sentence: Eyespots can only distinguish light from dark.
sentences_before: The earliest light sensors were photoreceptor proteins. They are eyespots, found in protists.
sentences_after: This is enough for photoperiodism and daily synchronization of circadian rhythms. They cannot distinguish shapes or determine the direction light is coming from.
concept_name: eyespot
headings: Evolution of the eye Early stages of eye evolution
categories: Eye Evolutionary biology