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Communities and ecosystems

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Aaron Brice
Aaron Brice

This document discusses key concepts in ecology including: - The chemical basis of life including organic/inorganic compounds and the role of energy from photosynthesis and respiration. - Ecosystems are made up of communities of interacting species and their abiotic environment. Food chains and ecological pyramids show how energy and matter are transferred between trophic levels. - Material cycles like the carbon and water cycles recycle nutrients and maintain the flow of matter and energy in ecosystems.

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Communities and Ecosystems Matter, Energy, and Life 1
o What is the chemical basis of life? o Organic/inorganic Compounds o Energy o Laws of Thermodynamics o Photosynthesis/Respiration o Ecosystems o Food Chains o Ecological Pyramids o Material Cycles 2
4
Law of Conservation of Matter Matter is neither created nor destroyed but rather re- cycled over and over. The atoms in your body may have been in a dinosaur. The idea that matter cannot be destroyed but is simply transformed from one form to another is termed conservation of matter. 5
Just four elements carbon, hydrogen, oxygen, and nitrogen - make up over 96% of the mass of most organisms. 6
Elements of Life 92 naturally occurring elements Elements Found in Living Organisms N CHOPS (macronutrients) C HOPKINS Ca Fe Mg B Mn Cu Cl Mo Zn The most common elements in a cell are: Hydrogen (H) 59% Oxygen (O) 24% Carbon (C) 11% Nitrogen (N) 4% Others such as phosphorus (P) and sulphur (S) 2% combined 7
Abundance of Elements (%) Nitrogen, 0.04 Everything else, 0.02 The most common elements in a cell are: Hydrogen (H) 59% Carbon, 0.11 Oxygen (O) 24% Hydrogen Oxygen Carbon (C) 11% Carbon Nitrogen (N) 4% Nitrogen Everything else Others such as phosphorus (P) and sulphur (S) Oxygen, 0.24 Hydrogen, 0.59 2% combined 8
Elements of Life Organic = carbon-based molecules Examples: C6H12O6, CH4 9
Organic Compounds Organic Compounds - Material making up biomolecules, which in turn make up living things. All organic compounds contain carbon. Four major categories of organic compounds: -Lipids -Carbohydrates -Proteins -Nucleic Acids 10
a. Butyric acid is the building block of lipids; propane is a hydrocarbon b. Glucose is a simple carbohydrate c. Amino acids form macromolecules called proteins d. Nucleic acids combine to form DNA chains 11
Elements of Life Inorganic = molecules without carboncarbon or carbonhydrogen bonds Examples: NaCl, NH4, H2SO4 12
13
Common Molecules 14
Thermodynamics Energy must be supplied (from the sun) to keep biological processes running, because as it flows through the various biological processes, it becomes dissipated. First Law of Thermodynamics - Energy is neither created nor destroyed. Second Law of Thermodynamics - With each successive energy transfer, less energy is available to perform work. Entropy (disorder) increases. 15
Energy for Life Ultimately, most organisms depend on the sun for the energy needed to carry out life processes. A few very ancient organisms called archaea are able to get their energy from inorganic compounds that bubble up from vents in the sea floor or from hot springs. These organisms represent one-third of all the biomass on the planet. The methane generated by these undersea communities could be a source of natural gas for us. 16
Energy from the Sun Solar energy is essential for (2) reasons: Warmth - Most organisms can exist only in a relatively narrow temperature range. Photosynthesis in plants -Radiant energy is transformed into useful, high- quality chemical energy in the bonds of organic molecules. All life on Earth depends on photosynthesis. 17
Energy For Life Of all solar radiation reaching the earths surface, about 10% is ultraviolet, 45% is visible, and 45% is infrared. Most of energy is absorbed by land or water, or reflected back into space. -Only about 1-2% of the sunlight falling on plants is captured for photosynthesis. 18
Electromagnetic Spectrum 19
Photosynthesis Occurs in organelles called chloroplasts within plant cells 6H20+6CO2 + solar energy = C6H12O6+6O2 Water and carbon dioxide in the presence of sunlight and chlorophyll (the green pigment in chloroplasts) yield glucose (sugar) and oxygen. Glucose serves as primary fuel for all metabolic processes. Energy in its chemical bonds can be used to make other molecules such as proteins or it can drive movement, transport, etc. 20
Photosynthesis 21
22
Cellular Respiration Photosynthesis captures energy, while cellular respiration releases energy. Cellular respiration splits carbon and hydrogen atoms from sugar and recombines them with oxygen to re-create carbon dioxide and water (opposite of photosynthesis). This is how animals get all their energy. The reason that you need to breathe is to supply this pathway with oxygen. C6H12O6 + 6O2 = 6H2O +6CO2 + energy 23
Energy Exchange in Ecosystems 24
5.1 Communities and Ecosystems 5.1.1 ECOLOGY The study of the relationships between living organisms and their environment 息 2008 Paul Billiet ODWS
How do organisms interact with one another? How do they interact with their nonliving environment?
5.1.1 Community All the populations of the different species living and inter-acting in the same ecosystem 7-spotted lady bird (Adephagia septempunctata) Bean aphids (Aphis fabae) Red ant (Myrmica rubra) and Broom plant (Cytisus scoparius) 息 2008 Paul Billiet ODWS
5.1.1 Ecosystem Community + Abiotic environment, interacting 息 2008 Paul Billiet ODWS
5.1.1 Species A group of organisms that can breed to produce fully fertile offspring 息 2008 Paul Billiet ODWS Great White Pelican Pelecanus onocrotalus
5.1.1 Population A group of organism of the same species which live in the same habitat at the same time where they can freely interbreed The black-veined white butterfly (Aporia crataegi) mating 息 2008 Paul Billiet ODWS
Biodiversity The total number of different species in an ecosystem and their relative abundance 息 2008 Paul Billiet ODWS Worcester City Museums
5.1.1 Habitat The characteristics of the type of environment where an organism normally lives. (e.g. a stoney stream, a deciduous temperate woodland, Bavarian beer mats) 息 2008 Paul Billiet ODWS
5.1.2 Energy and organisms Autotrophs Organisms which can synthesise their own complex, energy rich, organic molecules from simple inorganic molecules (e.g. green plants synthesis sugars from CO2 and H2O) 息 2008 Paul Billiet ODWS
5.1.2 Heterotrophs Organisms who must obtain complex, energy rich, organic compounds from the bodies of other organisms (dead or alive) 息 2008 Paul Billiet ODWS
5.1.3 Detritivores Heterotrophic organisms who ingest dead organic matter. (e.g. earthworms, woodlice, millipedes) Earth worm (Lumbricus terrestris) 息 2008 Paul Billiet ODWS
5.1.3 Saprotrophs Heterotrophic organisms who secrete digestive enzymes onto dead organism matter and absorb the digested material. (e.g. fungi, bacteria) Chanterelle (Cantherellus cibarius) 息 2008 Paul Billiet ODWS
Communities and ecosystems
Feeding relationships Predators & prey Herbivory Parasite & host Mutualism Competition Large blue butterfly (Maculinea arion) 息 2008 Paul Billiet ODWS
Parasitism? Mutualism?
The place of an organism in its environment Niche An organisms habitat + role + tolerance limits to all limiting factors 息 2008 Paul Billiet ODWS
THE COMPETITIVE EXCLUSION PRINCIPLE G.F. Gause (1934) If two species, with the same niche, coexist in the same ecosystem, then one will be excluded from the community due to intense competition 息 2008 Paul Billiet ODWS
Niche The niche of a species consists of: Its role in the ecosystem (herbivore, carnivore, producer etc) Its tolerance limits (e.g. soil pH, humidity) Its requirements for shelter, nesting sites etc etc, all varying through time 息 2008 Paul Billiet ODWS
The niche as a two-dimensional shape Species A Niche represented by a 2-dimensional area 息 2008 Paul Billiet ODWS
Separate niches Species A Species B No overlap of niches. So coexistence is possible 息 2008 Paul Billiet ODWS
Overlapping niches Species B Species C Interspecific competition occurs where the niches overlap 息 2008 Paul Billiet ODWS
Specialisation avoids competition Species B Species C Evolution by natural selection towards separate niches Species B Species C 息 2008 Paul Billiet ODWS Specialisation into two separate niches
This niche is not big enough for the both of us! Species A Species D Very heavy competition leads to competitive exclusion One species must go 息 2008 Paul Billiet ODWS
Total exclusion Species A has a bigger niche it is more generalist Species E has a smaller niche it is more specialist Specialists, however, do tend to avoid competition Here it is total swamped by Species A 息 2008 Paul Billiet ODWS
Example: Squirrels in Britain The Red Squirrel (Sciurus vulgaris) is native to Britain Its population has declined due to: Competitive exclusion Disease Disappearance of hazel coppices and mature Isle of Wight Tourist Guide conifer forests in lowland Britain 息 2008 Paul Billiet ODWS
The Alien The Grey Squirrel (Sciurus carolinensis) is an alien species Introduced to Britain in about 30 sites between 1876 and 1929 It has easily adapted to parks and gardens replacing the red squirrel Bananas in the Falklands 息 2008 Paul Billiet ODWS
Todays distribution Red squirrel Grey squirrel 息 2008 Paul Billiet ODWS
From Species to Ecosystems Ecosystem - biological community and its physical environment The physical environment includes non-living factors such as climate, water, minerals, etc. It is difficult to define the boundaries of an ecosystem. Most ecosystems are open in that they exchange materials and organisms with other ecosystems. 53
Food Chains and Food Webs Food Chain - linked feeding series Food Web - Most consumers have multiple food sources. Trophic level - An organisms feeding status in a food web. Plants are at the producer level while animals are consumers. Animals that eat plants are primary consumers while animals that eat other animals are secondary and tertiary consumers. (Some animals, called omnivores, eat both plants and animals.) Finally, there are organisms that recycle dead bodies and remove waste. 54
Food Chains and Food Webs 5.1.10 & 5.1.11 Energy flow in a Food Chain Energy losses between trophic levels include material not being consumed or material not assimilated, and heat loss through cell respiration. Energy transformations are never 100% efficient 55
Food Chains and Food Webs Photosynthesis is at the base of all ecosystems so photosynthesizers (usually plants) are called the producers. Productivity - the amount of biomass produced in a given area in a given period of time. Photosynthesis is called primary productivity because it is basic to all other growth in an ecosystem. Secondary productivity - manufacture of biomass by organisms that eat plants 56
Food Chains and Food Webs Food Chain 57
58
59
Trophic Levels Organisms can also be identified by the type of food they consume: Herbivores (Plants) {Deer} Carnivores (Meat) {Wolves} Omnivores (Plants/Meat) {Bears} Scavengers (Carcasses) {Crows} Detritivores (Debris) {Ants} Decomposers (All) {Bacteria} 60
Ecological Pyramids If the organisms at various trophic levels are arranged diagrammatically, they form a pyramid with many more producers than consumers. Due to the Second Law of Thermodynamics, energy is lost at each level of the pyramid. Energy is lost as heat in metabolic processes. Predator efficiency < 100% 10% Rule (Energy / Biomass) -100 kg clover 10 kg rabbit 1 kg fox 61
Units: energy per unit area per time 5.1.12 ie. kJ m-2 yr-1 Trophic Levels rule of 10: only ~10% of the energy is passed from one trophic level to the next 62
63
64
Energy Pyramid 65
Nutrient recycling 5.1.13 Energy enters and leaves ecosystems, but nutrients must be recycled. 5.1.14 Saprotrophic bacteria and fungi (decomposers) recycle nutrients Stop 66
Material Cycles Hydrologic Cycle - path of water through the environment Solar energy continually evaporates water stored in the oceans and land, and distributes water vapor around the globe. -Condenses over land surfaces, supporting all terrestrial systems Responsible for cellular metabolism, nutrient flow in ecosystems, and global distribution of heat and energy 67
Hydrologic Cycle 68
Carbon Cycle Begins with intake of CO2 during photosynthesis. Carbon atoms are incorporated into sugar which is eventually released by cellular respiration either in the plant or in organisms that consumed it. Sometimes the carbon is not recycled for a long time. Coal and oil are the remains of organisms that lived millions of years ago. The carbon in these is released when we burn them. Some carbon is also locked in calcium carbonate (shells, limestone). 69
Carbon Cycle 70
Carbon Cycle The parts of the cycle that remove carbon dioxide from the atmosphere (vegetation) are called carbon sinks. The parts of the cycle that release carbon dioxide are called carbon sources. Burning of fuels generates huge quantities of carbon dioxide that cannot be taken up fast enough by the carbon sinks. This excess carbon dioxide contributes to global warming. 71
Nitrogen Cycle Nitrogen is needed to make proteins and nucleic acids such as DNA (Chap. 2). Plants take up inorganic nitrogen from the environment and build protein molecules which are later eaten by consumers. Nitrogen-fixing bacteria change nitrogen to a more useful form by combining it with hydrogen to make ammonia. Other bacteria convert ammonia to nitrites and nitrates, which can be taken up by plants to make proteins. -Members of the bean family (legumes) have nitrogen-fixing bacteria living in their root tissue. 72
Nitrogen Cycle Nitrogen re-enters the environment: -Death of organisms -Excrement and urinary wastes Nitrogen re-enters atmosphere when denitrifying bacteria break down nitrates into N2 and nitrous oxide (N2O) gases. -Humans have profoundly altered the nitrogen cycle via use of synthetic fertilizers, nitrogen-fixing crops, and fossil fuels. 73
Nitrogen Cycle 74
Phosphorous Cycle Phosphorous is needed to make DNA, ATP (the energy currency of the cell) and other important biomolecules (Chap. 2). Phosphorous compounds are leached from rocks and minerals and usually transported in aqueous form. Taken in and incorporated by producers -Passed on to consumers Returned to environment by decomposition Cycle takes a long time as deep ocean sediments are significant sinks 75
Phosphorus Cycle 76
Sulfur Cycle Most sulfur is tied up in underground rocks and minerals. Inorganic sulfur is released into air by weathering and volcanic eruptions. Cycle is complicated by large number of oxidation states the element can assume. Human activities release large amounts of sulfur, primarily by burning fossil fuels. -Important determinant in rainfall acidity 77
Sulfur Cycle 78

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Communities and ecosystems

  • 2. o What is the chemical basis of life? o Organic/inorganic Compounds o Energy o Laws of Thermodynamics o Photosynthesis/Respiration o Ecosystems o Food Chains o Ecological Pyramids o Material Cycles 2
  • 3. 4
  • 4. Law of Conservation of Matter Matter is neither created nor destroyed but rather re- cycled over and over. The atoms in your body may have been in a dinosaur. The idea that matter cannot be destroyed but is simply transformed from one form to another is termed conservation of matter. 5
  • 5. Just four elements carbon, hydrogen, oxygen, and nitrogen - make up over 96% of the mass of most organisms. 6
  • 6. Elements of Life 92 naturally occurring elements Elements Found in Living Organisms N CHOPS (macronutrients) C HOPKINS Ca Fe Mg B Mn Cu Cl Mo Zn The most common elements in a cell are: Hydrogen (H) 59% Oxygen (O) 24% Carbon (C) 11% Nitrogen (N) 4% Others such as phosphorus (P) and sulphur (S) 2% combined 7
  • 7. Abundance of Elements (%) Nitrogen, 0.04 Everything else, 0.02 The most common elements in a cell are: Hydrogen (H) 59% Carbon, 0.11 Oxygen (O) 24% Hydrogen Oxygen Carbon (C) 11% Carbon Nitrogen (N) 4% Nitrogen Everything else Others such as phosphorus (P) and sulphur (S) Oxygen, 0.24 Hydrogen, 0.59 2% combined 8
  • 8. Elements of Life Organic = carbon-based molecules Examples: C6H12O6, CH4 9
  • 9. Organic Compounds Organic Compounds - Material making up biomolecules, which in turn make up living things. All organic compounds contain carbon. Four major categories of organic compounds: -Lipids -Carbohydrates -Proteins -Nucleic Acids 10
  • 10. a. Butyric acid is the building block of lipids; propane is a hydrocarbon b. Glucose is a simple carbohydrate c. Amino acids form macromolecules called proteins d. Nucleic acids combine to form DNA chains 11
  • 11. Elements of Life Inorganic = molecules without carboncarbon or carbonhydrogen bonds Examples: NaCl, NH4, H2SO4 12
  • 12. 13
  • 14. Thermodynamics Energy must be supplied (from the sun) to keep biological processes running, because as it flows through the various biological processes, it becomes dissipated. First Law of Thermodynamics - Energy is neither created nor destroyed. Second Law of Thermodynamics - With each successive energy transfer, less energy is available to perform work. Entropy (disorder) increases. 15
  • 15. Energy for Life Ultimately, most organisms depend on the sun for the energy needed to carry out life processes. A few very ancient organisms called archaea are able to get their energy from inorganic compounds that bubble up from vents in the sea floor or from hot springs. These organisms represent one-third of all the biomass on the planet. The methane generated by these undersea communities could be a source of natural gas for us. 16
  • 16. Energy from the Sun Solar energy is essential for (2) reasons: Warmth - Most organisms can exist only in a relatively narrow temperature range. Photosynthesis in plants -Radiant energy is transformed into useful, high- quality chemical energy in the bonds of organic molecules. All life on Earth depends on photosynthesis. 17
  • 17. Energy For Life Of all solar radiation reaching the earths surface, about 10% is ultraviolet, 45% is visible, and 45% is infrared. Most of energy is absorbed by land or water, or reflected back into space. -Only about 1-2% of the sunlight falling on plants is captured for photosynthesis. 18
  • 19. Photosynthesis Occurs in organelles called chloroplasts within plant cells 6H20+6CO2 + solar energy = C6H12O6+6O2 Water and carbon dioxide in the presence of sunlight and chlorophyll (the green pigment in chloroplasts) yield glucose (sugar) and oxygen. Glucose serves as primary fuel for all metabolic processes. Energy in its chemical bonds can be used to make other molecules such as proteins or it can drive movement, transport, etc. 20
  • 21. 22
  • 22. Cellular Respiration Photosynthesis captures energy, while cellular respiration releases energy. Cellular respiration splits carbon and hydrogen atoms from sugar and recombines them with oxygen to re-create carbon dioxide and water (opposite of photosynthesis). This is how animals get all their energy. The reason that you need to breathe is to supply this pathway with oxygen. C6H12O6 + 6O2 = 6H2O +6CO2 + energy 23
  • 23. Energy Exchange in Ecosystems 24
  • 24. 5.1 Communities and Ecosystems 5.1.1 ECOLOGY The study of the relationships between living organisms and their environment 息 2008 Paul Billiet ODWS
  • 25. How do organisms interact with one another? How do they interact with their nonliving environment?
  • 26. 5.1.1 Community All the populations of the different species living and inter-acting in the same ecosystem 7-spotted lady bird (Adephagia septempunctata) Bean aphids (Aphis fabae) Red ant (Myrmica rubra) and Broom plant (Cytisus scoparius) 息 2008 Paul Billiet ODWS
  • 27. 5.1.1 Ecosystem Community + Abiotic environment, interacting 息 2008 Paul Billiet ODWS
  • 28. 5.1.1 Species A group of organisms that can breed to produce fully fertile offspring 息 2008 Paul Billiet ODWS Great White Pelican Pelecanus onocrotalus
  • 29. 5.1.1 Population A group of organism of the same species which live in the same habitat at the same time where they can freely interbreed The black-veined white butterfly (Aporia crataegi) mating 息 2008 Paul Billiet ODWS
  • 30. Biodiversity The total number of different species in an ecosystem and their relative abundance 息 2008 Paul Billiet ODWS Worcester City Museums
  • 31. 5.1.1 Habitat The characteristics of the type of environment where an organism normally lives. (e.g. a stoney stream, a deciduous temperate woodland, Bavarian beer mats) 息 2008 Paul Billiet ODWS
  • 32. 5.1.2 Energy and organisms Autotrophs Organisms which can synthesise their own complex, energy rich, organic molecules from simple inorganic molecules (e.g. green plants synthesis sugars from CO2 and H2O) 息 2008 Paul Billiet ODWS
  • 33. 5.1.2 Heterotrophs Organisms who must obtain complex, energy rich, organic compounds from the bodies of other organisms (dead or alive) 息 2008 Paul Billiet ODWS
  • 34. 5.1.3 Detritivores Heterotrophic organisms who ingest dead organic matter. (e.g. earthworms, woodlice, millipedes) Earth worm (Lumbricus terrestris) 息 2008 Paul Billiet ODWS
  • 35. 5.1.3 Saprotrophs Heterotrophic organisms who secrete digestive enzymes onto dead organism matter and absorb the digested material. (e.g. fungi, bacteria) Chanterelle (Cantherellus cibarius) 息 2008 Paul Billiet ODWS
  • 37. Feeding relationships Predators & prey Herbivory Parasite & host Mutualism Competition Large blue butterfly (Maculinea arion) 息 2008 Paul Billiet ODWS
  • 39. The place of an organism in its environment Niche An organisms habitat + role + tolerance limits to all limiting factors 息 2008 Paul Billiet ODWS
  • 40. THE COMPETITIVE EXCLUSION PRINCIPLE G.F. Gause (1934) If two species, with the same niche, coexist in the same ecosystem, then one will be excluded from the community due to intense competition 息 2008 Paul Billiet ODWS
  • 41. Niche The niche of a species consists of: Its role in the ecosystem (herbivore, carnivore, producer etc) Its tolerance limits (e.g. soil pH, humidity) Its requirements for shelter, nesting sites etc etc, all varying through time 息 2008 Paul Billiet ODWS
  • 42. The niche as a two-dimensional shape Species A Niche represented by a 2-dimensional area 息 2008 Paul Billiet ODWS
  • 43. Separate niches Species A Species B No overlap of niches. So coexistence is possible 息 2008 Paul Billiet ODWS
  • 44. Overlapping niches Species B Species C Interspecific competition occurs where the niches overlap 息 2008 Paul Billiet ODWS
  • 45. Specialisation avoids competition Species B Species C Evolution by natural selection towards separate niches Species B Species C 息 2008 Paul Billiet ODWS Specialisation into two separate niches
  • 46. This niche is not big enough for the both of us! Species A Species D Very heavy competition leads to competitive exclusion One species must go 息 2008 Paul Billiet ODWS
  • 47. Total exclusion Species A has a bigger niche it is more generalist Species E has a smaller niche it is more specialist Specialists, however, do tend to avoid competition Here it is total swamped by Species A 息 2008 Paul Billiet ODWS
  • 48. Example: Squirrels in Britain The Red Squirrel (Sciurus vulgaris) is native to Britain Its population has declined due to: Competitive exclusion Disease Disappearance of hazel coppices and mature Isle of Wight Tourist Guide conifer forests in lowland Britain 息 2008 Paul Billiet ODWS
  • 49. The Alien The Grey Squirrel (Sciurus carolinensis) is an alien species Introduced to Britain in about 30 sites between 1876 and 1929 It has easily adapted to parks and gardens replacing the red squirrel Bananas in the Falklands 息 2008 Paul Billiet ODWS
  • 50. Todays distribution Red squirrel Grey squirrel 息 2008 Paul Billiet ODWS
  • 51. From Species to Ecosystems Ecosystem - biological community and its physical environment The physical environment includes non-living factors such as climate, water, minerals, etc. It is difficult to define the boundaries of an ecosystem. Most ecosystems are open in that they exchange materials and organisms with other ecosystems. 53
  • 52. Food Chains and Food Webs Food Chain - linked feeding series Food Web - Most consumers have multiple food sources. Trophic level - An organisms feeding status in a food web. Plants are at the producer level while animals are consumers. Animals that eat plants are primary consumers while animals that eat other animals are secondary and tertiary consumers. (Some animals, called omnivores, eat both plants and animals.) Finally, there are organisms that recycle dead bodies and remove waste. 54
  • 53. Food Chains and Food Webs 5.1.10 & 5.1.11 Energy flow in a Food Chain Energy losses between trophic levels include material not being consumed or material not assimilated, and heat loss through cell respiration. Energy transformations are never 100% efficient 55
  • 54. Food Chains and Food Webs Photosynthesis is at the base of all ecosystems so photosynthesizers (usually plants) are called the producers. Productivity - the amount of biomass produced in a given area in a given period of time. Photosynthesis is called primary productivity because it is basic to all other growth in an ecosystem. Secondary productivity - manufacture of biomass by organisms that eat plants 56
  • 55. Food Chains and Food Webs Food Chain 57
  • 56. 58
  • 57. 59
  • 58. Trophic Levels Organisms can also be identified by the type of food they consume: Herbivores (Plants) {Deer} Carnivores (Meat) {Wolves} Omnivores (Plants/Meat) {Bears} Scavengers (Carcasses) {Crows} Detritivores (Debris) {Ants} Decomposers (All) {Bacteria} 60
  • 59. Ecological Pyramids If the organisms at various trophic levels are arranged diagrammatically, they form a pyramid with many more producers than consumers. Due to the Second Law of Thermodynamics, energy is lost at each level of the pyramid. Energy is lost as heat in metabolic processes. Predator efficiency < 100% 10% Rule (Energy / Biomass) -100 kg clover 10 kg rabbit 1 kg fox 61
  • 60. Units: energy per unit area per time 5.1.12 ie. kJ m-2 yr-1 Trophic Levels rule of 10: only ~10% of the energy is passed from one trophic level to the next 62
  • 61. 63
  • 62. 64
  • 64. Nutrient recycling 5.1.13 Energy enters and leaves ecosystems, but nutrients must be recycled. 5.1.14 Saprotrophic bacteria and fungi (decomposers) recycle nutrients Stop 66
  • 65. Material Cycles Hydrologic Cycle - path of water through the environment Solar energy continually evaporates water stored in the oceans and land, and distributes water vapor around the globe. -Condenses over land surfaces, supporting all terrestrial systems Responsible for cellular metabolism, nutrient flow in ecosystems, and global distribution of heat and energy 67
  • 67. Carbon Cycle Begins with intake of CO2 during photosynthesis. Carbon atoms are incorporated into sugar which is eventually released by cellular respiration either in the plant or in organisms that consumed it. Sometimes the carbon is not recycled for a long time. Coal and oil are the remains of organisms that lived millions of years ago. The carbon in these is released when we burn them. Some carbon is also locked in calcium carbonate (shells, limestone). 69
  • 69. Carbon Cycle The parts of the cycle that remove carbon dioxide from the atmosphere (vegetation) are called carbon sinks. The parts of the cycle that release carbon dioxide are called carbon sources. Burning of fuels generates huge quantities of carbon dioxide that cannot be taken up fast enough by the carbon sinks. This excess carbon dioxide contributes to global warming. 71
  • 70. Nitrogen Cycle Nitrogen is needed to make proteins and nucleic acids such as DNA (Chap. 2). Plants take up inorganic nitrogen from the environment and build protein molecules which are later eaten by consumers. Nitrogen-fixing bacteria change nitrogen to a more useful form by combining it with hydrogen to make ammonia. Other bacteria convert ammonia to nitrites and nitrates, which can be taken up by plants to make proteins. -Members of the bean family (legumes) have nitrogen-fixing bacteria living in their root tissue. 72
  • 71. Nitrogen Cycle Nitrogen re-enters the environment: -Death of organisms -Excrement and urinary wastes Nitrogen re-enters atmosphere when denitrifying bacteria break down nitrates into N2 and nitrous oxide (N2O) gases. -Humans have profoundly altered the nitrogen cycle via use of synthetic fertilizers, nitrogen-fixing crops, and fossil fuels. 73
  • 73. Phosphorous Cycle Phosphorous is needed to make DNA, ATP (the energy currency of the cell) and other important biomolecules (Chap. 2). Phosphorous compounds are leached from rocks and minerals and usually transported in aqueous form. Taken in and incorporated by producers -Passed on to consumers Returned to environment by decomposition Cycle takes a long time as deep ocean sediments are significant sinks 75
  • 75. Sulfur Cycle Most sulfur is tied up in underground rocks and minerals. Inorganic sulfur is released into air by weathering and volcanic eruptions. Cycle is complicated by large number of oxidation states the element can assume. Human activities release large amounts of sulfur, primarily by burning fossil fuels. -Important determinant in rainfall acidity 77