Roundworms have taken this last body plan and adapted to thousands of environments with it. From microscopic to maybe a meter long, roundworms are just what they sound like-round worms. At one end, they have a mouth, at the other, an anus, with a tube digestive system in between.
Availability of two-factor authentication for Apple ID Two-factor authentication is an extra layer of security for your Apple ID designed to ensure that you're the only person who can access your account, even if someone knows your password.
When you enable 2-Step Verification (also known as two-factor authentication), you add an extra layer of security to your account. You sign in with something you know (your password) and something you have (a code sent to your phone). Go to the 2-Step Verification page. You might have to sign in to your Google Account.