What is an eyespot?
Q: What is an eyespot?
A: An eyespot is a simple organ used to detect light in small, simple invertebrates like Planaria and in single-celled protists like Euglena and Chlamydomonas.
Q: What are some other names for an eyespot?
A: An eyespot may also be called an ocellus or pigment pit.
Q: How do eyespots differ from our eyes?
A: Eyespots do not have lenses or any means of focusing, so they can only sense light from dark but do not give the animal a visual scene like our eyes do.
Q: How do animals with eyespots respond to light?
A: In many animals with eyespots, a pigment molecule called an opsin detects light, and a nerve fiber carries the information from the eyespot to the animal's simple nervous system. This allows the animal to move in response to things like a shadow passing over it.
Q: When did eyes first appear in the fossil record?
A: The first fossilized eyes date back to the early Cambrian period, about 540 million years ago.
Q: What is the "Cambrian explosion"?
A: The "Cambrian explosion" refers to a burst of rapid evolution that occurred during the early Cambrian period.
Q: What is one theory about how the evolution of eyes may have influenced this rapid evolution?
A: One theory is that the evolution of eyes sparked an "arms race" that led to a rapid spate of evolution. Organisms with better eyesight were better able to navigate their environments and find food, so they had a competitive advantage over organisms without eyes.
