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35 votes
Accepted

Did predators evolve eyes first?

Short answer Complex eyes may have evolved first in predator species, specifically in box jellyfish. Trilobites are another group of animals where complex eyes may have evolved first. The trilobites ...
AliceD's user avatar
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30 votes

Why do blood vessels in the eye not obstruct vision?

Avoid the fovea Figure 2 from the same paper shows the distribution relative to the fovea: As you can see, it's pretty much devoid of this superficial vasculature, so anything you are directly ...
Bryan Krause's user avatar
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20 votes

Did predators evolve eyes first?

AliceD's answer is great but just to address your points 1 and 2. Eyes are expensive. From a study on fish loosing their vision in caves. The cost of vision was calculated to be 15% of resting ...
Sam Dean's user avatar
  • 301
14 votes

Can mosquitoes be attracted by our voice?

Mosquitoes can hear the human voice. If they use human sound to hone in on us as a source of a blood feed is not known at this time, however research into this has just begun. This is especially ...
anongoodnurse's user avatar
13 votes

Why do blood vessels in the eye not obstruct vision?

You CAN see your blood vessels! Following-up from Bryan Krause's answer: Bryan mentioned that the blood vessels are typically not visible partially because they are unchanging (i.e., static). In ...
theforestecologist's user avatar
13 votes

Did predators evolve eyes first?

Eyes evolved multiple independent times in convergent evolution. Almost all the vertebrates have eyes. Those few that doesn't lost their eyes through evolution and live in deep ocean of in caves where ...
Victor Stafusa - BozoNaCadeia's user avatar
12 votes

Why do I see different hues of colors between each of my eyes?

This is an interesting phenomenon which I have been aware of for several years, but I haven't yet come across any official description of it or explanation for it. Nonetheless, the phenomenon is easy ...
Gwen's user avatar
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10 votes
Accepted

Can "red" cone cells actually see much red light?

This is a good question. The first thing to note is that human colour vision is very complex and still poorly understood. If you visit the wikipedia page on RGB, you will find that this correctly ...
Anon's user avatar
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9 votes
Accepted

Do humans learn to distinguish different senses?

Short Answer: Though the concept of development of perception in children is known (Vernon et al, 1961), the process of differentiation between different senses is largely innate, though some ...
another 'Homo sapien''s user avatar
9 votes

Do humans learn to distinguish different senses?

Mixing up input from different senses is actually a known neurological phenomenon called synesthesia. Synesthetes (ie. adults experiencing synesthesia) might see numbers in colors for example. Some ...
francoiskroll's user avatar
9 votes
Accepted

How do our eyes detect light at different frequencies?

Short answer Action potentials generated to different colors are indeed similar throughout the nervous system and do not encode color as such. Instead, the different color- sensitive cells in the ...
AliceD's user avatar
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9 votes

Can mosquitoes be attracted by our voice?

Mosquitos can certainly hear in the range of normal human speech. They are sensitive to the range of around 150-500Hz, and typical human speech is between 100-300Hz depending on your age and sex (DOI: ...
Joe's user avatar
  • 379
8 votes

Can any organisms see non-electromagnetic radiation?

Some fungi have radiotropism; they grow toward radiation sources. Melanin-expressing (melanotic) fungi migrate toward radioactive sources, which enhance their growth. According to this paper. These ...
BPinto's user avatar
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8 votes
Accepted

How do snakes determine the direction of prey from their thermal infrared sensing pit organs?

From Wikipedia: The facial pit actually visualizes thermal radiation using the same optical principles as a pinhole camera, wherein the location of a source of thermal radiation is determined by the ...
Bryan Krause's user avatar
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8 votes
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Can dogs see infrared radiation, i.e., heat?

A dog's nose can even sense weak thermal radiation, as found out recently by researches at at Lund University and Eötvös Loránd University. So strong thermal radiation can be detected from a couple of ...
iLuvLogix's user avatar
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7 votes
Accepted

Why do humans not have a powerful sense of smell?

Humans' poor sense of smell is a myth, borne of 19th century speculation rather than actual data. This is described in an excellent recent paper in Science , "Poor human olfaction is a 19th-century ...
Raghu Parthasarathy's user avatar
7 votes

Why do humans not have a powerful sense of smell?

There are several factors in human. we are upright, which brings the nose just about as far away for scents as it can get, you want your nose as close to the ground as possible for the most efficient ...
John's user avatar
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7 votes
Accepted

How does the brain immediately know when one's thirst has been quenched?

There are two different aspects to or drivers of thirst, osmolality and hypovolemia, with plasma osmolality elevation being the more potent stimulus of thirst. As stated by @arboviral (and supported ...
anongoodnurse's user avatar
7 votes
Accepted

What would happen if you "rewired" your eyes with your nose?

"Rewiring" the brain isn't quite that simple: simply splicing a nerve to another doesn't necessarily mean the axons of that nerve will then grow into area. I am unaware of any studies that cross these ...
Bryan Krause's user avatar
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7 votes
Accepted

Do creatures exist which can stop their hearing at will?

Yes Many echolocating bats use the stapedius muscle to separate the inner ear bones when they emit their call so they are not deafened by their own call. Their ears are highly sensitive to the very ...
John's user avatar
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6 votes
Accepted

Are there animal species that sense infrared light with their eyes?

Short answer As far as I can see, there are no animalia with high-sensitivity infrared photoreceptors in their retinae. Instead, infrared is detected at low thresholds with a dedicated sensory system ...
AliceD's user avatar
  • 52.5k
6 votes

Can LSD in very small amounts increase mental ability?

The phenomenon you are referring to is called microdosing. It was brand-new in terms of research focus when you initially asked your question, and it is still a fairly novel and little-studied subject....
TheChymera's user avatar
  • 1,336
6 votes
Accepted

How do we sweat immediately after drinking water on a hot day?

Not everyone sweats in seconds after drinking water in summer. Also, sweating in seconds after drinking water is not likely due to water being absorbed (Nutrition Reviews, 2015): Ingested fluids ...
Jan's user avatar
  • 8,079
6 votes
Accepted

How exactly does sensory substitution work?

Tot start of with your definition: Sensory substitution, when one of sensory modality changes into another sensory modality to help someone restore the ability to perceive defective sensory using a ...
AliceD's user avatar
  • 52.5k
5 votes

What is the smallest difference in light wavelength that the human eye can detect?

Is there a lower limit to the difference in wavelength (colour) our eyes can detect? The average human can detect differences in color as low a 1 nm depending on color subject to: minimum spot size -...
Rob's user avatar
  • 403
5 votes
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What is the smallest difference in light wavelength that the human eye can detect?

The eye really on can sense 3 colors, or to be more precise it only has three types color sensitive each of which detects a large range of wavelengths with no way to distinguish between them within ...
John's user avatar
  • 14.7k
5 votes

Are there animal species that sense infrared light with their eyes?

Yes, Mantis shrimp have 12 photo-receptors and can detect the low-end of IR. In H. trispinosa one of the photoreceptors, R3P, detects right at the edge of 'deep red' light and would detect infrared (...
Artem's user avatar
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