Energy and Biomass in Ecosystems

Energy and Biomass in Ecosystems

• Ecosystems rely on energy and matter
• The first thermodynamics law states energy can be transformed, but not created/destroyed
• Photosynthesis and cellular respiration transform energy and matter
• Photosynthesis converts light energy to chemical energy (glucose), stored as biomass in autotrophs
• Producers are the first trophic level in a food chain
• Cellular respiration converts glucose to usable chemical energy for living cells
• Some of this chemical energy becomes heat
• Second thermodynamics law dictates energy transformations in ecosystems are inefficient
• Consumers gain chemical energy (organic compounds) from other organisms
• Consumers have different strategies to get energy-containing carbon compounds
• Primary productivity is biomass production rate from an external energy source and inorganic sources of carbon and other elements
• Secondary productivity is biomass gain by consumers from absorbed and assimilated ingested food
• Net primary productivity is the base for food chains because it's the amount of carbon compounds available to primary consumers
• Autotrophs synthesize carbon compounds from inorganic sources
• Heterotrophs get carbon compounds from other organisms
• Photoautotrophs use light in photosynthesis
• Chemoautotrophs use exothermic inorganic chemical reactions in chemosynthesis
• Maximum sustainable yields (MSYs) are the net primary or secondary productivity of a system
• Sustainable yields are higher for lower trophic levels
• Ecological efficiency is the percentage of energy passed from one trophic level to the next
• Second law of thermodynamics says entropy increases as biomass passes through ecosystems
• Energy in systems is subject to the laws of thermodynamics and the principle of energy conservation
• The total energy in an isolated system remains constant while energy transforms
• Photosynthesis converts light energy to chemical energy
• Respiration converts chemical energy transforms into heat or kinetic energy
• Living things respire constantly, in both light and darkness
• Photosynthesis needs water, carbon dioxide, and sunlight, and occurs in plants, algae, and some microorganisms
• Water reaches plan leaves via transpiration
• Photosynthesis involves the conversion of light energy into chemical energy (glucose)
• Plant leaves contain chloroplasts with chlorophyll, where sunlight splits water, combines it with carbon dioxide to make glucose
• Glucose is a starting point for the plant to create other needed molecules
• Plants add nitrogen and sulfur to make amino acids and proteins
• Plants rearrange carbon, hydrogen, and oxygen, and add phosphorus to make fatty acids and lipoproteins for cell membranes
• Animals depend on chemicals produced by plants
• Humans can create most molecules needed from eating, digesting, and rebuilding food into enzymes, fats, and proteins
• Humans requires nine essential amino acids
• Photosynthesis' waste product is oxygen, used in aerobic respiration
• The compensation point is when a plant nether adds biomass nor uses it, occurring in dawn and dusk
• The second law of thermodynamics relates to energy quality
• Transferred energy changes to heat and means energy is lost from the food chain
• Efficiency is defined as the useful energy or work (output) divided by the energy consumed (input), expressed as a percentage
• Solar energy starts almost every food chain
• Some organisms get energy from heat released by deep ocean vents
• A food chain shows an ecosystem’s feeding relationships and energy flow from one organism to the next
• Arrows on a food chain represents the flow of energy

Trophic Levels

• Consumer (heterotroph) gains food from others
• A trophic level represents an organism’s specific place in the food chain
• Producer or autotroph, makes food via photosynthesis
• Organisms are grouped into trophic levels which start at primary producer (plant) and ends with top carnivore
• Primary producers provide energy requirements for other trophic levels
• Primary levels provide habitat for otehr organism
• Primary levels supply nutrients and bind soil
• PC, SC and TC remove old, weakened and diseased animals from population
• Secondary groups diperse seeds and flower
• Decomposers crucial for ecosystem, break down dead organisms and return nutrients back to cycle and controls disease

Food Webs

• Ecosystems usually don't have very simple food chains
• Food chains illustrate only a direct feeding link between other organisms and creates issues
• Diet of consumers is not limited to single species
• Voles for example eat insects and plants
• Top of food chain are always vulnerable to the effects of changes further down the chain and have limited resilience
• The second law of thermodynamics states that entropy of an isolated system will always trend to go up

Energy Transfer

• Energy losses limit the number of trophic energy in ecosystems and lost because of release from respiation as heat
• Trophic energy transfer (efficiency) averages about 10%, it can vary
• Community of small mammals might have efficiency of 0.1% lost through heat and respiration