Transcript ch03 (1) - Napa Valley College

3
Ecosystems and Energy
Overview of Chapter 3


What is Ecology?
The Energy of Life
 Laws
of Thermodynamics
 Photosynthesis and Cellular Respiration

Flow of Energy Through Ecosystems
 Producers,
Consumers & Decomposers
 Ecological Pyramid
 Ecosystem Productivity
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecology

Ecology
 “eco”
house & “logy” study of
 The study of interactions among and between
organisms in their abiotic environment

Biotic - living environment
 Includes

all organisms
Abiotic - non living or physical environment
 Includes
living space, sunlight, soil, precipitation,
etc.
© 2012 John Wiley & Sons, Inc. All rights reserved.
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecology

Ecologists are
interested in the
levels of life
above that of
organism
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecology Definitions

Species - A group of similar organisms whose members
freely interbreed

Population - A group of organisms of the same species
that occupy that live in the same area at the same time

Community - All the populations of different species that
live and interact in the same area at the same time

Ecosystem - A community and its physical (abiotic)
environment

Landscape - Several interacting ecosystems
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecology

Biosphere contains earth’s communities,
ecosystems and landscapes, and includes:
 Atmospheregaseous envelope
surrounding earth
 Hydrosphereearth’s supply of
water
 Lithosphere- soil
and rock of the
earth’s crust
© 2012 John Wiley & Sons, Inc. All rights reserved.
Energy


The ability or capacity to do work
Chemical, Thermal, Mechanical, Nuclear,
Electrical, and Radiant/Solar (below)
© 2012 John Wiley & Sons, Inc. All rights reserved.
Energy

Energy exists as:
 Potential
energy
(stored energy)
 Kinetic energy
(energy of
motion)

Potential energy is converted to kinetic energy
as arrow is released from bow
© 2012 John Wiley & Sons, Inc. All rights reserved.
Thermodynamics


Study of energy and its transformations
System- the object being studied


Closed System- Does
not exchange energy
with surroundings (rare
in nature)
Open Systemexchanges energy with
surroundings
© 2012 John Wiley & Sons, Inc. All rights reserved.
Laws of Thermodynamics

First Law of Thermodynamics
 Energy
cannot be created or destroyed; it can
change from one form to another

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)
© 2012 John Wiley & Sons, Inc. All rights reserved.
Photosynthesis

Biological process by which energy from the sun
(radiant energy) is transformed into chemical
energy of sugar molecules
6 CO2 + 12 H2O + radiant energy
C6H12O6 + 6 H2O + 6 O2
© 2012 John Wiley & Sons, Inc. All rights reserved.
Cellular Respiration

The process where the chemical energy
captured in photosynthesis is released within
cells of plants and animals
C6H12O6 + 6 O2 + 6 H2O
6 CO2 + 12 H2O + energy

This energy is then used for biological work
© 2012 John Wiley & Sons, Inc. All rights reserved.
Photosynthesis and Cellular
Respiration
© 2012 John Wiley & Sons, Inc. All rights reserved.
Energy Flow Through Ecosystems

Passage of energy through an ecosystem
© 2012 John Wiley & Sons, Inc. All rights reserved.
Food Chains- The Path of Energy
Flow

Energy from food passes from one organisms
to another based on their Trophic Level
 Def:
An organism’s position in a food chain, which
is determined by its feeding relationships




First Trophic Level: Producers
Second Trophic Level: Primary Consumers
Third Tophic Level: Secondary Consumers
Decomposers are present at all trophic levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Food Web
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecological Pyramids

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

Three main types
 Pyramid
of numbers
 Pyramid of biomass
 Pyramid of energy
© 2012 John Wiley & Sons, Inc. All rights reserved.
Pyramid of Numbers

Illustrates the number of organisms at each
trophic level


Fewer organisms
occupy each
successive level
Does not indicate:


biomass of organisms
at each level
amount of energy
transferred between
levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Pyramid of Biomass

Illustrates the total biomass at each successive
trophic level
 Biomass:
measure of
the total amt of living
material
 90% reduction in
biomass through
trophic levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Pyramid of Energy



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
Explains why
there are so few
trophic levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecosystem Productivity

Gross Primary Productivity (GPP)
 Total
amount of energy that plants capture and
assimilate in a given period of time

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

GPP – cellular respiration = NPP
 Only
NPP is available as food to organisms
© 2012 John Wiley & Sons, Inc. All rights reserved.
Variation in NPP by Ecosystem
© 2012 John Wiley & Sons, Inc. All rights reserved.
Human Impact on NPP

Humans represent 0.5% of land-based
biomass, but use 32% of land-based NPP!
 This

may contribute to loss of species (extinction)
This represents a threat to planet’s ability to
support both human and non-human
inhabitants
© 2012 John Wiley & Sons, Inc. All rights reserved.