Answer:
They use a hard shell, but not hard enough though because we humans can get through them hehehe
What is the question asking you?
Photoreceptor proteins are light-sensitive proteins involved in the sensing and response to light in a variety of organisms. Some examples are rhodopsin in the photoreceptor cells of the vertebrate retina,phytochrome in plants, and bacteriorhodopsin<span> and bacteriophytochromes in some bacteria.
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<span>Glycogen(for animals), Starch(for plants) </span>
