BIO 4730/5730 Environmental Biology Topic 3 Energy and Energetics Energy and Energy Metabolism ■ Energy is required for: Energy Availability on Earth ● Resisting entropy and maintaining ■ Energy is measured in joules (J) homeostasis Most of energy intake ● 1 J = 0.239 calories (actually, a gram-calorie, 1 g-cal = 4.186 J) (about 90%) is needed for this maintenance metabolism (supporting ● 1 kiloJoule (kJ) = 1000 Joules existing biological material) ● 1 megaJoule (MJ) = 1,000,000 J ■ Most adaptations are directly or ■ A calorie is the amount of energy required to increase the indirectly associated with maintaining temperature of 1 g water 1 °C at 15 °C homeostasis while increasing energy ● A kilocalorie (kcal) or Calorie = 1000 calories gain or decreasing energy wastage ■ Energy transfer requires the movement or flow of ■ Organisms must also produce new biological material (). Any energy from one point to the other (energy flux = energy that is assimilated but not power) needed for maintenance is available -1 ● Unit of power (energy/time) is the watt (W) = 1 J s for: -2 ● Earth receives and average of about 1 W m on its sunlit side ● Somatic (body) growth (ultimate limit to global energy input) ● Reproduction ● Humans supplement solar energy using stored energy reserves ■ This increase in biomass by growth and (fossil fuels) deposited over 100s of millions of years reproduction is known as production

Earth Area Available to Support Humans Energetics and Thermodynamics Productive sea Energy is the ability to do work, and is the ultimate and land area limiting for all living things available to support each First law of thermodynamics (Law of Conservation of person in Africa: Energy): energy can be neither created or destroyed, only 1.36 ha converted from one form to another (energy input = …on Earth: 1.90 ha energy output)

Each W. European/U.S. citizen: World 5.06/5.26 ha Wildlife Productive sea and land area needed to produce Fund, None of these ‘devourings’ creates any new Living Planet energy, they just pass along energy that came the products consumed by each U.S. citizen: from somewhere else. Where do you think the 9.71 ha (the CSU campus is 64.75 ha: enough to Report 2002. energy used by the organisms above comes sustain 12.3 U.S. citizens) from?

Energetics and Thermodynamics Energy Sources for Sunlight is generally considered to be the major ‘ ’ Second law of thermodynamics ( Law of Entropy ): energy energy source powering ecosystems transformations are not completely efficient ■ Only a small proportion of incoming solar ■ Whenever energy is used to do energy is captured by living organisms during work, some energy is lost as heat 30% ■ Result is that all complex systems 50% ■ In cells of photosynthetic organisms, reflected converted 19% powers tend toward increasing disorder to heat water cycle a series of enzymes converts CO2 and (entropy) H2O into a sugar (glucose), which can ■ Thus, all levels of life (organisms to ecosystems) require be stored energy inputs to maintain their structure and function

1% powers Less than 15% of the original photosynthesis chemical energy contained in gasoline actually moves the car

Eating is also inefficient: only a CO2 + H2O → Energy to break and form the necessary fraction of the chemical energy CH2O + O2 chemical bonds comes from light photons at in food is used by the certain specific wavelengths of sunlight. Molecular oxygen is released as a byproduct

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Ecological (Biomass) Production Energy-bearing Nutrients and Respiration : Cells use many organic molecules as fuel for respiration: ■ Production of (producer) biomass ■ capture and store their own energy and synthesize their own structural materials ■ Limited by photosynthetic rates Secondary Production: ■ Production of (consumer) biomass ■ ’ structural materials (and energy) must be obtained from their food ■ Limited by primary , number and efficiency of energy transfers, and other factors. Many chemical elements (e.g., Ca and P) must be provided in specific chemical forms or combinations

Energy-bearing Nutrients and Biosynthesis Energy-bearing Nutrient Types Food molecules are raw materials for biomass production Energy in the form of ATP used to assemble macromolecules: Carbohydrates (CH2O) ■ Manufactured by autotrophs from CO2 and H2O ■ Easiest of nutrients to respire ■ Form the bulk of the diet of many heterotrophs, yet are not essential nutrients for heterotrophs! ● Many exist on a carbohydrate-free diet, relying either on lipids or on deaminated amino acids for energy (e.g., vampire bats and other blood parasites, Inuit humans) ■ Two categories of carbohydrates: ● Highly digestible (e.g., starches and sugars) taken up by assimilative digestion ● Difficult to digest crude fiber (mostly cellulose): requires digestive symbionts (prokaryotes) to convert cellulose into bacterial biomass (fermentative digestion) before energy-bearing nutrients can be assimilated

Trophic Levels Trophic Levels First tropic level: primary producers Second tropic level: (autotrophs) primary (1°) consumers ■ Heterotrophs that feed ■ Photosynthetic Chemo- prokaryotes synthetic directly on autotrophs prokaryotes ● Sometimes referred to as ■ Photosynthetic grazers, these are the first microalgae: level of predators chlorophytes, diatoms, ● In , one organism (predator) obtains its energy dinoflagellates, etc. and/or nutrients from another living organism (prey) ■ Many are (technically, herbivory refers to leaf predators) ■ Macroalgae: large green, brown, and red algae ■ Important to humans because they convert cellulose ■ Plants: mosses, ferns, and other vascular plants in plants, which is not digestible by humans, into animal products (meat, milk, and blood), which are ■ Some fungi (e.g., lichens) and animals (e.g., corals) with algal endosymbionts serve as ‘primary producers’ in some systems digestible by humans

Page 2 BIO 4730/5730 Environmental Biology Topic 3 Energy and Energetics Trophic Levels Humans are Primarily Omnivorous Third tropic level: secondary (2°) ■ prey on both autotrophs and heterotrophs consumers ■ Humans obtain a highly variable percentage of their ● Heterotrophs that prey calories from animal sources exclusively on primary consumers ● In Inuit societies, nearly 100% of calories were from animal protein and fat ● These are predators in the ● In modern societies, 80% or more of calories comes from plants (in commonly-accepted sense U.S., about 38% of calories come from livestock calories and (that predator and prey are 62% from plants) butter ■ both heterotrophic, and the Some fishes we consume occupy (1° consumer) prey is alive until preyed upon very high trophic levels swordfish (6° consumer) ■ Fourth tropic level: tertiary (3°) consumers ■ Fifth tropic level: baked potato, squash, salad quaternary (4°) consumers (1° producers)

Terrestrial and Marine ‘Food Chains’ Detrivory (‘Saprophagy’) and 4° (quaternary) consumers are organisms that obtain red-tailed hawk killer whales their energy and nutrients from dead organisms, 3° (tertiary) consumers organism wastes, or lost prairie rattlesnakes mackerel body parts

Generally, detritivores are macroconsumers that feed on as-yet 2° (secondary) consumers undigested material (e.g., hyenas, vultures, earthworms) grasshopper mice sardines ■ A portion of the dead material is digested and a large portion of energy is lost by respiration of these organisms 1° (primary) consumers (‘herbivores’) ■ In many terrestrial systems, over 90% of 1° producer energy grasshopper zooplankton goes directly through pathways ■ Remaining undigested portion and/or simpler molecules 1° (primary) producers present in detritivores’ feces, excretions, and other exudates is green plants phytoplankton further processed during…

Decomposition Energy Transfers and Trophic Levels ■ Decomposers are microconsumers (heterotrophic bacteria, ■ If each receives all of its energy from the level protists, and fungi) below (i.e., if energy transfers are linear), then the resulting trophic structure is known as a ■ Obtain energy by converting chemical energy in monomers of ■ Energy loss due to respiration from each level is about 90%. once-living macromolecular material back into their original Produces ecological pyramids–as trophic level increases, there inorganic forms, e.g., Nitrogen/sulfur in amino acids into N2 are decreasing amounts of: gas/sulfates, etc. ● Stored energy in both: ❖ living matter (biomass) ■ Like detritivores, many decomposers ❖ Nonliving organic matter (e.g., fungi) convert macro molecules () back into monomers and use them ● Numbers of organisms for life processes, but their food ● Production source is more ‘biodegraded’ ❖ Less total energy available ■ Important! All organisms can convert carbon compounds back ❖ Greater respiratory into inorganic form (CO2) during respiration, but losses by (possibly endothermic) final decomposition of other elements (e.g., N and S) in organic predators material back into inorganic forms requires bacteria ● Turnover (‘recycling rates’ of biomass)

Page 3 BIO 4730/5730 Environmental Biology Topic 3 Energy and Energetics Livestock and Human Food Chains Food Webs ■ Often very short and linear: forage → livestock → human In most communities and ecosystems, trophic ■ Livestock are generally ruminants (mammals with specially-adapted fermentative digestion: cattle, sheep, goats, deer, and camels) structure is not linear ● Less energy efficient, ■ Feeding only from trophic level immediately below is not but can be fed a poor- energetically advantageous quality plant diet, converting it into food ■ Number of linear transfers is limited by the amount of (meat, milk, blood) that contains all energy at the 1° producer base (i.e., more 1° producer human dietary needs energy = longer food chain) ■ Availability of ruminants with suitable characteristics for ■ Numbers and biomass of predatory consumers often low domestication has been a major influence on civilization compared with detritivores and decomposers ● Most herding species originated in But Man is a carnivorous production, N. Hemisphere, e.g., sheep, goats, And must have meals, at least one meal a day; ■ Often very complicated trophic interconnections between cattle, camels, reindeer He cannot live, like woodcocks, upon suction, But, like the shark and tiger, must have prey; species: many organisms feed from multiple trophic levels ● S. Hemisphere ruminants (e.g., Although his anatomical construction ■ antelopes, gazelles, llamas) are Bears vegetables, in a grumbling way, These produce more elaborate trophic structures (food solitary (or have many predators) Your laboring people think beyond all question, webs) and are too fast, agile, nervous, or Beef, veal, and mutton, better for digestion. aggressive to be easily domesticated -George Gordon (Lord Byron), Don Juan

General Structure of Food Webs

Heat Heat Heat Heat

Secondary Tertiary (3°), Primary (1°) Primary (1°) (2°) Producers Consumers Quaternary Consumers (4°), etc. Consumers

Nutrient Detritivores Pool Detritus

Heat Energy and Decomposers Nutrient Sink

Energy Flow Heat Nutrient Flow

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