Chapter 3Ecosystems: How They Work

Copyright © 2008 Pearson Prentice Hall, Inc.

EnvironmentalScienceTenth Edition

Richard T. Wright

Ecosystems: How They Work

• Matter, energy, and life• Energy flow in ecosystems• The cycling of matter in ecosystems• Implications for human societies

Matter, Energy, and Life

• Matter in living and nonliving systems• Energy basics• Energy changes in organisms

The Four Spheres of Earth’s Environment

MATTER CYCLING ENERGY CONVERSION

Matter

• The basic building blocks of matter are atoms• Elements are made of one “kind” of atoms

(Atoms with same number of protons)• Isotopes are atoms of the same element but

having different number of neutrons• 94 elements occur naturally and 24 have been

synthesized by chemists and physicists• All matter is made up of various combinations of

atoms of the elements.

Atmospheric Gases

Molecules: O2, N2, CO2

Compounds: CO2

Water and Its Three States

Water is a polar molecule

Minerals: Dense clusters of atoms of two or more elements held together by the attraction of positive and

negative charges.

Na+ and Cl-

Ionic Substances

Interrelationships amongAir, Water, and Minerals

Dissolution: Ions surrounded by water molecules

Crystallization: via evaporation(or amorphous precipitation)

Elements of Life: A Summary

• Of the 94 naturally occurring elements in the universe, only 24 are utilized by living organisms.

• Six elements are required by all living things in large amounts?

• Which ones?

Match the Elements (Left) with Molecules (Right)

• Nitrogen• Carbon• Hydrogen• Oxygen• Phosphorus• Sulfur

• Glucose• Proteins• Starch• Fats• Nucleic acids• All of the above

The BIG SIX:Needed by all living things in large quantities

Organic Molecules

Matter and Energy

• Matter: anything that occupies space and has mass.– Cannot be created or destroyed.– Can be changed from one form into another.– Can be recycled.– Can be measured where gravity is present.

Matter and Energy

• Energy: anything that has the ability to move matter, has no mass and does not occupy space.– Cannot be created or destroyed.– Can be changed from one form to another.– Cannot be recycled.– Can be measured.

Forms of Energy

• Kinetic– Energy in its

active form• Potential

– Potential that systems have to release kinetic energy

Energy Conversions

Laws of Thermodynamics

First Law: (CHANGE) Energy is neither created nor destroyed but may be converted from one form to another. NO FREE LUNCHES!

Second Law: (LOSS) In any energy conversion, you will end up with less usable energy thanyou started with. YOU CAN’T BREAK EVEN!

So how do we survive?

Example of the Laws of Conservation of Matterand Thermodynamics

Global WarmingGlobal Warming

Acid RainAcid Rain SmogSmog

Burning Coal = CO2 + SO + H2O + Ash +(CxHxSxOx) Light + Noise + Heat

Where from?

Entropy: Energy Changes in Organisms• Systems will go

spontaneously in one direction only which is toward increasing entropy.

• Entropy measures the degree of disorder of a system

Entropy underlies the second law of thermodynamics / the most of usable energy.

Entropy

First Principle of Ecosystem Sustainability

• Ecosystems use sunlight as their source of energy.

– Ecosystems need a constant input of energy

– Why?

How Ecosystems Use Sunlight As Their Source of Energy

Food Assimilation in Consumers

Match Outcomes (Left) with Process (Right)

• Releases O2

• Stores energy• Releases CO2

• Uses CO2

• Releases energy• Produces sugar• Uses sugar• Uses O2

• Photosynthesis• Cell respiration• Both• Neither

Match Outcomes (Left) With Organisms (Right)

• Releases O2

• Stores energy• Releases CO2

• Uses CO2

• Releases energy• Produces sugar• Uses sugar• Uses O2

• Plants• Animals• Both• Neither

Violations of the First Principle of Ecosystem Sustainability

• Excessive use of fossil fuels

• Feeding largely on the third trophic level.

• Use of agricultural land to produce meats.

Energy Flow in Ecosystems

• Primary production• Energy flow and efficiency• Running on solar energy

– Freely available– Nonpolluting– Everlasting

Productivity of Different Ecosystems

Energy Flow Through Trophic Levels

The Second Principle of Ecosystem Sustainability

• Ecosystems dispose of wastes and replenish nutrients by recycling all elements.

The Cycling of Matter in Ecosystems

• The carbon cycle• The phosphorus cycle• The nitrogen cycle

The Carbon Cycle

• How and in what form does carbon enter and leave the cycle?

• How is the role of autotrophs and heterotrophsdifferent and the same?

• What are the human impacts on the cycle?

Global Carbon Cycle

Natural Production

Global Carbon Cycle

Human Activities

The Phosphorus Cycle

• How and in what form(s) does phosphorus enter and leave the cycle?

• How is the role of autotrophs and heterotrophsdifferent and the same?

• What are the human impacts on the cycle?

The Nitrogen Cycle

• How and in what form(s) does nitrogen enter and leave the cycle?

• How is the role of autotrophs and heterotrophsdifferent and the same?

• What are the human impacts on the cycle?

Nitrogen Fixation:Nitrogen gas to AmmoniumN2 NH3 NH4

+

Denitrification

Nitrate to Nitrogen gasNO3

- N2

DecompositionOrganic carbon NH3 or NH4

+

NitrificationNH4

+ NO3-

Nutrient Recycling and Energy Flow Through an Ecosystem

The Human System

Human Impact• Use of Ecosystem Capital

Is our use of ecosystems sustainable?Examples: heavy use of energy resources, deforestation

• Interference with Nutrient CyclesExample:Introducing too much carbon in the atmosphere

• Value Ecosystem Capital – What value does the market economy place on ecosystems

goods and services (soils formation, decomposition, water sheds, clean, etc.?

• Identification and Inventory of Ecosystem goods and services