Simplify the following text for a Grade 7 native English-speaking person.
Original: The quarks which determine the quantum numbers of hadrons are called valence quarks ; apart from these , any hadron may contain an indefinite number of virtual ( or sea ) quarks , antiquarks , and gluons which do not influence its quantum numbers .
Simplified: Quarks that make the quantum number of hadrons are named ` valence quarks ' .