Transcript Understanding Our Environment

Matter, Energy, and Life
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Outline
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Elements of Life
Organic Compounds and Cells
Energy
 Laws of Thermodynamics
 Photosynthesis / Respiration
Ecosystems
 Food Chains
 Ecological Pyramids
 Material Cycles
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ELEMENTS OF LIFE
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Matter - Everything that has mass and takes
up space.
 Solid - Liquid - Gas
Elements - Substances that cannot be
broken down into simpler forms by ordinary
chemical reactions.
 Periodic Table
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Elements of Life
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Atoms - Smallest particles exhibiting
characteristics of the element.
 Protons - Neutrons - Electrons
 Atomic Number: Number of protons
 Isotope - Forms of an element differing in
atomic mass.
- Different number of neutrons.
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Chemical Bonds
Molecule: Two or more atoms joined
together.
- Compound: Two or more different types
of atoms joined together.
 Chemical Bond - Forces (chemical energy)
holding atoms together in molecules.
- Covalent - Sharing of electrons.
- Ionic - Cations and Anions
- Hydrogen - Unequal attraction of shared
electrons.
 Water
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
Common Molecules
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Ions, Acids, and Bases
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Ions - Atoms that contain more or fewer
electrons than protons.
Acids - Substances that release Hydrogen
ions.
Bases - Substances that readily bond with
Hydrogen ions.
 pH Scale: 0-14
- < 7 Acidic
- > 7 Basic
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pH Scale
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Organic Compounds
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Organic Compounds - Material making up
biomolecules. Formed by rings and chains
of carbon.
 Four major categories:
- Lipids
- Carbohydrates
- Proteins
- Nucleic Acids
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Cells
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Cells - Minute compartments in a living
organism which carry out process of life.
 Surrounded by lipid membrane controlling
flow of materials in and out of cell.
 Interior sub-divided into organelles and
sub-atomic particles.
Enzymes - Class of proteins - molecular
catalysts regulating chemical reactions.
Metabolism - Multitude of enzymatic
reactions performed by an organism.
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ENERGY
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Energy - Ability to do work.
 Kinetic - Energy in moving objects.
 Potential - Stored energy.
- Chemical - Stored in food or fossil fuels.
Power - Rate of doing work.
Heat - Total kinetic energy in a substance not
associated with bulk motion.
Temperature - Measure of speed of motion of
atoms in a molecule.
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Thermodynamics
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Energy must be supplied from an external
source to keep biological processes running.
 Energy flows in a one-way path through
living systems and into a temperature sink.
First Law of Thermodynamics - Energy is
neither created nor destroyed.
Second Law of Thermodynamics - With each
successive energy transfer, less energy is
available to perform work.
 Entropy
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ENERGY FOR LIFE
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Ultimately, most organisms depend on the
sun for energy needed to carry out life
processes.
Solar energy is essential for (2) reasons:
 Warmth
 Photosynthesis
- Radiant energy transformed into useful,
high-quality chemical energy in the
bonds of organic molecules.
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Energy For Life
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Of all solar radiation reaching the earth’s
surface, about 10% is Ultraviolet, 45% is
Visible, and 45% is Infrared.
 Most of energy is absorbed by land or
water, or reflected back into space.
- Only about 1-2% of the sunlight falling
on plants is captured for photosynthesis.
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Electromagnetic Spectrum
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Photosynthesis
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Occurs in membranous organelles of green
plant cells called chloroplasts.
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6H20+6CO2 + solar energy = C6H12O6+6O2
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Water and carbon dioxide in the presence of
sunlight yields glucose (sugar) and oxygen.
Glucose serves as primary fuel for all
metabolic processes in plant cells.
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Photosynthesis
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Respiration
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Photosynthesis captures energy, while
cellular respiration releases energy.
 Cellular respiration splits carbon and
hydrogen atoms from the sugar molecule
and recombine them with oxygen to recreate carbon dioxide and water.
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C6H12O6 + 6O2 = 6H2O +6CO2 + energy
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Energy Exchange in Ecosystems
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SPECIES TO ECOSYSTEMS
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Population - All members of a species living
in a given area at the same time.
Biological Community - All of the populations
of organisms living and interacting in a
particular area.
Ecosystem - Biological community and its
physical environment.
 Somewhat user-defined.
 Open or closed boundaries.
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Food Chains
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Photosynthesis is described as Primary
Productivity because it is the basis for almost
all other growth in an ecosystem.
 Manufacture of biomass by organisms
eating plants is termed Secondary
Productivity.
Food Chain - Linked feeding series.
 Food Web - Most consumers have multiple
food sources.
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Food Web
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Trophic Levels
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Trophic Level - Expression of an organism’s
feeding status in an ecosystem.
 Producers (plants)
 Consumers
- Primary, Secondary, Tertiary
 Most terrestrial food chains relatively short.
 Aquatic food chains tend to be longer.
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Trophic Levels
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Organisms can also be identified by the type
of food they consume:
 Herbivores
(Plants)
{Deer}
 Carnivores
(Meat)
{Wolves}
 Omnivores
(Plants/Meat) {Bears}
 Scavengers
(Carcasses) {Crows}
 Detritivores
(Debris)
{Ants}
 Decomposers
(All)
{Bacteria}
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Ecological Pyramids
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Due to Second Law of Thermodynamics,
food chains often form an inverted pyramid.
 Metabolism
 Predator efficiency < 100%
 10% Rule (Energy / Biomass)
- 100 kg clover
 10 kg rabbit
 1 kg fox
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Energy Pyramid
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MATERIAL CYCLES
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Hydrologic Cycle
 Solar energy continually evaporates water
stored in the oceans and land, and
distributes water vapor around the globe.
- Condenses over land surfaces,
supporting all terrestrial systems.
 Responsible for cell metabolism,
nutrient flow in ecosystems, and global
distribution of heat and energy.
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Hydrologic Cycle
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Carbon Cycle
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Begins with intake of CO2 during
photosynthesis. Carbon atoms are
incorporated into glucose and then:
 Remain in plant material until death.
- Eaten by predator
- Respiration
- Excretion
- Incorporation
 Death (Decomposers)
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Carbon Cycle
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Nitrogen Cycle
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Plants uptake inorganic nitrogen from the
environment and build protein molecules
which are later eaten by consumers.
 Nitrogen-fixing bacteria change nitrogen to
a less mobile, more useful form by
combining it with hydrogen to make
ammonia - used to build amino acids.
- Members of bean family (legumes) have
nitrogen-fixing bacteria living in their root
tissue.
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Nitrogen Cycle
Nitrogen re-enters the environment:
- Death of organisms
- Excrement and urinary wastes
 Nitrogen re-enters atmosphere when
denitrifying bacteria break down nitrates into
N2 and nitrous oxide (N2O)gases.
- Humans have profoundly altered nitrogen
cycle via use of synthetic fertilizers,
nitrogen-fixing crops, and burning fossil
fuels.
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Nitrogen Cycle
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Phosphorous Cycle
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Phosphorous compounds are leached from
rocks and minerals and usually transported
in aqueous form.
 Taken in and incorporated by producers.
- Passed on to consumers.
 Returned to environment by
decomposition.
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Phosphorus Cycle
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Sulfur Cycle
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Most sulfur tied up in underground rocks and
minerals. Inorganic sulfur released into air
by weathering and volcanic eruptions.
 Cycle is complicated by large number of
oxidation states the element can assume.
 Human activities release large amounts of
sulfur, primarily by burning fossil fuels.
- Important determinant in rainfall acidity.
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Sulfur Cycle
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Summary
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Elements of Life
Organic Compounds and Cells
Energy
 Laws of Thermodynamics
 Photosynthesis / Respiration
Ecosystems
 Food Chains
 Ecological Pyramids
 Material Cycles
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