Final answer:
The hand signal 'hand-down' in Biology indicates the opposition movement of the thumb toward the fingers of the same hand, allowing us to grasp and hold objects.
Step-by-step explanation:
The hand signal hand-down is a movement of the hand from the palm forward position to the palm backward position.
It is commonly used in Biology to indicate the opposition movement of the thumb toward the fingers of the same hand, which allows us to grasp and hold objects.
This hand signal is important for various actions such as assisting in bending the hand up toward the shoulder, tilting the hand to the side away from the body, stabilizing the wrist, and bending the fingers to make a fist.