogen end of the molecule has a slightly positive charge and the oxygen end has a slightly negative charge, making water a polar molecule. This polarity allows a water molecule to form hydrogen bonds between the hydrogen of one molecule and the oxygen of a nearby molecule. What to do: Draw a diagram of three water molecules exhibiting hydrogen bonding.

2 Biology 20 Chapter 2.1_keyed Water has a lower density when it is a solid Ice floats on top of liquid water because it is less dense. When water cools, molecules of water slow down and allow for all of the possible hydrogen bonds to form; individual molecules are held at equal distances from each other resulting in a lower density. Water has a high boiling and melting point: Hydrogen bonding explains why water remains liquid over a large temperature range. An individual hydrogen is weak; hydrogen bonds break and re-form frequently. Many hydrogen bonds together are strong; require a large amount of energy to break them. Water will only change phase from a liquid to a solid (boil) when the many hydrogen bonds are broken; therefore, water has a high boiling point. Water will only change phases from a solid to a liquid (melt) when the many hydrogen bonds are broken; therefore, water has a high melting point. Water has special adhesive and cohesive properties Hydrogen bonding causes cohesion, the attraction of water molecules to each other. Cohesion is responsible for surface tension, the reason many insects can walk on water. Adhesion is the attraction of water molecules to the molecules of other substances. Adhesion is responsible for water sticking to the sides of a test tube or a tree s xylem vessels allowing water to move against the pull of gravity. Water has a high specific heat capacity Heat capacity is the amount of heat a substance can absorb or release for a given change in temperature. Water requires a large amount of energy to affect a small amount of change in temperature. Water takes a long time to heat and cool. Bodies of water such as oceans and lakes have a moderating effect on the air temperatures of nearby land. Question 1. Water is a polar molecule, what does this mean? Water has a slightly negative charge at the oxygen end of the molecule and a slightly positive charge at the hydrogen end of the molecule. Question 2. How does water s polarity affect the process of transpiration? Water is adhesive because of the molecules polarity. The water molecules are attracted to the unlike molecules of other substances and thus stick. Water sticks to the sides of the xylem vessels in a plant, allowing a column of water to resist the pull of gravity. The cohesive nature of water (due to the hydrogen bonds) allows the water to move as a continuous column up the plant.

3 Biology 20 Chapter 2.1_keyed The Hydrological Cycle Biogeochemical Cycle: the cyclical route that water or other chemical nutrients take through the biotic and abiotic components of the biosphere. The hydrologic cycle is a cycle of evaporation and condensation that determines the circulation of water through the atmosphere and biosphere. The hydrologic cycle includes the following processes: evaporation condensation precipitation infiltration runoff transpiration storage (in atmosphere, ice and snow, freshwater bodies, and oceans) As water travels through the biotic and abiotic components of the biosphere, it carries much material with it, including chemical nutrients. This links the hydrologic cycle with the biogeochemical cycles, through which nutrients travel. Societal Uses of Water Alberta has rich supplies of fresh water from rivers, lakes, wetlands, and undergrounds sources. Population growth, and increases agricultural and industrial uses has increased the demand for water in the province and on a global scale. Water that cannot be cleaned of toxic chemicals and pathogens is no longer useful. If it is released into the environment, it can cause great harm to the ecosystem.

4 Question 3. Based on the pie chart of water use in Alberta, which sector of water use should be decreased? Justify your response. What to do: watch the YouTube videos and answer the questions below. Question 4. Do you feel as though tap water is safe to drink? Why or why not? Question 5. What message(s) are the bottled water commercials sending to the consumers? Question 6. What is the estimated inflated cost of bottled water compared to tap water? Question 7. On average, how many bottles of water are bought in the US each week? Question 8. What is the percentage of water bottles that end up in the landfill? Question 9. Bottled water sales have begun to drop, what business is on the rise? 4

5 Chapter Two: Cycles of Matter (pages 32-65) 2.2 Biogeochemical Cycles (pages 42 52) In order to survive and grow, organisms must obtain nutrients that serve as sources of energy or chemical building blocks, or both. The cycling of matter through the biotic and abiotic components of the biosphere allows all organisms to obtain nutrients. All biogeochemical cycles involve some substances that are temporarily stored in nutrient reservoirs for various amounts of time, while some substances are moving through the environment between reservoirs. The substances that are involved in biogeochemical cycles are: water carbon oxygen sulfur nitrogen phosphorus Each substance can be considered to be part of its own cycle, while all of the cycles are said to be interconnected. Substances may be part of a rapid cycle or part of a slow cycle depending on the amount of time spent in a reservoir. Nutrient reservoir: A nutrient reservoir is a component in the biosphere in which nutrients temporarily accumulate. Examples include: soil, water and organisms The four nutrient reservoirs are categorized with respect to whether they involve biotic or abiotic components of the ecosystem and whether the nutrients they contain are directly available to living things. Nutrients that are directly available to living things are said to be part of a rapid cycle. Nutrients that are not available to living things are said to be part of a slow cycle. 5

6 What to do: read the information on pages of the text. Summarize the information in the table below. definition Substances cycle between nutrient reservoirs relatively quickly. Rapid Cycle Slow Cycle examples Carbon moves from producer to consumer to decomposer, and back into the atmosphere through rapid cycling. how substances move into and out of nutrient reservoir photosynthesis, cellular respiration, decomposition, excretion definition Substances accumulate and are unavailable to organisms. It can take millions of years for these substances to again become available to organisms. examples Organic carbon in the matter of living organisms is fossilized. The burning of fossil fuels millions of years later puts the carbon into the atmosphere. how substances move into nutrient reservoir fossilization, formation of sediments how substances move out of reservoir erosion, burning of fossil fuels, weathering The Carbon and Oxygen Cycles (pages 43 46) Rapid Cycling of Carbon Plants and animals play an important role in the rapid cycling of oxygen and carbon dioxide. Plants consume much greater amounts of carbon in the process of photosynthesis than plants and animals release in the process of cellular respiration. Much of the carbon in forest reservoirs is released back into the atmosphere as carbon dioxide from forest fires and the breakdown of organic matter by decomposers. Rapid Cycling of Oxygen Plants, animals, and decomposers also play an important role in the cycling or oxygen. Photosynthesis produces oxygen gas, which is needed for cellular respiration. 6

7 The Carbon and Oxygen Cycle The Slow Cycling of Carbon Living organisms also play an important role in the slow cycling of carbon. Organic carbon that is stored in the dead bodies of organisms may enter into a slow cycle if the carbon is not made immediately available by decomposers. Over millions of years, organic material that is not broken down by decomposers may become incorporated into rocks or contribute to petroleum (fossil fuel) deposits. Human activities influence the slow cycling of carbon in a number of ways. The combustion of petroleum deposits quickly releases carbon back into the atmosphere. Since the industrial revolution, levels of carbon dioxide in the atmosphere has increased by about 30%. Question 1. Using the diagram to the right, list the major carbon sinks (reservoirs) on the Earth. Major carbon sinks include: ocean, forests, petroleum deposits, limestone (CaCo 3 ) * note that the slow cycling of carbon is shown in bold against a darker background. 7

8 The Sulfur Cycle (pages 46 48) The sulfur cycle is a biogeochemical cycle that shows how sulfur is converted into different forms as it is transported through the air, water, and soil. All organisms require sulfur as an important component of proteins and vitamins What to do: Read the information of the sulfur cycle on pages of the text. Summarize the information in the table below and answer the questions that follow. Component of the Biosphere Sulfur in the Air Sulfur in the Water Sulfur in the Soil Summary of information: The decomposition of organic matter, volcanic off-gassing, and human activities all release sulfur into the atmosphere. Rain and snow soon return sulfur to Earth s surface via acid deposition. Plants and algae take up sulfur in the water-soluble form of 2 sulfate (SO 4 ). Decomposers quickly return sulfur to the soil or air as hydrogen sulfide (H 2 S). Soil bacteria use sulfur compounds in photosynthesis or cellular respiration, thus playing an essential role as they convert one form of sulfur to another. Some sulfur is taken out of rapid cycling when bacteria convert sulfur to forms that are layered down as sediments, eventually becoming part of rocks. 8

9 The Nitrogen Cycle (pages 48 49) The nitrogen cycle is a biogeochemical cycle that shows how nitrogen is converted into different forms as it is transported through the air, water, and soil. All organisms require nitrogen to make proteins and genetic material (DNA). What to do: Read the information of the nitrogen cycle on pages of the text. Summarize the information in the table below and answer the questions that follow. Component of the Biosphere Nitrogen in the Air Nitrogen in the Water Nitrogen in the Soil Summary of information: Nitrogen gas (N 2 ) makes up 78.1 percent of Earth s atmosphere by volume. Most organisms, however, cannot use atmospheric nitrogen. Nitrogen gas is removed from the atmosphere via nitrogenfixing cyanobacteria, which convert it into a form plants can use ammonium (NH + 4 ). Some types of aquatic bacteria then convert the ammonium into nitrate (NO 3 ), which plants can also use. Other bacteria convert nitrate back into nitrogen gas via denitrification. Nitrogen-fixing soil bacteria live in close association with plants. They convert nitrogen gas into ammonium. Decomposers also break down organic matter to produce ammonium. Soil bacteria then convert the ammonium into nitrite (NO 2 ) and then nitrate. Denitrifying bacteria then convert these compounds back into nitrogen gas. 9

10 The Phosphorus Cycle (pages 49 50) The phosphorus cycle is a biogeochemical cycle that shows how phosphorus is converted into different forms as it is transported through the water and soil. All organisms require phosphorus as a part of cellular DNA and ATP (the energy carrier essential to all cells). What to do: Read the information of the phosphorus cycle on pages of the text. Summarize the information in the table below and answer the questions that follow. Component of the Biosphere Phosphorus in the Air Phosphorus in the Water Phosphorus in the Soil Summary of information: Unlike carbon, nitrogen, and sulfur, phosphorus does not cycle through the atmosphere. Weathering gradually releases phosphorus trapped in rocks and makes it available to organisms. Plants and algae can only use phosphorus in the form of 3 phosphate (PO 4 ). Phosphorus is scarce in the environment. This keeps the growth of producers in balance, but it can also limit the growth of crops. The growth of algae in aquatic ecosystems is limited by the amount of available nutrients. Because it is scarce in the environment, excess phosphorus in aquatic ecosystems can result in algal overgrowth, known as an algal bloom. 10

11 Question 2. Human activities can greatly affect many of the biogeochemical cycles. The increase in phosphates due to agricultural run-off can be a major problem for near-by aquatic environments. Use the phrases below and re-order to show how an increase in the amount of phosphorus in the environment can cause ecosystem damage. Algal bloom and overgrowth occurs Decomposer population grows quickly, depleting oxygen Excess phosphorus enters the aquatic system Fish and other organisms requiring oxygen die Plants below the surface can no longer photosynthesize and die Sunlight cannot penetrate below the surface 11

12 Chapter Two: Cycles of Matter (pages 32-65) 2.3 The Balance of the Matter and Energy Exchange (pages 53 61) The Earth is a closed system in relation to matter and an open system in relation to energy. There is a constant input of energy into the biosphere and a constant output of radiant energy (heat) to space. The amount of sunlight that is received by an ecosystem affects the amount and the type of productivity of an ecosystem. Productivity: the rate at which an ecosystem s producers capture and store energy within organic compounds over a certain length of time. Commonly measured in terms of energy per area, per year; (J/m 2 /a) Productivity is the rate at which organisms produce new biomass. Productivity can also be expressed in terms of biomass of vegetation added to an ecosystem per year; (g/m 2 /a). Productivity varies among ecosystems; the rate of productivity depends on many variables: number of producers present in the ecosystem the amount of light and heat available (solar radiation) the amount of rainfall the system receives the amount of available nutrients Question 1. Explain how increased amounts of sunlight can have both positive and negative effects on productivity. Increased amounts of sunlight allows for more photosynthesis, and thus more productivity, as long as sufficient water is available. Too much ultraviolet radiation, however, can inhibit photosynthesis and limit the growth of plants. Question 2. What are two major factors (other than available nutrients) that can limit productivity? Other than nutrients, the two major factors that limit productivity are sunlight and water. The Gaia Hypothesis Organisms must maintain an internal balance to remain healthy (homeostasis). Proposed in 1979, by James Lovelock, the Gaia hypothesis considers homeostasis on a global level. The biosphere needs a constant input of energy and cycling of nutrients to maintain its internal balance. The Gaia hypothesis states: the entire range of living matter on Earth from whales to viruses and from oaks to algae could be regarded as constituting a single living entity capable of maintaining Earth s atmosphere to suit its overall needs and endowed with faculties and powers far beyond those of its constitute parts. Question 3. State the Gaia hypothesis in your own words. Earth is a single living organism 12

13 Human Activities and the Natural Balance Dead zones are regions or lakes or oceans in which aquatic life has suffocated due to algal blooms. Dead zones can occur seasonally in response to the turn-over of nutrientrich waters in warmer temperatures. Human activities often account the occurrence of dead zones. Nutrients can leach from soil into rivers by rain. Sewage discharged into large bodies of water contain high levels of phosphorus and nitrogen, promoting algal blooms Surface run-off from livestock operations carries nutrient rich wastes into water ways. Surface run-off from fertilized agricultural land and residential lawns can enter rivers and oceans. Question 4. How can an increase in available nutrients cause a dead zone to form in deep waters? Trace the steps involved from an increase in nutrients to the decrease in aquatic biodiversity. increase in nutrients such as phosphorus and nitrogen thick mat of algae forms at surface of water sunlight cannot penetrate to water below surface photosynthetic plants below the surface die decomposer populations flourish below the surface decomposers consume most of the O 2 dissolved in the water There is no longer enough O 2 left in the water to support life Question 5. Wetlands are often called the kidneys of the environment. Based on your knowledge of human physiology, what do the kidneys do? How do you think this relates to the discussion of excess nutrients in the water ways? The kidney filters harmful substances out of the bloodstream, ensuring that concentrations of these substances stay within safe limits. Solutions to environmental problems are often discovered in the biosphere itself. Because wetlands (marshes, swamps and bogs) are permanently saturated with water, they act as large filters. 13