Chapter 2Environmental Systems

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You can never do just one thing! How cats were parachuted onto Borneo

• Cats in Borneo example (1950s)– Borneo is an island in Southeast Asia– Borneo has a tropical climate and that leads to the breeding of mosquitos.– Mosquitos carry malaria and in the 1950s, there was a malaria outbreak– DDT pesticide was sprayed to kill mosquitos and reduce malaria– DDT killed the mosquitos and a parasitic wasp, but not the cockroaches– The parasitic wasps controlled the caterpillar population, so the caterpillar

population grew, ate though roof beams and roofs fell in.– DDT bioaccumulated in the cockroaches, and then in the geckos(who eat

cockroaches) making the geckos sick and slow– Cats caught and ate more of the slow geckos and DDT bioaccumulated in the cats

and the cats started to die– With fewer cats, the rat population increased, which increased the risk of typhus

and plague outbreaks which worried locals– So cats were helicoptered onto Borneo and dropped with parachutes to eat the

rats to prevent outbreaks of typhus and plague

http://www.skidmore.edu/~mmarx/ScribSem44/Borneo%201.pdf

Warm-up• Read the intro story for Ch 2 about Mono Lake and notice

another example of how “you can never do just one thing”• Make a list of what happened in the chain reaction starting

with Los Angeles deciding to divert water from Mono Lake and Owens Lake

Just a little historical

context about LA

water usage:

Systems

Open System• Most systems are open• Receives input from and

produces output to the outside of the system

Closed System • Not common in nature:

some underground caves

• No inputs and outputs

Sort of, but not really closed

Thermodynamics1st Law• Energy cannot be

created nor destroyed• Energy can change

forms• If energy is “lost” it was

really just converted to another type of energy

2nd Law• When energy is transferred,

the amount of energy stays the same, but the quality of the energy is reduced

• When energy changes form, some is converted to a less desirable form

• Energy Efficiency = work done/total energy available

• Higher efficiency generally means less energy is lost as heat

Which Law?• In a car, only some of the energy from the gasoline is used to

propel the car. The rest is lost as heat.–

• Nothing can ever be 100% efficient in terms of converting energy to work.–

• When you walk up a hill you gain the same amount of energy you will lose as you walk down.–

• Your computer, TV, and refrigerator all need a fan to keep from overheating.–

• There is no such thing as perpetual motion.–

Energy Quality, Efficiency and Loss

• Energy quality is how much work can be done with the energy. High quality energy is convenient, concentrated and able to do lots of work. Low quality energy is hard to harvest, transport and/or use.

• Energy efficiency is what percent of the energy expended can be used to do work. – Incandescent light bulbs are only 5% efficient. The

other 95% of the energy is lost as heat– LEDs can be 85% efficient, meaning on 15% of the

energy is lost as heat

Feedback Loops

• Positive loops are runaway cycles where a change in a certain direction causes further change in the same direction– Population growth : more people are born, more

people then reach reproductive age and have children, which leads to more people.

• Negative loops occur when a change in a certain direction leads to a lessening of that change– Thermostat

What kind of feedback?a. The baby boom resulted in lots of children which meant the US

population grew. Those children grew up and had more babies making the population continue to grow -

b. Cole takes a nap and gets a sticker when he gets up (yay stickers!) so the next day he takes a nap so that he will get another sticker -

c. Cole does not take a nap and has to go to bed 1 hour earlier meaning he misses out on taking a walk, so the next day he takes a nap so he can stay up for the walk –

d. Cole throws a temper tantrum, which means that Mommy stops doing whatever she is doing and he gets to sit in Mommy’s lap and “talk” about what he did wrong and then Daddy “talks” to him about it later that night, so he keeps throwing temper tantrums so he can have Mommy and Daddy’s undivided attention -

e. Air conditioner and thermostat – f. Compounding interest –

Half life math• Radium has a half-life of 1500 years. How long will it take for

250kg of Radium to decay down to less than 10kg?

• The half-life of Pa-234 is 6.75 hr. How much of a sample of this isotope remains after 20.25 hr?

pH math

• pH = -log [H+]• If the pH is 5, what is the [H+]?

• If the [H+] is 1 x 10-7M, what is the pH?

• How much more basic is something with a pH of 11 than something with a pH of 9?

Energy Efficiency Math• The second law of thermodynamics states that when energy is

converted from one form to another, some of the energy is converted to a less useful form of energy (i.e. heat). Compare the overall efficiency of an incandescent light bulb (5% efficient) and an LED light bulb (85% efficient) from power plant to light generation.– The conversion of coal to electricity is 35% efficient and the transfer of

the electricity from the power plant to your home is 90% efficient.

Math Warm-upYour electricity bill shows that you use 600 kWh of electricity each month. Your refrigerator, which is 15 years old, could be responsible for up to 25 percent of this electricity consumption. Newer refrigerators are more efficient, meaning that they use less energy to do the same amount of work. If you wish to conserve electrical energy and save money, should you replace your refrigerator? How can you compare the energy efficiency of your old refrigerator with that of the more efficient new models?Your refrigerator uses 500 watts when the motor is running. The motor runs for about 30 minutes per hour (or a total of 12 hours per day).• How much energy in kWh does your refrigerator use per year?

(multiply energy use in watts (W) by hours/day to get Wh/day, then convert to kWh/yr)

• How much more efficient is the best new refrigerator compared with your older model? The best new model uses 400 kWh per year.

• Assume that you are paying, on average, $0.10 per kilowatt-hour for electricity. A new refrigerator would cost you $500 with an energy saving rebate. If you replace your refrigerator, how long will it be before your energy savings compensate you for the cost of the new appliance?

Math Practice

• What is the pH of a pond with an [H+] of 1 x 10-4.5 M?

• What is the [H+] of a pond with a pH of 6.3?• If you started with 200 g of Carbon-14 and

Carbon-14 has a half-life of 5,730 years, how old is an item that has 12.5 g of Carbon-14 remaining?