10%
Explanation:
Only 10% of the energy absorbed by plants from the sun is passed to primary producers and converted to biomass. Similarly, only 10% of the energy fro primary producers is passed to secondary producers, and this continues up teh chain to Quaternary consumers. This is why energy of an ecosystem is represented as a pyramid (tapering at the top). Transfer of energy up an ecosystem is very inefficient with most of the energy lost to the environment as heat during the transfer. In this case, the oak tree is a primary producer which represents the base of the energy pyramid.
Learn More:
For more on energy pyramid check out these;
https://brainly.com/question/12477814
https://brainly.com/question/11465998
#LearnWithBrainly