Matter cycles through organisms and their surroundings. Decomposition returns materials that producers can reuse. Energy enters many ecosystems mainly as sunlight, transfers through food webs and becomes dispersed as heat. It is conserved, but does not cycle back from decomposers to the Sun in the same way that matter cycles.
Only part of one feeding level’s energy becomes available to the next. Energy also supports life processes and remains in uneaten material and waste. No fixed transfer percentage applies universally. Use the values supplied in the question. Subtract energy passed to the named next level from the starting amount to find the amount not passed there; this amount is not destroyed.
Example 1
A supplied model has 1000J at producers and 120J passed to herbivores. How much is not passed to those herbivores?
1000−120=880J. It may be used in life processes or remain in uneaten material and waste; it is not destroyed.
Example 2
Why do decomposers help matter cycle but not recycle sunlight?
They break down organic material and release substances that can be reused. Energy disperses as heat rather than returning to its original sunlight form.
Watch out:Matter cycles. Energy flows through and becomes dispersed as heat, although total energy is conserved.
Energy flow and matter cycling practice | Year 7 Science | Ascent Arcade