The study of the internal structure of organisms.

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Why Is Most Life Symmetrical Externally But Not Internally?

Mammals, reptiles, arachnids, insects, etc are all as far as I am aware symmetrical in appearance. Take a human for instance, make a line from the top of our head right down the middle. However, ...
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2answers
501 views

What is the morphological difference between Leydig cell in human and pig?

The pig is only an example, just an animal. Leydig cells have protein inclusions (Reinke crystals) that are mostly made of crystallised lipofuscin. They are secretory inclusions i.e. cells formed in ...
13
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1answer
277 views

Evolution of long necks in giraffes

In this question, the OP uses giraffe necks as a supportive example of evolution. Is the mechanism described in this post accurate? At some point, I thought I remember hearing that giraffes did not ...
13
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1answer
330 views

Do the majority of fish lack scales on their heads?

Based on pictures, it seems to me that a vast majority of fish species that have scales do NOT have scales on their heads. Is that fact true? To make this properly answerable: lets' define a ...
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3answers
613 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. ...
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1answer
1k views

Is there a correlation between muscle fibers and body types?

I have been told the number of muscle fibers a particular muscle has varies from person to person. Unfortunately, the person who told me this did not know much more than this. Initial searching on the ...
9
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1answer
762 views

Why are there nail growth differences between humans and other mammals?

When a cat is growing, his nails are growing with him to some extent. A grown cat has a fixed nail length that is not extending. By contrast, human finger nails just keep on growing, so we have to ...
8
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1answer
269 views

Do antigens protrude through the capsule/slime layer in prokaryotic organisms where these features are present?

In prokaryotic organisms that have a slime layer or capsule, do intrinsic/extrinsic proteins and other molecules that could be used as antigens protrude through the capsule? I assume that they ...
7
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1answer
212 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
396 views

Skeletal muscle without antagonist

Is there any skeletal muscle that does not have an antagonist? Excluding circular muscles such as around eye and mouth. The reason why I am wondering is because in biology normally nothing is ever ...
7
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1answer
404 views

What is the name of the appendage that mantis shrimp use to rub their eyes?

In this short clip, you can see the mantis shrimp using some sort of feathery arm/claw to rub its eyes. Looking at a diagram here, it appears possibly that it's using maxillipeds. Someone with ...
7
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1answer
135 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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Do other male mammals except for humans have nipples?

When I grew rabbits, I had a pair, one male and one female. And while the female's nipples were quite prominent, especially after giving birth, I don't remember the male having any nipples at all. Do ...
6
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1answer
351 views

evolutionary reason behind sharing the same path for food and air?

What is the evolutionary reason behind sharing the same path for food and air? For example, we have a nose and lungs, yet they are linked by the pharynx, which is shared with the mouth and ...
6
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1answer
184 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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5answers
2k views

Why do most mammals have long snouts?

It seems like most mammals, e.g. dogs, have long snouts. My pet dog's snout would seem to me like an evolutionary disadvantage, since her canine teeth are way out at the end of her jaw, which acts as ...
6
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1answer
1k views

What is the average Leg-to-Foot Length/Width Ratio?

I'm making a program that estimates a probable size (widest width and longest length) for a human's foot given the length and width of the leg to which it is attached. However, try as I might, I can't ...
6
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1answer
237 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 ...
5
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1answer
199 views

What limits the size of fish compared to marine mammals?

The largest extant fish species is the whale shark (Rhincodon typus). With a length of 13 meters and a mass of about 20-30 metric tons, the whale shark is relatively small compared to the largest ...
5
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1answer
239 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., ...
5
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1answer
42 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 ...
5
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2answers
150 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 ...
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2answers
612 views

Did dinosaurs have more than one brain? If so, why?

I once remember reading (15 years ago) that dinosaurs had two brains. One for their head and another one for their digestive functions. What is the current opinion on this theory? Has more evidence ...
5
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1answer
643 views

Why does the sacrum fuse together?

Everywhere I look describes how the 5 sacral vertebrae start fusing together during adolescence and are totally fused by the time you're 30 or so. But nobody seems to explain why this happens. It ...
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1answer
55 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 ...
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1answer
72 views

Is there differences in components of saliva among species

Are there differences in the components of saliva among species? Also, do the functions of saliva differ between species?
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2answers
362 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 ...
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3answers
2k views

Which organs do cats not eat on their prey?

My female cat is a very active hunter and brings me her prey daily. Except for shrews and birds, she always eats them entirely. This afternoon she brought me this: It was quite large (maybe ...
3
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1answer
115 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
76 views

What accounts for size variation in breeds of dogs?

My assumption is that dogs vary so much in size because of artificial selection pressures coming from human breeders, but are there genetic loci that roughly determine approximate size? Do other ...
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2answers
60 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?
3
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1answer
79 views

Text/resource with information on all skeletal muscles and their motor units

Something analogous to an encyclopedia on baseball players with a list of all thier stats would be ideal. I'm not looking for just generic muscle names, locations and illustrations. Good answers ...
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1answer
113 views

Identifying internal structures of dissected fish

Note : Images displayed below might be disturbing to some people. I have dissected a fish for the first time ! I have some idea of what some of the structures might be but I am not sure and so would ...
3
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1answer
388 views

Is there a difference between pig and cow anatomy that makes religious slaughter of the latter less painful?

This question is not for the squeamish. I was told that non-Kosher animals like pigs have a different anatomy in their neck compared to kosher animals like cows such that the Shechita method of ...
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0answers
72 views

Total number of pleura in the exoskeleton of cockroach

Basically as far as i know cockroach consists of 10 terga and 9 sterna but what are the total number of pleura present in the cockroach. Pleura are situated between tergum and sternum of a body ...
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1answer
42 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 ...
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2answers
60 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 ...
2
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1answer
23 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 ...
2
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1answer
36 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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0answers
48 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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0answers
73 views

Where are the gastralia (stomach ribs) attached?

Crocodiles and some dinosaurs have a second set of ribs between the sternum and pelvis called gastralia. Where are the gastralia attached to the rest of the skeleton?
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1answer
204 views

Raising two legs together while lying on bed

Let's do some exercise(duh!) Ok so lie on the bed. Lift your left leg. Put it down. Lift your right leg.Put it down. Easy? Now lift your left leg and without putting it down, lift your right leg. ...
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2answers
58 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 ...
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1answer
456 views

Why do rodents' teeth continue to grow?

Why do rodents' teeth continue to grow? Enamel formation and/or root formation continue throughout rodents' lives. What's the mechanism that causes this?
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1answer
44 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 ...
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1answer
20 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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1answer
293 views

Identifying structures from anterior end of dissected prawn

Note: This image might be disturbing. I want to know what the red and the black structures (directly posterior to the red structure) are. I guess it's the heart.
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1answer
113 views

Is stereo olfactory ability restricted to humans?

Most animals I see around seem to have two nostrils - humans, snakes, birds, fish .. and so on. From reading online I see that 2 nostrils provide a stereo olfactory effect. This stereo effect is ...
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0answers
23 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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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 ...