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This informative guide explores the principles of energy flow in ecosystems, encompassing the laws of thermodynamics, solar radiation pathways, and the efficiency of energy transfer through food webs. From the sun's energy input to the diversions and transformations within biological systems, delve into the intricate processes driving energy dynamics within ecosystems. Discover how energy is converted, transferred, and sometimes lost as heat or waste at different trophic levels. Gain insights into ecological efficiencies, energy partitioning, and the roles of producers, consumers, and decomposers in maintaining energy balance. Learn to construct and interpret energy flow diagrams to visualize the movement of energy through ecosystems. Enhance your understanding of the interconnectedness and sustainability of energy flow within living systems.
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Energy in living systems • Food chains, webs and pyramids, ultimately show energy flow • Obey the laws of thermodynamics • Obey systems laws – input, transfer, transformation, output
Thermodynamics Review Universal laws that govern all energy changes in the universe, from nuclear reactions to the buzzing of a bee. • The 1st law: Energy can be transferred and transformed but not created or destroyed - Energy flow in the biological world is unidirectional: • Sun energy enters system and replaces energy lost from heat • Energy at one trophic level is always less than the previous level
Thermodynamics Review (b) The 2nd law: Energy transformations proceed spontaneously to convert matter from a more ordered, less stable form, to a less ordered, more stable form • Energy lost as heat from each level • Energy at one level less than previous because of these losses
Energy Flow in Communities • Energy unlike matter does not recycle through a community it flows • Energy comes from the sun • Converted by autotrophs into glucose
Energy Flow in Communities • Amount of Light energy converted into chemical energy by autotrophs in a given time period - Gross Primary Production GPP • The amount to pass on to consumers after plants have used their share - Net Primary Production NPP • NPP = GPP - R
Figure 3-10Page 52 15 10 Energy emitted from sun (Kcal/cm2/min) 5 0 0.25 1 2 2.5 3 Wavelength (micrometers) Visible Light is The usable Energy
What is the sun? • 72% hydrogen, 28% helium • Temp and pressure high so H nuclei fuse to form He releasing energy • Fusion energy radiated as electromagnetic energy • Earth receives 1 billionth of the suns Energy • Most reflected away or absorbed by atmospheric chemicals
Energy to Earth • 30% solar energy reflected back into space by atmosphere, clouds, ice • 20% absorbed by clouds & atmosphere • 50% remaining • Warms troposphere and land • Evaporates and cycles water • Generates wind
Energy to Earth • < 0.1% captured by producers for photosynthesis • Energy eventually transformed to heat and trapped by atmosphere “Natural Greenhouse Effect” • Eventually reradiated into space
So if sunlight in = sunlight + heat out What state is the system in? Stable Equilibrium
Summary of solar radiation pathways • Incident radiation comes in, it is then… • Lost by reflection (ice caps) and absorption (soil, water bodies) • Converted from light to chemical energy (photosynthesis in producers) • Lost as chemical energy decreases through trophic levels • Through an ecosystem completely converted from light energy into heat • Reradiated as heat back to the atmosphere
Energy Flow II • Energy measured in joules or kilojoules per unit area per unit time • Energy conversion never 100% efficient • Some energy lost as heat • Of visible light reaching producers, only 1% is converted to chemical energy • Other levels are 10% efficient – only assimilate %10 of energy from previous level
Energy Flow and Food webs • Biomass = the total dry weight of all organisms in one trophic level • Usable energy degraded with each transfer • Loss as heat, waste, metabolism
Energy Flow and Food webs • % transferred = ecological efficiency ranges from 5-20% • More trophic levels = less energy available at high levels
If that loss happens at every trophic level think about how much energy is lost. Makes the lower trophic levels most efficient in terms of overall energy available in the system
Energy Flow through Producers • Producers convert light energy into chemical energy of organic molecules • Energy lost as cell respiration in producers then as heat elsewhere • When consumers eat producers energy passes on to them • In death organic matter passes to saprophytes & detritivores
Energy Flow through Consumers • Obtain energy by eating producers or other consumers • Energy transfer never above 20% efficient, usually between 10 – 20%
Energy Flow through Consumers • Food ingested has multiple fates • Large portion used in cell respiration for meeting energy requirements (LOSS) • Smaller portion is assimilated used for growth, repair, reproduction • Smallest portion, undigested material excreted as waste (LOSS)
Figure 54.10 Energy partitioning within a link of the food chain
Energy flow through Decomposers • Some food is not digested by consumers so lost as feces to detritivores & saprophytes • Energy eventually released by process of cell respiration or lost as heat
Construct and analyze energy flow diagrams for energy movement through ecosystems • Trophic level boxes are storages – biomass per area (g m-2) • Energy Flow in arrows – rate of energy transfer (g m-2 day-1)
Energy values in KJ m-2y-1 Often the size of the boxes and arrows is proportional to their amount
