Biology 20 Unit A: Energy and Matter Exchange in the Biosphere Chapter 2: Energy Flow in the Biosphere.

What is the source of almost all the energy on Earth? That’s right kiddiwinks, the Sun!!!

Much of the sun’s energy that enters the Earth’s atmosphere is filtered out before it reaches the surface. Only a tiny portion is actually used by green plants for photosynthesis.

2.1 Energy Transfer and Food Webs We can begin to understand how energy flows through ecosystems by categorizing living things into trophic levels. (trophic comes from a Greek word meaning “feeder”)

Organisms can be classified by whether they make their own food (autotrophs or “self-feeders”), or rely on consuming other organisms to gain the energy necessary for life processes (heterotrophs). The relationships of organisms in an ecosystem can be depicted in a food chain or a food web. What is the difference between these two? What do the arrows illustrate in food webs and food chains?

In places where the abiotic factors limit the number of organisms, the webs begin to look more like food chains. Can you think of a location on earth that this may be the case?

Photosynthesis is the process by which green plants and some other organisms use solar energy, carbon dioxide and water to produce carbohydrates. All organisms, including plants, undergo cellular respiration in order to use the energy in their food.

In a few ecosystems, such as caves or deep oceans, producers convert simple molecules into more complex compounds without solar energy, by a process called chemosynthesis. Chemoautotrophs are organisms that require only carbon dioxide, water and an energy source (other than solar energy) to make nutrients. Chemical energy is extracted from inorganic chemicals such as hydrogen sulfide (H2S), ammonia (NH3) or sulfur (S8). http://www.youtube.com/watch?v=D69hGvCsWgA

Limits on Energy Transfer Plants use much of the energy gathered through photosynthesis to carry out the processes it needs to live. Primary consumers do not digest everything they ingest. Some of the energy is eliminated in the form of feces. Some is used for life processes. Some of the remaining energy is lost as thermal energy. Much like primary consumers, secondary consumers will lose energy during digestion, and body maintenance. How much energy is passed down to each trophic level? (percentage)

Laws of Thermodynamics The first law of thermodynamics states that although energy can be transformed from one form to another, it cannot be created or destroyed. The second law of thermodynamics states that during any energy transformation, some of the energy is converted to an unusable form, mostly thermal energy, which cannot be passed on. Each time energy is transformed, some energy is lost from the system.

Ecological pyramids representing energy flow through the ecosystem can be illustrated in three different ways. Name and describe each. (pgs. 28-31) Describe the similarities and differences between the pyramids.

Human Use of Energy in Ecosystems Read page 33 in your text book, and describe the effects of the following induced changes. What are the effects for humans? Hunting and Fishing: Monocultures: To prepare yourself for your quiz, and unit test, try the review questions found in your textbook.