NATS 1840
LECTURE NOTES
Environmental Science & Thinking (UNIT 1)
SEPT. 13, 2011
Environment
- Everything that surrounds you, from just outside your skin to the edge of the universe.
- The environment consists of all those parts of the physical world that help to sustain life.
o If a part of the environment is under stress (a change), then its ability to sustain life may be threatened.
Environmental Science
- The study of how the environment works, and of humanity’s impact upon it.
o A science
o Interdisciplinary (draws upon many varieties of science knowledge)
o Both theoretical and applied science (understand the changes that take place and the causes of the
change)
Science
- The systematic study of how and why nature works the way it does.
- Uses empirical methods (testing one’s offered explanations) to test possible explanations of observations.
- Seeks to uncover basic underlying principles so that predictions may be made.
- A rational process drawing upon two forms of reasoning….
o Inductive reasoning – synthesis, creativity, inspiration and imagination
o Deductive reasoning – logic, self-consistency, rigour, mathematics
Induction: Reasoning Based on Experience
- The mode of thinking used in the formation of a hypothesis
- General conclusion from limited number of observations
- Synthesis of many observations
- Bottom-up approach (starts with observations)
- Limited by finite number of observations – not logically valid.
o Inductive conclusions can only be “proved” in the sense that they are very likely, but not guaranteed, to
be true.
- Ex. All objects ever observed fall to the ground when dropped. Therefore, all objects fall to the ground.
Deduction: Logical Reasoning
- Crucial in analyzing the consequences of a hypothesis
- Specific conclusions drawn logically from a generalization.
- Conclusions are reliable, at least internally.
- A top-down approach.
- Limited by quality of assumptions
o Deductive conclusion only as good as its premises
o Although logically valid, any deductive conclusion based on incorrect premises is invalid
The Scientific Method
-
-
Based mainly on inductive reasoning and observations
Deductive reasoning crucial for designing tests (usually called experiments)
o Observation(s)
o Question(s)
o Hypothesis
o Test hypothesis…do an experiment
o Critically evaluate the results of the test
o Determine if hypothesis is supported or contradicted
o Disseminate (5) and (6), usually in a refereed (peer reviewed) publication
Hypothesis disproved: question still remains
Hypothesis supported: deductive consequences of that hypothesis must be tested.
What is a good scientific statement?
- A hypothesis must be falsifiable (can be disproved), at least in principle. Examples:
o The moon is made of cheese
o Cell phones cause brain cancer
o Sun’s energy source is nuclear fusion
- A hypothesis that can’t be falsified (is untestable) isn’t a scientific statement
o God & Afterlife
o Before the Big Bang
o Some ‘conspiracy theories’- example UFO
The Hierarchy of Scientific Statements
- Hypothesis
o Tentative answer to a question, i.e. an assumption
o Weakest scientific statement
- Theory
o (based on inductive ideas) (experiments are made through deductive reasoning)
o A hypothesis, or set of hypotheses, that has survived many tests
o More robust than a hypothesis, in that there is greater confidence that it is right
- Law
o A theory that has passed so many tests that it is considered a fact
o Observation seen so often that it becomes a fact
o Most robust of all scientific statements
Scientific Experiments
- To be a useful test of a hypothesis, can experiment must be
o Controlled
o Statistically significant
o Repeatable
- Absence of one or more of these criteria means a flawed experiment whose results shouldn’t be trusted until
they have been reproduced by a reliable experiment.
Controlled experiments
- Many variables may influence the outcome of an experiment
- Outcome of a controlled experiment depends on only one variable.
Control Group
Group 1
Subject Group
Common Experiment
(many variables)
Group 2
Act on one variable
Observe Responses
Group 1
-
Group 2
Any difference in response between subject and control must be due to the single different variable.
NATS 1840
LECTURE NOTES
Environment Science & Thinking (UNIT 1)
SEPT 15, 2011
Statistical Significance & Scientific (Un)certainty
- The outcome of any measurement is characterized by
o Accuracy  how close the outcome if to the ‘true’ value
o Precision  the degree to which repeated measurements yield the same value
- Uncertainty in a measurement describes the range within which the ‘true’ value most likely lies
o For instruments (ruler, thermometer….) uncertainty is one half of the smallest division on the scale.
o Uncertainty in the average of several measurements decreases with the number of measurements in
sample.
N = 10 (uncertainty =31%)
N = 100 (uncertainty = 10%)
Statistical Significance
- Controlled experiment with N1 and N2 controls (or measurements). Averages differ and have some uncertainty.
- Is the difference real? Or just the result of random choice?
o To be statistically significant the difference in the averages must be greater than the error ranges.
- Random fluctuations might mimic a real response in a controlled experiment. Statistical significance ensured by
o Conducting experiment with many subjects and controls
o Repeating several times
Repeatability
- An experiment should be describable in sufficient detail to allow any independent replication to yield the same
outcome. This helps to reduce:
o Uncertainties
o Mistakes
o Bias
- Detailed notes must be kept at each step
- Repeatability argues against ‘proprietary’ or ‘trade’ secrets, and in favour of full disclosure of date and methods.
NATS 1840
LECTURE NOTES
Environment Science & Thinking (UNIT 1)
SEPT 20, 2011
Junk Science
- Term reserved for results that are presented as scientifically valid, but fail to conform to normal scientific
standards and/or are only partially true.
o Can be motivated by ego, greed, etc.
- Problems typically include
o Selectivity  results picked to support a priori favoured view.
o Distortion of conclusions (eg. “it is possible…” becomes “it is confirmed…”)
o No peer review
o Publication in places of questionable repute
Detecting Junk Science
- Reliability of unexpected/extraordinary claims may be gauged by asking questions such as:
o Are the sources reliable?
o Do they have an ulterior agenda?
o Have the results been verified (reproduced) by others?
o Does the result represent the majority view among scientists?
o Does it make sense?
o Is previous knowledge accommodated?
o Is the presentation balanced? Are criticisms addressed?
o What were the sources of funding?
o Has there been peer review?
- Multiple ‘negative’ answers might be an indicator of junk, but not necessarily so.
- Caution! Less clear at the frontiers of knowledge. Consensus might change rapidly.
Pseudoscience (Pseudo = False)
- Knowledge presented as if it has a scientific foundation, even though it does not
o Includes astrology, creation science/intelligent design.
- Quality of any results obtained is irrelevant
- Typically,
o Isn’t self-correcting;
o Doesn’t establish theoretical underpinning;
o Dismisses skepticism as narrow-mindedness.
NATS 1840
LECTURE NOTES
Environmental Decision Making (Unit 2)
What kind of decisions?
- Any decision likely to have some impact on the environment
o Problem prevention;
o Problem remediation;
o Evaluation of alternatives;
o Policy direction
SEPT 20, 2011
-
o Regulation
Often more challenging then it might appear because of the need to weigh many competing factors.
What influences decision-making?
- Science underpins the decision-making process. But decisions are also informed by:
o One’s environmental worldview
o Risks relative to likely benefits
o Associated costs
- Risk and costs can be quantified objectively, but worldviews and the perception of risk are both highly
subjective.
Environmental Worldview
- An individual’s beliefs about
o How the world works;
o Their role in the world;
o Right and wrong environmental behaviour
- Reflects the value one places on Nature
- Instrumental (Utilitarian) value:
o Something is useful to us
- Intrinsic value
o Something has value by its mere existence
NATS 1840
LECTURE NOTES
Environmental Decision Making (Unit 2)
Anthropocentric (human-centered) worldview
-
Humans have intrinsic value
Nature has utilitarian value
Humans are in charge of the Earth and can act as masters and/or caretakers of the environment
Biocentric (life-centered) worldview
-
All living creatures have intrinsic value
The non-living environmental has utilitarian value
Humans should aim to preserve Nature’s life-sustaining abilities
Ecocentric (Earth-centered) worldview
-
Entire environment has intrinsic value
Humans have no special claim on the environment
Humans are just one of millions of interdependent species
Ecosystems must be protected in their entirety
Humans must adjust their needs to ensure a sustainable future
SEPT 22, 2011
Example: Neo-Malthusians (Ecocentric)
-
Human population is too high already;
Present resource use & growth is unsustainable;
Pollution should be prevented rather than remedied;
Best technology is small & decentralized
Thomas Malthus predicted (-1800) that mass starvation would soon visit humanity
Example: Cornucopians (Anthropocentric)
-
Increased population means more in genuity;
Ability to Earth to support growth is unlimited;
Economic growth leads to technological advances, less pollution & improved health;
Consequences of pollution to be addressed as needed, provided growth not impeded;
Large, centralized technological solutions
Earth as the horn of plenty
What is your own worldview?
-
Wide spectrum of views and philosophies
o Most will disagree with at least some of the ideas at either extreme
o Worldviews should be founded upon some knowledge of the fundamental issues
o New information available on a regular basis, so outlook should be flexible
Risk
-
The possibility of suffering harm or loss
Everyday risks  instinct
When instinct is insufficient, rely on experience and best estimates to assess risk objectively
o Scientific evidence and plausible assumptions used to estimate the probability of harm
RISK = PROBABILITY – LIKELIHOOD OF AN OUTCOME
Probability (an example)
-
Consider a tree with four applies on it, two of which are ripe.
-
Pick two applies with eyes closed. Q: What is the most likely number of ripe apples in your hands?
Suppose ALL apples are picked. Two are guaranteed to be ripe. So, probability of having one ripe apple after one
pick is 50% (or 0.5).
o When two applies are picked the number of ripe apples is most likely to be 2 × 0.5 = 1. (But not
guaranteed since a given attempt may yield zero or two ripe apples).
Known facts about apples on tree used to estimate probability
-
Example: “There is a 10% probability of rain today.”
-
Means: 10 out 100 times that the state of the atmosphere is like that presently existing, it rains. (Based on
experience)
Suppose the atmosphere is like this 20 times in one year. How many times is it likely to rain?
o Answer: 20 days × 10% = 2 days of rain
Example: You are 10 times more likely to die from cancer as a result of smoking than from consuming alcohol.
-
Means: Ten times more cancer deaths can be attributed to smoking as compared to alcohol. (Based on
experience)
Estimating Risk
-
-
Partly the job of science to obtain the data needed to estimate probabilities
o Dose-response curves from laboratory data
o Real-world failure/accident rates
But what is there isn’t enough data? (ex. no recorded deaths or injuries)
Probabilities of possible scenarios leading to harm. (Subject to continual refinement as new information is
uncovered)
Most challenging in situations where a significant lag exists between cause (exposure) and effect
Total Risk
-
-
Combination of two factors
o The probability of harm
o The probability of exposure
Multiplied together to yield the actual risk to an individual or community
Example: Suppose graphs show LD50 instead of ED50
o Dose-response = prob (death) is 50% at LD50
o If exposure at LD50 level has a probability of 5%, total risk of death is 0.5 × 0.5 = 0.025 (2.5%)
NATS 1840
LECTURE NOTES
Environmental Decision Making (Unit 2)
SEPT 27, 2011
Perception of Risk
-
-
Often different from the objective risk. Reasons are mainly psychological.
o We accept greater risk, if taken voluntarily
o We underestimate risks associated with familiar activities and overestimate those of unfamiliar ones.
o When consequences of something going wrong, are major, associated activity perceived as riskier.
o If persons, “in charge” of the risk are decreased trustworthy, risk is perceived to be lower.
o If activity gets lots of media coverage, seen as riskier.
Decision makers must reconcile perception with reality, if their conclusions are to be rational.
Costs
-
Often, assessing economic costs means performing a costs benefit analysis
o Identify possible impacts and their likelihood;
o Evaluate expected value/cost of each
o Compare value of the positive impacts to costs of negative impacts
Inputs
(Internal costs)
Process
Product
(Benefits)
Inputs
(Internal costs)
Difficult to assign economic value to intangibles (beauty, cleanliness,…) and externalities.
Externality
-
-
Cost borne by persons other than those reaping the benefit. Often overlooked, leading to “The Tragedy of the
Commons.”
Value of intangibles & externalities, very difficult to assess objectively.
o Some suggest inclusions in price of goods, allowing market forces to resolve environmental problems –
controversial
o How to implement if no agreement on external costs?
If external costs are unquantifiable or ignored, is an economically rational choice possible?
Cost benefit analysis
-
Cost benefit analysis remains a controversial way to settle environmental issues and shouldn’t be the sole basis
of the decision. But it is a place to start.
Ultimately, objective information about risk, costs, and benefits is interpreted through the filter of your
worldview, so even with good science a spectrum if to be expected.
Decision Making – An Example (Hocking Article)
Paper vs. Styrofoam?
-
-
1990, McDonald’s stops using polystyrene packaging. Most other food chains, soon follow. It is now rare to find
a Styrofoam cup in a coffee shop.
Public perception -> polystyrene is environmentally bad
o Doesn’t decompose in landfill
o Ozone-destroying chemicals omitted during productions
Paper cups and packaging seen as environmentally friendly. Are they?
What if all factors are considered? (Hocking, 1991)
Polystyrene involve CFC which is environmentally bad and when dumped they will last long.
Life Cycle Assessment: Step 1  Inventory Analysis
FACTOR
1 PAPER CUP
1 FOAM CUP
6
1
Raw Materials
12
1
Steam (heat)
36
1
Electricity
2
1
Cooling Water
200
1
Waste Water
Emissions (by weight)
2.5
1 (Pentane)
During Production
Methane
NONE
After Use (Landfill)
Poor
Good
Recyclability
2.5
1
Cost
Cutting Trees
Oil Extracting
Intangibles
- (Pentane has no impact on ozone; methane is 50x more potent a greenhouse has than pentane)
- So, is Styrofoam really so bad in comparison to paper?
Life Cycle Assessment: Step 2  Impact Prioritization
-
-
Each inventory factor must be assigned a priority such assignments reflect one’s worldview as well as objective
risk analysis
Criteria might include
o Geographical scale of impact
o Severity of hazard
o Degree of exposure
o Penalty for being wrong
Only once a complete life-cycle assessment has been done can a rational choice be made. But two individuals
might still disagree.
NATS 1840
LECTURE NOTES
The Ecosphere
SEPT 29, 2011
Ecology
- The study of the interactions among living things, and between living things and their physical environment
- A major part of environmental science
Living Things – A Hierarchy:
Community
BIOSPHERE (Life)
Community
Pop.
Community
Community  a collection of populations living in
one area at one time.
Population
Population  members of a species living in one
place.
Pop.
Species  living things that can breed with one
another.
Organisms of a Species
Ecosystem
Community
Environment
The Physical Environment
- Can be divided into three broad compartments
o The Atmosphere (air)
o The Hydrosphere (water)
o The Lithosphere (rocks & soil)
- Nutrients and energy are continuously exchanged between the three components and the biosphere
Ecosystem
- Combination of a community and its physical environment, including all interactions between compartments
Community
-
Environment
Ecosystems exhibit great complexity in both structure and interactions
o Tempering with one small part can easily affect the whole, often unpredictably.
Biome (on land)
- Collection of similar ecosystems
o Often in one geographical area
o Characterized by common climate & similar forms of life
o A major ecosystem
BIOME
Ecosystem
Ecosystem
Ecosystem
Similar climate  long-term weather conditions
Similar life forms  well-adopted to the climate
Major Terrestrial Biomes: Tundra
- Very low average rainfall
- Very low average temperature
- Treeless
- Dominant plants: small shrubs, grasses, mosses & lichens
- Comparatively low biodiversity
Major Terrestrial Biomes: Taiga (Boreal Forest)
- Low average rainfall
- Low average temperature
- Dense forests
- About 20 species of conifers (cone-bearing evergreens) dominate much of this biome
Major Terrestrial Biomes: Temperate Forests
- Moderate rainfall
- Moderate temperature
- Trees drop their leaves each season (deciduous)
- Deep shade limits animal life to small mammals
Major Terrestrial Biomes: Temperate Grasslands
- Low rainfall
- Moderate temperature
- Tall grasses and small shrubs dominate
- Greatest variety of large mammals
Major Terrestrial Biomes: Tropical Rainforest
- Very high rainfall
- Very high temperature
- Enormous diversity of plants and animals
Biome (in the water)
- Characterized by four factors
o The depth to which sunlight penetrates
o The temperature of the water
o The nature of the bottom substrate (the stuff at the bottom of the body of water)
o The amount of dissolved salts (salinity)
- Based on salinity alone we have
o Freshwater ecosystems (lakes, rivers, etc.)
o Marine ecosystems (Oceans)
o Transitional zones (Coastal wet lands)
The Ecosphere
BIOME
BIOME
BIOME
ECOSPHERE
BIOME
-
BIOME
All life on Earth and its environment
A small part of the planet, but the only part that sustains life
NATS 1840
NATS 1840
NATS 1840
TEST # 1
FALL ASSIGNMENT
LECTURE NOTES
Scientific Notation
OCT 4, 2011
OCT 6, 2011
OCT 18, 2011
Scientific Notation
- For very small or very large quantities, the usual way of writing numbers becomes awkward.
- The more compact way of writing very large or very small numbers is called scientific notation. Based on powers
of ten.
o Given some integer ‘n’, 10n = 10 × 10 × 10 × …. × 10 a total of n times. If n is less than zero, then 10n =
1/10 × 1/10 × 1/10 × …. ×1/10 n times.
- E.g. 74, 000, 000, 000 = 74 × 109
1. Count the number of zeros to set the exponent
2. Multiply by the remaining number
3. If less than 1 then change the sign of the exponent
- E.g. 0.00000000034 = 3.4 × 10-10
- Note: 100 = 1
a) Addition (or subtraction)  (2 × 103) + (7.4 × 104)
= (2 × 103) + (74 × 103)
= 76 × 103 = 7.6 × 104
b) Multiplication  (2 × 103) × (7.4 × 104)
= (2 × 7.4) × 103 × 104
= 14.8 × 107
= 1.48 × 108
Metric (SI) Prefixes:
- When measurements yield very mall of very large quantities it is preferable to express the result in terms of the
‘natural’ scale of the situation
- E.g. 103 metres = 1 kilometre = 106 millimetres
Biogeochemical Cycles: The Cycling of Matter & Energy in the Environment
Preamble:
- Living organisms consume nutrients and energy to thrive
o Six “macronutrients” are constantly recycled – carbon, oxygen, hydrogen, nitrogen, phosphorus, and
sulphur
- Biogeochemical cycles: physical and chemical processes which ensure the exchange of matter & energy between
the biotic and abiotic parts of the ecosphere.
- To understand these cycles, we must understand the nature of matter and energy
Biogeochemical Cycles Part I – Matter
- Matter: anything that takes up space and has mass.
o Composed of atoms of elements which interact chemically with one another to form more complicated
molecules of compounds.
- Elements: basic chemical constituents of matter, i.e. the stuff from which all things are made.
o Each element has distinct physical properties
o Elements cannot be further broken down by chemical means.
- Atom: basic physical unit of an element, i.e. smallest piece of matter that exhibits the properties of that element
o The physical characteristics of an atom determine the properties of the corresponding element.
- Atoms themselves are composed of tiny sub-atomic particles:
o Electrons, protons, neutrons  the basic constituents of all atoms.
- Structure of an atom: Small, dense nucleus of protons and neutrons, surrounded by large, diffuse cloud of
electrons.
o Size: about 10-10 m
- Each sub-atomic particle carries a specific electric charge. The electromagnetic force acts between charged
particles, exerting a force which depends on the charges involved.
o Two positively –charged (+,+), or two negatively –charged (-,-) particles repel each other
o
o
Two oppositely-charged (+,-) particles attract one another
Particles that are electrically neutral (carry on charge) do not experience this force.
 Protons (+) positive charge
 Neutrons (0) neutral charge
 Electrons (-) negative charge
Identity of Atoms:
What gives an atom its particular chemical properties (and determines which elements it corresponds to)?
1. Overall electric charge of the atom
2. Nuclear charge ( = # of protons): Atomic Number
3. Nuclear mass ( = # of protons + # of neutrons): Mass Number
- Atomic number uniquely determines the chemistry of an atom (and the element involved)
- Atoms with different mass numbers but the same atomic number are called isotopes of that element. Isotopes
of an element differ mainly in their nuclear properties.
- Chemical Notation
o E.g. the element with atomic # = 6 => called Carbon, symbol C
 Explicitly…
 6C6 = C12 => put the atomic number on the left of the symbol (6), put # of neutrons on
the right, and the mass # is always above the symbol (C). Anything in the right hand
corner indicates the number of extra electrons.
NATS 1840
LECTURE NOTES
Biogeochemical Cycles (Con’t)
OCT 20, 2011
Noble gases => ‘Closed Shells”
Halogens (F, Cl…)
- One electron of a closed shell
- Want extra electron
Alcali Metals (Li, Na, K…)
- Have one extra electron above closed shell
- Want to get rid of it
Molecules and Compounds:
- Compound: substance consisting of two or more elements whose chemical properties are distinct from those of
its constituent elements
- Molecule: Two or more atoms bound to one another.
o Can involve atoms of the same element, yielding the molecular form of that element, OR
o If the atoms involved are of two different elements, then the molecule is the fundamental unit of a
compound
o Molecules are to compounds as atoms are to elements
Identity of Molecules:
- Identities by names and quantities of their constituent atoms, as well as any net charge. Eg. “carbon dioxide”
means one atom of carbon and two atoms of oxygen, i.e. CO2
- Environmentally important molecules include:
o Molecular Hydrogen – H2
o Molecular Oxygen – O2
o Molecular Nitrogen – N2
o Water (dihydrogen oxide) – H2O
o Carbon dioxide – CO2
o Ozone – O3
o Methane – CH4
o Nitogen Dioxide – NO2
o Ammonia – NH3
- Organic compound: involves chains or rings of carbon atoms
- Carbohydrates: contain mostly carbon, hydrogen, & oxygen. Eg. glucose = C6H12O6
Reactions:
- Processes in which nuclei, atoms, or molecules interact in a manner which changes how they are bound
Ingredients
Products
Reaction
- If products are more tightly bound overall compared to the ingredients, reaction is exothermic – energy is
released (from the ingredients) in the reaction.
- If products are less tightly bound than the ingredients, reaction is endothermic – energy must be added to the
ingredients for the reaction to occur.
Chemical Reactions:
- Only atoms and molecules undergo chemical reactions. Only the electron clouds participate – nuclei are
unaffected and remain intact. As a result, two important rules apply to chemical reactions:
1. Nuclei are conserved. So, the number of atoms of each element remains the same through a
chemical reaction
2. The total charge remains the same through the reaction
- Example: Consider burning methane (natural gas) in air:
o Methane = CH2
o Burning (or combustion) means combining with oxygen (O2)
o CH4 + O2  CO2 + H20 + Heat + Light => reaction cannot happen as written (chemically cannot occur)
o CH4 + 2O2  CO2 + 2H20 + Heat + Light => each side must equal to each other (chemically can occur)
Nuclear Reactions:
- Only the protons and neutrons of the nucleus are involved. They can either be re-arranged or transformed.
1. Fission reaction: A heavy nucleus breaks apart into two or more lighter pieces
2. Fusion reaction: Two or more light nuclei bind together to form a heavier nucleus
3. Decay reaction: A small piece of a nucleus breaks off; or a neutron turns into a proton; or a proton
turns into a neutron
- In a nuclear reaction, the sum of the number of protons and neutrons are unchanged. But, because the number
of protons can change the elements involved change
Two Ecologically Important Chemical Reactions:
- Photosynthesis & Respiration
o Chemical reactions which serve to move nutrients and energy through an ecosystem
- Photosynthesis is an endothermic reaction
o Energy (light from sun) +6H2O (water from hydrosphere) + 6CO2 (Carbon dioxide from atmosphere) 
C6H1206 (glucose stores energy) + 602 (waste by-product ‘oxygen’) + Energy
- Aerobic Respiration is an exothermic reaction
o C6H12O6 (glucose) +6O2 (oxygen from atmosphere)  6H20 (waste water) + 6CO2 (waste carbon dioxide)
+ Energy (useful energy plus waste heat)
- Respiration is how energy stored in food is released for biological work by oxygen-breathing organisms. All living
things respire.
NATS 1840
LECTURE NOTES
OCT 25, 2011
REFWORKS
- Rwyorku  Group code
Chemistry Practice
- Number on top left corner is Atomic mass/Mass number
- Number on top right corner is electron gain/loss
- Number on bottom right is neutrons
- Number on bottom left corner is protons
1. 207  207 Atomic Mass
? Pb125 125 neutrons  82 protons (207-125)
2. C3H8 + O2  4H2O + 3CO2 + heat  BALANCED  C3H8 + 5O2  4H2O + 3CO2
3. Fe + O2 + H2O  Fe2O3(H2O)  BALANCED  4Fe + 3O2 + 2H2O  2Fe2O3(H2O)
NATS 1840
LECTURE NOTES
Biogeochemical Cycles – Part II – Energy
OCT 27, 2011
Work:
- Work is done when matter moves (or changes its state of motion) as a result of the application of a force upon
it.
Energy:
- The ability of a system to move matter through some distance. i.e. the ability to do mechanical work.
Power:
- Rate at which energy is consumed or received or delivered.
- Power = Energy/Time
Forms of Energy:
- Some are closely associated with tangible physical objects, such as atoms. Other forms, such as the energy
carried by light, are less tangible.
- We will be mainly concerned with
o Kinetic Energy
o Potential and Internal Energy
o
o
Thermal Energy
Electromagnetic Energy
Kinetic Energy
- Associated with motion. A moving object has the ability to do work (e.g. in a collision)
- Intuitively, a faster object can do more work than a slow-moving object, and a more massive object can do more
than a light object.
Kinetic energy increases with speed and mass.
Potential Energy
- Represents the ability to do work stored in a physical system that is not in motion.
o Height above ground (gravity)
o Bending/stretching of a solid object (elasticity)
o Electric charge difference between objects (electricity)
o Binding of two or more atoms (chemical energy)
- Often the result of mechanical work done against a force at some prior time.
Thermal Energy
- Kinetic energy associated with the random motion of the molecules making up a substance. Also known as heat.
- Temperature is a measure of the average kinetic energy per molecule in a system.
- E = 3/2 × k × T
o Temp is in °K
o 0 °C = 273 °K
o k = 1.38 × 10-23 J/K
More thermal kinetic energy
Faster moving molecules
Hotter object
Thermal Energy Transfer (Conduction)
- A fast-moving molecule in a hot object collides with slower-moving molecule in a cooler one. Collision transfer
kinetic energy to the slow molecule, and this thermal energy to the cold object.
- Thermal energy flows from hot to cold until both objects share the available thermal energy equally. No further
net energy transfer between the objects. A steady state is reached – both objects have the same temperature.
Thermal
HOT
COLD
Energy
Electromagnetic Energy
- Vibrating electric charge causes ripples in the surrounding electromagnetic (E.M.) field
o Creates a E.M. wave which propagates away from the vibrating charge
- E.M. waves carry energy, since they can do work on other charges; travel at the speed of light (3 × 108 m/s in
vacuum).
-
Any given E.M. wave has a specific frequency and wavelength.
Electromagnetic Energy
- Wavelength  distance between successive cycles
- Frequency  number of full cycles of the wave passing a fixed point in space each second.
- Frequency and wavelength are related in such a way that
Higher Frequency
-
Shorter Wavelength
Greater Energy
Energy carried depends on frequency (wavelength); higher frequencies (shorter wavelengths) correspond to
more energy.
The Electromagnetic Spectrum
-
Long waves (Low Energy)
Radio waves
Infra-red (associated with heat)
Visible Spectrum  Electromagnetic energy in the range of wavelengths
to which our eyes happen to be sensitive.
Short wavelengths (High Energy)
Heat and Electromagnetic Radiation
- Intimately connected in a manner crucial to understanding climate and climate change.
- Example: A rock is exposed to sunlight. Its surface absorbs E.M. energy continuously:
o Molecules average speed increases
o Thermal energy (temperature) increases
ROCK
NATS 1840
LECTURE NOTES
Biogeochemical Cycles – Part II Energy (Cont’d)
ROCK
-
Motion of molecules causes emission of E.M. Radiation
o Rock loses thermal energy in E.M. form at the same time as it absorbs it.
o Frequency of emitted radiation determined by object’s temperature.
NOV 1, 2011
o
The Object ‘glows’
Radiation Equilibrium:
- Constant temperature (steady state) reached when
o (Total energy absorbed)/sec = (Total energy radiated)/sec
- No further net energy build-up in the object
- At night no energy is absorbed, but rock continues to ‘glow’ (lose energy) due to the thermal content. It cools.
- All objects glow in this way. Average frequency of glow increases with object’s temperature.
o ‘Glow’ is distributed over a range of (spectrum) of frequencies with the peak determined by
temperature.
Units of Energy and Power:
- Energy: Metric unit is the Joule (J). 1 J = 4.18 Calories (cal)
o 1 calorie = energy needed to raise temperature of 1 gram of water by 1 degree C.
- Power: Watt (W) defined as 1 Joule per second
o Often, if power is expressed in kilowatts (kW) then energy is given in units of kilowatt-hours (kWh).
o 1 kWh = 1000 W × 1 hr = 3.6 × 106 J = 3.6 MJ
Everyday energy scales – some examples:
- 100 W light bulb on for one hour = 360 kJ
- Clothes dryer running for one hour = 18 MJ
- Human body (one day; at rest) = 6-8 MJ (1600 kcal)
- Car travelling at 100 km/h = at least 460 kJ
- Jumbo jet at take-off speed = at least 1.3 GJ
- JUMBO jet at cruising altitude (11 km) = at least 45 GJ
Energy Transformations:
- Energy can be converted from one form to another. Eg. E.M. energy converted into thermal energy, and vice
versa.
o For tire swing, continuous conversion of potential energy (1) into kinetic energy (2) and back again.
o At intermediate stages the energy is partly kinetic and partly potential (3)
- Example (Car being pushed a hill and brought down a hill):
o Chemical potential energy (from food) transformed to potential energy by driver as car is pushed uphill.
When car comes down potential energy converted to kinetic energy. After engine starts, chemical
energy in fuel converted to kinetic energy (and heat)
-
Energy transformations are subject to two fundamental rules with profound consequences for the ecosphere.
o The Laws of Thermodynamics
 First Law of Thermodynamics:
 In any physical or chemical change energy can neither be created nor destroyed, but
only transformed from one form to another.
 For a closed system (no energy in or out), total energy is a constant.
 Earth isn’t a closed system, but the Sun is our only external source of energy.
o Must make do with whatever energy we receive from the Sun plus whatever is
already stored in the ecosphere.
 Second Law of Thermodynamics – Entropy:


A physical process only occurs spontaneously if the net result is an increase in the
entropy of the universe.
 Entropy: A measure of the level of disorder in a system
o Disorder = homogeneous (featureless)
o Entropy increase is not spontaneously reversible.
 E.g. Two cups of water, one hot and one cold – mix them.
o Will they ever ‘unmix’? Practically impossible.
 Local decrease of entropy possible if energy is expended, and if entropy increases
somewhere else.
o Order in ecosphere results from solar energy input
o Solar fusion reactions increase entropy greatly.
Second Law of Thermodynamics – Conversion:
 When energy is transformed from one form to another, some is always degraded to a
less useful form.
 Energy quality: an intuitive description of how easily useful work can be extracted from
a given course of energy
o Very High Quality
 High-temperature heat
 Electricity
 Nuclear fission
 High-speed wind
 Concentrated sunlight
o High Quality
 Gasoline
 Natural Gas
 Coal
 Food
o Low Quality
 Low-temperature heat (below 100 C)
 Dispersed geothermal heat
Conversion Efficiency:
- Laws of thermodynamics are unforgiving. First, we cannot create energy from nothing. Second, we can’t even
break even!
- Ratio of remaining useful energy, after transformation, to input energy is called conversion efficiency.
- Efficiency = Useful energy (output)/Input Energy
- For Heat Engines => Efficiency = 1 – TC / TH (Temperatures must be in degrees Kelum)
- Selective efficiencies:
o Electric generator = 99%
o Oil furnace = 65%
o Cellular respiration (food to energy) = 40%
o Automobile engine = 25%
o Fluorescent lamp = 20%
o Incandescent light bulb = 4%
o Photosynthesis = 2 – 5%
NATS 1840
LECTURE NOTES
Biogeochemical Cycles Part III – Energy Flow
NOV 3, 2011
The Sun (our source of energy)
- All of the energy available on Earth comes to us from the Sun.
- Facts about the Sun:
o Size: 110 × Earth (diameter)
o Mass: 330, 000 × Earth
o Temp: 6000 degrees (surface), 10 7 (core)
o Composition: 90% Hydrogen, 10% Helium
o Energy source: Hydrogen fusion
- Sun’s power output varies continuously, but with some regularity.
o 11-year sunspot cycle correlated with solar output
o Brightness (output) on a long term increasing trend; has probably resin by 25% since protostar phase.
- When supply of hydrogen runs out, Sun will die out and become a white dwarf….in about 5 billion years
Earth (our home)
- Distance from Sun: 150, 000, 000 km
- Diameter: 12, 745 km
- Mass: 5.9 × 1024 kg
- Age: 4.6 billion years
- Lithosphere: Solid rock crust floating on a liquid interior.
- Hydrosphere: Temperature allows liquid water (71% of surface)
- Atmosphere: Mainly nitrogen (78%) and oxygen (21%)
Solar Energy Revised:
- Earth intercepts only a fraction of Sun’s total power output. An average about 1360 W/m2 (the solar insolation)
at top edge of atmosphere.
- Most of this energy is delivered in the form of visible light.
- Amount of solar energy that reaches surface and is absorbed by planet also depends on:
o Albedo
o Chemical composition of the atmosphere
Albedo:
- Amount of power reflected away from the Earth (or any planet), expressed as fraction of incident power.
Depends on nature of surface and of atmosphere.
- Albedo = (power reflected)/(power received)
- High Albedo
More power reflected
Less power absorbed
Cooler (all else being equal)
- Clouds and ice have high albedo, water, rocks and forests have low albedo
- Earth’s average albedo: about 30%
Chemical Composition of the Atmosphere:
- A given gas allows EM radiation (light) to pass through at some frequencies, but strongly absorbs others.
- Some atmospheric gases strongly absorb the sane range of infra-red EM frequencies which the surface of the
Earth emits as a result of its temperature.
Greenhouse Gases (e.g. Water vapour [most significant], carbon dioxide, methane….)
-
Ozone in the upper atmosphere also strongly absorbs light at ultra-violet frequencies.
The Greenhouse Effect:
- Without greenhouse gases average surface temperature would be about 33 degrees colder than it actually is.
- Because of atmospheric greenhouse gases atmosphere, Earth must raise surface temperature by about 33
degrees to achieve a steady state.
- Atmosphere acts as blanket, ensuring a warmer temperature than would otherwise be the case. This is
greenhouse effect.
Net Energy Input to the Ecosphere:
- 30% of incident solar energy is reflected (albedo), atmosphere and clouds absorb 25% and most of remainder is
absorbed by surface (hydrosphere and lithosphere). A mere 0.023% (!) is absorbed by biosphere via
photosynthesis.
Energy Flow in the Biosphere:
- Organisms in the ecosphere feed on one another. Energy is transferred along a food chain.
- Different organisms occupy different positions along a food chain. Positions are based on organisms’ diet and
are called trophic levels.
- Its trophic level reflects how far removed (how many feeding levels away) an organism is from the original
source of energy in its ecosystem.
1st Trophic Level: Autotrophs
- Organisms that absorb energy directly from environment and make their own food. Also called producers.
- Autotrophs use some of their production (the food they make) to satisfy their own needs (growth,
reproduction). The rest is stored in their tissues. Amount of stored energy is organism’s net primary production.
- The total net production of all autotrophs in an ecosystem is its primary production.
2nd Trophic Level: Primary Consumers
- Animals are not able to make their own food. Such organisms are called heterotrophs. Heterotrophs that feed
directly on autotrophs (i.e. herbivores) are called primary consumers.
3rd Trophic Level: Secondary Consumers
- Heterotrophs who feed exclusively on primary consumers. In other words, some carnivores.
4th Trophic Level: Tertiary Consumers
- Heterotrophs that feed only on secondary consumers, i.e. carnivores who eat other carnivores.
- Usually at the top of the food chain in a given ecosystem.
Omnivores:
- Heterotrophs that can feed at any trophic level.
Detrivores:
- Wastes and dead matter (detritus) from all trophic levels are consumed by organisms called detrivores (or
decomposers)
- Break down organic matter into simpler nutrients, allowing for recycling in the ecosystem.
Food Webs and Thermodynamics:
- Why so many producers and so few tertiary consumers?
o Loss of degradation of energy
- Second law limits efficiency of energy transfer from one trophic level to another. At best, 10%.
o Rest used by organisms in the lower level and ultimately lost as waste heat.
- Feeding at lower trophic levels means access to more of primary production
- Earth can sustain more herbivores than top carnivores. (Eating more grains/vegetables, and less meat, might be
a way of increasing food supply)
NATS 1840
LECTURE NOTES
Biogeochemical Cycles – Part IV Matter Cycles
NOV 8, 2011
Generic Matter Cycle
Carbon Cycle
- Carbon is backbone of all life on Earth. Organic molecules provide structure, food, etc. for living things.
- Found in the
o Biosphere (in living organisms)
o Lithosphere (in sedimentary rocks)
o Hydrosphere (dissolved CO2 gas in oceans and lakes)
o Atmosphere (CO2 gas)
- Continuously exchanged between all compartments
-
CO2 gas is only 0.03% of the atmosphere, but the exchange between air and the biosphere is at the root of the
carbon cycle.
Carbon Cycle
-
-
-
Most Carbon stored in
o Sedimentary rocks (lithosphere)
o Oceans (hydrosphere)
Only one way to remove CO2 from the atmosphere, but many ways to add it.
o Cutting down trees;
o Burning fossil fuels;
o Increased water acidity
o Warming oceans
These processes increase the rate at which CO2 is returned to the atmosphere, but none increases rate at which
it is taken out again by plants.
Hydrologic Cycle
- Water cycle driven by solar energy, causing evaporation of surface water. Water vapour carries this energy in
thermal form.
o Vaporization of 1kg of water requires 2260 kJ
o Energy released to air upon condensation
-
Flowing water shapes surfacing of the Earth over long time scales. Flowing water transports vital biological
nutrients.
Other Cycles:
- Other macronutrients also cycle through the ecosphere
o Nitrogen
o Phosphorous
o Sulphur
o Calcium
- In all cases, the biosphere plays a crucial role in the cycle.
Biogeochemical Cycles – Closing Comments
- Matter is continuously recycled in the ecosphere via
o Biological processes
o Chemical processes
o Geological processes
o Physical processes
- Matter can neither be created nor destroyed and the Earth is a closed system with respect to matter. The
ecosphere must make do with the limited resources that are already here.
- Ecosphere continuously receives solar energy, which flows through the ecosphere providing
o Warmth for the atmosphere and oceans
o Energy for the hydrologic cycle
o Food for living organisms via photosynthesis
- Each time energy is transformed, some of it is degraded into low quality (useless heat)
o Energy is not recycled.
- Key feature of biogeochemical cycles: ‘bio’ part, i.e. the important role played by life itself in establishing
prevailing environmental conditions…
NATS 1840
TEST # 2
NOV 10, 2011
NATS 1840
LECTURE NOTES
Life I – Origins & Chemistry
NOV 15, 2011
In the Beginning….
- Planets formed from same cloud of gas and dust as the Sun, about 4.6 billion years ago
- Being made of the same ‘stuff’, terrestrial planets were very similar to one another at first
- Earth has changed significantly. Current conditions on Mars and Venus suggest what primordial Earth may have
been like
Primordial Atmosphere:
- Earth’s original atmosphere probably looked much like those of Venus and Mars today.
- Gases likely to have been present include:
o Carbon dioxide (CO2)
o Nitrogen (N2)
o Water (H2O)
o Methane (CH4)
o Ammonia (NH3)
o Hydrogen Sulfide (H2S)
o Hydrochloric Acid (HCI)
o Molecular Hydrogen (H2)
- Notice absence of molecular Oxygen in the list (O2)
Origins of Life:
- Accepted scientific view of our origins begins with conditions on the newly-formed planet Earth
- Early environment likely featured:
o An unpleasant atmosphere
o High ultra-violet (UV) radiation from the Sun
o Frequent lightning discharges
- Is it plausible that life appeared under such conditions?
o Yes
Chemical Basis of Life:
- All known life forms are built up from organic molecules.
- Many of these molecules are gigantic. Such macromolecules involve thousands of atoms and come in four main
types:
o Proteins – form the basis of every component of an living organism
o Nucleic Acids (DNA, RNA)
o Carbohydrates (sugars)
o Lipids (fats)
- All are polymers made up of chains of simpler molecules called monomers.
Proteins:
- Composed of one or more chains of amino acids, folded into a unique shape.
o Tens of thousands of different proteins, each with a specific function. Classified into 7 groups:
 Structural proteins
 Contractile proteins
 Storage proteins (for developing embryos)




Defensive proteins
Transport proteins
Signal proteins
Enzymes (regulators)
Nucleic Acids:
- Direct the manufacture of proteins.
- Building blocks are nucleotides, which form a chain.
o Sugar-phosphate chain with nitrogenous base appendages.
Nitrogen-Containing Organic
Base
Phosphate
PO4-2
o
-
5-Carbon-Sugar
Only 5 distinct nitrogenous bases: A (adenine), G (guanine), C (cytosince), T (thymine), U (uracil)
Two forms of nucleic acids exist in all living cells
Deoxyribonucleic Acid (DNA)
- Two chains of nucleotides joined at the bases, and twisted.
o Only A-T or G-C base links are allowed
o Sugar is deoxyribose
o Has a double helix geometry
-
DNA encodes hereditary information on how to make proteins.
Ribonucleic Acid (RNA):
- Only one chain of nucleotides, with exposed nitrogenous bases.
o Bases are A, G, C, and U (thymine is replaced with Uracil)
o Sugar is ribose
o Has the geometry of a ribbon
- RNA decodes hereditary information found in DNA, and directs protein production accordingly.
Protein Production (Schematic):
- Each three-base codon in a DNA molecule corresponds to a specific amino acid. A DNA molecule contains many
distinct sequences of codons, each defining how to build a specific protein. Such a sequence is called a gene.
o DNA molecule ‘unzips’ at the gene for the desired protein.
o RNA assembled from free nucleotides to match gene base sequence (transcription)
o RNA leaves cell nucleus; DNA ‘rezips’
o RNA enters a protein factory inside cell
o Amino acids assembled according to RNA codon chain
o RNA is disassembled.
DNA Replication
- When cell reproduces (divides into two by mitosis), hereditary information in nucleus must be copied.
o DNA starts to ‘unzip’ at one end, exposing base pairs
o Free nucleotides bind to their counterparts on each half of the original molecule.
o Result is two identical copies of original molecule. Each cell gets one of the molecules.
Urey-Miller Experiment (1952)
- Tried to reproduce conditions believed to have existed on Earth after outer crust solidified.
o H2, H2O, NH3, CH4 combined in a flask;
o Electrical sparks generated in flask to simulate lightning
-
-
-
After one week, flask contained a reddish-brown ‘muck’
Substance was found to contain
o Hydrocarbons (lots)
o Amino Acids (2%)
Recall, amino acids are the building blocks of all known proteins.
Experiment demonstrated that
o Organic molecules can be synthesized from inorganic ingredients without the presence of life
o Amino acids appear readily in the process
Our understanding of Earth’s primordial environment has changed since 1952. But experiment’s fundamental
conclusion has withstood the test of time.
Conclusion  Life was likely a natural outcome of conditions which prevailed on Earth 4 billion years ago.
Chemical Evolution
- First billion years witnessed slow but steady chemical evolution
o Exactly how increasingly complex organic molecules combined to form living organisms is not known.
- ‘Clumping’ hypothesis proposes that increasingly large assembles of organic molecules formed at random
o ‘Clumps’ which were most adapt at processing matter and using energy became the first protocells.
- A proof of principle experiment is still awaited….
The Big Picture
Traits & Their Chemical Basis:
- Trait  a single feature or quantifiable characteristic of an organism. Result of many biochemical processes
involving specific proteins.
o E.g. Hair, skin, eye colour, gender, ability to break down lactose, etc.
- Nucleus of each human cell contains 46 chromosomes which work in pairs to set traits.
o Single highly-coiled molecule of DNA
o Each has a counterpart that carries information about the same traits (one from each parent)
o Slight variations in the genes on each member of a pair (different alleles) possible, corresponding to
differences in the relevant trait (eg. brown eyes vs. blue eyes)
Mutations:
- Sometimes, DNA replication goes awry resulting in changes in a gene sequence. Such a change is called a
mutation.
- Changes in DNA lead to changes in RNA and thus in the proteins encoded
- Most mutations are fatal to the affected cells. But sometimes a mutation occurs that creates a new viable allele
of a gene, i.e. a new version of the associated protein.
- A viable mutation in a sex cell of an organism may be passed onto future generations. This phenomenon drives
evolution.
Basic Genetics:
- Not all alleles of a gene are equal (biochemically)
- Suppose gene for some trait has only two alleles. One of them is dominant (D) – will be expressed – and the
other is recessive (R) when they are combined in a cell.
- When chromosomes of a mother and father are mixed there are three possible genotypesfor any offspring with
regard to this trait:
DD, Dr, rD, rr
-
Inherited from mother
Inherited from father
If individual’s genotype includes at least one dominant allele of the gene, then the dominant versionof the
associated trait results. The expressed trait is the organism’s phenotype.
The recessive form of the trait is only expressed if both genes are of the recessive allele
NATS 1840
LECTURE NOTES
Life II – Evolution & Diversity
NOV 17, 2011
The First 2.5 Billion Years….
- Life first appeared 3.5 to 4 billion years ago in top layers of the oceans and/or in shallow muddy sediments.
- First living organisms had to be producers.
- Prokaryotic cells:
o No nucleus
o Anaerobic
o Obtained energy directly from methane & sulfur compounds, i.e. chemoautotrophs
The Oxygen ‘Catastrophe’
- Photosynthesizers appeared about 3 billion years ago, causing a major problem!
o Changed the composition of the Earth’s atmosphere (over time) by introducing oxygen
o Many organisms poisoned by oxygen, or had their food supply destroyed by it
o Biggest pollution crisis ever
- Organisms that could use oxygen to extract energy from carbohydrates became dominant
- Introduction of oxygen in atmosphere led to the formation of the ozone layer, which filters out UV radiation
o Allowed life to emerge from the oceans onto land (about 1 billion years ago)
Eukaryotes
- Cells have distinct nucleus containing genetic material
o Appeared 1.5 – 2.0 billion years ago
o Complex cell structure, with many organelles
o Resulted of symbiosis and fusion of prokaryotes
o Basis of multi-cellular life forms, including plants and animals
ANIMAL CELL
PLANT CELL
Evolution of Life
Biodiversity:
- The variety of different species and the genetic variability within a species.
- Biologists classify all living things into five major kingdoms
-
-
-
How can the observed level of diversity b explained?
o Random errors may occur during DNA replication
o Some errors lead to new alleles of a gene
o Environmental conditions dictate which traits survive
Charles Darwin and Alfred Russel Wallace proposed (1858) a way of understanding the propagation and variety
of traits.
o Followed 20 years of observations and reflection
Evolution through Natural Selection
Evolution through Natural Selection
- Basic description of theory includes six ideas, some of which are based on observation, and others on reasonable
conjecture.
o Species are fertile enough to quickly overpopulate their habitats.
o The resources in any given habitat are finite.
o Therefore, there must be intense competition between individuals of each species for the available
resources.
o Because of natural heritable variations within a species, it is reasonable that survival is in part influenced
by genetic differences in abilities.
o
-
Individuals that are more capable have a better chance of surviving long enough to reproduce. Their
genetic attributes will be disproportionately represented in future generations.
o Over long periods of time, such natural selection leads to evolutionary changes within populations, and
eventually to the evolution of new species.
“Survival of the Fittest” = Ability to produce offspring
Microevolution
- Minor changes in a trait within a population of species.
- Usually, in a population, most individuals exhibit one particular allele of a trait as a result of environmental
pressures.
o Environmental change can modify allele frequency
Stabilizing Selection
Directional Selection
Disruptive Selection
Example: The English Pepper Moth
- Most common colour is whitish tan, with fewer individuals having darker or lighter colouring
o Difficult to see against bark of lichen-covered trees
o Uncommon (darker & lighter) colours are easier for predators to see
- Coal soot blackened bark of trees in England in early 1900’s
o Some populations of pepper moth became noticeably darker since darker individuals now had the
advantage
- Population-level genetic change, driven by external pressure
- With reduced pollution the number of darker moths has dropped once again
Recap
- Natural variation determined at molecular level (allele of genes)
- Prevalence, or frequency, of alleles in a population determined by environmental conditions
- Before it can be the most common, a trait must first exist within a population
NATS 1840
LECTURE NOTES
Life II – Evolution & Diversity (CONT)
NOV 22, 2011
Speciation (Macroevolution)
- New species result from long-term evolutionary divergence of populations.
o Might result from migrations, or other causes of physical/environmental isolation
o Physical isolation, followed by longer periods of microevolution, leads to reproductive isolation
Evolution – Common Misconceptions Clarified:
- Populations evolve. Individuals do not.
- “Fittest” does not refer to physical strength. The fittest individuals are those able to leave most descendants
- There is ‘no plan.’ Genetic mutations underlying evolution appear to be completely random
Evidence for Evolution:
- Comparative Anatomy
o Structural features common to many species of plants or animals, suggesting a common lineage
 Eg. limb structure in four-legged animals
 Eg. insect mouth parts
 Eg. basic structure of flowers
- Fossil Record
o Chronological arrangement reveals changes in structure and complexity
o Reveals species that are now extinct
o Comparison with today’s organisms shows progression of common features
o Limited by rarity of fossils – there are gaps in the record
Filling the Gaps – Example: Tiktaalik
- A link between fish and tetrapods (four-legged animals). Now extinct, the species names Tiktaalik had
o Gills and scales
o Half-fish and half tetrapods limbs – wrist joint with fins instead of toes
o Tetrapods ribs, lungs and mobile neck
More Evidence of Evolution:
- Comparative embryology
o Similarities in the early stages of embryo development
- Comparative biochemistry
o Common chemical basis of all living organisms; DNA, RNA, ATP, proteins
o Similarities/differences in genetic sequences
- Experiments in speciation
o Populations subjected to different environment conditions observed to become reproductively isolated.
Long-Term Evolution in the Lab:
- (Blount, Borland, and Lenski, June 2008)
- Twelve initially identical E. Coli populations founded in 1988
o Allowed to evolve under identical conditions in a glucose growth medium also containing citrate
o E. Coli cannot use citrate under normal conditions
o Sample of each population frozen every 500 generations
o Ability to use citrate appeared in only one population and only after 31, 500 generations – one rare
mutation, or a specific sequence of ‘ordinary’ mutations?
o In ‘replays’ using frozen samples, only the original population re-evolved the trait, and only if the replay
began after the 20,000th generation
- Crucial mutation occurred by the 20, 000th generation which enabled later appearance of citrate-use trait
Extinctions:
- Fossil record also reveals mass extinctions, which occur on a regular basis
- Perhaps in periods of rapid or catastrophic environmental change
o Earthquakes
o Meteor impacts
- Slower ongoing changes cause lower background extinction rate of between 1 and 5 species per year.
- 99.9% of all species that have ever existed are now extinct.
Why Biodiversity Matters
- Each species contains some distinctive genetic material , the result of 3.5 billion years of evolution
- Biodiversity is a valuable store of potentially useful genes
o We can now make use of existing genes, but we can’t make new (viable) genes
- Within a species, diversity improves the chances of its survival
o Our increasing reliance on only a few varieties for our food poses a potential risk
- Diversity also has an intrinsic value by mere virtue of its existence
Modern Extinctions
- Since the appearance of modern humans, rates of extinction have increased due to
o Hunting, fishing
o Deforestation to make room for farming
o Disruption and pollution of habitats
o Introduction of exotic species into ecosystems
o Monocultures
- Increased rates of extinction pose a threat to biodiversity
NATS 1840
LECTURE NOTES
Humanity’s Effect in the Atmosphere (PART 1 – CLIMATE CHANGE)
NOV 24, 2011
Preamble:
Highly charged and politicized topic.
- Claims that “debate is over” common;
- Skeptics vilified and questions unanswered;
- Vast sums of money at stake and possible planet’s climate status quo
What follows is sampling of climate change science, including some important open questions
- It isn’t possible to prove a scientific hypothesis i.e “end the debate”
- It’s possible to establish strong support for it.
- Details are important in judging strengths of support
Observations-climate:
- Measurements suggest that Earth’s average surface temp is rising on short time scale- ‘Global Warming’
- Increase in mean temp since 1880:0.76 +/- 0.2 °C
Further Evidence
- Receding Polar ice
- Rising sea level
Anecdotal evidence
- Heat waves
- ‘Extreme’ weather
- Changes in migrating habits
Some factor which determines climate change must be changing…
What factors govern climate?
- Distance to sun:
o Properties of Earth’s orbit are variable
o Cyclic changes occur in shape of orbit, inclination of Earth’s axis, and direction of that axis
o These changes may be responsible for ice ages
- Suns Power output
o Changes by 0.1% over 11 year cycle
o More sunspots corresponding to higher power output
o Unclear connection to climate variations
- Earth’s Albedo:
o The fraction of solar energy reflected back into space
o Changes in land use, shrinking ice coverage, and increase atmospheric dust all contribute to changing
planetary albedo:
 Decrease albedo means that the earth is becoming more efficient at absorbing solar energy
- Composition of atmosphere:
o Greenhouse gases (GG) trap outgoing I.R radiation in atmosphere neutral greenhouse effect.
o Scale of effect depends on GG
o GG would enhance greenhouse effects
Earths thermal steady state;
- Two major components: surface and atmosphere
o Each must be in a steady state to have a constant temperature
o If both atmosphere and surface are in a steady state (overall), than the whole planet is also in steady
state
Energy absorbed and re-emitted to differing degrees by different components.
- Detailed exchanges of energy between atmosphere and surface critical to life on earth.
Earth’s energy budget: pic on moodle
What are the major greenhouse gasses?
- Water vapour:
o Includes clouds and suspended moisture;
o Responsible for most of greenhouse effect (66-89%)
- Carbon dioxide:
o Produced in biological and physical processes;
o Produced by combustion of organic matter
o Responsible for 9%-26% of greenhouse effect
- Methane:
o Produced of decomposition
o Produced in large amounts by cattle herds (ruminants)
o 25 times more efficient at trapping heat than carbon dioxide
o Responsible for 4%-9% of greenhouse effect
NATS 1840
LECTURE NOTES
NOV 29, 2011