Transcript Ecology bio 9 Ch 23 and 24

Ecology and Human impact on
the environment
Announcements
Lecture Outline
• The scope of ecology
• Energy flow through ecosystems
•
Laws of thermodynamics
•
Trophic levels on earth
• Nutrient cycling in ecosystems
– The carbon cycle
– The nitrogen cycle
• Human impact on the earth
Ecology is the study of life and its
interactions with its environment
The environment of a living thing
includes many things
Other individuals of the same
species (populations)
Different species (communities)
Nonliving elements- nutrients,
sunlight, temperature (ecosystem)
Ecology is studied from the level of the
individual up through the entire biosphere
More of this
Less of this
Ecology studies different life
strategies that species have for
success in their environment
Ecology compares familiar patterns of life that arise
under similar conditions in different places on earthsuch areas are called climax communities
Energy flow through ecosystems
Laws of thermodynamics
Energy and Thermodynamics
All Living Things Require and Consume
Energy
• We get our energy from
food
• Ultimate source of
energy for all life on
earth is the sun
Energy is the capacity to do work
• There are many forms
of energy:
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Kinetic energy
Potential energy
Chemical energy
Electrical energy
The First Law of Thermodynamics
• Energy cannot be
created or destroyed
• The amount of energy
in the universe is
constant
• Energy can be
interconverted from
one form to another:
– Potential energy
– Kinetic energy
– Radiant energy
Kinetic energy
• Energy of motion
• KE= 1/2mv2
• Temperature is a
measure of molecular
kinetic energy
Potential energy
• Energy is the ability to
do work
• Potential Energy of
position
• Gravitational potential
energy
• Chemical potential
energy
Chemical potential energy
Enthalpy = Energy in chemical bonds
Energy is released when chemical bonds are formed
While matter is recycled, energy flows
continually through living systems
The 1st Law of Thermodynamics:
Energy can be interconverted from one
form to another
More energy interconversions
The 2nd Law of Thermodynamics
The Law of Entropy
• Interconversions of
energy are never 100%
efficient
• Entropy!
• Entropy is a measure of
disorder (i.e. chaos,
randomness)
• Each interconversion of
energy involves loss of
usable energy
:
Biochemical reactions are inefficient
The price of minimizing entropy is the
constant expenditure of free energy
Closed systems will deplete
themselves of usable (free) energy
• Given a finite amount of
energy, each energy
interconversion will
result in an everincreasing amount of
unusable energy
(entropy)
Trophic levels on earth
Earth is bathed in energy from the
sun
Plants & algae capture the sun’s energy,
storing in chemical bonds as food
Photosynthesis
• CO2 + H2O + sunlight  C6H12O6 + O2
• Carbon dioxide + water glucose
oxygen
Primary consumers feed on plants
• Secondary consumers
are predators on
primary consumers, one
trophic level below
them
• Actual food webs
involve several food
sources and several
trophic levels
Energy is transferred from
producers to consumers
• There is inefficiency in
each system
• Entropy ensures there is
always heat loss
Energy transfers between trophic
levels are inefficient
• Energy transferred
consists only of the
energy remaining in the
chemical bonds of the
food, not the food
consumed over a
lifetime
Humans, like many animals,
consume at many levels
• There are
ecological
consequences for
consumption at
each level
A certain species of flea only drinks the blood of
elephants. How would you describe this flea's
trophic level?
• A) Producer
• B) Primary consumer
• C) Secondary consumer
• D) Decomposer
Nutrient cycling within ecosystems
While energy flows into and out of
earth, mass stays
• Earth is a closed system
for mass
• Nutrients must be
cycled over and over
throughout the ages
• Atoms of your body
were in bodies of plants
or other creatures
millions of years ago
Living things are made of four
major macromolecules
Carbohydrates contain
carbon, hydrogen, & oxygen
Lipids are mostly carbon and
hydrogen
Living things are made of four
major macromolecules
Amino acids of proteins have
nitrogen & carbon
Nucleic acids, like DNA, have
nitrogen phosphorus & carbon
Where do all these atoms come
from?
The Carbon cycle
Producers can “fix” carbon from
the air
• Carbon fixationcapturing gaseous
carbon dioxide
from the air, and
converting it to
solid glucose
• Photosynthesis
does this
The carbon cycle
• Life is based on
carbon
• Fossilization has
sequestered carbon
for millions of years
• Mining of fossil fuels
returns CO2 to the
atmosphere
Carbon Dioxide is a greenhouse gas
Bicycles require pedals, wheels, saddles and handlebars.
If Jane has 21 wheels, 14 pedals, 14 saddles and 8
handlebars, how many bicycles can she build?
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4
7
8
14
21
The nitrogen cycle
80% of our air is Nitrogen gas
• N2’s triple bond is very
difficult to break
• Ages ago, only lightning and
meteor impacts, and certain
bacteria could fix nitrogen
When nitrogen is depleted in soil,
plants grow poorly, and crops fail
Maple leafs
Corn
Nitrogen fixing bacteria were the primary source
of all nitrogen on earth
Nitrogenase enzyme
Nitrogen fixing bacteria can live in
endosymbiotic partnership with legumes
The Haber process now produces 100 million
tons of nitrogen fertililzer per year
• 3–5% of world natural gas production
is consumed in the Haber process (~1–
2% of the world's annual energy
supply).That fertilizer is responsible for
sustaining one-third of the Earth's
population, as well as various
deleterious environmental
consequences.
• Fritz Haber:
– Nobel prize, 1918
– Developed weaponized chlorine gas for
use in WWI
– Viktor Grignard, phosgene, France
– Developed Zyklon B, an insecticide
– Exiled from native Germany, 1933
Anthropogenic nitrogen fixation now
exceeds all natural processes
High temperatures in auto engines cause
N2 to react, forming Nox pollutants
Phosphorus and nitrogen are often
the limiting nutrient in ecosystems
Minerals and toxins
Minerals and toxins which are removed from
cells slowly become concentrated through
trophic levels
Human impact on the earth
All populations have a finite carrying
capacity in their environment
Humans have the unique ability to raise
their carrying capacity through technology
• This ability has been
challenged, but so far
not yet defeated
Raising earth’s carrying capacity for
humans
Norman Borlaug and the
green revolution
Fritz Haber and chemical
fertilizers
Humans’ need for more resources
comes at a cost for the earth
Human population grows by a
combination of factors
High Birth rates
Increased lifespan
Earth’s resources are not used
equally by all societies
Ecological footprint of various
societies
Human food choices and the
resources they require
Pollution
Carbon dioxide is a significant
greenhouse gas
CO2 levels on earth are
steadily increasing
CO2 traps solar radiation
The effects of global warming on climate
change are difficult to predict
The increase of agricultural yields due to the
development of high-yield varieties of crops and
the use of modern cultivation methods is
referred to as the:
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A) wonder crops.
B) crop revolution.
C) green revolution.
D) farm aid.