AP Biology Module 3.docx - AP Biology Module 3 Capturing...

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AP Biology Module 3 Capturing and Using Energy Energy and Living Systems All forms of life require a highly ordered system. Such order is maintained by constant flow of free energy into and out of the system. The organized flow of energy and matter is important at all levels of life, from cells to ecosystems. Order and Free Energy In many biological processes, cells create ordered structures from less organized starting materials. For example, cells assemble amino acids together to form polypeptide chains and use proteins to build membranes and organelles. This may seem like the cells are violating the second law of thermodynamics, which states that entropy (disorder) increases over time. However, it is important to remember that just as some biological processes decrease entropy, others increase entropy. For example, whenever large macromolecules such as starch and proteins are broken down into smaller molecules, entropy increases. Order is maintained by coupling cellular processes that increase entropy with those that decrease entropy. When the energy input is greater than the energy lost to entropy, cellular processes can be powered and order is maintained. In a similar way, exergonic reactions that release energy can be coupled with endergonic reactions that require energy. Use this activity to review how ATP is used to power endergonic reactions. Energy and Populations Just as free energy is required for the functioning and survival of individual cells and organisms, populations and ecosystems must have adequate free energy to grow and survive. Let’s explore the effects of energy availability on populations and trophic levels. Consuming Different Trophic Levels
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The available amount of usable energy decreases from one trophic level to the next. This is generally accompanied by a smaller number of organisms at the higher trophic levels. Let’s use some general data to compare how consuming different trophic levels can affect energy availability. Question 1 For the purposes of this exercise, we will make the following assumptions: One farmer consumes one chicken per day, or 365 per year. One chicken consumes 25 grasshoppers per day, or 9,125 per year. One thousand grasshoppers have a mass of 1 kilogram. One grasshopper requires about 30 grams of soybeans per year. One human requires about 650 grasshoppers per day, or 237,250 per year. Soybeans contain approximately 3.5 calories per gram. How many grasshoppers are needed for a year’s supply of chickens (365 chickens) for the farmer? Question 1 Answer The farmer eats 365 chickens per year, and each of those chickens consumes 9125 grasshoppers per year. How many kilograms of soybeans are needed to feed that amount of grasshoppers for one year? Question 2 Answer 3,330,625 grasshoppers are needed, each eating 30 grams of soybeans per year.
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