10/5/2011 Objective: Understand the significance of energy in biological systems Warm-Up: Why are autotrophs called “producers?” Why might “producers” be a misleading term?

10/10/2011 Objective: Be able to solve quantitative problems related to energy content Warm-Up: What is the relationship between “calorie” as discussed in science textbooks and the calories listed on food labels?

Energy 10/3/2011

Energy Energy can be defined as the capacity to do work or to cause change Organisms store energy in organic molecules Review: Which organic molecules are used for energy? Energy stored in molecules is called chemical energy

Using Energy During chemical reactions, some of the stored chemical energy is released This “released” energy is called free energy It’s called “free” because it is now available to do work; “free” here means usable Free energy is used for chemical work Making and breaking down complex molecules Free energy is also used for transport and mechanical work What are organisms transporting? What’s an example of mechanical work?

Getting Energy Organisms that obtain energy by consuming other organisms are called heterotrophs Example? Organisms that can get energy and nutrients from nonliving sources are called autotrophs Vocab tip: “hetero” means other, “auto” means self, and “troph” means feed

Energy in Ecosystems Autotrophs supply energy to the whole biosphere Can you explain why? In an ecosystem, autotrophs are the producers Why are they considered producers? Heterotrophs are consumers in an ecosystem Decomposers, organisms break down dead plants and animals, are vital to ecosystems Why?

Energy Flow 1st Law of Thermodynamics: Energy cannot be created or destroyed, but it can change form Total energy of the universe is constant What does this mean for organisms? 2nd Law of Thermodynamics: systems tend towards disorder Disorder of a system is called entropy As free energy is released, the world becomes more disordered

When a large molecule is broken down into smaller molecules, free energy is released and there is more disorder (entropy). Putting small molecules together to make bigger molecules decreases entropy, so it requires energy.

Energy Flow (cont.) Organisms have a high level of organization Maintaining organization requires energy “Lost as heat” You’ll hear this quite a bit—I’ll even say it sometimes!—but it’s not quite right Energy is never lost! All organisms release some heat energy This energy cannot be used for work—it is not free energy Organisms are inefficient

Check Your Understanding What’s the difference between chemical energy and free energy? Why are autotrophs classified as producers? Why are decomposers important? What does the 1st Law of Thermodynamics have to do with biology? Do organisms violate the 2nd Law of Thermodynamics? Why or why not?