The study of the internal structure of organisms.

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What is the term for toes that pull together with an upstep?

I fairly recently learned the term digitigrade, to describe the anatomy of a creature that stands on its toes rather than on the flat of its foot, like cats and ...
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0answers
26 views

Distribute work for writing a lab report [closed]

I'm doing a laboration report on human vs chicken bones in a group, how should we distribute the work for writing the report, should we do one part of the chicken each or in some else way? We follow ...
4
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1answer
72 views

What causes the opaque green colour in Lepidoptera?

Link here to what I mean by 'opaque' colouration on the insect, the colour intensity remains constant despite changes in light intensity and angle (not shown by the picture but the moth exhibits this ...
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1answer
138 views

Examples of animals with 12-28 legs?

Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list: snakes have 0 Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs) ...
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0answers
13 views

Does this habit present any harm? [closed]

Sometimes I am able to put one knee down on the floor, rest my weight on that knee, and then relax it in order to make the knee cap go up and "crack" the knee. I can do this with both knees, I think ...
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3answers
266 views

Symmetry of species [duplicate]

I've got a silly question, sorry for that. I know, that we probably have no the right answer and the current answer could be "that's evolution, external conditions". I'd like to speculate, why most of ...
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0answers
30 views

Why are belly buttons on the stomach (why does the umbilical cord end up attached to the stomach)?

Belly buttons are at the site where the umbilical cord was attached to us as we developed inside our mothers. The same is true for all placental mammals. Why are belly buttons on the stomach? Why ...
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0answers
26 views

What is the lack of nipples in male horses and mice? [duplicate]

do male mice and horses create nipples in embryonic period then lack the or Whether these structures(nipples) are created from scratch?? Thank you!
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29 views

Why do male rats and horses lack nipples? [duplicate]

I have read many articles about why male rats and horses lack nipples, however, I still don't understand why! Do male rats, mice, and horses have nipples in early embryonic life and then lose them?
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1answer
50 views

Why does the kidney of a cow have lobules, why the kidney of a human hasn't any?

The kidney of a cow has lobules, while the kidney of a human hasn't any. I can't think of any reason why it would be good for a kidney to have lobules. It would be good if the kidney needed to have a ...
2
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0answers
51 views

Front versus back in animal anatomy [closed]

Throughout various species, there seems to be a clear distinction between the front and the back. The musculature of the front, when engaged, closes or curls up the body, protecting it, while the ...
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1answer
57 views

Is the prostate problem unique to humans?

In human males the urethra goes through the prostate rather than around it, which tends to create problems for older men as the prostate enlarges. Is this only a human problem or do other animals, ...
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16 views

Organ secretions

If an animal secrets an enzyme from an organ that is entirely dedicated for the same secretion, can one or cannot one just use the gene coding for that protein to obtain the protein in vitro. How much ...
4
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2answers
150 views

Why do snakes not have eyelids?

Why is it that snakes do not have eyelids? Is it due to that fact that they are not as evolved as we humans and other organisms that have eye lids, or is there any other significance behind it if ...
3
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1answer
96 views

Please identify organ

This is the gut area of an Eastern Grey Kangaroo taken of a property in the Southern Highlands of NSW, Australia. The top red organ appears to be the spleen but what is the elongated tubular organ ...
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0answers
29 views

Is lung size/shape a factor in long-continuous running of animals?

Apart from other factors, does lung shape/structure/size play any role in long-continuous running animals. Is there any similarity in lung structure between different long-continuous running species? ...
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5answers
3k views

Why are there no known animals with an odd number of legs?

In my 6th grade science book it is said that there are no three legged animals, and that no animal with an odd number of limbs exists. I checked Wikipedia and could confirm this: There are no ...
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0answers
18 views

How much force can connective tissue withstand?

I have been studying a 3D anatomy model. Based on visual observation, it doesn't look like the bones would be able to stabilize themselves at all without the connective tissue like ligaments. In the ...
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2answers
563 views

Why do adult insects have 6 legs?

Apparently, there is an advantage to having 6 legs in the insect world. What is that advantage, if anything? Why would such an advantage exist for insects, but not for other, larger land animals? ...
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0answers
16 views

What is the radius of the Ora Serrata and lens in rabbits?

I'm interesting in estimating the surface area of the hyaloid membrane connecting the vitreous and aqueous chambers. This is a crude estimate however i'm struggling to find parameter values for ...
4
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1answer
2k views

How does this headless fish still move?

There is a (VIDEO) on Facebook where the fish starts to flail around despite no heart or internal organs. What causes the fish to flail around the way it does? My theories: It is because of ...
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0answers
15 views

What is the permeability of proteins across the hyaloid membrane of vitreous to retina?

Does anyone know of any experimental work to test the permeability of the hyaloid membrane between the vitreous humour of the eye to the retina to proteins? Currently the largest molecule I can find ...
3
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2answers
166 views

How do other primates treat their fingernails?

Do all primates have to trim their fingernails in some way, or do some primates' fingernails wear off through natural use? Also, is constant nail growth common to all primates?
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1answer
283 views

Why did Opabinia have 5 eyes?

I recently read about a fossil called Opabinia. What intrigues me is that it had five eyes. I was under the impression that most features, such as eyes, ears and legs are always even-numbered, i.e., ...
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1answer
118 views

Does “squinting” make you concentrate better on a logic test?

We have all had those moments of intense concentration on some tough exam, perhaps a college test or whatever... Why is it that when we squint, it feels like we can focus and concentrate better on ...
6
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1answer
295 views

How can bats hear such high frequencies?

I attended a talk that glossed over some biology as it was talking about a certain protein. The speaker mentioned humans can hear up to, often less than 20kHz frequencies, whereas bats can hear up to ...
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1answer
32 views

is left brachiochephalic vein and left pulmonary artery is same?

I am reading about ligamentum arteriosum which connects the left pulmonary artery and descending aorta. But I am seeing that if any figure shows left brachiochephalic vein it does not show left ...
2
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0answers
56 views

Differing number of “things” in mammals [closed]

I'm not a biology expert, but I have often wondered about the following facts of life: All mammals have precisely 5 fingers on each of our 4 extremities. Granted, some may not be seen, but the bone ...
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1answer
1k views

Evolutionarily, why do male rats and horses lack nipples?

Developmentally male rats don't have nipples because (reddit) Testosterone release in the fetal male rat happens before the stage of mammogenesis where the teat is formed whereas other species ...
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0answers
32 views

Bolyerine Snakes maxillary bone, split?

How is the maxillary bone split in the Bolyerine Snakes described in T.H Frazzetta's "From Hopeful Monsters to Bolyerine Snakes?" In T. H. Frazzetta, "From Hopeful Monsters to Bolyerine Snakes?" He ...
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2answers
315 views

Horns in animals and birds [closed]

Are there any carnivores with horns (whether extinct or currently alive)? Do any flying creatures have horns? By horns I mean horn like structure.
2
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1answer
53 views

Serious question about a piece of meat

Does anyone know some scientific rigorous way to look at a slice of meat. I am not asking what kind of meat it is or which part of the animal it came from. I wonder what is the different lining on ...
5
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1answer
55 views

Stretching and compressing bones

The Young's modulus of elasticity when a bone is stretched is : 16×109 and when it is compressed, it is 9×109 N/m2. That means, change in length will be more if you compress a bone as compared to ...
2
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1answer
28 views

By what method do ants dissect and hold soil

Not sure if this is the correct stackexchange site - please migrate/advise as you see fit. I'm interested in the method by which ants "break off" a small amount of soil and then hold it in their jaws ...
3
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1answer
133 views

How do cats survive falling from great heights?

Among mammals, cats are able to land safely when falling from great heights. For example, when compared to dogs or humans they can survive drops from relative large heights. How do they manage? A ...
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1answer
45 views

Does the size or mass of a body affect the time it takes for rigor mortis to sets in?

Does the size or mass of a body affect the time it takes for rigor mortis to sets in? For example: compare a 300 pound man to 100 pound girl to 5 pound animal.
7
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1answer
233 views

Can humans live without their right atrium?

The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated ...
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3answers
1k views

How many cells does the smallest animal have?

Note: question rewritten to prevent misunderstanding and make it more answerable I know that some small animals like C. elegans display surprising sophistication with a very small number of cells. ...
0
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1answer
26 views

Relation between trigeminal and facial nerve in sympathetic response

In my neuro-anatomy course notes I found that the facial nerve "uses" the trigeminal nerve to reach its targets. However, I have yet to find any diagram or reference that indicates how this is done. ...
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20 views

Terrestrial Vertebrate Limbs

This question is regarding the conversation that took place here: Why don't mammals have more than 4 limbs?. I'm not sure if someone mentioned this and I just missed it, but everyone is talking ...
3
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2answers
570 views

Why do we have to exhale (or inhale) in order to speak?

Every time we speak, sing, or make any other kind of advanced noise with our throats, we exhale, or to put it that way, blow air through our throats. Why is this required? After all, speakers do not ...
6
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1answer
519 views

Why do some internal organs regenerate?

I have been reading about the human liver and zebra fish heart muscle having the ability to regenerate. It seems to me that these organs have very little chance to become damaged or worn out. At the ...
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1answer
120 views

The suspended cat clavicle

I know the clavicle of the cat floats freely as opposed to be attached as in humans. This is supposed to allow them to be able to squeeze through spaces, according to a quick google search. But how ...
4
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1answer
56 views

Comparative leg sizes

When I was a child, my father showed me the classic essay "On Being the Right Size", J. B. S. Haldane. It talks (among other things) about how large animals need stockier legs to support their ...
2
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1answer
56 views

Why is the vermis of the cerebellum associated with speech?

I've found multiple sources claiming that damage or impairment as a result of alcohol to the vermis of the cerebellum results in speech impairment. I find this a bit surprising, since the only areas I ...
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1answer
23 views

Lateral corticospinal tract and termination

I'm studying the motor pathways of the brain and I'm a bit confused about how the lateral corticospinal tract descends. From Neuroanatomy: Text and Atlas by ...
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0answers
44 views

Why are there no animals with a length greater than 30-40 meters or with a mass greater than 200 tonnes? [duplicate]

The biggest and heaviest aquatic animal is the blue whale: 30 meters long and a mass of 200 tonnes. The biggest and heaviest terrestrial animal was a Sauropod (plant-eating, long-necked dinosaur): 40 ...
5
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2answers
236 views

Why do small organisms make faster movements than big organisms?

I hesitated to ask this question because it seems so obvious and intuitive. However, I am not able to explain this tendency. Background It seems to me that small organisms make faster movements than ...
7
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1answer
389 views

What are the atmospheric requirements for large dinosaurs?

What are the atmospheric requirements for large dinosaurs? and are the atmospheric constituents for supporting large dinosaurs any different from the atmosphere today?
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2answers
61 views

Periodic Muscular Growth in Humans

If a healthy human is at a certain muscle state and then experiences muscular atrophy solely due to disuse/lack of exercise, is it easier to gain that muscle back than if the human had never reached ...