Symetry

[Jamin4422]

Why don't you understand geology much? I can give you a copy of geology 101 textbook.

If your giving away books give me one. Although I am sure I could get one very cheap on Amazon.

 

[NailsII]

Development is controled by the Hox Gene.

homeobox genes. (pleural).

 

[juvenissun]

If your giving away books give me one. Although I am sure I could get one very cheap on Amazon.

I have too many books (the book buyers don't want them any more). I don't mind to send you one, two, or three at all.

 

[juvenissun]

That didn't answer the question.

It did. For example, I know you don't know much about geology either. A correct prediction shows the best answer in the background.

 

[juvenissun]

In evolutionary terms, the intestinal tract is one of the oldest structures of animals - and I'll stick my neck out here, waiting to be shot down by someone who knows more, but I believe that it evolved before bilaterism and so may not be under it effect.
In embryology, the GI tract grows from the anus to the stomach and is also on of the first structures to develop.

This may explain the difference - it is made by different genes, which function earlier.

I don't think the lungs are symmetrical, they most certainly are not in snakes.

One major point which is missing from this thread, is that being roughly the same on both sides externally is a massive advantage for locomotion.
Could you imagine how a fish like Nemo would really swim?

Interesting.

But would the motion be more agile if the body has no symmetry at all? I think symmetry might be a burden to evolution in any circumstances.

 

[Mr Strawberry]

It did. For example, I know you don't know much about geology either. A correct prediction shows the best answer in the background.

As you are a young earth creationist, you'd be better off trying to read one of your introductory geology books yourself rather than giving them away. Although if they're written in English, and English isn't your first language, I can see you might struggle with them. No offence like.

 

[Wiccan_Child]

Interesting.

But would the motion be more agile if the body has no symmetry at all? I think symmetry might be a burden to evolution in any circumstances.

Why?

Take binocular vision, for instance. That only works if you have two eyes doing the same thing with a lateral gap between them. Asymmetry would hamper depth perception.

Wings work by applying thrust to the bird upwards and forwards. Asymmetry to the wings would cause thrust to be disproportionately one-sided, making them yaw or turn in circles. The same is true of most modes of motion - a cheetah sprinting can't be falling over onto one side.

 

[Elendur]

It did. For example, I know you don't know much about geology either. A correct prediction shows the best answer in the background.

Of course you know I don't know much about geology, I'm quite certain I've stated that earlier.

That still doesn't change it:

How can you conclude that he doesn't understand geology from this?

Not only him, but you too.

You did not answer the question. He asked how.

 

[juvenissun]

Why?

Take binocular vision, for instance. That only works if you have two eyes doing the same thing with a lateral gap between them. Asymmetry would hamper depth perception.

Wings work by applying thrust to the bird upwards and forwards. Asymmetry to the wings would cause thrust to be disproportionately one-sided, making them yaw or turn in circles. The same is true of most modes of motion - a cheetah sprinting can't be falling over onto one side.

You think so because you are preoccupied by examples.

Rocket has one (direction) propeller, monocycle is more agile in turns, the movement of one is simpler than that of two or more.

I am not sure, but I think it is very possible. It is much easier to be unsymmetrical.

On the other hand, a perfect symmetry like a sphere is also very good. Why don't we see some spherical animals?

 

[Wiccan_Child]

You think so because you are preoccupied by examples.

Well, yea - you made a claim, and I pointing to real-world examples were it wasn't true. Thus, your claim is false.

Rocket has one (direction) propeller, monocycle is more agile in turns, the movement of one is simpler than that of two or more.

And, you'll notice, rockets and motorcycles are symmetrical.

I am not sure, but I think it is very possible. It is much easier to be unsymmetrical.

On the other hand, a perfect symmetry like a sphere is also very good. Why don't we see some spherical animals?

We do (bacteria, some species of diatom, etc).

 

[Loudmouth]

On the other hand, a perfect symmetry like a sphere is also very good. Why don't we see some spherical animals?

Volvox - Wikipedia, the free encyclopedia

Sea urchin - Wikipedia, the free encyclopedia

Sponge: http://i1.trekearth.com/photos/6974/the_sea_sponge.jpg

I can find more if you like.

 

[CabVet]

On the other hand, a perfect symmetry like a sphere is also very good. Why don't we see some spherical animals?

Sometimes I wonder if we live in the same planet... There are about 700 species of these guys:

 

[Wiccan_Child]

Sometimes I wonder if we live in the same planet... There are about 700 species of these guys:

That's what irks me about sci-fi aliens - if terrestrial life has things as far flung as humans, anenomes, and jelly-fish, why is the most alien life we can imagine something with such ordinary arms/legs/tentacles, bilateral symmetry, a distinct head with eyes, nose, mouth, etc...

If you want an alien, just look in the oceans

 

[juvenissun]

Volvox - Wikipedia, the free encyclopedia

Sea urchin - Wikipedia, the free encyclopedia

Sponge: http://i1.trekearth.com/photos/6974/the_sea_sponge.jpg

I can find more if you like.

No. These don't count. Even they are spherical in shape, they do not take the advantage of the spherical symmetry in locomotion. They still move linearly and it makes them very cumbersome.

 

[CabVet]

No. These don't count. Even they are spherical in shape, they do not take the advantage of the spherical symmetry in locomotion. They still move linearly and it makes them very cumbersome.

LOL, move the goalpost much? Now you don't just need to be spherical, you need to "take the advantage of the spherical symmetry in locomotion". Please, explain what type of locomotion would favor a spherical symmetry, and while you do that, try to explain why engineers don't design spherical boats, cars or airplanes. That way I can give you an example and you can move the goalpost again.

 

[Tiberius]

How does evolution explain symmetry? Nearly every species is symmetrical. Now just because there are a few that aren't, you can't use that as evidence because it ignores the fact that most are, and as evolution is just something based on random mutations how can it produce hundreds if not thousands of symmetrical species. Just because all species would be likely to survive better with a balanced body doesn't mean it's impossible for it to survive with an imbalanced body.

How could evolution "know" to sprout an identical body part on the exact opposite of the body? And don't give me any garbage about some body parts on people might be a little smaller or a little longer or slightly off symmetry, that's nit picking and fact of the matter is nearly identical is unlikely enough in regards to evolution.

When life started evolving ways to move through water in a conscious act rather than drifting, a front end and a back end was established. It makes sense for sense organs to be clustered around the end of the organism that encounters things first, so the front end gained all the sense organs. Now, there are different risks from above and below (you are more likely to get attacked from above if you swim near the seafloor, for example), so that explains the differences between top and bottom. But there's no reason why you are more likely to be attacked from the left rather than the right. So this explains why there is a top/bottom difference, front/back difference but no left/right difference.

 

[AECellini]

No. These don't count. Even they are spherical in shape, they do not take the advantage of the spherical symmetry in locomotion. They still move linearly and it makes them very cumbersome.

they don't "take advantage" of it because there aren't environmental pressures for characteristics like being able to roll around to be optimal.

you only asked for organisms with spherical shape.

 

[juvenissun]

they don't "take advantage" of it because there aren't environmental pressures for characteristics like being able to roll around to be optimal.

you only asked for organisms with spherical shape.

But what is the environmental pressure to the development of a bilateral symmetry? If there were no such pressure, then why not spherical?

 

[juvenissun]

When life started evolving ways to move through water in a conscious act rather than drifting, a front end and a back end was established. It makes sense for sense organs to be clustered around the end of the organism that encounters things first, so the front end gained all the sense organs. Now, there are different risks from above and below (you are more likely to get attacked from above if you swim near the seafloor, for example), so that explains the differences between top and bottom. But there's no reason why you are more likely to be attacked from the left rather than the right. So this explains why there is a top/bottom difference, front/back difference but no left/right difference.

So, if the shape is spherical and can roll, then all the worries would disappear.

 

[juvenissun]

LOL, move the goalpost much? Now you don't just need to be spherical, you need to "take the advantage of the spherical symmetry in locomotion". Please, explain what type of locomotion would favor a spherical symmetry, and while you do that, try to explain why engineers don't design spherical boats, cars or airplanes. That way I can give you an example and you can move the goalpost again.

Think about the superior movement of a flying saucer. It is a 2D sphere.

You are right, the gravity gives a limitation to the vertical movement. But why aren't most lives disk in shape?