What does the tapetum lucidum do?

The correct option is "gives animals night vision".

Step-by-step Explanation:

1. Understanding the Tapetum Lucidum:
The tapetum lucidum is a specialized layer of tissue located behind the retina in the eyes of many vertebrates, particularly nocturnal animals (such as cats, dogs, deer, and owls).

2. How it Works:
When light enters the eye, it passes through the retina, where photoreceptors detect it. In low-light conditions, some light passes through the retina without being absorbed. The tapetum lucidum acts like a retroreflector (mirror), reflecting this light back through the retina a second time. This gives the photoreceptors another opportunity to detect the light, effectively magnifying the incoming light signal.

3. Visual Effect and Night Vision:
This double-exposure of light increases the animal's sensitivity to dim light, which significantly enhances their ability to see in the dark (gives them night vision). This reflection is also what causes the familiar "eyeshine" or glowing appearance of animal eyes when illuminated by light at night.

4. Evaluating the Other Options:
• "it is the coloured part of the eye": This describes the iris.
• "it is the area where the optic never attaches": This refers to the blind spot (optic disc).
• "transparent jelly-like fluid": This describes the vitreous humor.
Therefore, the primary function of the tapetum lucidum is to give animals night vision.