Wikipedia article selection
editFirst article that needs to be corrected and reviewed is the article on Tetrachromacy. The physiology portion needs to be expanded and currently the statement is incorrect that tetrachromats possess cone cells as opposed to rod cells. What it needs to be corrected to is that tetrachromats possess four cone cells - 3 that absorb the wavelengths in the visible spectrum and the fourth that absorbs UV wavelengths as well as possessing rod cells which are required for scotopic vision. Tetrachromats have both rods and cones.
The second article that needs to be reviewed is the page on Cone cell. The portion on colour blindness needs to be elaborated on since it does not have a clear explanation. Colour blindness occurs when any cone cell is faulty or absent. Most people with colour blindness can't distinguish between red and green shades and are considered dichromatic. Also, the image of the cone cell with an oil droplet also needs to be explained since humans lost the oil droplet adaptation, the presence of the oil droplet in the distal region of the cone cell is specific to certain species.
The last article that I would review is the article on Blue tit. Under the section heading Behaviour I would add the subheading Signaling. The UV reflection from the Blue tit's crest is used in sexual signaling. A study by Limbour et al. underlines the importance of UV colouration to sexual selection in birds where female blue tits adjust their parental investment in multiple ways to mate attractiveness. Blue tit UV colouration is one of the best understood signals of sexual attractiveness
Tetrachromacy edits
editArticle to review:Tetrachromacy
Tetrachromcy is vision that is capable of detecting wavelengths of the visual spectrum as well as ultraviolet wavelengths. Humans are trichromatic and possess 3 cone photoreceptor cells sensitive to red, blue and green wavelengths. Tetrachromats possess the same 3 red, blue and green cone photoreceptor cells in addition to a fourth cone cell that can detect ultraviolet light.
A clearer explanation is required. It is important to know that organisms do not possess their own visible spectrum. The visible spectrum and ultraviolet range are both continuous on the electromagnetic spectrum.
Photoreceptor cells in vertebrate retinas can be classified into two large groups:
edit- Rods
- Cones
Rods
Photoreceptive rod cells are responsible for dark-adapted vision (scotopic) and have rhodopsin as a visual pigment which transmits the visual signal. Rhodopsin is broken-down in light conditions, therefore in dim-lighting higher concentrations of rhodopsin remain intact which results in photon amplification allowing for better vision[1]
Cones Photoreceptive cone cells are responsible for light adapted vision (photopic) and have opsin as their visual pigment.In the tetrachromatic retina there are red, blue, green and UV cone cells.
Here it is important to know that both rod and cone cells are present in the tetrachromatic retina since it was mentioned that cone cells exist opposed to rod cells when both are present.
Birds
editBirds are tetrachromatic which means they have a fourth UV cone cell. This UV cone cell allows rapid motion detection which is essential for birds who are often involved in high-speed pursuit with prey or when escaping predation. Birds also have a much higher critical flicker frequency (CFFs) compared to humans. The critical flicker frequency is the frequency at which a flickering light stimulus can no longer be resolved and appears continuous[2] . With the addition of a photoreceptive UV cone cells, birds have the capacity to perceive a greater frequency of flickering light which means that in high-speed pursuits, the temporal resolution is greatly improved in birds with the addition of this fourth UV wavelength transmission
This is important to note because it was believed it was the double cone cell responsible for temporal resolution, this study shows how dynamic the UV cone cell is in comparison to other visual pigment cones.
A Birds eye-view:
edit| Feature | Humans | Birds |
|---|---|---|
| Cone cells | 10,000 cones per mm2 | 120,000 cones per mm2 |
| Types of cones | 3 types sensitive to red, green,& blue wavelengths | 3 red, green, blue & UV sensitive |
| Rod cells | 200,000 rod cells per mm2 | upwards of 1,000,000 rod cells per mm2 |
References
edit- ^ Okano (1995). "Molecular-Basis for Tetrachromatic Color-Vision". Comparative Biochemistry and Physiology B-Biochemistry & Molecular Biology. 112 (3): 405–414. doi:10.1016/0305-0491(95)00085-2. PMID 8529019.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Rubene (2010). "The Presence of UV Wavelengths Improves the Temporal Resolution of the Avian Visual System". J. Exp. Biol. 213 (Pt 19): 3357–3363. doi:10.1242/jeb.042424. PMID 20833929.
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