Chapter 3 Ecosystems and Energy

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27 Οκτ 2013 (πριν από 4 χρόνια και 9 μήνες)

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Chapter 3

Ecosystems and 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

Ecology


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


Species


A group of similar organisms whose members freely
interbreed to produce viable offspring.

o
Population


A group of organisms of the same species that occupy
the same area at the same time

o
Community


All 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


Ecology

o
Biosphere contains earth’s communities,
ecosystems and landscapes, and includes:



Atmosphere
-

gaseous envelope
surrounding earth


Hydrosphere
-

earth’s water supply


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


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)


Photosynthesis

o
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

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.

C
6
H
12
O
6

+ 6

O
2
+ 6 H
2
O

6 CO
2

+ 12 H
2
O + 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


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


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

Human Appropriation of NPP