Matter and
Energy Flow
WCPSS/NC
8th Science
Key Vocabulary
•
Autotrophs: producers; organisms that produce complex organic compounds from
simple inorganic molecules using a source of energy such as sunlight
•
Food chain: a description of the path by which energy moves from the sun to plants
and animals
•
Food web: a diagram that shows how food chains in a community are related and
interlinked
•
Heterotrophs: consumers; organisms that obtain carbon from outside sources
•
Nitrogen cycle: model describing how nitrogen moves from the atmosphere to the soil,
to living organisms, and then back to the atmosphere
•
Photosynthesis: a process in which plants use sunlight, water, and carbon dioxide to
produce sugar and release oxygen
•
Cellular respiration: the process of consuming oxygen and releasing carbon dioxide
•
Water cycle: model describing how water moves from Earth’s surface to the
atmosphere and back to the surface again through evaporation, condensation, and
precipitation
Everything is connected!
• Organisms interact constantly with other organisms, most
often when one feeds on another.
• Food contains nutrients and energy need for survival.
• When one organism is food for another, some of the energy
in the first organism (the food) is transferred to the second
organism (the consumer).
• The transfer of energy does not stop here! When organisms
die, other organisms, decomposers, take in energy as they
break down the remains of the organisms.
• This constant movement of energy through a community
can be diagrammed as a food chain or a food web.
Food Chains
• A food chain is a simple way of showing how energy, in the
form of food, passes from one organism to another.
• For example, a pond food chain may look like this:
Aquatic plants → insects → bluegill (fish) → bass (fish) → humans
• Food chains usually have only 3-4 links because the available
energy decreases from one link to the next.
• At each energy transfer, some energy is lost as heat because
of the activities of the organisms.
• In the final link there is only a small amount of energy left
from the first link in the chain.
http://www.tutorvista.com/content/science/science-ii/environment/foodchain.php
http://moodle.oakland.k12.mi.us/os/mod/book/view.php?id=37527&chapterid=
1417
This image shows where the energy
starts for a plant. Only a small amount
of that plant’s energy is left for the lion
at the end of the chain.
Another example of the energy flow
from plant to owl. Again, not much
energy is left from the flower by the
time the owl eats the snake.
Food webs
• Food chains are too simple to describe the many interactions
among organisms in an ecosystem.
• A food web is a series of overlapping food chains that exist in
an ecosystem.
• A food web provides a more complete model of the way
energy moves through an ecosystem and are more accurate
because it shows how many organisms are part of more than
one food chain in an ecosystem.
Example of Food Web
http://www.bigelow.org/edhab/fitting_algae.html
Aquatic
Food Web
Example
Image: http://www.pride2.org/NewPrideSite/Asia/Lesson7/FoodWebs.html
Ecological Pyramids
• Most of all the energy in the biosphere comes from the sun.
• Producers take in and transform only a small part of the energy
that reaches Earth’s surface.
• When an herbivore eats a plant, some of the energy in the plant
passes to the herbivore.
• The majority of the energy from the plant is given off into the
atmosphere as heat.
• This continues to happen as other animals eat.
• An ecological pyramid is a model of the number of organisms at
each level. The bottom is always the producers of an ecosystem.
An Ecological/Energy Pyramid
http://www.biocab.org/energy_pyramid.html
Energy Pyramid
• An energy pyramid compares the energy available at each
level of the food chain in an ecosystem.
• A pyramid of energy usually has 3-4 levels (like a food
chain).
• Only about 10% of the energy at each level of the pyramid is
available to the next level.
• By the time the top level is reached, the amount of energy
available is greatly reduced.
Energy Pyramid
http://pdsblogs.org/pdsapes512/2011/09/29/ecological-efficiencyenergy-flow/
The Cycles of Matter
• Water Cycle: the constant recycling of water throughout the
Earth through evaporation, condensation, and precipitation.
• Nitrogen Cycle: the transfer of nitrogen from the
atmosphere to producers then to consumers; the nitrogen
then moves back to the atmosphere or directly into
producers again
http://www.kidsgeo.com/geography-for-kids/0161-the-nitrogen-cycle.php
Resources
• Images: cited beneath
• Information:
• Chapter 9, Section 3: Matter and Energy
Glencoe Science, North Carolina Science Grade 8
• Guidance from
http://scnces.ncdpi.wikispaces.net/file/view/Unpacked_Conte
nt_Grade8Science_RevisedSeptember2012.docx.pdf