DP Bio Topic 4-2 Energy Flow

1. Topic 4.2 Energy Flow
IB BiologyR. Price
v. 1 2015

2. Allott 213

3. #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)

4. Allott 214

5. #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

6. #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

7. #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

8. #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

9. Allott 216

10. #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 tissue
Cannot convert heat energy into any
other form of energy

11. #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

12. #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 heat
2. 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

13. Allott 218

14. Allott 219

15. 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.
Images
Unless otherwise noted, images are obtained from Pixabay
(www.pixabay.com) and used under the CC0 Public Domain license.