Do scientists have evidence to support their hypotheses about the early evolutio

Question

Do scientists have evidence to support their hypotheses about the early evolution of eyes? a) No. Scientists have only a hypothesis based on the structure of proteins. b) No. The evidence for the evolution of eyes is inconsistent among lineages, such as bilaterians and cnidarians. c) Yes. Scientists know exactly how the eye evolved based on a series of steps involving mutations of different proteins. Od) Yes. Scientists have evi from phylogenies based morphological structures as well as gene sequences and entire genomes.

Explanation / Answer

d) Yes, Scientists know exactly how the eye evolved based on a series of steps involving mutations of different proteins.

Vertebrate eyes contain ciliary photoreceptor cells, whereas the invertebrate eyes contain rhabdomeric photoreceptor cells. Both are morphologically different and express distinct types of opsin protein. Ciliary receptors express c-opsin and rhabdomeric receptor express r-opsin protiens. Both the receptor types are present in one way or the other (as a result of mutation) in both vertenerates and invertebrates. The ganglion cells of vertebrate retinas also express r-opsins. The invertebrate Platynereis  have ciliary photoreceptors in the brain and rhabdomeric receptors in the eyes. These shows that the common ancestor of vertebrates and invertebrates had both types of photoreceptor cells which they used them for different purposes.  

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