Laws of Energy • First Law: Energy is neither created nor destroyed, it simply changes form. • Energy transformations are very important in living systems. • Second Law: Systems naturally move towards more disorder. • It takes a lot of energy to maintain organization (like that found in a living creature). • All energy ultimately ends up as the very disordered entity we call heat. • Energy flows through ecosystems because the Earth is an open system to energy • The Earth constantly receives energy from the sun
Heat co2 + Chemical energy H2O B. Second law: For example, disorder is added to the cheetah’s surroundings in the form of heat and the small molecules that are the by-products of metabolism. A. First law: For example, the chemical (potential) energy in food will be converted to the kinetic energy of the cheetah’s movement in (B). Laws of Energy
Energy Flows Through Ecosystems Producers absorb sunlight and convert radiant energy into “food” Only plants, some algae (protists), and certain bacteria All forms of life depend on this process (very few exceptions)
Energy Flows Through Ecosystems Consumers (heterotrophs) Can only acquire energy from other organisms Must either ingest or absorb nutrients Some bacteria, archaebacteria, protists All animals and fungi • Herbivores • Carnivores • Omnivores • Detritivores • Decomposers • eat only plants • eat other animals • eat plants and animals • eat plant and animal remains • break down organic matter
Feeding Relationships For consumers, we call the energy that flows through and ecosystem “food” Most simple feeding relationship example is a food chain
Trophic Levels The word “troph” comes from the Greek and refers to food or feeding Refers to each step in a food chain or web Trophic level 3 Trophic level 2 Trophic level 1
Ecological Pyramids • 1. Pyramid of Biomass • Shows the total amount of living or organic matter in an ecosystem at any time (biomass). • The most biomass occurs in producers • Biomass decreases as you move from lower to higher trophic levels.
Ecological Pyramids 2. Pyramid of Numbers Shows the relative number of organisms at each trophic level 1 hawk 8 finches 24 snails or worms 48 green leaves
Ecological Pyramids 3. Pyramid of Energy Shows energy as it moves from one feeding level in a food chain to another. Only 10 %of energy available at each level is transferred to next From the sun to producers, only 1% is transferred Only 10 %of energy available at each level is transferred to next From the sun to producers, only 1% is transferred
The Ecology of a Meat-Based Diet vs. a Vegetarian Diet • What do ecological principles tell us about availability of energy to humans?
Pyramid of Numbers (# organisms): Bluegrass Pasture Carnivore/ Secondary Consumer Bird 3 Grasshopper Herbivore/ Primary Consumer 708,624 Grass/Grain Autotroph/ Primary Producer 5,542,424 Land can support more producers (plants) than consumers.
Pyramid of Biomass (lb/acre): Bluegrass Pasture Carnivore/ Secondary Consumer Bird 1 Herbivore/ Primary Consumer Grasshopper 54 Autotroph/ Primary Producer Grass/Grain 4,190 Land can support more plant mass than consumer mass.
Pyramid of Energy (calories): Bluegrass Pasture Energy Lost Bird/Carnivore 9 1 Insect/Herbivore 10 90 Plant/Autotroph 100 9,900 CALORIES Solar Energy 10,000 CALORIES Plants provide more energy than consumers.
Effect of Feeding at Lower Trophic Levels Number of adult humans supported for one year Adult Human One 600 fish Thirty 180,000 frogs Nine Hundred 54 million grasshoppers 4 million pounds plants (grains, corn, potato, rice, etc) Two Thousand
Ecological Preference: Eat Plants, Not Animals • Energy is lost in each food chain transition, so it is more efficient to “eat lower on the food chain” • “More efficient” means that less land is needed to support survival on plants • In other words, the same amount of land needed to support 1 person eating a meat-based diet can support 10-20 vegetarians
Energy Cost for Meat Production • One half of the USA agriculture energy goes into livestock production • Energy Ratio: kcal of energy to produce one kcal of protein (kcal of fossil fuel: kcal protein) • Beef 54:1 • Lamb 50:1 • Pork 17:1 • Turkey 13:1 • Chicken 4:1 • Grain 3.3:1
Conversion of Plant Protein to Animal Protein (USA) • 41 million tons of plant protein are needed to produce 7 million tons of animal protein • 26 million tons grain • 15 million tons grass • Many people in the poor areas of the world cannot afford the “luxury” of converting grain to meat
Law of Conservation of Matter • In any chemical or physical process, no matter is created or destroyed. • All matter cycles through an ecosystem • The Earth is a closed system for matter • There is no “away”
Law of Conservation of Matter: Trophic Level Effects • Bioaccumulation • Some substances aren’t easily excreted • Instead build up in fat and other tissues of an organism • Some substances are toxic (e.g., DDT) • Biomagnification • An increase in the concentration of a substance as it moves through the food chain from one organism to another • Because some substances accumulate in tissues, when an organism is consumed, all these accumulated substances are passed on to the next trophic level • Organisms at the top of the food web may end up with huge amounts of toxic substances stored in their tissues
Matter Cycles in Ecosystems: Biogeochemical Cycles Sulfur Phosphorous (never stored in the atmosphere) Oxygen Water/hydrologic (driven by solar energy (evaporation) & gravity (precipitation)) Nitrogen Carbon
The Nitrogen Cycle The most complex of the cycles N2 = 78% of the troposphere However, N2 cannot be used directly by plants or animals People can give their plants usable nitrogen by applying a fertilizer or by planting legumes (beans or clover) Nitrogen cycle steps: nitrogen fixation, nitrification, assimilation, ammonification and denitrification
The Nitrogen Cycle 1. Nitrogen Fixation: N2 converted to ammonia (NH3) By bacteria in soil/water and bacterium Rhizobium in root nodules of legumes (peas, clover, beans, etc.)
The Nitrogen Cycle 2. Nitrification: Ammonia converted to nitrite (NO-2)and then nitrate (NO-3), the most usable forms of nitrogen Both reactions carried out by bacteria
The Nitrogen Cycle 3. Assimilation: These usable forms are taken in by plants and animals. Plant roots absorb nitrates that are then converted into organic compounds like proteins and DNA. And of course, animals eat plants.
The Nitrogen Cycle 4. Ammonification: The organic compounds, wastes, caste-off particles, dead bodies, etc., are converted into simpler compounds (e.g., ammonia NH3) By decomposer bacteria
The Nitrogen Cycle 5. Denitrification: Ammonia (NH3) is converted back to N2 Mostly by anaerobic bacteria in waterlogged soil, bottom sediments of lakes, swamps, bogs and oceans
Significant Human Interventions Internal combustion engine exhaust (i.e., fossil fuel burning) Results in O2 being added to the atmosphere Combining O2 with atmospheric nitrogen results in nitric acid, a significant component of acid rain Farming, agriculture and cities Nitrogen-rich fertilizers from farms and sewage from municipalities runs off into bodies of water This stimulates the growth of algae and aquatic plants which then die and are broken down by aerobic decomposers This aerobic decomposition reduces the dissolved oxygen (DO) content in the water, killing fish and other aquatic animals (creates a “dead zone”)
The Carbon Cycle Carbon cycles closely with oxygen in two reactions 1. Respiration (all organisms) Aerobic respiration: C6H12O6 + 6O2 > 6 CO2 + 6H2O + 38 ATP 2. Photosynthesis (autotrophs) Photosynthesis: 6CO2 + 6H2O + light energy > C6H12O6 + 6O2 CO2 also naturally enters the atmosphere by volcanic activity CO2 is a heat-trapping gas, and an important component of the earth’s thermostat More CO2 = higher temperatures with the greenhouse effect
Significant Human Interventions There are two major human actions that lead to increasing levels of CO2 in the atmosphere 1. Vegetation removal/deforestation 2. Fossil fuel burning and wood burning Reason for concern: magnified natural greenhouse effect A. Altered global food production due to shifting climate belts B. Altered wildlife habitat due to changes in temperature and precipitation (e.g., loss of Arctic sea ice impacts polar bears) C. Altered species interactions (e.g., births and food supplies) D. Rise in sea levels due to melting ice and thermal expansion of water as troposphere temperature increases (e.g., Tuvalu) Another reason for concern: increasing CO2 in the oceans
Carbon Dioxide & the Oceans The oceans help regulate the CO2 in the atmosphere because CO2 can be dissolved in water There is an increasing amount of CO2 in the oceans This causes the oceans to become more acidic through the reaction: H20+ CO2 > H2 CO3 (carbonic acid) Acidic water negatively impacts corals, mussels, and other marine organisms by slowing the rate of calcification