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Questions tagged [symmetry]

Symmetry is the balanced distribution of duplicate body parts or shapes within the body of an organism.

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2 votes
0 answers
112 views

Is there an animal which does not have any kind of symmetry?

Bilateral symmetry is a common feature of animals, and starfish have rotational/circular symmetry. But is there any animal that has no symmetry?
6 votes
4 answers
9k views

What is Biradial Symmetry?

I am trying to visualize biradial symmetry. I have read the section in the Wiki entry on Symmetry in Biology but it is quite brief and there is no example to illustrate it. I haven’t been able to find ...
0 votes
0 answers
116 views

Why are trees so symmetric?

Many trees have a quite symmetrical overall shape. Some are extremely symmetric. Yet when you look at the branches and limbs of any tree their distribution seems completely random. Often even the ...
3 votes
0 answers
39 views

Spiral lichen forms

I recently spotted many examples of a bilaterally symmetric lichen with a spiral form. This was on Navajo sandstone at the Utah-Arizona border. I found one paper that indicates this is likely Lecidea ...
1 vote
1 answer
48 views

Estimates for the volume and mass of most ancestral multicellular organism, and a similar question for alive animals with radial symmetry

please I'm interested in an estimate for the volume and weight, the mass, of (most) ancestral multicellular organisms. Wikipedia has the article Multicellular organism, and my main interest are ...
4 votes
1 answer
161 views

Are 99% of animals bilaterally symmetric?

The Wikipedia article for "Symmetry in Biology" claims: "Animals with bilateral symmetry are classified into a large group called the Bilateria which contains 99% of all animals (...
3 votes
1 answer
538 views

Is there any relation between phyllotaxis and the Fibonacci sequence?

I had to modify the question to get into a clearer answer. I originally asked this: Original question Watching some TV series, I saw the claim that all flowers have a number of petals that is related ...
0 votes
0 answers
25 views

What is the minimum-volume : neutral-volume : maximum-volume of the molecules that make up the SARS-Cov-2 virus-fusion machine?

The "neutral-volume" is the over-lapping volume between minimum-volume & maximum-volume of the molecules that make up the SARS-Cov-2-fusion machine. Those identifying potential ...
2 votes
1 answer
83 views

Development of radial symmetry in starfishes and other animals

How does nearly perfect radial symmetry arise in an animal like the starfish? My confusion lies in the fact that cells are fluid & amorphous, & that these characteristics seem to make it ...
0 votes
0 answers
42 views

Symmetry in Biology

It seems a curious fact to me that all organisms I can think of exhibit some definite symmetry on a large scale (much larger than molecules), and in particular mirror symmetry. Since it is so wide ...
13 votes
2 answers
325 views

Are there certain symmetric-pair muscles that are slightly bigger and NOT due to handedness?

Ok, hear me out, I was just thinking about an article in Nature I read in the past titled "Scrotal asymmetry in man and in ancient sculpture"$^{\dagger}$ and more recently an entire medical textbook ...
6 votes
1 answer
119 views

Are there any known consequences of the right-handedness of the DNA double helix?

In this article it is suggested (without evidence) that the right-handedness of DNA may be the cause that "kick[s] off asymmetry in the early embryo [of snails]". On the one hand we know that ...
0 votes
2 answers
177 views

Why is facial symmetry of the opposite sex attractive?

Why do we give so much importance to the symmetry of face in the opposite sex? Why do we yearn to reproduce with a person with a beautiful face? How is it important for survival, if at all? Is there a ...
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0 answers
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Biological & Evolutionary Reasons for Palm (Bi)Symmetry

The fingers of the human palm exhibit a (bi)symmetrical pattern with regards to their size, in the sense that the thumb and the pinky are almost the same size, and the same holds for the index and ...
84 votes
2 answers
32k views

Why is the heart not in the middle of the body?

All mammals that I can think of have a high degree of bilateral symmetry (In fact, almost every animal I can think of is like this). So why is the human heart not exactly in the middle of the body? ...
1 vote
2 answers
552 views

What is bilateral symmetry in "bilateria", an actual symmentry

Wikipedia defines bilateria as : animals with bilateral symmetry, i.e., they have a head ("anterior") and a tail ("posterior") as well as a back ("dorsal") and ...
3 votes
0 answers
74 views

Why might the chirality of gastopods be dominantly dextral?

This wikipedia page on gastropods provides a definition of chirality, and briefly describes the genetic mechanisms behind why a shell is wound left (sinistral) or right (dextral) handed. It also ...
1 vote
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58 views

How symmetrical can an organism be?

The majority of living things have some form of symmetry. Many mammals and fish have bi-symmetry, and anemones, starfish and jellyfish (among others) have radial symmetry. However, there usually are ...