Chapter 3 Ecosystems and Energy
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Chapter 3Ecosystems and Energy
o Ecology
o Species
o Population
o Community
o Ecosystem
o Atomosphere
o Lithosphere
o Hydrosphere
o Heterotrophs
o Omnivores
o Detritus
o Trophic levels
o Gross primary productivity (GPP)
o Net primary productivity (NPP)
o Potential vs. Kinetic energy
o 1st law of thermodynamics
o 2nd law of thermodynamics
o Photosynthesis
o Cellular Respiration
o Chemosynthesis
o How energy flows through an ecosystem
o Producers
o Consumers (primary, secondary, tertiary)
o Decomposers/Saprotrophs
o Ecological pyramid (numbers, biomass, energy)
Overview of Chapter 3
o Ecology
o Energy• First Law of Thermodynamics
• Second Law of Thermodynamics
o Photosynthesis and Cellular Respiration
o Flow of Energy Through Ecosystems• Producers, Consumers & Decomposers
• Ecological Pyramid
• Ecosystem Productivity
Ecologyo Ecology
• “eco” house & “logy” study of
• The study of interactions among and between organisms in their abiotic environment
• Broadest field in biology
o Biotic-• living environment
• Includes all organisms
o Abiotic-• non living or physical environment
• Includes living space, sunlight, soil, precipitation, etc.
Ecology
o Biology is very organized
o Ecologists are interested in the levels of life above that of organism
Ecology Definitions
o Species• A group of similar organisms whose members freely
interbreed
o Population• A group of organisms of the same species that occupy
that live in the same area at the same time
o Community• Al the populations of different species that live and
interact in the same area at the same time
o Ecosystem• A community and its physical (abiotic) environment
o Landscape• Several interacting ecosystems
Ecology
o Biosphere contains earth’s communities, ecosystems and landscapes, and includes:
• Atmosphere-gaseous envelope surrounding earth
• Hydrosphere-earth’s supply of water
• Lithosphere- soil and rock of the earth’s crust
Energy
o The ability or capacity to do work• Chemical, radiant,
thermal, mechanical, nuclear, electrical
o Energy exists as:• Stored energy
(potential energy)
• Kinetic energy (energy of motion)
Thermodynamics
o Study of energy and its transformations
o System- the object being studied
• Closed System- Does not exchange energy with surroundings (rare in nature)
• Open System-exchanges energy with surroundings
Laws of Thermodynamics
o First Law of Thermodynamics• Energy cannot be created or destroyed; it can
change from one form to another• Ex: organisms cannot create energy they need to
survive- they must capture it from another source
• Focus is on quantity
o Second Law of Thermodynamics• When energy is converted form one form to
another, some of it is degraded to heat• Heat is highly entropic (disorganized)
• Focus is on quality
Photosynthesis
o Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of sugar molecules
o Energy captured by plants via photosynthesis is transferred to the organisms that eat the plants
6 CO2 + 12 H2O + radiant energy
C6H12O6 + 6 H2O + 6 O2
Cellular Respiration
o The process where the chemical energy captured in photosynthesis is released within cells of plants and animals
o This energy is then used for biological work• Creating new cells, reproduction, movement,
etc.
C6H12O6 + 6 O2 + 6 H2O
6 CO2 + 12 H2O + energy
Energy Flow
o Passage of energy in a one-way direction through an ecosystem• Producers
• Primary consumers
• Secondary consumers
• Decomposers
Food Chains- The Path of Energy Flow
o Energy from food passes from one organisms to another• Each “link” is called a trophic level
Food webs represent interlocking food chains
that connect all organisms in an ecosystem
Ecological Pyramids
o Graphically represent the relative energy value of each trophic level• Important feature is that large amount of
energy are lost between trophic levels to heat
o Three main types• Pyramid of numbers
• Pyramid of biomass
• Pyramid of energy
Pyramid of Numbers
o Illustrates the number of organisms at each trophic level• Usually, organisms at the base of the pyramid
are more numerous• Fewer organisms occupy
each successive level
o Do not indicate the biomass of the organisms at each level or the amount of energy transferred between levels
Pyramid of Biomass
o Illustrates the total biomass at each successive trophic level• Biomass: measure of the total amt of living
material• Biomass indicates the
amount of fixed energy at a given time
o Illustrates a progressive reduction in biomass through trophic levels
Pyramid of Energy
o Illustrates how much energy is present at each trophic level and how much is transferred to the next level• Most energy dissipates between trophic levels
o Explains why there are so few trophic levels• Energy levels get too
low to support life
Ecosystem Productivity
o Gross Primary Productivity (GPP)• Total amount of energy that plants capture and
assimilate in a given period of time
o Net Primary Productivity (NPP)• Plant growth per unit area per time
• Represents the rate at which organic material is actually incorporated into the plant tissue for growth
o GPP – cellular respiration = NPP• Only NPP is available as food to organisms
Variation in NPP by Ecosystem
Human Impact on NPP
o Humans consume more of earth’s resources that any other animal• Humans represent 0.5% of land-based biomass
• Humans use 32% of land-based NPP!
o This may contribute to loss of species (extinction)
o Humans’ high consumption represents a threat to planet’s ability to support both human and non-human inhabitants
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