Environmental Science

Transcription

1 Richard T. Wright Environmental Science Tenth Edition Chapter 3 Ecosystems: How They Work Copyright 2008 Pearson Prentice Hall, Inc. Ecosystems: How They Work Matter, energy, and life Energy flow in ecosystems The cycling of matter in ecosystems Implications for human societies Matter, Energy, and Life Matter in living and nonliving systems Energy basics Energy changes in organisms

2 The Four Spheres of Earth s Environment MATTER CYCLING ENERGY CONVERSION Matter The basic building blocks of matter are atoms Elements are made of one kind of atoms (Atoms with same number of protons) Isotopes are atoms of the same element but having different number of neutrons 94 elements occur naturally and 24 have been synthesized by chemists and physicists All matter is made up of various combinations of atoms of the elements. Atmospheric Gases Molecules: O 2, N 2, CO 2 Compounds: CO 2

3 Water and Its Three States Water is a polar molecule Minerals: Dense clusters of atoms of two or more elements held together by the attraction of positive and negative charges. Na + and Cl - Ionic Substances Interrelationships among Air, Water, and Minerals Dissolution: Ions surrounded by water molecules Crystallization: via evaporation (or amorphous precipitation)

4 Elements of Life: A Summary Of the 94 naturally occurring elements in the universe, only 24 are utilized by living organisms. Six elements are required by all living things in large amounts? Which ones? Match the Elements (Left) with Molecules (Right) Nitrogen Carbon Hydrogen Oxygen Phosphorus Sulfur Glucose Proteins Starch Fats Nucleic acids All of the above The BIG SIX: Needed by all living things in large quantities Organic Molecules

5 Matter and Energy Matter: anything that occupies space and has mass. Cannot be created or destroyed. Can be changed from one form into another. Can be recycled. Can be measured where gravity is present. Matter and Energy Energy: anything that has the ability to move matter, has no mass and does not occupy space. Cannot be created or destroyed. Can be changed from one form to another. Cannot be recycled. Can be measured. Kinetic Energy in its active form Potential Potential that systems have to release kinetic energy Forms of Energy

6 Energy Conversions Laws of Thermodynamics First Law: (CHANGE) Energy is neither created nor destroyed but may be converted from one form to another. NO FREE LUNCHES! Second Law: (LOSS) In any energy conversion, you will end up with less usable energy than you started with. YOU CAN T BREAK EVEN! So how do we survive? Example of the Laws of Conservation of Matter and Thermodynamics Global Warming Where from? Acid Rain Smog Burning Coal = CO 2 + SO + H 2 O + Ash + (C x H x S x O x ) Light + Noise + Heat

7 Entropy: Energy Changes in Organisms Systems will go spontaneously in one direction only which is toward increasing entropy. Entropy measures the degree of disorder of a system Entropy underlies the second law of thermodynamics / the most of usable energy. Entropy First Principle of Ecosystem Sustainability Ecosystems use sunlight as their source of energy. Ecosystems need a constant input of energy Why?

8 How Ecosystems Use Sunlight As Their Source of Energy Food Assimilation in Consumers Match Outcomes (Left) with Process (Right) Releases O 2 Stores energy Releases CO 2 Uses CO 2 Releases energy Produces sugar Uses sugar Uses O 2 Photosynthesis Cell respiration Both Neither

9 Match Outcomes (Left) With Organisms (Right) Releases O 2 Stores energy Releases CO 2 Uses CO 2 Releases energy Produces sugar Uses sugar Uses O 2 Plants Animals Both Neither Violations of the First Principle of Ecosystem Sustainability Excessive use of fossil fuels Feeding largely on the third trophic level. Use of agricultural land to produce meats. Energy Flow in Ecosystems Primary production Energy flow and efficiency Running on solar energy Freely available Nonpolluting Everlasting

10 Productivity of Different Ecosystems Energy Flow Through Trophic Levels The Second Principle of Ecosystem Sustainability Ecosystems dispose of wastes and replenish nutrients by recycling all elements.

11 The Cycling of Matter in Ecosystems The carbon cycle The phosphorus cycle The nitrogen cycle The Carbon Cycle How and in what form does carbon enter and leave the cycle? How is the role of autotrophs and heterotrophs different and the same? What are the human impacts on the cycle? Global Carbon Cycle Natural Production

12 Global Carbon Cycle Human Activities The Phosphorus Cycle How and in what form(s) does phosphorus enter and leave the cycle? How is the role of autotrophs and heterotrophs different and the same? What are the human impacts on the cycle?

13 The Nitrogen Cycle How and in what form(s) does nitrogen enter and leave the cycle? How is the role of autotrophs and heterotrophs different and the same? What are the human impacts on the cycle? Nitrogen Fixation: Nitrogen gas to Ammonium N 2 NH 3 NH 4 + Denitrification Nitrate to Nitrogen gas NO 3- N 2 Decomposition Organic carbon NH 3 or NH 4 + Nitrification NH 4+ NO 3 -

14 Nutrient Recycling and Energy Flow Through an Ecosystem The Human System Human Impact Use of Ecosystem Capital Is our use of ecosystems sustainable? Examples: heavy use of energy resources, deforestation Interference with Nutrient Cycles Example: Introducing too much carbon in the atmosphere Value Ecosystem Capital What value does the market economy place on ecosystems goods and services (soils formation, decomposition, water sheds, clean, etc.? Identification and Inventory of Ecosystem goods and services

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