Photoreceptors, Biology

Assignment Help:

Photoreceptors

Photoreceptors are concerned in absorption of light by photosensitive pigments. The chemical change involved produces the impulse concerned in the nerve cells. The pigments involved are carotenoid derivatives containing retinine (vitamin A aldehyde) combined with a protein (opsin). Rhodopsin is one of the general pigments. Simple eyes are extremely common; extremely differentiated compound eyes have evolved in many arthropods, and well differentiated camera type eyes, as comparable to vertebrate eyes occur in cephalopods. You will see among several non-chordates a variety of eyes ranging between these extremes. Simplest eyes in Platyhelminthes and annelids are in the form of pigment spots containing sensory cells associated with pigment cells. They serve differentiation of light from darkness. In several polychaetes they reach higher level of organization. The cup may often secrete a lens. The cephalopod eye is the result of highest elaboration of vesicular eye. Actually the eye in Octopus reaches the structural complexity of that of vertebrate eye, resembling it in considerable details. Though, the cephalopod retina is direct type with sensory ends of the receptor cells directed towards the source of light whereas the retina of vertebrate eye is inverted with the sensory ends turned away from the source of light.


Related Discussions:- Photoreceptors

Compare and contrast changes in carbon, Compare changes in the carbon cycle...

Compare changes in the carbon cycle to that of the nitrogen cycle on human health. Please make a conceptual graphical model for how changing the carbon cycle is likely to impact hu

How potassium dichromate dissolved in water, How would you prepare 90 ml of...

How would you prepare 90 ml of .01 M potassium dichromate dissolved in water? Molecular mass of potassium dichromate is 294 g/mol.

Heart, how the blood is circulated with the help of heart

how the blood is circulated with the help of heart

What are the main human diseases caused by virus, What are the main human d...

What are the main human diseases caused by virus? Between diseases caused by virus are common cold, flu, mumps, variola (considered eradicated nowadays), rubella, AIDS, measles

Do squids and octopus have exoskeleton, Q. Do squids and octopus have exosk...

Q. Do squids and octopus have exoskeleton? Squids and Octopus generally do not produce external shell (some squid species can have an internal shell). One cephalopod group the

Diversity in living organisms, which organism are called primitive and how ...

which organism are called primitive and how are they different from the so-called adavnced organisms

Explain prosoma in details., Explain Prosoma in details. First tagma of...

Explain Prosoma in details. First tagma of a cheliciform consisting of the first six segments of the body. Appendages on the prosoma are involved in locomotion and feeding. Pro

Define nutritive aspects of food constituents, Define Nutritive aspects of ...

Define Nutritive aspects of food constituents and effect of processing and handling? Nutrient stability; effects on nutrients of agricultural practices, handling, processing an

What is the formula of the dpd for withered plant, Q. What is the formula o...

Q. What is the formula of the DPD for withered (shrunken) plant cells and how is that situation possible? Withered plant cells are those that have shrunk due to loss of water b

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd