51
Short answer
Intermittent locomotion can increase the detection of prey by predators (e.g. rats), while it may lead to reduced attack rates in prey animals (e.g., rats and chipmunks). It may also increase physical endurance.
Background
Rather than moving continuously through the environment, many animals interrupt their locomotion with frequent brief ...
16
In addition to @AliceD's excellent answer, I would like to add that a simple mechanistic relationship between body size and "snappiness" may explain the observed pattern.
Basics of biophysics
Difference in snappiness may result from a difference in the ability to accelerate your movement.
An increase in body size over one dimension (=body length) $x$ ...
11
Mainly because of the characteristics of the pelvic joint with the femur and the foramen magnum (the hole the spinal cord uses to connect with the encephalon). Also, there are more specimens other than Lucy, and there also exist fossil footprints (for instance the Laetoli footprints). All this evidence points to a bipedal walking.
Source: http://www....
6
Flexion: the movement that decreases the angle between two parts [1]. Examples: clenching the hand into fist, sitting down.
Contraction: the property of muscle to generate tension when actin and myosin filaments are crossing. There are a few types of contractions. The isometric contraction is when the muscle generates tension but its length doesn't change (...
6
Speed of transmission is going to vary depending on the neuron fiber subtype.
Specifically, the biggest gains will be seen with cross-sectional area (feel free to ask why on physics.stackexchange.com) and neurons with myelin sheathes (fat wrappings which affect saltatory conduction rates).
You're specifically asking about Efferent neuron transmission rates,...
6
Short answer
Proprioceptic receptors provide a feedback mechanism from the body to the brain, telling the brain what our limbs are doing and where they are with respect to the body without visual feedback being needed.
Background
Muscles, skin and joints contain proprioceptic receptors. They sense position and movement of our limbs and trunk, they register ...
6
No they are not made of muscles. Glands are modified epithelial tissues. Glands are basically of two types Endocrine and Exocrine glands.
Endocrine gland
It is a gland that lacks a duct system. The secretions are directly
poured into the bloodstream. They secrete hormones through exocytosis mostly.
Exocrine gland
It is a gland with a duct system. ...
5
The expression of emotion is a complex thing and the answer to this is somewhat dependent on the variation within the individual. There are a little over 40 muscles in the human face, including the orbicularis oris (muscle around your mouth), the risorius (that pulls the corners of the mouth backwards) and the temporalis (the mouth muscle used for chewing). ...
4
It is about the movement of the bone along its major axis of movement. A hinge joint moves like a lever while a pivot joint involves rotation side to side like an axle.
It helps if you look at a example of a bone that has both types of joints. The radial head is part of both a pivot and hinge joint, with the ulna it rotates allowing the hand to pronate and ...
4
The body indeed uses lateral inhibition / surround inhibition. When using a muscle, neighbouring muscles are sometimes activated to. So active muscles are excited while nearby muscles are (partially) inhibited (Beck and Hallet 2011)
This surround inhibition is true for fingers (Sohn and Hallet 2004).
4
Many (if not most) of the Echinoderms (to which starfish belong as well) have five-fold symmetry, such as many sea liliy (Crinoidea) and sea urchin (Echinodea) species.
Five-fold symmetrical sea lilly:
Sand dollar (type of sea urchin):
3
I think that you got a bit confused about terminology. In fact Chemotrophic is an organism that obtain energy by organic or inorganic molecules.
In your case I think that you want to know the difference between Chemotropism and Chemotaxis.
Chemotropism
Chemo-tropism is the growth of organisms (or parts of an organism, including individual cells) such as ...
3
Short answer: Only some stages of plasmodium are motile. These use "gliding motility".
Gliding motility relies on actin filaments, which enable the organism to deform it's shape, facilitating movement.
This video provides a good visual representation of the filament-based motility.
"Gametocytes develop into gametes in the insect midgut, and then ...
3
Layman's hypothesis, but... It seems an animal using intermittent movement alternates between a hard-to-see state and a hard-to-catch state, with some degree of safety in both. Operating at a slower, sustained pace offers neither of these benefits and significantly less safety.
Wondering if "small mammals" is the right descriptor. The obvious examples seem ...
2
Flagella in prokaryotets is very different from that of eukaryotes.
The main structural protein in a prokaryotic flagellum is flagellin. The flagellar motion is caused by a molecular motor similar to Mitochondrial ATP-synthase; molecular motion generated by the chemiosmotic energy.
Eukaryotic flagella or cilia are made of microtubules with dynein attached ...
2
Hmm want to visualize. Draw a rainbow. take a measuring tape, and measure the length of the curves. You'll find that the curves from convex, "outer" regions, are longer, and the curves towards concave, "inner" regions are shorter and shorter. Like this.
.
In reverse, if you take 2 rods or sheets of different length, and try to fuse them side-by-side, the ...
2
Think about say the left side of a shoot growing more than the right side. That way the left side will be longer and will be pulled back by the right side. This causes the shoot to turn to the right. By controlling the differences in the rates of growth in the two sides (using plant hormones) the plant can control exactly how much the shoot will turn.
Most ...
2
Rats make rather abrupt movements too. I would expect the difference you observe in movement speed is caused by size more than it is caused by being a bird vs a mammal. But why size would matter?
An increase in the linear dimension $x$ lead to an increase in the cross-section of muscles $x^2$ and an increase in the volume (and hence mass) of $x^3$. The ...
1
The additional degrees of freedom are provided by the entire cervical spine, rather than the atlantoaxial joint alone, which is the joint between C1 and C2. What you're describing as roll (when you point one ear to the ground), is provided by contraction of the sternocleidomastoid. The sternocleidomastoid muscle pulls the mastoid process (behind the ear) ...
1
The easy way to explai the first phenomenon is that at rest, your fingers - all of them - curl. Relax on your bed on your back. No matter what direction your hands face, they will curl inward as if loosely holding an egg. That's the anatominal position of the hands at rest, because the finger flexors are stronger than the extendors. So once you set the ...
1
[..] if a geneticist finds no significant difference between 2 subpopulations that have temporal spatial overlap
This isn't clear. Significance difference between what? What statistical hypothesis are you testing for which one would found no signicant difference (accepted the null hypothesis). Are you maybe thinking about a t-test between testing difference ...
1
Assuming the case where you move a mouse left and right with the wrist and up and down with the fingers, then yes, finger movements are more precise. The fingers and facial musculature are body parts with the most exquisite fine motor-control. The wrist, on the other hand, probably less so. The wrist is definitely involved in fine motor skills such as ...
1
Been a sprinter for 12 years, so from that perspective, I don't think it would matter. The angle that you take when turning is not drastic enough to have a musculoskeletal difference; step height differs only a few inches. Additionally, turns never account for more than 50% of a race (barring a couple distance events, where turns act much more like ...
1
It is generally not a one-way process. The lag also depends on which frequencies you look at (the brain and limbs kind of speak using several channels at the same time). Near 10 Hz the lag is few dozen milliseconds.
Look for articles about EMG and EEG (or MEG) coupling for more precise info.
Use the paper http://homes.mpimf-heidelberg.mpg.de/~mhelmsta/pdf/...
1
Nictitating membrane (inner eyelid) of sharks can cover sharks eye as it moves from the upper to the lower eye lid (http://en.wikipedia.org/wiki/Nictitating_membrane).
1
Actaully there are quite a few animals which actually moves there lower eyelids:
Most of the birds
Reptiles(Except Snake)
Amphibians
Only top voted, non community-wiki answers of a minimum length are eligible
