Page 76 - How It Works - Book of Amazing Answers To Curious Questions, 12

AMAZIG ANSWERS TO CURIOUS QUESTIONS -------------------

Do dogs see in Why do bats
black and white? insist on sleeping

upside down?
ontrary to popular belief, dogs do have
C some colour vision - though this is
undoubtedly different to the vision of T his is partly because they can't grip with
humans. In the human eye there are two their 'hands' so use their feet instead, but
types of photoreceptors called rods and the feet wouldn't support their weight if they
cones. Rods help us to determine differences stood on them. Also, bats can't launch
in brightness and darkness where cones are themselves from the ground to take off like
sensitive to colour. We have three types of birds do, so from a hanging position they can
cones: some are sensitive to red light, some use gravity to their advantage to get airborne,
are sensitive to green and some to blue. as well as being protected from predators.
Dogs have more rods than humans and fewer
cones. Rods need less light to work and this
accounts for dogs having better night vision
than humans. Humans rely more on cones
and the differences in wavelength are harder Why don't
to detect when there is less light, hence we
don't see very well in the dark. whales get the
Dogs are said to have dichromatic vision;
they can only see a part of the range of bends?
colours which are in our visible spectrum. It
is thought that dogs can see different shades ny scuba diver is aware of the dangers
of yellow and blue as they have cones which A of decompression. When you dive deep
correspond to being able to detect these in high pressure water, the air which you
wavelengths of light. Whether their yellow is breathe from your tank will have the same
the same as yours or mine is a different pressure that the water is exerting. If this
matter entirely. were not the case then the air wouldn't come
out of your tank. At a depth of 33 feet the air How do Venus
Dogs do have some pressure is twice that of atmospheric air
pressure on land.
colour vision - though dissolves in your bloodstream and water in fiytraps work?
High pressure nitrogen from this air
enus flytraps, like the rat-eating
this is different to the your body. Anyone who had unscrewed a lid Vcarnivorous plant, tend to grow in
on a shaken fizzy drink bottle knows that
bubbles start to fizz up due to the lessening
vision ofhumans of pressure. The same effect happens to the boggy soil that's low in nutrients, hence they
need to find another source of food to
nitrogen in the bloodstream of a diver if they sustain them, namely insects that happen to
ascend too quickly. land on their leaves. These leaves are about
So, how do whales and other marine eight to 15cm long and are 'hinged' along the
Do fzsh really mammals handle this tremendous pressure The folding and trapping action is triggered
midline with spiny teeth around the edges.
increase? They have adapted to collapse their
have a three­ thoracic cavity, lungs, and alveolar sacs. by pressure on six sensitive hairs that, when
Whales have very weak and flexible rib
stimulated will snap the leaf shut in about
second memory? cages. While diving, the thoracic cavity is half a second, although the actual nature of
the action is still debated. As well as these
collapsed so no air can get in. When this
collapse occurs, there is still air with high
sensitive hairs, the leaf also has glands on its
T his is a myth and there have nitrogen levels present, in the alveolar sac, surface that secrete a sap which digests the
been various studies disproving which is the site of gas exchange. Marine insect's body. This process takes about ten
the commonly held belief. In January mammals have adapted to this by creating a days, after which the leaf reopens.
2009, researchers from the Technion cartilage build up in the bronchioles. This
Institute of Technology in Israel allows for alveolar collapse and storage of The folding and
taught fish to respond to a sound the air in the bronchioles. This is important
that meant feeding time in captivity. because nitrogen is no longer at the site of trapping action is
The fish remembered the sound gas exchange and cannot be absorbed into
months later having been returned to the body. Therefore the nitrogen will not triggered by pressure
the wild, returning to a certain spot fizz in their bloodstream upon ascent,
for feeding. therefore making them effectively immune on six sensitive hairs
to the bends.

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