Barrier — Science definition
A defence that prevents entry — unbroken skin, mucus in the airways, tears, stomach acid — each closing a particular route.
Where it is taught
- Microorganisms, Barriers & Immune Defense — Coordination, Defense & Reproduction, Life Science & Scientific Inquiry, Grade 7
Questions using barrier
Problem 1
Does an entry barrier prove no agent can ever enter?
Answer and explanation
No. It can reduce entry, while effectiveness depends on conditions and other pathways.