Population Biology I: Population Growth

A population is agroup of organisms of a single species that live and reproduce in the same area.

Types of variables
State variable: ratio
Rate variable: how fast a state variable changes

Single species model
Starts out with continuous exponential growth.
Exponential growth is the first principle of population dynamics. A population will grow exponentially as long as the environment remains constant.
A continuous model implies rapid feedback, continuous births, and overlapping generations. Uses differential equations.
A discrete model implies births in specific periods, non-overlapping generations, and uses difference equations.

Nt = population size (number of individuals) at a certain time 't'.
N0 = initial population size (at time 0)
B = Total Births
D = Total Deaths
I = Immigration
E = Emigration

Nt = N0+B+I-D-E

Assuming a closed system, there will be no I nor E, thus Nt = N0+B-D
Nt - N0 = B - D
∆N = B-D

b = birth rate per capita
d = death rate per capita
r = intrinsic rate of increase; r is species-specific and can change within a species
r = b-d

∆N = B-D
∆N = bN-dN
∆N = (b-d)N
∂N/∂t = (b-d)N
∂N/∂t = rN

Nt = N0e^(rt)

Doubling time: time it takes to double the population

tdouble = ln(2)/r

Discrete exponential growth

lambda = Nt/N0 (N at a future time/initial population)
lambda = finite rate of increase
lambda > 1.0 population increases
lambda = 0 population constant
lambda < 1.0 population decreases

Best estimate of lambda occurs when the population reaches a Stable Age Distribution (SAD).
SAD: relative proportion of individuals in each class remains constant

Nt = lambdaN0

Two models converge when the time step (interval) in the discrete model becomes shorter. It allows conversion from one model to the other.

lambda = e^r
r = ln(lambda)

Probability of extinction
Pex can be seen as a function of N0
Pex=(d/b)^N0
A lower initial population increases the probability of extinction.
Highlights the importance of population size for persistence of populations.

Life Histories II: Allocation

Principle of Allocation
Organisms have a limited amount of energy to spend so they much allocate it to competing demands.
How are resources divided among life history stages or functions?

Energy Budget
C = P - R - (U + F)

C = energy consumed
P = production (excess energy)
R = respiration
U = urea
F = feces
(U+F = W; waste)

Growth/Reproduction Tradeoff
The excess energy must be used either for growth or reproduction. It is a dynamic situation and it is not characteristic of an organism's entire life history.
Examples:

• Douglas fir width of growth rings vs. number of cones per tree
• Goldenrod increased biomass dedicated to reproduction when found in sunny areas.

Parent/Offspring Conflict

There is an optimum energy expenditure from the parents in order to ensure offspring fitness. Beyond that point there is decreased return of energy expenditure.

Size/Number Tradeoff

The optimal number and size of eggs to produce occurs at intermediate clutch sizes. 

Observed in birds, mammals, lizards, amphibians

Mean fitness of offspring is inversely proportional to the total number of offspring produced.

Example: lizards fed to satiation still exhibited similar, albeit weaker, pattern.

An alternate hypothesis is that hatching mass is limited by maximum body capacity rather than by energy.

Effect of offspring survival as a function of size: Bryozoans; larger egg size, better survival

Size vs. Number in Varying Quality of Environment for Offspring

As environmental quality deteriorates, the organism should produce fewer and larger gametes.

Shell vs. Tissue Growth

Seen in Littorina snail preyed upon by crabs. 

Allocation to defense vs. maintenance

Crab chemicals cues influenced shell growth

Clonal, Modular, and Unitary Organisms

Clonal organisms can respond quickly to environmental conditions to take advantage of resources to reproduce.

Unitary/Aclonal

• Germ line separate from somatic cell line. (Germ line - reproductive)
• Fixed cell fates
• Body form is highly determinative

Clonal

• Cell fates are not fixed. Great deal of plasticity.
• Body form is indeterminate. There is an ability to change body type or body plan.

Within clonal organisms, there can be modular an non-modular organisms.

Modular

• Grow by repeated iteration of parts
• Bryozoans, corals, ascidians

Non-modular

• Do not grow by repeated iterations of parts
• Lizards, plants, aphids, daphnia

Clone: assemblage of individuals genetically identical by descent.

Genet: whole organism of one genotype

Ramet: clonally produced part of genet

Being clonal can sometimes yield a competitive advantage.

Clonal organisms can reproduce asexually by fission, fragmentation, budding, parthenogenesis.

Consequences of cloning

Advantages:

• Enables fit genotypes to be inherited intact
• Enables rapid colonization, particularly over short distances
• Reproductive output doesn't necessarily decrease with age.
• Rapid utilization of food resources
• Polymorphism: specialization of modules for different functions
• Can survive partial mortality
• Reduce risk of genotype mortality by replicating parts of clone

Disadvantages

• Mutational meltdown: accumulation of deleterious mutations
• Inability to respond quickly to environmental change via natural selection due to loss of genetic variation
• May have poor long distance colonizing ability
• Fission may divide organism into smaller than optimal body size

Life Histories and Dispersal

Life history refers to the schedule of reproduction, along with the allocation tradeoffs of reproduction and survival.
Dispersal is the spread of reproductive products (propagules, larvae, seeds) or individuals (juveniles or adults) from a single source. It is molded by natural selection.

Reproductive strategies: Frequency of reproduction during lifetime

1. Iteroparous: organisms reproduce more than once
• Benefits: Many chances to increase fitness
• Costs: Continued allocation of energy throughout lifetime
• Mast seeding: episodic, synchronous production of large seed crops by a population of plants. Masting is geographically disperse.
• Maple trees
• Fruit trees
• Lowland rainforest trees
• Conifers
• Oaks
• Beech
2. Semelparous: organisms reproduce only once
• Benefits: Delay the cost of reproduction and allocate energy to growth and maintenance.
• Advantages: Often associated with mortality (ultimate loss of fitness)
• The investment of reproduction is sometimes too great that the organism dies. 
• Bamboo
• Squid
• Yucca century plant

Three major hypothesis for the origin of masting

1. Predator satiation
• Reduce per capita seed mortality; swamp predator (especially specialists)
2. Wind pollination
• Increase chances of fertilization; no animals
3. Environmental facing (prediction)
• Species track weather
• Masting after El Niño rains
• Fires in Australia synced to masting
• New hypothesis: difference in temperatures between two and one years previous to masting

'r' vs. 'k' selection

Population growth curve for r-selected species is exponential.

r = intrinsic rate of increase

dN/dt = rN

Traits:

1. High reproductive investment
2. High dispersal
3. Poor competitor

Examples:

• Weedy species
• Invasive species
• zebra mussels
• cheat grass
• purple loofstrife

Population growth curve for k-selected species is logistic.

k = carrying capacity; limit to population size set by resources.

dN/dt = rN(1-N/k)

Traits:

1. Low/Moderate reproduction investment
2. Lower dispersal
3. Good competitors

Examples:

• Some tree species
• Some corals

Dispersal

All organisms can exhibit three subtypes of dispersal

1. Fragmentation: organisms break and disperse
2. Migration: adults and juveniles
3. Individuals of new generation

Why should organisms disperse?

• Disperse away from habitat with poor resources or low amounts
• Increase survival by reducing competition
• Spread genotypes in place where they'll have high fitness
• Prevent local extinction by maintaining connectivity among populations
• Dispersal can save species from extinction

Escape hypothesis

"Get away from parents". 

Survival increases with increased distance from parents.

Selective force for dispersal; escape high mortality close to parents

Sources of high mortality

1. High competition for resources; low light, low nutrients
2. High predation on seeds; seed shadow; predators aggregate near base of tree
3. Pathogens; high risk from molds or fungi

Janzen-Connel Model

Hobbel Model

Exact Compensation Model

Dispersal distances

Short distance dispersal

• Seeds (maple seeds); propagules
• Sea palms: drip zoospores
• Ascidians: asexual fragmentation

Long distance dispersal

• Pacific trade winds
• Dominance of passive dispersal

Dispersal vectors

• Animals: seeds ingested and defecated
• Wind
• Seed burrs: hooks attach to animals

Behavior can influence dispersal. Example: bellbirds drop seeds away from canopy when showing off for females

Behavioral Ecology I - Foraging

Foraging refers to a species eating habits - what to eat, when to eat, where to eat, and when to stop feeding in a certain area. Foraging is molded by natural selection. Essentially, energy gained by feeding affects reproduction and without food there is no survival.

Energy consumed either gets absorbed or is voided as feces. From the energy absorbed, some of it is lost through respiration, digestion, tissue maintenance and movement. The energy left is used for growth. The energy is divided into energy used for somatic growth and energy used for reproductive output. (There are allocation tradeoff, but more on that later.)

Consumer types

There are several consumer types. Although they can be grouped into specialists and generalists, these are not discrete categories, but rather a continuum.

• Monophagous: 1 prey type
• Oligophagous: few prey types
• Polyphagous: many prey types

However, for comparison purposes, we will classify consumer types into two broad categories.

1. Specialists: Feed on one/few type(s) of prey.
• Advantages include being adapted to one single prey, which means they can overcome prey defenses. There is less competition.
• Disadvantages include the risk of prey extinction, making them vulnerable. There may also be nutrition problems due to unmixed diet. In areas of low prey population density, there is an increased search time.
2. Generalists: Feed on multiple types of prey.
• Advantages include low search time and diffused effect of prey toxins.
• Disadvantages include a high or strong interspecific competition. Generalists are also vulnerable to prey defense due to lack of local adaptation.

Optimal Foraging Theory

Optimal Patch Use Model

This model describes the ideal pattern a species should follow to obtain the maximum energy gain. This model takes into account certain assumptions:

1. Food is found in discrete patches
2. No energy is gained when traveling from patch to patch
3. Consumers can assess food's energy value in a patch

The model is represented as an energy gain curve. There's an optimal time to remain in a given patch and an optimum energy gain described by the tangent (with the steepest slope) to the energy gain curve.

Marginal value theorem: Optimum time to reside is defined by the rate of energy gain at the time of leaving the patch.

[Foxglove flower example]

Optimal Diet Model

Maximum foraging is calculated by E/T where E is the energy content and T is the total time spent searching and handling prey. 

T = s + h (searching + handling)

Organisms can behave as time minimizers or energy maximizers.

1. Time minimizers
• Minimize time to gain specific amount of energy
• Mouse - high risk of predation
• Antelopes - males minimize foraging to defend females against other males.
• Snails feeding on barnacles - eat small barnacles quickly, whereas eating large barnacles takes longer
• Prefer small barnacles due to less risk of predation
• Large barnacles expose snails to predators
2. Energy maximizers
• Focus on increasing prey profitability
• Bison, deer, penguins, birds, sunfish

Prey profitability

The profitability of a specific prey can be obtained by dividing its energy content by its handling time (E/h). Handling time refers to the time it takes a predator to attack, kill, and consume a prey once it has encountered it. This is assuming a simple system where there are only two prey types.

Rules of thumb:

(assuming prey type 1 is more profitable than prey type 2)

• If a predator encounters prey type 1 eat it on the spot. Always eat.
• If predator encounters prey type 2, eat if the gain from eating it exceeds the gain from rejecting it and searching for prey type 1.
• if E2/h2 > E1/(s1+h1) where s1 is the additional search time.

Other important notes:

1. A predator will specialize on a prey type only if its search time is low
2. A predator will switch from a specialist to a generalist as average search time for prey 1 increases

Simplifying assumptions of OFT Models:

1. A predator can sense the energetic value of a prey
2. Foraging behaviors are heritable
3. The model only considers 2 prey types
4. Energy content is the only influence on prey choice. (Does not consider other factors such as salt, H2O, etc.)

It is a simplistic theory, but there is a great amount of evidence that supports it.

Scaling

Scaling means relating an organism's body size to an entity of process. It is usually done with power functions. Body size is important because it affects a variety of aspects:

1. Metabolisms
2. Growth and shape
3. Survival
4. Impact of predation and competition
5. Population density and growth
6. Territory area
7. Food acquisition
8. Species diversity
9. Reproduction

Some key aspects to consider:

1. There are general scaling rules that apply across organisms
2. Scaling relationships can be inter-related producing counterintuitive insights.

Power functions

Y= Yom^b

log(Y) = log(Yo)+ b*log(m)

m=mass

b= predictive of slope.

Log transformations allow a better appreciation of the slope of the function.

b = 1.0 means it is isometric, which indicates that the process/pattern to mass ratio is 1:1. (This is rare)

b ≠ 1.0 means it is allometric

b = 0 means there is a scale invariance

Scaling can also be geometric, this means shape doesn't change with body size:

b = 1/3 means the scaling process is in relation to length

b = 2/3 means the scaling process is in relation to area

Types of scaling:

1. Within organisms
• Tree cross-sectional area
• Geometric scaling with area M^0.66
• M^0.75 gives a greater slope. Extra scaling gives tree an advantage against buckling and fractures in high flow forces
• Mammalian heart rate
• M^-0.25
• Number of heart beats per lifetime does not vary with body size
2. Among individuals
• Standard metabolic rate
• Energy expenditure at rest; Kleiber's rule (1932)
• MR = M^0.75
3. Scaling at population-community levels
• Scaling of body mass and population density of mammalian herbivores
• (Population density)(Metabolic rate) = M^0 = scale invariance
• Energetic Equivalence Rule (EER) =  population energy flux of individuals is invariant with body size
• Species of different body sizes use approximately equal amounts of energy
• Plants: Population density related to mass; M^-0.75
• Metabolic resource use in plants; M^0.75
• EER applies to marine and terrestrial plants

Types of size-density relationships

1. Global size-density relations
2. Local size-density relations
• All population data taken from a single region

Biomechanics

There are many aspects of biomechanics that can be seen and studied in nature. However, this lecture focuses on how moving fluids affect organisms. In order to approach this topic it is necessary to first talk about the boundary layer. All life occurs in boundary layers, in the case of marine ecosystems, this can be seen as a flow gradient and the velocity you experience depends on where you are in the boundary layer. The following image explains better than I can what a boundary layer is.

(Image obtained from http://www.grc.nasa.gov/)

As it can be seen in the image above, the velocity increases as you move closer to the top. At the very bottom, the velocity is practically zero. This is known as the no slip condition. This means that fluid immediately in contact with the solid surface does not slip or move relative to the surface. 

With this knowledge, we can talk about the force that acts upon on organisms. Newton's third law states that an action produces an equal and opposite direction. This means that fluid exerts force on an object and an organism responds by exerting equal force on the fluid but in the opposite direction. The force exerted by a fluid is known as drag. Drag can be calculated using the following equation:

Fd=0.5*p(U^ß)AcCd

Fd = drag force

p = (Greek letter ro) = density of fluid

U = velocity of fluid

ß = usually 2

Ac = area perpendicular to flow, also known as characteristic area

Cd = drag coefficient

There are two types of drag: pressure drag and skin friction drag. Pressure drag is due to upstream/downstream differences in pressure. The pressure builds up on one side of the body. This is the most ecologically important type of drag. Skin friction drag refers to the fact that the more surface or 'skin' the organism has, the greater its drag will be. This type of drag is mostly relevant at low velocities.

Nature is smart and organisms have developed drag minimizing strategies. Some of them are:

• Increased flexibility
• This can be seen in sea fans, which bend over with the current. They become parallel to flow and manage to go down near the boundary layer. This is helpful because even though they have a great characteristic area, they are able to be near the low velocity zone of the boundary layer.
• Another example is the strategy seen in holly leaves, which bundle up and collapse as flow increases. 
• A sea anemone's tentacles collapse in high velocities.
• Intertidal and subtidal seaweed also exhibits great flexibility.
• Drag resistance
• This property is related to material strength, such as that seen in wood. Large tropical trees have wide bases (buttress), which gives them support. Having a great basal width offers drag resistance because the center of gravity is distributed over a large area. Basal width increases the distance from the rotation point. Trees also have a considerable weigh that would require great force in order to uproot them.
• Reduced drag coefficient
• A streamlined body shape results in a lower drag coefficient. This can be seen in animals such as dolphins, fish, sharks, among others. Streamlining affects fitness and is an example of convergent evolution.
• Another strategy is to transcend the air/water barrier, as seen in dolphins and flying fish. Since air is roughly 830 times less dense than water, moving temporarily out of the water is a valid strategy to reduce drag.

In order to study pressure-flow relations it is necessary to look at the principle of continuity and Bernoulli's principle. The principle of continuity states that velocity is inversely proportional to cross-sectional area. Bernoulli's principle states that velocity is inversely proportional to pressure.

The principle of continuity can be seen in sponges and their 'biological nozzle'. These organisms reduce the area of aperture to increase excurrent velocity. They expel water at great velocities to minimize the chance of refiltering the same water.

Bernoulli's principle allows us to compare velocities and pressure at different points in an ecosystem. At a point with high pressure, there will be low velocity and vice versa, at a point with low pressure there will be high velocity.  

Induced flow is the coupling of external to internal flow which results in the fluid being drawn passively through an object or organism. An example of this is the prairie dog burrow, in which a reduction in pressure between two points allows air to be passively drawn in through the structure. This is also seen in sponges, where a change in pressure passively draws food-laden water into sponge and augments filter feeding.

Other examples of pressure-flow relationships include fish experiencing pressure flow differentials across their bodies. This allows water to passively enter mouth and go through gills. It also offer advantages for respiration and visual acuity (there is zero pressure at the eyes).

Another force to be considered when taking about pressure is lift. Lift is concerned with pressure differences between the top and the bottom. There is also an equation that can be used to quantify the lift force experienced by an organism. 

Fl = 0.5p(U^2)AcCl

Fl = lift force

p = ro = density of fluid

U = velocity

Cl = lift coefficient

Ac = characteristic area (projected fluid perpendicular to flow)

As with drag, there are lift minimizing strategies (e.g. limpets), but unlike drag there are also lift maximizing strategies (e.g. flight)

Lift can be generated with an oncoming wind and a circulation. In stationary organisms, an adaptation is to have a body tapered in direction of lift so as to decrease the characteristic area and thus reduce the lift force.

However, it is important to consider that velocity is not always stationary. 

acceleration reaction = pCmVa

p = density of fluid

Cm = added mass coefficient (inertia)

V = volume of organism

a = acceleration

With these three equation, one can calculate the total (net) force on an organism, which is the sum of forces due to drag, lift, and acceleration. It is calculated by the Morrison equation.

Morrison equation:

Total net force = √[(Fd+Fa)^2 + Fl^2]

Biomechanics and the principles of drag and lift are also important because of the ecological consequences of high flow forces. Some ecological manifestations and effects are:

1. Hurricane impacts
• Hurricanes have restructured forests by reshaping species distribution and abundance. 
• Example: 1983 hurricane
• There have been species-specific effects, such as tallest trees experiencing the highest velocities.
• Landscape can be predictable as to how wind speed will impact it.
2. Wind speed effects
• Wind speed has had a negative effect on barn swallow fitness.
• Survival rate of birds depends on wind speed.
• Intertidal snails survived perfect storm because of smaller body size.
• smaller drag and lift forces
• High flow forces have selection of a population
3. Distribution of organisms
• Hypothesis: Sea urchins could not occupy shallow areas in exposed site because they get dislodged. 
• Conclusion: Sea urchins did not occupy shallow areas because they could not move and feed.
4. Size and reproduction of organisms
• Seaweed blade area reduced in high flow (lower area)

Conclusion -  High flow affects:

• Shape and performance
• Exchange processes
• Fitness and survival
• Distribution of organisms
• Transport processes
• dispersal
• recruitment
• nutrient transport

Ecology: Introduction

Ecology is the study of "home life of living organisms. It comes from the Greek word oikos, meaning house. It is the study of the interactions that determine the distribution and abundance of organisms. These interactions can be both physical and biological factors.

Studies in ecology deal with a variety of questions. These are some of them:

• Why do populations fluctuate?
• What is controlling population density?
• How do organisms allocate energy to competing life processes?
• Why do predators consume one prey and not another?
• Where do new organisms come from and how are they dispersed?
• How can a sustainable population be achieved?
• What is the effect of removing or adding species to a food web?
• Why do biodiversity hotspots occur? What processes enable it? Why do they occur where they occur?
• What triggers abrupt shifts in ecosystems and do they result in alternate states?
• How are human impacts damaging ecological systems?

Within an ecosystem, there are subtle, and sometimes indirect, interactions that are numerous because of the many different species and the wide variety of factors that play a role. It should also be said that ecological interactions are not static and are constantly evolving.

When talking about evolution, we should mention genetic change, natural selection and fitness. Genetic change consists of mutations and other processes that produce new and variant forms of genes. Natural selection is a process that operates on individuals with different combinations of these genes to endow the most fit a survival advantage. It occurs by differential reproduction and survival of genetically distinct individuals in the population, and involves death and limits to reproductions. Natural selection also ensures that existing species are suited to their environment. Fitness is the proportionate contribution of individuals to future generations. The fittest individual equals 1.0, while all the rest are <1.0. The individuals leaving the greatest number of descendants relative to others are the fittest of the population. There are ways to measure the correlates of fitness, such as reproduction and fertility, survival and mortality, and growth.

Endler (1986) offers ~140 demonstrations of natural selection in the wild. It is one of the best evidences demonstrating a) variability in a trait, b) that trait variation is heritable, and c) that a trait can confer a fitness advantage. These traits can also be observed in Grant and Grant (1993).

Rapid evolution is defined as the evolutionary changes occurring in a population in less than a hundred years. Four categories of rapid evolution affecting species' interaction are:

1. Evolution of trophic links via specialization
• During the 1982-1983 El Niño there was an especially high amount of rainfall which caused a change in seeds. This put selective pressure on finches, leading to a rapid evolution of beak sizes. This event favored granivorous finches. (Grant and Grant 1993)
2. Evolution of defense
• Cryptic coloration in moths responded to changes in color of habitat. By 1900, tree bark was darkened by pollution and the percentage of dark moths increased significantly. (Kettlewell 1995)
3. Rapid loss of traits in absence of interaction
• Guppies exhibited loss of defensive antipredator traits when predation diminished. These traits included cryptic coloration, body size, and specific behaviors. (Endler 1995)
4. Change in outcome of interaction
• The Myxoma virus was introduced in Australia to control the rabbit population, but soon rabbits evolved resistance while the virus evolved decreased virulence. This is an example of coevolution and reciprocal genetic change.

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Niche Theory

A niche is an organism's place in the environment. It is defined by both physiological tolerances and resource requirements and availability. A fundamental niche is a multidimensional space that is quantifiable. Also referred to as a 3D space called hypervolume. It is where a species could live. A realized niche is the space constrained by biological interactions among species. It is the "post-interactive" niche and it is where the species actually lives. The key question now is what determines the width of the realized niche?

An Update

This blog was originally used as a means to take notes and make summaries of my course of Environmental Systems and Societies. This was two or three years ago when I was in high school and working towards my International Baccalaureate diploma.

I've decided to start posting again. This time, I am now in college working towards my degree in Biology. I'm taking a course on Principles of Ecology and thought it would be a good idea to post here my class notes as I study for exams.

Note: The contents of the posts from now on contain information provided by my professor and in no way do I take credit for the contents. Most of the things written will be copied verbatim from lecture notes and presentations. This is not my work, rather a compilation of course material made available and which I am now compiling as a study method. 

Evaluating Biodiversity and Vulnerability

Identifying factors that lead to loss of diversity

Main five pressures on biodiversity are still present and even intensifying:

1. Habitat loss and degradation
2. Climate change
3. Excessive nutrients and other pollutants
4. Over-exploitation and unsustainable use of resources
5. Invasive alien species

There is something known as the Red List that shows the status of species in terms of their conservation status. You can see the list here.

It should be mentioned that biodiversity conservation is crucial. Biodiversity, be it genetic, habitat, or species, is one of the determining factors in an ecosystem's health. The above mentioned factors are putting pressures on the planet that it cannot absorb fast enough. Ecological footprints are exceeding the Earth's capacity to recover. All of this leads to a persistent loss in biodiversity that slowly reduces our ecosystems' resilience and compromises the resources on which we depend.

There are certain world trends that are occurring around the world:
- Habitats are declining.
- Abundance and distribution of species are declining.
- Change in status of threatened species.
- Threats in genetic diversity in domestic animals, cultivated plants, and fish species. This is due to interference with natural selection.
- Coverage of protected areas are increasing
- Marine Trophic Index has shown an increase, but has regional fluctuations.
- Ecosystems have become more fragmented.
- Water quality in aquatic ecosystems has been declining. Some areas have increased their water quality by dealing with point-source pollution.
- Nitrogen deposition has increased.
- The amount of invasive species has increased and are now a threat.
- Areas of forest, agricultural, and aquaculture ecosystems under sustainable management have increased, but there are several areas that still require more efforts.
- Humanity's Ecological Footprint is still rising.

Evaluating Contrasting Human Perceptions of the Issue of Global Warming

There are many different postures regarding the global warming phenomenon. Some state that global warming is a myth. Others do not deny it, but simply hold that the temperature rise is normal and is even beneficial to the Earth. Personally, I believe that there is enough scientific data to prove that the Earth's temperature is in fact rising. Also, regarding the point of view that it benefits our ecosystems, I believe it may be true in certain places. However, the changes in temperature are also harming other ecosystems that are just as important as the ones that are being benefited.

Another important issue that needs to be addressed when talking about global warming is the extinction and loss of biodiversity. Massive extinctions result from global warming, and the drastic changes in the environment can lead to loss of habitat which in turn limit the biodiversity in a given ecosystem.

I believe global warming is something that occurs naturally, but scientific and historic records clearly demonstrate that the rate at which the Earth is heating up is faster, and it is human activity that which is accelerating this process. I also hold that the planet is resilient enough to recover from the damages it suffers, but again, the damage is being done constantly and we are not giving the Earth enough time to absorb the pressures we are putting on it.

While I believe that global warming is a threat, I also consider that there are things that can be done. CO2 emissions are a major contributor to the temperature rise and while we cannot stop them completely, we could greatly reduce them. Corporations and governments should work at a large scale to reduce emissions, but also individuals and society as a whole should become more conscious and aware of the impact that each of our actions has on the planet. Only when we have reached true awareness will we be able to say that we are doing all we can to help the Earth.

Urban Pollution: Key Terms

Photochemical Smog: It is the product of several chemical reactions. Main components are nitrogen oxide and ozone after the reaction caused by UV light. Hydrocarbon free radicals found in smog can form aldehydes and peroxyacetylnitrate (PAN). Common in large cities.
PAN in photochemical smog can irritate the eyes.
Ozone: causes breathing difficulties, headaches, and fatigue.

Nitrogen Dioxide can be split into nitrogen monoxide and a free oxygen molecule that is then available to form ozone.
Nitric oxide can remove ozone.
When the ratio of NO2 to NO is greater than 3, the formation of ozone is the dominant reaction. If the ratio is less than 0.3, then the nitric oxide destroys oxygen.


Peroxyacetylnitrate: Products of the reaction between nitrogen dioxide, oxygen and hydrocarbons.

Catalytic Converters: These are used to reduce the carbon monoxide and nitrogen oxide emissions. It is made up of either platinum or a combination of platinum and rhodium.
Platinum catalyses the reaction of unburt hydrocarbon and oxygen to produce carbon dioxide and water.
The rhodium catalyses the reaction of carbon monoxide and nitric oxide to form carbon dioxide and nitrogen gas.

Reduction of NO to N2 must proceed more quickly than the oxidation of carbon monoxide to carbon dioxide or else all the carbon monoxide will be oxidized to carbon dioxide before it can be used to reduce the nitric oxide.

Acid deposition: The effect that acid rain has on ecosystems. The effects may not be immediately seen, but the restoration process takes a very long time.

Acid rain in soil - Each H+ replaces key nutrients. Hydrogen ions replace potassium or calcium ions. Plants begin to suffer due to scarce nutrients.

Heavy Metals

Article on Heavy Metals in Landfills by the New Jersey Harbor Estuary Program. Click here.

Pollution Management Strategies

Key Questions
1. What challenges does each type of pollution present?
2. Why?
3. What can be or is being done?

Three level model
-Human activity producing pollutants
+Altering human activity through education, incentives, and penalties to promote:
*Development of alternative technology
*Adoption of alternative lifestyles
*Reducing, reusing, recycling

-Release of pollutants into environment
+ Regulating and reducing point of emissions
*Standards
*Measures to extract pollutants from emissions

-Long-term impact of pollutants on ecosystem
+ Cleaning up pollutants and restoring ecosystems
*Extracting and removing pollutants from ecosystem
*Replanting and restocking animal populations

How to Assess Pollution

Notes Jan. 18 (cont. from yesterday)

Direct Methods
-In situ (field work)

• It is reliable
• It gives straightforward data.
• Measures directly in the source.
  
• Can have technical difficulties (Instruments: costly or not portable)

- Ex Situ (lab work)

• Use a wider variety of methods and instruments
• More flexible (Test more variables, have more repetitions)
• Samples are not fresh. The time after the sample was extracted may affect it and alter the results.

Direct measurements can assess
*Concentration of gases
*Particulate matter
*pH
*Dissolved oxygen in water
*Biomass content
*Salts
*Conductivity
*Turbidity
*Temperature
*Density

Indirect measurement is done through
*BOD
*Indicator species
*Biodiversity
*Spectroscopy
*Chromatography

Pollution Management

Detection and monitoring of pollution can be done directly or indirectly

Directly: Measuring the concentration of pollutants

• Acidity of rain
• Amount of gases in atmosphere or emissions
• Soil pH
• Concentration of nitrates, phosphates, sulfates in soil and water
• Amount of organic matter in soil and water
• Amount of bacteria
• Concentration of (heavy) metals
• BOD (biochemical oxygen demand: the amount of oxygen used by microorganisms to break down organic matter in water): used to determine the pollution of water. The greater the BOD, the more pollution.
  

Indirectly

• Absence or presence of indicator species
• 
  

Air Pollution

Notes Jan. 14

Atmosphere levels
Troposphere
Stratosphere: Ozone layer located here.
Mesosphere
Thermosphere

Pollution concentrate in the troposphere. Climate change is due to the change on temperature in the troposphere.
Greenhouse gases: CFCs, Methane, carbon dioxide.

Primary pollutant: come directly from specific sources such as volcanoes or dust storms. Most hydrocarbons, most suspended particles. Human primary pollutants come from vehicles, factories and industrial activities, and houses. Examples: CO, CO2, SO2, NO, NO2.

Secondary pollutants: these pollutants generate from primary pollutants due to chemical activities in the atmosphere or water. Most of these reactions are enabled by sunlight. Photochemical smog and ozone are examples of secondary pollutants. Examples: SO3, HNO3, H2SO4, O3, nitric and sulfuric ions.

Indoor pollution
Pollution that builds up in houses and buildings can be is known as indoor pollution. It can be divided into several areas:
Bedrooms - Areas of sleep: Dust mites, bacteria and viruses. Can be reduced through good ventilation. Special mattresses and linen as well as good hygiene help reduce bedroom pollutants.
Bathroom - Areas of hygiene: Plumbing leaks, cleaning supplies, heavy metals found in the plumbing, carpeting and flooring, bacteria and viruses, dampness, garbage.
Kitchen - Areas of cooking: Cooking smoke, gas appliances, household cleaning agents, garbage, plumbing leaks.
Garage and Attic - Areas of storage: Storage of chemicals, old things release pollutants. To reduce this, do not store potentially polluting stuff and keeping the area well ventilated.
Living rooms: Tobacco, incense, and environment fresheners, carpets and furniture store pollen, dust and debris. Choose furniture that is not prone to store pollutants (too many cushions, excessive fluff, etc.)
Yards: Pesticides, herbicides, naturally produce pollen and dust. To promote a more eco-friendly yard, the plants in the house must be regional plants that do not need exceptional care.

To be continued...

Major Pollutants

Pollutant	Causes and Sources	Effects
Carbon monoxide	Forms during the incomplete combustion of carbon-containing materials. Motor-vehicles, burning and forest and grasslands, inefficient stoves, open fires	CO reacts with hemoglobin, reducing blood's ability to transport oxygen. Can also cause headaches, nausea, drowsiness.
Carbon dioxide	A result of the carbon cycle, the burning of fossil fuels, and industrial processes	Can alter the pH of water bodies and because of excessive quantities, it is contributing to the greenhouse effect. In the human body, excessive CO2 can cause asphyxiation and kidney damage.
Nitrogen oxides and nitric acid	Combustion of fossil fuels. Motor vehicles are a major contributor. Nitric acid can come from sewage and fertilizers.	Nitrogen oxides harm airways and can lead to respiratory diseases. It also contributes to the formation of ozone. Nitric acid leads to acid rain.
Sulfur dioxide and sulfuric acid	Burning of coal and oil, and is also a byproduct of metal and industrial processes.	Both cause acid rain wich results in acidified soils and bodies of water. Health effects include respiratory and cardiovascular problems
Suspended Particulate Matter	Motor vehicles, coal-burning, fireplaces, power plants.	Causes pulmonary problems such as asthma and decreased lung function. In the environment, it reduces visibility.
Ozone	Formed by the reaction of VOCs and nitrogen oxides.	Causes shortness of breath, wheezing and coughing, but can lead to severe lung problems such as reduced function and irritation.
Volatile Organic Compounds (VOCs)	Motor vehicles, chemical plants, refineries, factories.	Eye, nose, and throat irritation, headaches, dizziness.
Radon	Produced by the decay of uranium in soil and water.	Lung cancer.

Sources of Pollution per Type

Air
Point source: Ammonia is a pollutant that is commonly released because of industrial processes.

Non-point source: Nitrogen oxides are pollutants that are released into the air due to the combustion of fossil fuels and other human activities such as cars and other vehicles, and agricultural sources.

Water
Point source:
Wastewater treatment plants are a source of pollutants ranging from organic nutrients to chemical agents. This is considered a point source pollutant because the plants have identifiable discharge pipes.

Non-point source:

1. Excess nutrients that can come from industrial or agricultural runoff or even animal wastes and soil gathered along a water's path.
2. Chemical contaminants that enter a body of water through urban runoff and contaminated stormwater.
   

Soil
Point source: Industrial wastes and agricultural pesticides are a source of contaminants that release chemicals into the soil, compromising its health.
Non-point source: Runoff can also affect soil because contaminated groundwater seeps into it. If the runoff carries excessive nutrients, these could also become soil pollutants.


Notes
It can be seen in this comparison that when talking about waste and pollution management, each case need to be considered on an individual basis because a pollutant can come from a non-point source or a point source.

Pollution and Wastes

Notes Jan. 12, 2011

Waste is any unwanted byproduct of a certain activity, but it is not considered pollution when its levels surpass what nature can handle.
A pollutant is any waste in excessive amounts.

Every living thing produces waste, but even the waste from other species could turn into pollution when its levels skyrocket. Example: an uncleaned aquarium, algal blooms.

When there is an uncontrolled growth of population, the amount of wastes produced by the organisms becomes so much that it is said the it pollutes the ecosystem. Pollution limits growth, harms health, or has otherwise negative effects.
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What is pollution?
The presence of a waste or an agent in quantities higher than what the environment can naturally handle.

Every waste or agent has different tolerance levels. Some wastes are considered pollutants just by the fact of being produced, i.e. chemicals.The agents and wastes that are considered pollutant the instant they are produced are those that are not naturally present in an environment.

Types of pollution

• Point source: Pollutants that can be tracked to a particular source.
• Non-point source: Pollutants for which a clear source cannot be precisely identified.

Pollution is constantly present due to human activity. Pollution management is a term that has been present since the Industrial Revolution, but it was not until the 20th century when the concept started becoming important. During the time of the Industrial Revolution, the people did not consider that the wastes produced by the industrial processes would become a major pollutant that would compromise the health of different ecosystems. This era was characterized by unprecedented and uncontrolled development.

Policies and their Effect on Human Population

The objective of this activity is to discuss how international and national development policies and cultural influences can affect human population development and growth.

The following outline presents a comparison between the countries of Australia and United Kingdom in terms of sustainability policies and the effect on their respective populations.

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Australia
Population facts

• Ageing population (Baby boomers are growing old)
• High levels of immigration into the country
• Consistent growth, but uneven across the different regions
• Great majority of population lives in urbanized areas

Aims

• Economic stability
• Address labor shortages
• Prepare accordingly for when the population pyramid finally inverts
• Sustainability across the country
• Improve connections between regions
• Improve infrastructure
• Increase food production without compromising the environment
  

Policies

• Immigrants on work visas will face a much more simplified process.
• Infrastructure development projects will focus on those areas that present the most growth.
• Economic policies are working to strengthen connections with international companies.
• Agricultural policies are working to increase food production, but limiting the amount of additional resources that are used. (Target: Low input, high yield)
• Working to relocate people in order to limit the growth of urbanized areas so as to protect biodiversity and avoid the habitat degradation and loss.

United Kingdom
Population facts

• Aging population (Baby boomers)
• Growing population
• Population divided by regions
• There is a certain level of immigration

Aims

• Control population growth
• Manage population segments before the population pyramid inverts
• Protect natural resources
• Achieve high employment levels
  
• Sustainability through education
  

Policies

• Government support will help provide jobs and training.
• Prevent emigration by creating communities where people will want to live and work.
• Provide family planning services
• Work toward social inclusion of all citizens
• Focusing on education and sustainability through educating the population
• Work together with international organization to determine sustainability policies
• Health care available to increase the population's well-being.
  

Conclusions
It can be seen in both cases, the policies are made according to the population conditions. This means that policies issued are based on the needs identified in a specific population. At the same time, the policies have an effect on the people, so it goes both ways. For example, Australia has a high immigration rate and the growth of its own population is constant but not enough to cause significant problems. This is why Australia focuses on taking advantage of immigration to target labor shortages which will become an increasing problem as the population ages. United Kingdom also has an aging population, but it is focusing more on retaining its current population and training them to address the labor shortages.

Both countries are focusing on achieving sustainability, but each of the policies are made considering the culture, geography, and needs of each country's population.