The reason why veins( and hence the blood flowing inside them) appear blue has to do with different colours and their respective wavelengths. Red with higher wavelength can penetrate deeper into skin surface unlike blue. Since veins are at such depths that allow only red colour to penetrate while the blue gets reflected, veins appear blue in colour.
How does water rise to great heights in trees like coconut and redwood?
The long distance transport of water in a plant takes place in the xylem of vascular bundles or in the wood. The conducting elements are called vessels( tracheae, tracheids); they have the dimensions of capillaries. They form long capillary tubes with uninterrupted pathways for water transport. The uninterrupted columns of water in the vessels are characterised by large tensile strength. This characteristic is due to the cohesion of water molecules by intermolecular hydrogen bonds. The tensile strength of water threads in vessels has limits that are species specific. The adhesion of water to the vessel walls is so strong that even under strong suction( hydrostatic tension) the capillary water threads do not collapse. The stiffened vessel walls are able to withstand strong suction within the vessels. This makes possible the rise of water to greater heights in plants.
SCIENCE FACTS
WINSPIRE: Empowering youth | January, 2017
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How does eel produce electricity?
Each animal that hunts for its food depends upon definite cues in the search. For this they develop special adaptations which help to increase biotic potential. Although almost any individual kind of animal demonstrates such adaptations in sensory mechanisms related to food acquisition, some are sufficiently spectacular to earn special mention. One such is the sensory adaptations found in certain members of Teleost fishes, which have independently developed organs, which produce electricity. These are used for defense, the capture of prey and perhaps as direction finders. The best-known is the so called Electric `eel’( Electrophorus)— a blind, superficially eel-like fish which grows to a length of about eight feet, and is almost as thick as a man’ s thigh and lives in shallow muddy parts of the Amazon and other South American rivers. On land Electrophorus can discharge about 500 volts. In water the charge is partly short circuited and the shock is about 250 volts, but still sufficiently strong to cause great discomfort to man or to activate an electric buzzer. The electric organ consists of some seventy columns, each of which contain a series of about 600 disc-shaped syncytial electroplaxes( Electroplate cells). The cells are probably formed from striated muscle-cells and together constitute a jelly like mass located in the postero-ventral four-fifth of the body and tail.
Each electroplate is innervated and shocks are normally transmitted only when the fish is molested or when it comes within the range of its prey, which is stunned and then swallowed whole. These fishes that can generate high voltages have protective insulation around their own nervous system, shielding them from damage.