Sustainable Eating Activity
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ward
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science
Recommended Grade Level(s):
Appropriate for: 9–12, College
Time Requirements:
Activity Time: 15 minutes per day over the course of one to three weeks; analysis time depends
on depth of investigation.
Teaching Topics & Concepts:
• This activity illustrates the concepts of assimilation efficiency and production efficiency in consumers by measuring biomass,
and the limits on the number of trophic levels.
• This activity relates to the sustainability of different diets.
• This activity introduces students to the concepts of recording data over time, analyzing data, and drawing conclusions.
Materials:
• Butterfly caterpillars
• Plastic vial with foam plug (e.g. fruit fly vial)
• Butterfly medium
• Weigh boats
• Balance (readability: 0.01 g minimum)
• Notebook or other means to record data
Safety
• Don't hurt yourself. Check vials for cracks or sharp edges that might cut skin. Wash hands thoroughly
before and after handling organisms.
!
Background
When consumers feed on other organisms, they first ingest their food (this is the total input of energy to the organism). They then
excrete and egest some of it in the form of urination, defecation and regurgitation (loss of energy). The remaining input is assimilated.
The ratio of assimilated to ingested energy is the assimilation efficiency. Organisms then use some of this energy in the form of respira-
tion, and the rest is put into production (growth, storage and reproduction). The ratio of production to assimilation is the production
efficiency. Another way to describe production is simply biomass.
INGESTION ASSIMILATION PRODUCTION
GROWTH, STORAGE,
REPRODUCTION
ASSIMILATION/INGESTION =
ASSIMILATION EFFICIENCY
PRODUCTION/ASSIMILATION =
PRODUCTION EFFICIENCY
EGESTION (DEFECATION,
REGURGITATION) & EXCRETION
RESPIRATION
Figure 1: The pathway of biomass through the organism.
