Evolution and vision.

[Vindhya]

Are bats considered as link between nocturnal animals and animals who can see proparly as humans in evolution ?

 

 

As bats have eyes but can't see ,what is their place in evolution ?

 

I am a high school student plesae clarify .

[CDarwin]

Are bats considered as link between nocturnal animals and animals who can see proparly as humans in evolution ?

 

 

As bats have eyes but can't see ,what is their place in evolution ?

 

I am a high school student plesae clarify .

 

First off, I don't know if a bat would agree that it didn't see "properly." It would probably be quite offended at that. In any event, only some bats have poor vision (and even they can actually see, just not well). These are the microbats and use echo-location to navigate, as I'm sure you know. This is by no means typical of nocturnal mammals, however. Most nocturnal mammals are like the macrobats, or Old World fruit bats, who have very large eyes with a reflective layer known as the tapetum lucidum to concentrate sparse light.

 

The earliest primates probably saw much like macrobats, and many living species still do today, so you're not far off in talking about humans having nocturnal ancestors. In fact one of the distinguishing features between living "primitive" primates of the group Strepsirhini and living "advanced" primates of the Haplorhini (which includes humans) is the presence of the tapetum lucidum. So really, if you want to look for sort of "link" between primitive, nocturnal mammals and animals with human-like vision, it would be best to point to the tarsier, a nocturnal animal who never-the-less lacks a tapetum lucidum. In reality the common Haplorhine ancestor was probably the inverse of a tarsier: a diurnal species with a tapetum lucidum who eventually lost it to permit greater visual acuity.

 

 

As for any better information on bat evolution, that's not really my forte. There has been a group proposed called the Archonta which links bats, primates, flying lemurs, and treeshrews all together as fairly close relatives, and there are multiple variations on that theme where bats are seen as fairly close to one or some of those groups. They're not horribly primitive mammals, and they don't appear to occupy any crucial space in mammalian evolution, just an extrememly interesting ecological niche.

[Sisyphus]

I don't know exactly what the evolutionary place of bat is, but it's definitely not a link like you describe. They're cousins, not ancestors. Their eyes, like everything else, are evolved for their own purposes. They can see, as CDarwin says, to varying degrees, and generally have as good vision as they can make use of, given their environment, diet, other senses, etc.

 

What it's important to understand about evolved traits is that they won't appear if at any point their costs outweighs their advantages. And so you won't ever have an animal that suddenly develops useless eyes, nor will you really have an animal that has better eyesight than it really needs, because eyes are "expensive" in terms of bodily resources. That's why cave fish, which are descended from seeing fish, often evolve to become totally blind and eventually lose their eyes entirely.

[BumFluff]

recently, can't remember what site I read it on, but there was an article concernign some recent findings about the evolution of eyes and some fossils they have discovered.

[Radical Edward]

Are bats considered as link between nocturnal animals and animals who can see proparly as humans in evolution ?

 

 

As bats have eyes but can't see ,what is their place in evolution ?

 

I am a high school student plesae clarify .

 

no, Eyes are a basal feature of mammals (the common ancestor to all mammals had eyes) - indeed eyes are basal to the tetrapods. The the last common ancestor to all of the bats would also have had good eyesight.

 

Now not all bats (Chiroptera) have bad eyesight, the Megachiroptera (megabats, including fruit bats) have excellent eyesight, and even better smell. Microchiroptera on the other hand predominantly use echolocation as they chase insects in dark caves.

 

About the eyesight though. as the microchiroptera developed better and better echolocation, their eyesight would degrade as it became less important to their way of life. Operating eyes and the relevant bits of the brain takes a substantial amount of energy, and if the eyes are not even being used to their full extent, that is a waste of resources, and so mutations to the eyes and brain parts reducing them to what they are now would actually be beneficial.

 

regarding humans seeing properly, well it's difficult to say what you would mean by "properly". Many nocturnal birds have much better visual acuity than we do, for example owls.

[Vindhya]

Actualy what I mean by "properly as humans" is comparing it with humans.