Biometrics security is a technology which provided security based on the Human body. Like it can check the finger prints of a human as security base or can use to scan eyes as security etc.

Security controls (which include physical controls)

Encryption

For security ! To protect your personal data from prying eyes. If we didn't use passwords - then anyone could see what files you had on the computer.

In case of an accident during take off at night, your eyes must be used to the dark so it is for security

Security.... when you're foraging for food on the ground, many eyes watching for predators is a safer bet than if a squirrel was on its own.