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

First of all, let me make it clear that the heart is at the vertical centre of the body -- it is not shifted towards left (or right). However, it is slightly tilted towards the left in most cases. ...
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79 votes
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How come large herbivores have such thin legs?

Elephant, rhinoceros, &c all have much thicker legs in proportion. The answer, I think, lies in the fact that the animals you mention all evolved as cursorial animals (that is, they run to escape ...
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  • 3,613
59 votes

Do "shooting" animals exist?

A good exemple should be the “harpoon” in cone snails (Conidae), which is created from a modified tooth inside their proboscis. (Cone snail with proboscis, from KQED.org) The harpoon is launched at ...
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53 votes

How come large herbivores have such thin legs?

This is a mistake in comparative anatomy which is somewhat common. When looking at four-legged animals, people often mistakenly map the parts of the hind legs. Here is an image that shows the ...
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  • 1,377
32 votes
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Does the octopus have an anus? What does it look like?

The anus of Octopus is channeled into its siphon. Image taken from Carina M. Gsottbauer Note: Siphon is a tube that leads from the mantle to the outside. Octopuses use their siphon to force water ...
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25 votes
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Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions?

According to the highly respected WORMATLAS: A Database of Behavioral and Structural Anatomy of Caenorhabditis elegans, the number is invariable in this animal, one of the most studied in the world. ...
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23 votes

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

It depends what you mean by 'leg'. The instinctive way to define a 'leg' is based on its functional use: we use legs to walk on. But if we adopt that definition of 'leg' then there certainly are ...
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  • 3,294
23 votes

Where can I find the list of all tendons in the human body?

Your best bet is the Terminologia Anatomica, which is the international standard for anatomical terminology. The 1998 edition is freely available. It lists only a few named tendons though, which is ...
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22 votes

Do "shooting" animals exist?

An excellent example (unless you consider this a tool) of a weapon using animal would be the "web casting spiders" which are a diverse group of spiders known as the Deinopidae. These spiders ...
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  • 7,818
21 votes

How come large herbivores have such thin legs?

How come large herbivores have such thin legs? They don't. The following book does an extensive comparison of the bones of humans with other animals: Adams BJ, Crabtree PJ. 2008. Human vs Horse. In: ...
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20 votes
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What is the anatomical term for a two jointed leg?

Welcome to Biology.SE! I think you are talking about plantigrade, digitigrade and unguligrade. Please note that the number of joints in mammals does NOT vary, but only the relative length (and shape)...
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17 votes
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Why is the opposite of plantar flexion called "dorsiflexion"?

Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking ...
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17 votes

Why do adult insects have 6 legs?

Short answer Six legs allow for locomotion, while maintaining a supportive tripod at all times. Background There are several million species of insects, all on 6 legs. This implies that any change in ...
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  • 51.2k
17 votes

Do "shooting" animals exist?

Although not a hard projectile the Archerfish shoots water https://en.wikipedia.org/wiki/Archerfish
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16 votes
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Evolutionarily, why do male rats and horses lack nipples?

Male mice lack nipples too. Mice are frequently used for embryonic research as they are small and reproduce quickly. It is thought that male mice do develop nipples, but that they regress during ...
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  • 51.2k
16 votes
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Examples of animals with 12-28 legs?

As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one ...
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14 votes

Do male mammals other than humans have nipples?

Most mammalian males have nipples. The duck-billed platypus does not have nipples but you begin to see development of nipples in marsupials (Park and Lindberg 2004) like the opossum and kangaroo. ...
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14 votes
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Using anatomical terms for human organs and parts of plants

First, for reference, see here for a discussion about the difference in directional terms between bipeds and quadrupeds as well as a fairly complete explanation of word meanings/etymology. The ...
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13 votes

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

Short answer The body plan of terrestrial organisms that feature limbs is typically bilaterally symmetric, and hence these organisms have an even number of appendages. Background Terrestrial animals ...
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12 votes
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How many cells does the smallest animal have?

Rotifers are microscopic protostomes with around 1000 cells apiece. This website claims the smallest rotifers have less than 100 cells, but I couldn't confirm this. Most rotifers are eutelic — ...
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  • 1,564
12 votes

Where can I find the list of all tendons in the human body?

The FMA lists 705 tendons, but note that it includes separate terms for left and right instances. As @kmm says, many of these simply shadow the list of skeletal muscles (and is likely incomplete). ...
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  • 291
11 votes

Can birds touch their wing tips together either in front or behind (not above and below)?

Black herons (Egretta ardesiaca) can overlap their wing tips in front of them while doing what is known as canopy feeding.
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  • 5,306
10 votes

How many cells does the smallest animal have?

I don't know about all known animals, or actual cell count. However, males of the wasp Dicopomorpha echmepterygis are considered the smallest known insects with a body size of 139 μm. This should at ...
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10 votes
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Can defibrillation be done with a car battery?

In general, no. Car batteries are designed to provide a large amount of amperage, to turn the starter with a high amount of torque via an electric motor. Generally this is done at 12 or 24 volts. ...
10 votes
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What is the rest state for eyelids - Open or Closed?

This depends to some extent on how you define "resting state" (it matters). Innervation of the eye occurs in the brainstem and upper spinal column, so is, like most brainstem functions, on autopilot ...
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10 votes
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Dorsal vs Posterior and Ventral vs Anterior

Short Answer This page on wikipedia gives a good synopsis of these concepts. The confusion lies in the fact that many websites on anatomy discuss/describe/define these terms in relation to humans. ...
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10 votes

Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions?

Many Nematodes do not use traditional hox genes instead the have a strange set up which controls cell placement directly. This means individual adults of many nematode species have the exact same ...
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  • 13.2k
10 votes
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Why is Heart Rate Recovery after exercise reasonably well described by a mono-exponential decay?

I think most people would take exponential decay in a circumstance like this to be the null hypothesis. That is, if you had something not exponential decay, that would be curious and interesting and ...
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  • 36.7k
9 votes

What are the atmospheric requirements for large dinosaurs?

Oxygen levels have changed greatly throughout Earths's history starting with very little atmospheric oxygen and gradually increasing as photosynthetic activity appeared until all the oxygen sinks such ...
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  • 5,288
9 votes
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Horns in animals and birds

Males of the carnivorous Jackson's chameleon (Trioceros jacksonii) have three hornlike structures on their heads (also found in a couple of related species). From what I know, these are true horns, ...
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