The Flow of Energy in Ecosystems

Three Factors Sustain Life on Earth One-way flow of high-quality energy beginning with the sun Cycling of matter or nutrients Gravity

Some Types of Energy Are More Useful Than Others Energy Quality: a measure of energy’s capacity to do useful work High-quality energy High temperature heat nuclear fission, concentrated sunlight, energy released by burning fossil fuels Low-quality energy Heat dispersed in the air or oceans 3

Some Forms of Matter Are More Useful than Others High-quality matter Low-quality matter 4

Energy Changes Are Governed by Two Scientific Laws First Law of Thermodynamics Energy input always equals energy output ENERGY CANNOT BE CREATED OR DESTROYED Second Law of Thermodynamics Energy always goes from a more useful to a less useful form when it changes from one form to another 5

* Chemistry Review: Law of conservation of matter Matter consumption We Cannot Create or Destroy Matter Matter consumption Matter is converted from one form to another 6

The Second Law of Thermodynamics in Living Systems 7

Active Figure: Energy flow

3-3 What Are the Major Components of an Ecosystem? Concept 3-3A Ecosystems contain living (biotic) and nonliving (abiotic) components. Concept 3-3B Some organisms produce the nutrients they need, others get their nutrients by consuming other organisms, and some recycle nutrients back to producers by decomposing the wastes and remains of organisms. 9

Ecosystems Have Living and Nonliving Components Abiotic: the non-living components of the world Water Air Nutrients Rocks Heat Solar energy Biotic: The living (or once living) components of the world Plants, Animals… you get the idea 10

Major Biotic and Abiotic Components of an Ecosystem 11

Producers and Consumers Are the Living Components of Ecosystems (1) Producers, autotrophs: make their own food Photosynthesis Chemosynthesis Consumers, heterotrophs: must feed on other organisms Primary Secondary Third and higher level 12

Producers and Consumers Are the Living Components of Ecosystems (2) More Consumers Decomposers: digests parts of dead organisms or cast-off fragments & wastes of living organisms *mode of eating is to absorb soluble nutrients Detritivores: digests parts of dead organisms or cast-off fragments & wastes of living organisms *mode of eating is “chomp chomp” Aerobic respiration: breakdown of glucose WITH oxygen Anaerobic respiration, fermentation: breakdown of glucose WITHOUT oxygen 13

Detritivores and Decomposers on a Log 14

3-4 What Happens to Energy in an Ecosystem? Concept 3-4A Energy flows through ecosystems in food chains and webs. Concept 3-4B As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases. 15

The Main Structural Components of an Ecosystem 16

Energy Flows Through Ecosystems in Food Chains and Food Webs Series of organisms in which each eats or decomposes the preceding one Food web Complex network of many interconnected food chains 17

A Food Chain 18

Simplified Food Web in the Antarctic 19

Active Figure: Categories of food webs

Usable Energy Decreases with Each Link in a Food Chain or Web Biomass The total dry weight of all living organisms Ecological efficiency The percentage of energy transferred from one trophic level to another in a food chain or food web Pyramid of energy flow A diagram representing the flow of energy through each trophic level in a food chain or food web. With each transfer, only about 10% of the usable energy is transferred to the organism at the next trophic level 21

Pyramid of Energy Flow 22

Some Ecosystems Produce Plant Matter Faster Than Others Do Gross primary productivity (GPP) The rate at which producers capture and store chemical energy as biomass Net primary productivity (NPP) The total energy stored by the producers, minus the energy they use for respiration Ecosystems and life zones differ in their NPP 23

Estimated Annual Average NPP in Major Life Zones and Ecosystems 24

2-5 What Are Systems and How Do They Respond to Change? Concept 2-5A Systems have inputs, flows, and outputs of matter and energy, and their behavior can be affected by feedback. Concept 2-5B Life, human systems, and the earth’s life support systems must conform to the law of conservation of matter and the two laws of thermodynamics. 25

Systems Have Inputs, Flows, and Outputs System: set of components that function and interact in some regular and theoretically predictable manner Inputs from the environment Flows, throughputs Outputs 26

Inputs, Throughput, and Outputs of an Economic System 27

Systems Respond to Change through Feedback Loops Positive feedback loop: feedback loop that causes a system to change further in the same direction Negative, or corrective, feedback loop: feedback loop that causes a system to change in the opposite direction from which it is moving 28

Positive Feedback Loop 29

Negative Feedback Loop 30

Time Delays Can Allow a System to Reach a Tipping Point Time delays vary Between the input of a feedback stimulus and the response to it Tipping point Threshold level at which an environmental problem causes a fundamental and irreversible shift in the behavior of a system 31

System Effects Can Be Amplified through Synergy Synergistic interaction, synergy Interaction of two or more factors or processes so that the combined effect is greater than the sum of their separate effects Helpful E.g., a letter writing campaign/petition Harmful E.g., Smoking and inhaling asbestos particles 32

Animation: Feedback control of temperature

Human Activities Can Have Unintended Harmful Results Deforested areas turning to desert Coral reefs dying Glaciers melting Sea levels rising 34