Final answer:
The magnetosphere, which contains the Van Allen radiation belts, is responsible for trapping cosmic rays and shielding life on Earth from excessive radiation.
Step-by-step explanation:
The component that traps cosmic rays and shields life on Earth from excessive radiation is the magnetosphere. The magnetosphere contains the Van Allen radiation belts, which are regions above the Earth's atmosphere where charged particles such as ions and electrons from cosmic rays are trapped by the Earth's magnetic field. This trapping action forms intense radiation belts that protect the biosphere by preventing most of the harmful cosmic radiation from reaching the Earth's surface. Noteworthy phenomena associated with these belts include the aurora borealis and the consideration of radiation exposure during manned space flights, as astronauts must traverse this region quickly to minimize harmful exposure.