Topic 4.2 Energy Flow

IB BiologyR. Price

v. 1 2015

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#1: Most ecosystems rely on a supply of energy from sunlight

• Initial source of energy in most biological communities is sunlight• Producers like plants, eukaryotic

algae, & cyanobacteria use photosynthesis (autotrophs)• Consumers, detrivores, &

saprotrophs use the carbon in their food (heterotrophs)

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#2: Light energy is converted to chemical energy in carbon compounds by photosynthesis

• Producers absorb sunlight using chlorophyll & other photosynthetic pigments• Converts light energy to

chemical energy• Chemical energy (ATP) used to

make carbs, lipids, and all other carbon compounds in producers

#3: Chemical energy in carbon compounds flows through food chains by means of feeding

• Food chain is a sequence of organisms, each of which feeds on the previous one• Two – five organisms in a chain is

normal• Producers always first• Producer -> primary consumer ->

secondary consumer -> tertiary consumer• Arrow indicate the direction of

energy flow

#3: Chemical energy in carbon compounds flows through food chains by means of feeding

• Consumers obtain energy from the carbon compounds in the organism on which they feed

#4: Energy released by respiration is used in living organisms and converted to heat

• Organisms use chemical energy for life processes (ATP)• Cells produce ATP by cell

respiration.• Carbohydrates & lipids are

oxidized and the chemical energy is transferred to ATP• Energy transformation is not

100% efficient. Some is lost as heat

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#5: Living organisms cannot convert heat to other forms of energy

Living orgamisns can perform various energy conversions• Light energy to chemical energy in

photosynthesis• Chemical energy to kinetic energy in

muscle contraction• Chemical energy to electrical energy in

nerve cells• Chemical energy to heat energy in heat

generating adipose tissueCannot convert heat energy into any other form of energy

#6: Heat is lost from ecosystems

• Heat passes from hotter to cooler bodies (laws of thermodynamics)• Heat produced in living organisms

(including plants) is lost to the abiotic environment• Heat is radiated from the

environment into the atmosphere• All energy released by respiration

will be ultimately lost from an ecosystem

• By Arno (www.nutscode.com) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

Infrared image of fruit bat

#7: Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

Loss of energy between trophic levels:1. Most energy in digest food used in

respiration and lost as heat2. Consumers may not eat the entire

plant or animal, such as roots, hairs, or bones

3. Not all ingested food is digested and absorbed. Indigestible food passes in feces

Around 10% of energy of biomass in one trophic level is available to next

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Sources

Content Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014 ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.

Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge: Cambridge UP, 2014. Print.

ImagesUnless otherwise noted, images are obtained from Pixabay (www.pixabay.com) and used under the CC0 Public Domain license.