Chapter 3 Ecosystems and Energy

draweryaleMechanics

Oct 27, 2013 (3 years and 10 months ago)

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Chapter 3

Ecosystems and Energy

Overview of Chapter 3

Ecology

Energy

First Law of Thermodynamics


Second Law of Thermodynamics

Photosynthesis and Cellular Respiration

Flow of Energy Through Ecosystems


Producers, Consumers & Decomposers


Ecological Pyramid


Ecosystem Productivity

Ecology

Ecology


“eco” house & “logy” study of


The study of interactions among and between
organisms in their abiotic environment


Broadest field in biology

Biotic
-

living environment


Includes all organisms

Abiotic
-

non living or physical environment


Includes living space, sunlight, soil,
precipitation, etc.

Ecology

Biology is very
organized

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

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

The ability or capacity
to do work


Chemical, radiant,
thermal, mechanical,
nuclear, electrical

Energy exists as:


Stored energy
(potential energy)


Kinetic energy (energy
of motion)

Thermodynamics

Study of energy and its transformations

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)
Entropy Rules!


Focus is on quality

Photosynthesis

Biological process by which energy from the
sun (radiant energy) is transformed into
chemical energy of sugar molecules






Energy captured by plants via photosynthesis
is transferred to the organisms that eat the
plants

6 CO
2
+ 12 H
2
O + radiant energy

C
6
H
12
O
6

+ 6 H
2
O + 6 O
2

Cellular Respiration

The process where the chemical energy
captured in photosynthesis is released within
cells of plants and animals




This energy is then used for biological work


Creating new cells, reproduction, movement,
etc.

C
6
H
12
O
6

+ 6

O
2
+ 6 H
2
O

6 CO
2

+ 12 H
2
O + energy

The Energy of Life

Case
-
in
-
Point:


Life Without the Sun

Energy Flow

Passage of energy in
a one
-
way direction
through an
ecosystem


Producers


Primary consumers


Secondary
consumers


Decomposers

Food Chains
-

The Path of Energy Flow

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


The Path of Energy Flow

Case
-
in
-
Point: How Humans Have Affected
the Antarctic Food Web

Krill

Baleen whales

Squid

Fishes

Toothed whales

Seals

Penguins

What would happen if you
eliminated krill?

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

Pyramid of Numbers

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

Do not indicate the
biomass of the organisms
at each level or the
amount of energy
transferred between
levels

Pyramid of Biomass

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

Illustrates a progressive
reduction in biomass
through trophic levels

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


Energy levels get too
low to support life

The Path of Energy Flow

Example: Thermodynamics in Action

Desert: Primary producers
= 100 g / m
2

Temperate forest: Primary
producers = 1,500 g / m
2

Food webs very simple, very
few tertiary consumers

Food webs very complex,
more tertiary consumers,
some quaternary.

The Path of Energy Flow

Desert Biomass Pyramid

Primary producers = 100 g / m
2

Primary consumers = 10 g / m
2

Secondary consumers = 1.0 g /
m
2

Tertiary consumers = 0.1 g / m
2

Tertiary consumers must range over large areas to obtain
enough energy to subsist.

13.5 kg coyote must
range ~12 ha to subsist
(30 acres).

The Path of Energy Flow

Temperate Forest Biomass
Pyramid

Primary producers = 1,500 g /
m
2

Primary consumers = 150 g / m
2

Secondary consumers = 15 g / m
2

Tertiary consumers = 1.5 g /
m
2

13.5 kg coyote only
needs ~1 ha to subsist
(2.5 acres).

Also, possibility of quaternary
consumers, like bears.

NOTE: just
relative
examples,
not accurate

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

Variation in NPP by Ecosystem

Human Impact on NPP

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!

This may contribute to loss of species
(extinction)

Humans’ high consumption represents a
threat to planet’s ability to support both
human and non
-
human inhabitants