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CH. 4
Ecosystems and Energy
LEVELS OF
BIOLOGICAL
ORGANIZATION
ECOLOGY
“eco-” = house
 The study of the interactions among
organisms and between organisms and their
abiotic environment
 Abiotic factors: sunlight, wind, living space,
precipitation, temperature, soil, wind
 Studies levels of biology above the individual

Populations: groups of species (members
breed naturally to produce fertile offspring)
 Communities: all the populations in an area
 Ecosystem: the community including the
abiotic factors.


Biosphere – layer of earth containing all
living things. A study would include the air,
water, land and organisms.
 Atmosphere:
gaseous layer surrounding Earth
 Hydrosphere: Earth’s water– frozen and liquid
 Lithosphere: soil and rock of Earth’s crust
ENERGY





Essential for life
The capacity/ability to do
work
Units: Joules (J) – units
of work - or calories (cal)
– units of heat energy
Forms: chemical,
radiant/solar, heat,
mechanical, nuclear, and
electrical
Can be stored –
potential energy – or as
moving energy – kinetic
energy.
BIOLOGICAL EXAMPLE

A plant that a meadow vole (rodent) eats
contains chemical potential energy and is
converted to kinetic energy and heat as the
vole moves.
THERMODYNAMICS



Study of energy and its
transformations
Closed system – an
object being studied
that exchanges energy,
but not matter with its
surrounding.
Open system – an
object studied that can
exchange
energy/matter with its
surroundings.
FIRST LAW OF THERMODYNAMICS

Energy cannot be created or destroyed. It can
transform from one form to another.
Ex: absorb energy from the sun or give off energy to
surroundings. It changes, but wasn’t created or
destroyed.
 All living things need energy and can’t create it.
They must get it from their environment. Plants get
solar energy and convert to chemical energy in the
bonds of sugar. Animals get energy (chemical) from
eating plants/animals and convert energy to
mechanical energy for movement.

SECOND LAW OF THERMODYNAMICS

When energy transforms, some usable energy
degrades into heat, a less-usable form of
energy.
Usable energy for biological work decreases through
an ecosystem.
 Entropy: a measure of disorganized, less-usable
energy.
 If all energy were heat, life would cease to exist.
 Entropy increases through an ecosystem.

EFFICIENCY OF ENERGY CONVERSION
Energy conversion is never 100% efficient,
some energy is always “lost” as heat.
 And automobile is about 25% efficient
converting chemical energy of gas to
mechanical energy
 Cellular metabolism is about 50% efficient.

PHOTOSYNTHESIS
Producers are essential for getting energy into
organisms  photosynthesis and chemosynthesis
(from hydrogen sulfide – H2S @ hydrothermal
vents)
 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

Energy captured by plants via photosynthesis is
transferred to the organisms that eat the plants
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
 Creating
new cells, reproduction, movement, etc.
PRODUCERS, CONSUMERS, DECOMPOSERS

Producers/autotrophs: land – mainly plants; water
– algae, phytoplankton

Consumers/heterotrophs: primary, secondary,
tertiary and herbivores, carnivores, omnivores,
detritus feeders/detrivores

Decomposers/saprotrophs – microbial, return
inorganic molecules (carbon dioxide, salts) to
environment
ENERGY FLOW THROUGH AN ECOSYSTEM




One way; once energy has been used biologically, it
becomes unusable
Follows food chain
10 %
Trophic levels
rule!!!
Food webs – realistic model
FOOD WEB
NOTE: ARROW DIRECTION, LOCATION OF PRODUCERS
ECOLOGICAL PYRAMIDS

Pictures to represent available energy
PYRAMID OF NUMBERS


# of organisms
with appropriate
area according
to size.
Inverted
pyramids do
exist:
decomposers,
parasites
PYRAMID OF BIOMASS

Biomass= measure of
total amount of living
material
PYRAMID OF ENERGY



Units typically
kilocalories per
square meter per
year
Less energy
available at each
successive trophic
level.
10% rule
PRIMARY PRODUCTIVITY

Gross primary productivity (GPP):
 Total
amount of energy captured during
photosynthesis (for a given time period)
Net primary productivity (NPP):
 The amount of energy left after cellular
respiration in the plant; plant growth per unit
area per unit time)
 NPP = GPP – plant respiration
 NPP is the energy available to consumers

CHECK FOR UNDERSTANDING

If a forest nets 1500
g/m2/yr and uses 1000
g/m2/yr. How much
energy does that forest
capture annually?



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4 – I feel extremely confident
about any calculations
regarding primary
productivity
3 – I feel confident about
primary productivity
calculations
2 – With a bit more help I
could do these calculations
1 – I really don’t get this
What abiotic
factors
effect
productivity?
Know the
most/least
productive
environme
nts and
why they
are/are not
productive.