Energy Transfer and Food Webs What is all this talk about ENERGY?

Objective To explain how energy in the biosphere can be perceived as a balance between both photosynthetic and chemosynthetic activities and cellular respiratory activities

Focusing Questions: What is photosynthesis and why is it important? What is chemosynthesis and why is it important? How does energy get into photosynthesis and chemosyntheis? Where does the energy go?

The source of almost all the energy on Earth is the Sun.

Capturing Energy for Life on Earth Energy storage in living systems is a balance between photosynthesis and cellular respiration.

Photosynthesis From all the suns energy that penetrates into the lower atmosphere only 0.023% is actually used by green plants for photosynthesis. Photosynthesis is a process that converts solar energy into chemical energy. The process of photosynthesis is carried out by green plants, green algae and euglena (bacteria).

Photosynthesis cont... These organisms take energy from the abiotic components of the environment (sunlight, CO 2, water) and transfer the energy into biotic components of the environment (green plants). Chemical Formula: 6CO 2 + 6H 2 O sunlight-----  6O 2 + C 6 H 12 O 6 carbon dioxide + water -----sunlight----> oxygen + glucose The chemical energy produced (C 6 H 12 O 6 ) is used to support the ecosystem.

Chemosynthesis This is process in which carbohydrates (i.e., glucose) are manufactured from carbon dioxide and water using chemical nutrients as the energy source, rather than sunlight. There are certain groups of bacteria, referred to as chemosynthetic autotrophs, that are fuelled by the oxidation of simple inorganic chemicals, such as sulphates or ammonia (NH 3 ).

Chemosynthesis cont... Some small ecosystems thrive in the hot (350°C/660°F) water found around hydrothermal vents on the ocean floor. In these ecosystems, the primary producers in the food web are bacteria whose life functions are fuelled by inorganic chemicals that seep up from the earth’s crust. v=jbpmJiI66wc v=jbpmJiI66wc

Cellular Respiration Cellular respiration in the process that allows organisms to utilize the chemical energy stored through photosynthesis. Cellular respiration breaks down glucose releasing the energy stored in the bonds. Chemical Formula: C 6 H 12 O 6 + 6O enzymes-----  6CO 2 + 6H 2 O glucose + oxygen enzymes ---> carbon dioxide + water

Think-Pair-Share 1. Where does the energy that reaches the earth come from? 2. Through what process is solar energy converted into chemical energy? What is the formula? 3. What is chemosynthesis? 4. Could we live without cellular respiration? Why or Why not?

The Transfer of Energy in Ecosystems Trophic Level: A category of living things defined by how it gains it’s energy; the first trophic level contains autotrophs, and each higher level contains heterotrophs

The Transfer of Energy in Ecosystems Three Basic Niches: 1) Producers: Autotrophs able to transform light (or chemical energy) into food – photosynthesis, chemosynthesis

The Transfer of Energy in Ecosystems 2) Consumers: Heterotrophs depend on producers directly or indirectly for chemical bond energy primary consumers: eg: herbivores secondary consumers: eg: carnivores tertiary consumer (feeds on secondary consumers) quaternary consumers (feeds on tertiary consumers)

The Transfer of Energy in Ecosystems 3) Decomposers: includes bacteria and fungi unlock nutrients from detritus and make them available for use by other organisms

Energy Transfer is represented by Food Chains – step-by-step sequence of whom eats whom in the biosphere Food Webs – a more complex (and realistic) description of who eats whom in a community, often involving many interlocking food chains. Stable ecosystems have complex food webs Battle at Kruger

What is this an example of?

Examples of Food Chains On your notes sheet, write down an example of a food chain. This first one is done for you: 1. Grass → squirrel → fox → coyote 2. ___________________________________

Discussion: which organisms would be autotrophs / heterotrophs? which organisms would be producers, primary, secondary, tertiary, etc consumers? What trophic level is each organism at?:

Limits on Energy Transfer: Every time energy is transferred between the components of an ecosystem, the amount of energy available to the next trophic level is reduced. Why? Energy lost as heat Energy is needed for life processes (i.e., digestion, etc) Not usable energy (i.e, excreted as waste )

Laws of Thermodynamics: First Law of Thermodynamics Energy is neither created nor destroyed; only converted in form Eg: a car engine converts the chemical potential energy of gasoline into heat, mechanical energy and kinetic energy.

Laws of Thermodynamics: Second Law of Thermodynamics: Each time energy conversion takes place, some energy becomes more diffuse and thus less useful eg: lost as waste heat. Conversion efficiency is often very low. Incandescent light bulbs are better at converting electricity into heat than light. Eg: Easybake Oven Therefore, the amount of available energy in each step of a chain of transformation is always less than the amount of energy available at the previous step. (i.e., food chains)

Laws of Thermodynamics

An example of a human induced change Biological Magnification (or amplification) Many organic pesticides (eg: DDT) are soluble in fat and are therefore not easily removed from living systems. Since these molecules are not lost, their concentration increases as consumed matter moves up the pyramid. Danger is greatest for consumers at the top of the food chain eg: Peregrine falcon

To Do: Practice Questions pg. 27 # 1-8