NEET BIOLOGY

Detailed explanation-1: -eyespot, also called stigma, a heavily pigmented region in certain one-celled organisms that apparently functions in light reception. The term is also applied to certain light-sensitive cells in the epidermis (skin) of some invertebrate animals (e.g., worms, starfishes).

Detailed explanation-2: -Eyespots are composed of photoreceptor proteins and typically red to orange carotenoid screening pigments. This association of photosensory pigment with screening pigment allows for detection of light directionality, needed for light-guided behaviors such as positive and negative phototaxis.

Detailed explanation-3: -The eyespot apparatus (or stigma) is a photoreceptive organelle found in the flagellate or (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids.

Detailed explanation-4: -Euglenids have many unique cellular structures, some of which include their flagella, eyespot, contractile vacuole, and chloroplasts. The eyespot helps the organism to detect light sources in order to photosynthesize.

Detailed explanation-5: -Euglena are able to perceive light and the direction it comes from through the use of 2 organelles, an eyespot and a photoreceptor.