1. About how many years of human existence passed before the world population reached its first billion? What factors restricted population before that time. and what factors contributed to growth after that point?

It took all of human existence up to 1804 before the world population reached its first billion. Before then, hunting and gathering societies never managed to pass a few million, with scarce food supplies and a nomadic lifestyle limiting growth. The agricultural revolution and the domestication of animals provided a stable food source necessary for population to start growing. Better nutrition and healthcare following the Industrial Revolution accelerated this growth to what it is now.

2. Describe the pattern of human population growth over the past 200 years. What is the shape of the growth curve (recall chapter 3)?

In the past 200 years, human population growth has become exponential. This is a growth curve in the shape of a J.

3. Define ecological footprint. Why is it helpful, but why might it also be inaccurate?

An ecological footprint is an estimate of the relative amount of bioproductive land required to support each person. It is useful in that it allows comparisons of different lifestyles, but can also be inaccurate because the formula used to calculate it relies on many assumptions: that resource use can be readily converted to land area, that land use is mutually exclusive for each resource, and that technology levels are fixed. The last assumption has already been disproven in the last century as technological progress has drastically increased food production worldwide.

4. Why do some economists consider human resources more important than natural resources in determining a country's future?

More people result in larger markets, more workers, and higher efficiency in the manufacturing of goods. More people can also mean higher intelligence and ingenuity in a population as well, leading to new solutions in harvesting and using existing resources. The long-term benefits of this can pay off more in the long run than just natural resources alone (see what is starting to happen with the oil-rich Middle East states).

5. In which regions of the world will most population growth occur during the twenty-first century? What conditions contribute to rapid population growth in these locations?

The highest population growth in the world occurs in sub-Saharan Africa and the Middle East. This is because of the economics, politics, religion, and civil unrest in the region that keeps birth control use low and fertility rates high.

1. Google Steve Chu: where does he work? Where did he work before? On what? What did he get an award for? Why is this important to the end of the story?

Steven Chu is the current United States Secretary of Energy. He was previously the professor for physics at Stanford University and the University of California, Berkeley and the director of the Lawrence Berkeley National Laboratory. Chu's research mostly concerned the study of biological systems at the single molecule level. He won the Nobel Prize in Physics along with Claude Cohen-Tannoudji and William Daniel Philips in 1997 for the "development of methods to cool and trap atoms with laser light". His work at the Lawrence Berkeley National Laboratory included research into the development of cellulosic ethanol energy sources, which is predicted to revolutionize the way ethanol is produced on a scale even greater than that of sugar ethanol in Brazil.

2. Google Dan Kammen: where does he work? On what? Why does he cite Brazilian sugar ethanol as sustainable? Compare this with corn ethanol grown in the US (e.g. Nebraska).

Dan Kammen is the director of the Renewable and Appropriate Energy Laboratory at the University of California, Berkeley, where he works on "designing, testing, and disseminating renewable and appropriate energy systems". Kammen cites Brazilian sugar ethanol as being sustainable for sugar cane is easy and fast to grow and is simple to process into ethanol, but the most significant reason for why it is sustainable is because of how Brazil's energy economy has become centered around ethanol to the point where it is not possible to buy gasoline in Brazil without some measure of ethanol content added. American corn ethanol is five to six times less efficient than sugar cane ethanol, and it competes with the production of a major food crop, hence why ethanol has not been embraced in the United States to the same degree as it has been in Brazil.

3. Compare sugar ethanol from Brazil with US corn ethanol. Which competes for food? Which needs petrochemical to fertilize? What is the energy balance like for each? What is/was bagasse used for? What is bagasse made of? How did sugar cane mills here in Hawaii fuel their boilers? Was sugar indigenous, and could it grow here again? Explain.

Corn ethanol in the United States competes directly with food production, and it also requires the use of petrochemicals to fertilize. The energy balance for sugar cane ethanol is seven times greater than that of corn ethanol. Bagasse is the leftover plant matter that remains after sugar cane or sorghum stalks are crushed in the extraction of juice, which is usually burned by sugar cane mills to supply energy to the mill with power to spare. Bagasse consists of about 50% cellulose, 25% hemicellulose, 24% lignin, and 1% ash and wax. Sugar cane mills in Hawaii fueled their boilers by burning bagasse leftover from the production of sugar. While sugar cane was not indigenous to the islands, Hawaiians have been growing them since the pre-European contact era. The decline of sugar growing in Hawaii had nothing to do with natural or environmental factors, but rather because of changing geopolitical factors that made it no longer a feasible business on the islands. If the political climate changes, and sugar cultivation becomes profitable again in Hawaii, it could certainly be grown again here.

4. Google Vijay: what is he involved in now?

Vijay Vaitheeswaran is the senior editor for The Economist covering politics, economics, business, and technology as they relate to energy. He recently published a book called Power to the People: How the Coming Energy Revolution Will Transform an Industry, Change Our Lives, and Maybe Even Save the Planet, aiming to the raise awareness of alternate energy sources for the future.

5. Oil embargo: when did this happen? Why? What happened? How did this change the lifestyle of people in the US? Is this similar to today?

The Arab Oil Embargo started in October 1973 and ended in March 1974 when members of Organization of Petroleum Exporting Countries imposed an oil embargo on the United States in response to its decision to aid Israel in the Yom Kippur War.

Oil exports to the United States significantly dropped, and a shortage led to massive price increases as well as the introduction of rationing across the country. National campaigns to cut consumption

were imposed, as was a nationwide speed limit and year-round daylight savings time. Ironically, the exploration and development of renewable energy sources was discouraged, as government price controls were meant to stimulate oil exploration. While the 1973 oil crisis was instrumental in starting consumer trends such as the move to smaller and more fuel-efficent vehicles, today's reality is not that much different from before the energy crisis, with dependency on foreign oil as entrenched as ever.

6. Corn ethanol: why is this so prevalent in the US? Who backs it and why? Who was president in 2002, when many of the corn ethanol policies began? What was his line of work before? What about the vice president?

Corn ethanol is so prevalent in the United States as corn was already a major crop cultivated in the Midwest. The major push for it happened under the presidency of George W. Bush, who was president during 2002. Before he embarked to Washington D.C. to help his father run for the presidency in 1988, Bush was active in the oil industry owning and working for several oil exploration companies. His vice president, Dick Cheney, served as the CEO and chairman of Halliburton, the world's second largest oilfield services corporation, from 1995 until 2000.

7. Cars: why do you think VW has put more research into biofuel cars than hybrids? When were CAFE standards started? What is a CAFE standard? What was made exempt from CAFE standards around 1995? What impact did this have on the country?

Volkswagen developed flex-fuel cars for Brazil because that was the nature of the market there. The infrastructure for ethanol was already mature and in place; developing a hybrid car would have not made sense as Brazil did not invest any money into the infrastructure necessary to sustain hybrid cars (charging stations, battery replacement/recycling programs...). The Corporate Average Fuel Economy standards were first imposed in 1975 to raise the fuel economy of vehicles in the United States in the wake of the 1973 oil embargo. However, exemptions for SUVs were allowed around 1995, and the average fuel economy for vehicles in the United States now have dropped back to their normal levels.

8. Cellulosic Ethanol: what is this? How is it different from corn ethanol or sugar ethanol? Now rethink your bagasse question from above. Why is Steve Chu key to this? Imagine Brazil with sugar ethanol AND cellulosic ethanol - your thoughts?

Cellulosic ethanol is ethanol produced from other parts of plants that are inedible, unlike corn ethanol and sugar ethanol which is made from starch, polymers of alpha-glucose monomers. Steve Chu, during his time at the Lawrence Berkeley National Laboratory, pioneered research in the development of cellulosic ethanol as a viable fuel source. If perfected, any sort of plant waste, including bagasse, can be converted into ethanol instead of just being crudely burnt for heat. A Brazil utilizing both sugar ethanol and cellulosic ethanol will be completely energy independent and hopefully serve as a model for how sustainable energy can be viable as well as economical for the future.

8. Which wavelengths do our eyes respond to, and why? About how long are short ultraviolet wavelengths to microwave lengths?

Our eyes only respond to the wavelengths in the range of visible light, which is from 0.4 μm to 0.7 μm. From the beginning of ultraviolet wavelengths to the longest microwave lengths is from 10 nm to about 1 cm.

9. Where do extremophiles live? How do they get the energy they need for survival?

Extremophiles are organisms that gain their energy through chemosynthesis, or the extraction of inorganic chemical compounds.

They thrive in extreme environments such as in the Earth's crust, on the ocean floor, and in hot springs. The energy that they collect help to fuel an ecosystem deep underwater near thermal vents, as they supply the initial energy that will eventually be cycled up the food chain.

10. Ecosystems require energy to function. From where does this energy come? Where does it go?

All the energy in an ecosystem stem from the sun at the most basic level. Primary producers (which are mostly all plants, organisms that can perform photosynthesis) are at the most basic trophic level, being able to extract energy directly from sunlight. As these plants are eaten by herbivores, the energy is cycled up a trophic level to primary consumers. Carnivores that prey on herbivores would then be secondary consumers in the ecosystem, getting energy again from the previous trophic level. However, the efficiency for this process is not very high, as much as 90% of the energy is lost for every change in level.

11. How do green plants capture energy, and what do they do with it?

Green plants possess chloroplasts which contain chlorophyll that plants use to conduct photosynthesis. A light-dependent reaction happens that takes water and carbon dioxide (along with other lipids, sugars, proteins, and nucleotide molecules) and turns it into sugar and oxygen. This sugar stores energy in its chemical bonds, and when it is cycled up the trophic levels, organisms higher up in the chain conduct cellular respiration to release this stored energy.

12. Define the terms species, population, and biological community.

Species is all the organisms of the same kind that can interbreed to produce fertile offsprings. A population consists of all the members of a species in a select area at a given time. A biological community includes all the populations of all organisms in an area.

13. Why are big fierce animals rare?

Large animals are very high up in trophic levels and require lots of energy to survive. However, as only about 10% of energy is available for every trophic level from the previous one, a huge amount of land (and thus, area and space) is required to have enough plants to provide the sufficient energy at the very first trophic level to make its way up to the top predator.

14. Most ecosystems can be visualized as a pyramid with many organisms in the lowest trophic levels and only a few individuals at the top. Give an example of an inverted numbers pyramid.

The amount of bacteria as a function of time can be envisioned as an inverted numbers pyramid. If a certain species of bacteria doubles every 36 hours, then one can envision each step to represent a 36 hour block, and each block up would be twice the width of the previous one.

15. What is the ratio of human-caused carbon releases into the atmosphere shown in figure 2.22 compared to the amount released by terrestrial respiration?

Humans release a total of about 7 gigatons of carbon into the atmosphere every year while terrestrial respiration releases a combined 100 gigatons of carbon into the atmosphere. While the amount of carbon released by humans may seem insignificant, the problem is that this extra amount of carbon is not being offset by photosynthesis, hence the steady increase of carbon dioxide in the atmosphere for the last 150 years.

1. What two problems did Arcata, California, solve with its constructed wetland?

The constructed wetland simultaneously beautified Arcata's blighted waterfront area and solved the sewage treatment problem of the town.

2. What are systems and how do feedback loops regulate them?

A system is a network of connected components and processes involving the flow of matter and energy from one part to the next. Feedback loops help to maintain stability in a system through either positive or negative feedback that can affect the population of another organism that is next in the chain.

3. Your body contains vast numbers of carbon atoms. How is it possible that some of these carbons may have been part of the body of a prehistoric creature?

The principle of conservation of matter states that matter is neither created nor destroyed, only transformed; as such, carbon atoms which probably formed part of some prehistoric plant or animal have been reused in many other different creatures in its history, of which humans unsurprisingly would also be a part of.

4. List six unique properties of water. Describe, briefly, how each of these properties makes water essential to life as we know it.

Water molecules are polar, allowing it to act as a nearly universal solvent in dissolving polar or ionic substances. This property is what enables cells to carry nutrients.

Water is the only inorganic substance to exist naturally as a liquid, allowing organisms to synthesize organic compounds that are liquid at room temperature. Water molecules exhibit cohesion to each other, and as a result has the highest surface tension of any natural liquid. This allows plants to draw water up through their stems using capillary action alone. Water expands when it freezes, which causes ice to be less dense than water. This permits aquatic life to exist under polar ice caps where the water is warmer than surface ice temperatures. Water has a high heat of vaporization, allowing many animals to cool off and maintain homeostasis through mechanisms of releasing water such as sweating which helps to carry off excess heat. Finally, water also has a high specific heat, which is what permits it to act as a moderator for global temperatures, keeping everything within limits suitable for life to exist.

5. What is DNA, and why is it important?

DNA, short for deoxyribonucleic acid, are strands of nucleotides that are the genetic blueprints for all living things. They contain directions for the growth and development of an organism as well as help in protein synthesis.

6. The oceans store a vast amount of heat, but this huge reservoir of energy is of little use to humans. Explain the difference between high-quality and low-quality energy.

Even though energy can be used repeatedly, as it flows through a system, more of it is released and dissipated. This is essentially the transformation of high-quality energy, which can be used to do work, to lower-quality energy that has increased entropy which lessens its usefulness and makes it harder to harness.

7. In the biosphere, matter follows circular pathways, while energy flows in a linear fashion. Explain.

Conservation of matter dictates that matter is neither created nor destroyed, only transformed. Because of that, while matter is constantly cycled through the environment in different states, at some point or another it will return to an earlier form and start the cycle again. Energy is also conserved in all systems; however the difference is that as it changes state, much of it is dissipated and thus, less useful energy is available higher up a chain.

1. Describe how fishing has changed at Apo Island, and the direct and indirect effects on people's lives.

Thirty years ago, the use of destructive fishing techniques such as dynamite fishing, trawling, and muroami had severely impacted the state of reefs and fish habitats, depleting fish stocks in the area. In response to this, scientists came to Apo Island to collaborate with the locals to develop reserves that allowed fish populations to replenish as well as to restrict any future fishing activities to low-impact methods such as lines, traps, and hand-nettings. The direct effect of this was that the available amount of fish went up, allowing locals to obtain fish with much greater ease. As they didn't have to spend as much time obtaining food, the locals had more time to devote themselves to building up the island's economy through other avenues such as tourism or through the development of infrastructure (such as schools).

2. What are some basic assumptions of science?

Science assumes that the world is knowable and that it can be learned through observation and logical reasoning. Science relies on testable evidence to provide explanations for these phenomena's.

3. Distinguish between a hypothesis and a theory.

A hypothesis is a testable explanation for a phenomenon, whereas a theory is an explanation that is generally accepted by scientists and has facts and evidence to back it up.

4. Describe the steps in the scientific method.

The steps are observe, hypothesize, test, collect data, and interpret. Observation produces a question which an attempt to answer is made through the development of a hypothesis. Testing produces data, which are then interpreted to either confirm or disprove the hypothesis.

5. What is probability?

Probability is the measure of how likely something is to occur, typically represented as a value between 0 and 1, where 0 represents no chance of something happening (an impossible event), and 1 representing the absolute certainty of something happening.

6. In a graph, which axis represents the independent variable? The dependent variable?

The x axis (horizontal axis) represents the independent variable, while the dependent variable is represented by the y axis (vertical axis).

7. What's the first step in critical thinking according to table 1.4?

Determining the purpose of the thinking.

8. Distinguish between utilitarian conservation and biocentric preservation. Name two environmental leaders associated with each of these philosophies.

Utilitarian conservation does not concern itself with preservation but rather the strategic use of natural resources for human advancement. In contrast, movements supporting biocentric preservation argue that nature should be left alone for the important roles that it plays in ecosystem and for its own sake. Prominent conservationists include Theodore Roosevelt and Gifford Pinchot, while some prominent preservationists include John Muir and Aldo Leopold.

9. Why do some experts regard water as the most critical natural resource for the twenty-first century?

1.1 billion people already lack access to safe water, and more don't have access to sanitary water supplies. The United Nations projects that by 2025, three-fourths of the world could be living under similar conditions. Water resources are finite, while population growth in the last decade alone has been exponential.

10. Where in figure 1.7 do the largest areas of persistence of greening occur? What is persistence of greening?

The largest areas of persistence of greening occur in parts of the Ukraine, Belarus, and Lithuania. Persistence of greening is the phenomenon where flora remains green longer year round in polar regions, evidence that there is global climate change.

11. Describe some signs of hope in overcoming global environmental problems.

Marine reserves are being established, legislation is being written to cut down on pollution in urban areas, and deforestation around the world, while still prevalent, has been slowing down. These movements show that we still have hope in reversing the trend of environmental destruction of recent years.

12. What is the link between poverty and environmental quality?

People in poverty find themselves in circumstances where their foremost priority is often basic survival. As a result, they may take actions which are not favorable for the environment, such as overharvesting or overfishing.

13. Define sustainability and sustainable development.

Sustainability is the use of resources in a way that allows their use to last over a long period of time. Sustainable development refers to the idea that development of the poorest parts of the world can be done without causing irreparable environmental harm.