The study of the internal structure of organisms.

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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 ...
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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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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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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 ...
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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 ...
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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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613 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 ...
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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 ...
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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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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 ...
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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 ...
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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 ...
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763 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 ...
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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 ...