Simplify the following text for a Grade 7 native English-speaking person.
Original: Bilateria are all animals having a bilaterally symmetrical animals , they have front and a back end , as well as an upside and downside .
Simplified: The bilateria are all animals having a bilateral symmetry , i.e. they have a front and a back end , as well as an upside and downside . Radially symmetrical animals like jellyfish have a topside and downside , but no front and back .