Transcript File - Down the Rabbit Hole

Energy Flow
Through
Ecosystems
An Introduction to Energy and
Laws of Thermodynamics
Ecosystem Ecology
• Examines interactions between the living and non-living world
• Ecosystem- the sum of all the organisms living within its boundaries
(biotic community) and all the abiotic factors with which they
interact
Levels of Organization
Biosphere
Biome
Ecosystem
Community
Population
Organism
Thermodynamics
• Physical Laws that govern energy relationships
• Involves Two Processes:
• Energy Flow
– Energy cannot
be recycled
therefore there
must be a constant
supply
• Chemical Recycling
– Matter can be
recycled and
Nature does it with
perfection.
First Law of Thermodynamics
Conservation of Energy
• The study of energy
transformation
– In short, the law of conservation
of energy states that energy can
not be created or destroyed, it
can only be changed from one
form to another or transferred
from one body to another, but the
total amount of energy remains
constant (the same).
Chemical
energy
(a)
First law of thermodynamics: Energy
can be transferred or transformed but
Neither created nor destroyed. For
example, the chemical (potential) energy
in food will be converted to the kinetic
energy of the cheetah’s movement in (b).
Second Law of Thermodynamics
Law of Entropy
• In any energy transformation, some energy is lost as unusable
energy in the sense that work cannot be performed. This is
usually in the form of heat.
Heat
co2
+
H2O
(b)
Second law of thermodynamics: Every energy transfer or transformation increases
the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s
surroundings in the form of heat and the small molecules that are the by-products
of metabolism.
Two Important Questions
• Where does the energy needed for living
organisms originate?
• How is energy used by these organisms?
Flow of energy through life = Metabolism
• The totality of an organism’s chemical reactions
– driving life processes by transforming energy from one
form to another
organic molecules  ATP
& organic molecules
sun
solar energy 
ATP & organic molecules
organic molecules 
ATP & organic molecules
Metabolism
Chemical reactions of life Oxidation – Reduction
Anabolic reactions
› Forming bonds between
molecules
› Consume energy
Catabolic reactions
› Breaking bonds between
molecules
› Release energy
Living Organisms
• Temporary
storage units for
useful energy,
whereby one
organism can be
used by another
as a source of
energy.
The Source of High Quality Energy
• Most of the
Energy arrives as
electromagnetic
radiation from the
sun
• Supports
photosynthesis
(less than 2%)
• Powers the cycling
of matter
• Drives climate and
weather that
distribute heat
and H2O
Solar
radiation
Energy in = Energy out
Reflected by
atmosphere (34%)
UV radiation
Absorbed
by ozone
Lower Stratosphere
Visible (ozone layer)
Greenhouse
light Troposphere
effect
Heat
Absorbed
by the earth
Radiated by
atmosphere
as heat (66%)
Heat radiated
by the earth
Earth
Autotrophs are producers
• They capture energy and
•
•
•
synthesize their own organic
nutrients.
They can do this by
photosynthesis or
chemosynthesis.
Chemosynthetic bacteria get
energy and raw materials
from vents called "smokers"
on the ocean floor.
Tube worms rely upon the
bacteria that coexist with
them to make food at the
bottom of the ocean.
Photoautotrophs
• Autotrophs (=self-nourishing) are called primary
producers.
• Photoautotrophs fix energy from the sun and store
it in complex organic compounds
•
•
•
•
green plants
algae
some bacteria
some protists
light
simple
inorganic
compounds
photoautotrophs
complex
organic
compounds
Chemoautotrophs
• Chemosynthesis.
• Chemosynthetic bacteria get energy and
•
raw materials from inorganic sources
Oxidize reduced inorganic substances
(typically sulfur and ammonia compounds)
and produce complex organic compounds.
• Nitrifing bacteria
• Halophiles (found in highly concentrated
salt lakes)
• Thermophiles (found in hot springs and
geysers)
oxygen
reduced
inorganic
compounds
chemoautotrophs
complex
organic
compounds
Heterotrophs are Consumers
• Heterotrophs are consumers, they must
consume preformed organic nutrients
synthesized by other organisms.
Heterotrophs
• Heterotrophs (=other-nourishing) cannot produce their
•
own food directly from sunlight+ inorganic compounds.
They require energy previously stored in complex
molecules.
Examples of heterotrophs
–
–
–
–
–
complex
organic
compounds
Herbivores – eat plants
Carnivores – eat meat
Omnivores – eat both plants and meat
Scavengers – eat carrion
Saprophytes – eat dead or decaying material
heterotrophs
heat
simple
inorganic
compounds
this may include several steps, with several different types of organisms
Components of Ecosystems
• Abiotic cycles
• Producers (autotrophs)
– Source of all food
• Photosynthesis
• Chemosynthesis
Consumers (heterotrophs)
Aerobic respiration
Decomposers
(bacteria, fungus)
– Oxygen
Anaerobic respiration
– Methane, H2S
Decomposers
Heat
– Matter recyclers…
– Release organic compounds into
soil and water where they can
be used by producers
Heat
•
•
•
•
Abiotic chemicals
(carbon dioxide,
oxygen, nitrogen,
minerals)
Heat
Heat
Producers
(plants)
Consumers
(herbivores,
carnivores)
Heat
Solar
energy
PHOTOSYNTHESIS
6CO2
+
Carbon Dioxide
6H2O + LIGHT
Water
C6H12O6
Glucose
+ 6O2
Oxygen
CELLULAR RESPIRATION
C6H12O6
Glucose
+
6O2
Oxygen
6CO2
+
Carbon Dioxide
6H2O
Water
+ ENERGY
ATP
Primary Productivity
• Primary productivity determines
•
•
•
the amount of energy available
in an ecosystem
Primary productivity is affected
mostly by light in aquatic
ecosystems
• Limiting nutrient is
phosphorus or nitrogen
Temperature and moisture are
key control factors in terrestrial
ecosystems
Evapotranspitation
• Water transpiration
Primary Productivity
• Gross Primary production
• Total primary production in an
ecosystem
• Not the amount of energy
available to consumers!
• NPP=GPP-R
• R= energy used for
respiration
• Energy expended: Plants use
the energy captured in
photosynthesis for
maintenance and growth.
Trophic Levels – Energy Pyramids
• An energy pyramid provides
a means of describing the
feeding and energy
relationships within a food
chain or web.
• Each organism in an
ecosystem is assigned to a
feeding (Trophic) level
based on source of energy
• The greatest amount of
energy is found at the base
of the pyramid.
• The least amount of energy
is found at top of the
pyramid
Tertiary
consumers
Secondary
consumers
Primary
consumers
Producers
Energy Flow
Heat
First Trophic
Level
Second Trophic
Level
Third Trophic
Level
Fourth Trophic
Level
Producers
(plants)
Primary
consumers
(herbivores)
Secondary
consumers
(carnivores)
Tertiary
consumers
(top carnivores)
Heat
Heat
Heat
Solar
energy
Heat
Heat
Detritvores
Heat
Energy Pyramid
• Each step shows that some energy is stored or utilized in the
organism which eats the preceding one.
• Shows that much of the energy is lost when one organism in a
food chain eats another. Most of this energy which is lost goes
into the environment as heat energy.
• It is estimated that only 10% of the energy at each trophic level
is available to organisms at the next higher level.
 Energy is sometimes considered in
terms of biomass = the dry weight
of tissue of all the organisms and
organic material in an area.
 Producer organisms represent the
greatest amount of living tissue or
biomass at the bottom of the
pyramid.
 There are more plants on Earth
than there are animals.
 Bio=life
Mass=weight
 Bio + Mass = Weight of living things
within an ecosystem.
Biomass
Why we transform each species into
biomass instead of absolute numbers
Numbers Pyramid
Biomass Pyramid
Implications of Pyramids….
• Why could the earth support more people if
the eat at lower trophic levels?
• Why are food chains and webs rarely more
than four or five trophic levels?
• Why are there so few top level carnivores?
• Why are these species usually the first to
suffer when the the ecosystems that
support them are disrupted?
Average number
of links = 3.5
10
Streams
Lakes
Number of observations
8
Terrestrial
6
4
2
0
1
2
3
4
Number of links in food chain
5
6
Food Webs
• A food web is a series of
•
•
interrelated food chains
which provides a more
accurate picture of the
feeding relationships in an
ecosystem
More than one thing will
usually eat a particular
species.
A species will many times
feed at multiple levels on the
trophic pyramid
Generalized Food Web of the Antarctic
Humans
Blue whale
Sperm whale
Killer
whale
Note:
Arrows
Go in direction
Of energy
flow…
Elephant
seal
Crabeater seal
Leopard
seal
Emperor
penguin
Adélie
penguins
Petrel
Squid
Fish
Carnivorous plankton
Herbivorous
zooplankton
Krill
Phytoplankton