1. Ch 5 What do we know about ecosystems?

2. An ecosystem consists of all the organisms (biotic) in a community and the environment (abiotic) with which they interact. Ecosystems can be as small as the microorganisms living on your skin or as large as the entire biosphere.

3. Energy flows THROUGH ecosystems – open system Nutrients cycle WITHIN ecosystems – closed system

4. HOW DO ECOSYSTEMS WORK ? FOLLOW THE FLOW OF ENERGY THROUGH AN ECOSYSTEM FOLLOW THE CYCLING OF MATERIALS THROUGH AN ECOSYSTEM FOLLOW THE CHANGES IN AN ECOSYSTEM

5. The Earth’s Life-Support Systems Atmosphere Troposphere -weather Greenhouse gases Stratosphere Lower portion (ozone) filters out harmful sun rays Allows life to exist on earth Geosphere - Lithosphere Earth’s crust Hydrosphere Water 3% is fresh Biosphere Living and dead organisms

6. Solar Capital: Flow of Energy to and from the Earth Greenhouse gasses water vapor CO2 Methane Ozone Increases kinetic energy, Helps warm troposphere. Allows life to exist (as we know it) on earth. As greenhouse gasses increase, temperature of troposphere increases.

7. Ecosystem Components Abiotic factors energy mineral nutrients CO 2 O 2 H 2 O Biotic factors Range of tolerance for each species

8. ABIOTIC components: Solar energy provides practically all the energy for ecosystems. Inorganic substances, e.g., carbon, oxygen, sulfur, boron, tend to cycle through ecosystems. Organic compounds, such as proteins, carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

9. BIOTIC components: The biotic components of an ecosystem can be classified according to their mode of energy acquisition. In this type of classification, there are: Autotrophs and Heterotrophs

10. Life Depends on the sun

11. Natural Capital: Sustaining Life of Earth One-way flow of energy from Sun Cycling of crucial elements Gravity

12. Three hundred trout are needed to support one man for a year. The trout, in turn, must consume 90,000 frogs, that must consume 27 million grasshoppers that live off of 1,000 tons of grass. -- G. Tyler Miller, Jr., American Chemist (1971)

13. Types of energy: 1.heat energy 2.chemical energy = energy stored in molecular bonds 3.Light 4.Mechanical 5.Nuclear 6.Electrical 7.Magnetic 8.gravitational

14. First Law of Thermodynamics Energy is neither created nor destroyed Energy only changes form You can’t get something for nothing – Or “There is no such thing as a free lunch!” ENERGY IN = ENERGY OUT Energy flow is a one-directional process. sun---> heat (longer wavelengths)

15. Second Law of Thermodynamics In every transformation, some energy is converted to heat You cannot break even in terms of energy quality

16. SECOND LAW of THERMODYNAMICS Transformations of energy always result in some loss or dissipation of energy or In energy exchanges in a closed system, the potential energy of the final state will be less than that of the initial state or Entropy tends to increase (entropy = amount of unavailable energy in a system) or Systems will tend to go from ordered states to disordered states (to maintain order, energy must be added to the system, to compensate for the loss of energy)

17. Internal combustion engines in cars are 25% efficient in converting chemical energy to kinetic energy; the rest is not used or is lost as heat. My desk goes from a complex, ordered state to a simpler, disordered state

18. ENERGY FLOW IN ECOSYSTEMS All organisms require energy, for growth, maintenance, reproduction, locomotion, etc. Hence, for all organisms there must be: A source of energy A loss of usable energy

19. Life depends on the sun Energy in an ecosystem originally comes from the sun Energy in an ecosystem originally comes from the sun Energy enters an ecosystem Energy enters an ecosystem when a plant/algae uses when a plant/algae uses sunlight to make sugar in sunlight to make sugar in photosynthesis photosynthesis

20. Photosynthesis is the process of converting solar energy into chemical energy stored in food CO 2 + H 2 0 ---> C 6 H 12 O 6 + O 2

21. Light strikes leaf Energy absorbed by chemical pigments Absorbed energy drives chemical processes to convert CO 2 into larger molecules Energy absorbed in building larger molecules, released as they are broken down How Photosynthesis Works

23. Absorption spectra of chlorophylls and carotenoids Wavelength reflected

24. In many plants production of chlorophyll ceases with cooler temperatures and decreasing light other pigments become visible

25. CO 2 must enter though stomata stomata (sing., stoma) are tiny holes on the undersides of leaves CO 2 enters and moisture is released In hot, dry climates, this moisture loss is a problem

26. 6 CO 2 + 6 H 2 0 SUNLIGHT C 6 H 12 O 6 + 6 O 2 ENERGY RICH CARBOHYDRATES GLUCOSE

27. Organisms are classified by the source of their energy PRODUCERS – organisms that make their own food Also known as AUTOTROPHS Examples: plants, algae, some bacteria CONSUMERS – get energy by eating other living things Also known as HETEROTROPHS

28. TWO TYPES OF PRODUCERS AUTOTROPHS Photosynthetic – algae, plants, some bacteria that use sun’s energy to synthesize organic compounds Chemosynthetic – bacteria that synthesize organic compounds from inorganic chemicals (hydrogen sulfide, ammonia) use energy in chemical bonds

29. Autotrophs (=self-nourishing) are called primary producers. Photoautotrophs fix energy from the sun and store it in complex organic compounds (= green plants, algae, some bacteria) simple inorganic compounds photoautotrophs complex organic compounds ligh t CO 2 + H 2 O chloroplasts Glucose C 6 H 12 O 6

30. Chemoautotrophs (chemosynthesizers) are bacteria that oxidize reduced inorganic substances (typically sulfur and ammonia compounds) and produce complex organic compounds. reduced inorganic compounds oxygen chemoautotrophs complex organic compounds

32. Other chemoautotrophs: Nitrifying bacteria in the soil under our feet

33. When an animal eats a plant, energy is transferred from the plant to the animal. l

34. Respiration is the process of releasing chemical energy stored in food to be used by living things. C 6 H 12 O 6 + O 2 ---> CO 2 + H 2 0

35. Heterotrophs (=other-nourishing) cannot produce their own food directly from sunlight+ inorganic compounds. They require energy previously stored in complex molecules. complex organic compounds heterotrophs simple inorganic compounds heat glucosemitochondriaCO2 + H2O + ATP

36. TYPES OF CONSUMERS HETEROTROPHS Herbivore - Carnivore - Omnivore - Scavenger - Detrivore - Decomposer -

37. Hummingbirds, moths, aphids, sap suckers … Classes of Herbivores Browsers – woody material Grazers – plant material Granivores - seeds Frugivores – fruit Other: nectar & sap feeders

39. ENERGY TRANSFER Follow energy transfer through an ecosystem: – Food chain: follows path of energy – Food web: multiple food chains – Energy pyramids: shows loss of energy as you move up trophic levels – The arrow follows the flow of energy

40. Food chain Plantrabbit snake Arrows follow the flow of energy NOT who eats who __________________________________ NO: Plant rabbit snake

41. Food chain

44. Problems Too simplistic No detritivores Chains too long

45. Rarely are things as simple as grass, rabbit, hawk, or indeed any simple linear sequence of organisms. More typically, there are multiple interactions, so that we end up with a FOOD WEB.

46. Food Web Multiple food chains Rarely does 1 organism only eat 1 thing Shows many possible feeding relationships that are possible in an ecosystem. Arrows still follow the flow of energy from producers through consumers to the top of the food web.

53. Energy Pyramids & Trophic levels Trophic levels: feeding levels, each step of energy transfer – 1 st trophic level – producers – 2 nd trophic level – primary consumers (herbivores) – 3 rd trophic level – secondary consumers (carnivores) – 4 th trophic level – tertiary consumer (predator)

54. Trophic Level: Position in a food web determined by number of energy transfers from primary producers to current level: Primary producers occupy first level. Autotrophic, energy from sun or chemicals. Primary consumers occupy second level. herbivores Secondary consumers occupy third level. Omnivore or carnivore Tertiary consumers occupy fourth level. Carnivore

59. ENERGY LOSS Each time energy is transferred, energy is lost (as heat) Less energy is available for the next trophic level 90% of the energy in food used in respiration to keep organism alive 10% stored in body to be passed to next energy level

60. ENERGY LOSS Decreased loss of energy at each trophic level affects the organization of an ecosystem: – Fewer organisms are found as you move up the trophic levels – Loss of energy limits the number of trophic levels in an ecosystem to no more than 4 or 5

61. 5% of electricity is changed into useful light. 95% is lost as low-quality heat.

63. Primary productivity Primary productivity is the rate of energy capture by producers. = the amount of new biomass of producers, per unit time and space

69. Gosz studied solar energy flow: 15% reflected 41% converted to heat 42% absorbed during evapotranspiration 2.2% fixed by plants as gross primary production 1.2% used in plant respiration 1% left for primary production sun 30% reflected, 20% absorbed by atmosphere 50% absorbed by ground, water or vegetation 1% left for photosynthesis

70. Keystone species exert strong effects on their community structure, despite low biomass.

72. Exotic species have dramatic impacts on communities because they were outside the evolutionary experience of local prey populations. Nile Perch (Lates nilotica) exotic fish predator in Lake Victoria. Fish fauna dramatically reduced.

75. Christian observed native ants disperse 30% of shrubland seeds in fynbos of South Africa. Seed-dispersing ants bury seeds in sites safe from predators and fire. Argentine ants have displaced many native ant species that disperse large seeds. Substantial reductions in seedling recruitment by plants producing large seeds.

78. Consumers Producers Decomposers heat This pattern of energy flow among different organisms is the TROPHIC STRUCTURE of an ecosystem.

79. Biomass--the dry mass of organic material in the organism(s). (the mass of water is not usually included, since water content is variable and contains no usable energy) Standing crop--the amount of biomass present at any point in time.

80. Gross primary production (GPP) = total amount of energy captured Net primary production (NPP) = GPP - respiration Net primary production is thus the amount of energy stored by the producers and potentially available to consumers and decomposers.

81. Secondary productivity is the rate of production of new biomass by consumers, i.e., the rate at which consumers convert organic material into new biomass of consumers. Note that secondary production simply involves the repackaging of energy previously captured by producers--no additional energy is introduced into the food chain. And, since there are multiple levels of consumers and no new energy is being captured and introduced into the system, the modifiers gross and net are not very appropriate and are not usually used.

82. The standing crop, productivity, number of organisms, etc. of an ecosystem can be conveniently depicted using “pyramids”, where the size of each compartment represents the amount of the item in each trophic level of a food chain. Note that the complexities of the interactions in a food web are not shown in a pyramid; but, pyramids are often useful conceptual devices--they give one a sense of the overall form of the trophic structure of an ecosystem. producers herbivores carnivores

83. A pyramid of numbers indicates the number of individuals in each trophic level. Since the size of individuals may vary widely and may not indicate the productivity of that individual, pyramids of numbers say little or nothing about the amount of energy moving through the ecosystem.

85. Mechanical defenses – spines Chemical defenses Digestion disrupting chemicals – tannins, silica, oxalic acid Toxins – alkaloids More common in tropical species How do animals respond? Detoxify Excrete Chemical conversions – use as nutrient How do plants respond to feeding pressures by herbivores?

86. Carnivores Predators must catch and subdue prey - size selection. Usually eliminate more conspicuous members of a population (less adaptive). act as selective agents for prey species. Adaptations of Prey to being preyed upon Predator and prey species are engaged in a co- evolutionary race. Avoid being eaten – avoid starving/becoming extinct Defenses: Run fast Be toxic – and make it known Pretend to be toxic Predators learn to avoid

87. Consume nutritionally-rich prey. Cannot choose prey at will. Prey Defenses: Aposomatic Coloring - Warning colors. Mullerian mimicry: Comimicry among several species of noxious organisms. Batesian mimicry: Harmless species mimic noxious species

88. Detritivores Consume food rich in carbon and energy, but poor in nitrogen. Dead leaves may have half nitrogen content of living leaves. Fresh detritus may still have considerable chemical defenses present.

89. All other things being equal,more abundant prey yields larger energy return. Must consider energy expended during: Search for prey Handling time Tend to maximize rate of energy intake. What would a starving man do at an all you can eat buffet?

91. Slow-moving coastal plain stream choked with algal bloom caused by nitrogen and phosphorus from upstream farmland.

94. NUMBERS PYRAMID

95. BIOMASS PYRAMID

96. ENERGY PYRAMID