23

There are lots of papers on this. A good summary article is Why sauropods had long necks; and why giraffes have short necks, by Taylor​ and Wedel. They list a number of anatomical features that allowed sauropods to support such long necks: Several anatomical features enabled this extreme elongation, including: absolutely large body size and quadrupedal ...


23

An older answer that referred to the physiological feats of ancient humans, and why modern humans are wimps made me look up a couple of papers on running speeds a while ago. One of the examples used to support the statement that modern humans are "wimps" is a study of ancient fossilized footprints from Australia, which claim that the individuals making the ...


7

It is logically clear that the ankle could only partly be analyzed in the group of joints that are below its height. There is no direct way to measure the pressure on ankle joint (on talus bone), but from the logic it is clear that it should be the point of highest pressure in the group of points lister in the question, however the pressure is distributed ...


7

Nice question. I must say it took me many hours to get satisfactory answer. Hairs are made of keratin molecules, which contain cysteine. Cysteine has thiol (-SH) group, by which it can form disulfide (-S-S-) bond with another cysteine of another keratin, causing bending of hair. See this image from here: Curling of hair can be justified on both microscopic ...


6

The resting membrane potential is due to internal/external differences in ion concentrations and very importantly differences in permeability to those ions. The fact that the sodium/potassium pump does not move an equal number of ions in each direction does not actually matter at all for resting membrane potential; the resting membrane potential would be ...


5

Note nowhere in the article does it mention the rear wings flapping. The rear wings do not provide lift, they are acting as control surfaces to improve stability and maneuverability. (think of the tail of a plane).earlier/proto flies have far more demand for control surfaces than developed/derived fliers due to lacking more precise control of flight surfaces....


5

Poison dart frogs have aposematic colouration, making them the exact opposite of camoflaged. They are also predators, since they feed on ants, termites and beetles.


5

The various species of nautilus use a combination of active transport of salts and passive diffusion of water for buoyancy (Denton and Gilpin-Brown 1966, Ward 1979, Greenwald et al. 1980). The chambers are filled with seawater. Salts from the seawater in the chambers is removed by a structure called the siphuncular epithelium. This process makes the ...


4

Short answer Yes they can, but with less efficiency. Background Efficiency of sticking to a glass surface decreases about 20-fold when the gecko's feet are wet (Stark et al., 2012). On dry glass, Gekko gecko holds on with about 18 N, which is about 18 times their own body weight. Hence, the gecko attachment system is over-designed (Knight, 2012). Wetted ...


4

The range from mean to maximum of wolve's bite force is huge. Is it really? According to this Wikipedia page, (Scully, C. (2003). Oxford Handbook of Applied Dental Sciences. p. 151) claims that human masticatory forces range from 70 N to 700 N. Also, (Kim et al., 2018) claims that domestic dogs have a bite force of (147-3417) N, so I don't think it's too ...


4

There is a good attempt at a simulation of 4 winged flight of Microraptor on BBC's Planet Dinosaur. There's another Planet Dinosaur video about their venomous teeth and hunting tactics. And a Microraptor locomotion video on Attenborough's Conquest of the Skies (Sky 3D).


3

From what I can tell, marine mammals can't dynamically control buoyancy during a dive. They ease the beginning of the dive by starting with a small lung volume to reduce buoyancy. Pinnipeds like seals do this by exhaling half their breath before diving. Deep-diving whales actually breathe in before diving, but their lungs are small relative to body size ...


3

What is a predator? As discussed in the comments by @MarchHo and @AMR, there is discrepancy between the definition of predation in the biology literature and in the every day use. Population definition From the Oxford dictionary predation- The preying of one animal on others; the behaviour of a predator (predator n. 2); (also occas.) an instance of ...


3

I'm going to try to break this up a bit to address your sub-questions. Most of it is summarized from Williams et al 2008--and almost all of the work I'm referencing comes from the Royal Veterinary College Structure and Motion Lab. Acceleration Profiles: So, I can't find an acceleration curve over time for these, but we do know about the potential ...


2

Mamizuka et al. (2007) calculated acceleration data of the patellar reflex. Their study measured the reflex generated in response to the tapping force applied to the patellar tendon with a customized tendon hammer. They measured using a tri-axial accelerometer placed at the ankle joint. They found: the time delay (29.6+/-6.0 ms) and the acceleration ...


2

This question is waaaay too broad, but I'll give some short and simplified answers to the hypothetical you asked at the end. First, let's reformulate your example a little bit: How does the ribosome move along a strand of RNA? How would it do it? By hydrolyzing GTP and somehow coupling the free energy associated with that reaction to forward motion. Keep ...


2

As the siphuncle pumps cameral liquid out of a chamber, the pressure of the chamber falls and nitrogen, oxygen, and some carbon dioxide diffuse into the chamber. Sea water gas pressures are in equilibrium with atmospheric gases (oxygen and nitrogen) and are in equilibrium with nautilus blood. Hence as cameral liquid is pumped out of the chamber, gases ...


2

Note that estimations in this answer are very very crude. I can speak with confidence that the mean pressure of ankel joint is greater than the heel and the metatarsus. However I do not trust that it can pin down the point with most pressure. @Ilan gave a very good synopsis on foot pressure distribution. However, pressure in ankles was not analyzed in his ...


2

Proper in this instance means the main body of the hand, the part that has no other identifier. the fingers and wrist have other terms to identify them, the hand proper does not. If I say the the hand you are not sure whether I mean the hand as a whole or that part in particular so it is called the hand proper. Its an old usage of the word, but that is ...


2

It does function in the rotation and stabilization of the foot, but that is not why we have it, even species in which it serves no function still have it. A bone does not necessarily have to have a purpose in an organism, instead it can have on in its ancestors. We have this arrangement becasue we inherited the basic limb bone arrangement from our fishy ...


2

Hexapedal. From wiki > Hexapedal Having six legs Note that Hexapoda is a taxonomic group including insects and the smaller groups that are Collembola, Protura, and Diplura.


1

In this article (Bite forces and evolutionary adaptation to feeding ecology in Carnivores) they say, that bite forces of wolf (Canis lupus) is 774 N. Literature (Maximum estimated bite force, skull morphology, and primary prey size in North American Carnivores) gives that: "the wolf had a mean maximum estimated bite force of 2255 N".


1

Here is a video by Brady Barr (video in YouTube) measuring 5000 lbf for an adult Nile Crocodile. This is equivalent to 22.24 kN (more than 2.2 tonnes of force). This result is also refered here (Getty Images). Source: Gianfranco Gori, Wikipedia


1

Short answer The adaptation process in Pacianian corpuscles (PCs) is mediated via the outer capsule. This capsule is an onion-like structure that quickly molds itself to pressure stimuli, thereby rapidly desensitizing the receptor. Background The Pacinian corpuscles are rapidly adapting (RA) skin receptors, as opposed to the slowly adapting (SA) ones, such ...


1

First I would in return ask why the actin-myosin coupling should not qualify - the many repetitions of this contractile unit never contract at exactly the same time, and their combined contractile force certainly accumulates in a ratchet-like fashion across the microsecond time scale (with other units contracting before previous units have relaxed). Just ...


1

Several models have been proposed, challenged, and revised over the past two decades: Origin of Flight: Could ‘four-winged’ dinosaurs fly?, Nature (2005) A previously published reconstruction shows that the hindwing of Microraptor supported by a laterally extended leg would have formed a second pair of wings in tetrapteryx fashion. However, this wing ...


1

how exactly the brain interfaces/controls/disables such automatic muscle reflexes when it needs to? A: At multiple places within a hierarchical system: In a simplified way, the Motor cortex is the executor of movement via projections to the brain stem and spinal cord, this is accomplished via excitatory signals to a muscle, the agonist, and inhibitory ...


1

In principle this can happen, but you have to read up on flagellar dynamics and polymorphic transitions (Real-Time Imaging of Fluorescent Flagellar Filaments, Turner et al. 2000). From Howard Bergs lab page: Runs can occur with filaments of any polymorphic form; although, the normal form predominates. For a cell to tumble, not every filament needs to ...


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