Learn English with American Primary School Textbooks

Chapter 35 Nature's Wonderful Nature (5)
Exchange more interesting common sense with your classmates.
Translation
To keep from digesting itself, your stomach has to build a new lining every two weeks.

Owls are the only birds that can see blue.

In a 70-year life, you spend about 23 years sleeping.

When you sneeze and people say "God bless you," it's because your heart stops beating for a millisecond.

Pigs have the ability to become alcoholics.

Cats have 32 muscles in each ear.

All polar bears are left-handed.

Butterflies taste with their feet.

Bats use ultrasound to identify vibrations from their prey.

People typically have 10 to 15 hairs on their heads.

Your hair grows 10 to 13 millimeters per month.

Nails grow 3mm every month.

In the solar system, Earth is a lucky planet because it has the right temperature to recirculate water.

Exercise
Share other interesting knowledge with your classmates.

09 Whether Fish have Nostrils Are the two holes above the fish mouth nostrils?
Fish have holes that look like nostrils, does that mean they can smell?

Smell, or olfaction, as scientists call it, is an important sense for many fish. Those little holes that look like nostrils are called nares. Nares don't lead to the throat the way nostrils do in mammals, but open up into a chamber lined with sensory pads. Not all fish move water in and out through these nares in quite the same ways, but the key to a strong sense of smell for fish is the ability to move water rapidly over these sensory pads. Some fish can pick up chemical signals when immobile by pumping water through their olfactory system via tiny hairs called cilia. Other fish can pump water by a muscular movement. Some fish, such as smaller species of mackerel, have an olfactory system that requires them to swim in order to get water moving through their nares. When the sensory pads pick up chemical signals, they transmit them to the fish's forebrain, which interprets the signal and incites the fish to respond appropriately.
If the chemical signal food, the fish will pursue the food. Or, if the chemical signal danger, they will flee. But fish use chemical cues in all sorts of ways. For instance, a large group of fishes release a chemical when they' re wounded that incites other fish to flee. And then there are salmon, which are known for a superb sense of smell that enables them to sense the stream where they were born, so that they may return to it to spawn.
Vocabulary
Nostril ["n? stril; -tr? l] n. nostril
olfaction[? l"f?k??n] n. smell
chamber ["t? eimb?] n. (in the body or organ) chamber, chamber, room, clubhouse
Sensory ["sens? ri] adj. Sensational, perceptual, conveying sensation
immobile [i"m? ubail, -bi:l] adj. Fixed, unchanged, stable

interpret [in"t?:prit] vt. explanation, interpretation;
vi. to explain, to translate

incite [in"sait] vt.
superbb [sju"p?: b, s?-] adj. Excellent, gorgeous, magnificent

Practice
Do you know how the fish breathe and swim?

Translation
There are two holes on the head of the fish that look like nostrils. Does this mean that the fish can smell?

Smell is an important sense for many fish.Unlike mammals, the nostrils of fish do not communicate with the throat, but instead form a separate cavity, which is connected to the smell-sensing tissue.Not all fish move water in and out of their nostrils in the same way, but the key to a keen sense of smell is the fish's ability to move water quickly through their olfactory receptors.Some fish can pick up chemical signals (in water) by letting water pass through their olfactory organs through small hairs called cilia when they are still.Some fish do this through muscle movement.Other fish, such as small mackerel, need to swim to get water through their respiratory system.When the olfactory receptors receive chemical signals, they pass them on to the forebrain, which analyzes the signals and allows the fish to respond appropriately.

For example, if the chemical signal is food, the fish will hunt for it.Alternatively, the chemical signal is danger, and they flee.But the cues provided by the chemicals have multiple uses for fish. For example, when injured, many species of fish release a chemical that causes other fish to flee.Known around the world for their sense of smell, salmon are able to smell the water currents where they were born so they can return home to reproduce.

Exercise
How do fish breathe and swim?Talk about what you know about them.

10 Squirrel VS. Rattlesnake
So let's say you're a common ground squirrel. Just for a moment, pretend you're minding your own business, searching for seeds, doing whatever it is that squirrels like to do. Then, suddenly, out from behind a bush slithers a Huge, sinister rattlesnake, coiled and ready to strike. What do you do?

Obviously, you run away, play dead, or perhaps negotiate a deal of some sort. In any case, given that you're a furry, gentle squirrel and the snake is a deadly, rattling killer, whatever you do, you don't stand your ground and fight. Right?

Wrong! Calling upon the instincts passed down from your ancient squirrel ancestors, you rush at the snake, kick sand in its face, try to bite its tail, and then turn your back on it and whip your tail around.
Now why on earth, you might be wondering, would my squirrel self take such suicidal measures? Kicking sand and biting might do some good, but tail waving? Why further taunt a venom-fanged snake already bent on violence?

As you may have guessed, there is a method to such madness. When confronted by a rattlesnake, squirrels' tails heat up, getting hotter by almost four degrees Fahrenheit. The infra-red sensors built into rattlesnakes' eye sockets sense this increase in temperature as a big, waving, fiery blotch.
This alarming display, plus the fact that squirrels are partially immune to rattlesnake venom, actually gives the squirrel a distinct advantage when it confronts a rattlesnake. More often than not, the rattlesnake will slither away in search of a less intimidating foe.
Vocabulary
squirrel ["skw?: r?l, "skwi-,"skw?-] n. Squirrel, squirrel fur

Sinister ["sinist?] adj. Insidious, ominous, catastrophic, left
negotiate [ni"ɡ? u? ieit, -si-] vt. negotiate, cross, transfer;

vi. to negotiate, negotiate

instinct ["insti? kt] n. Instinct, intuition, nature;
adj. full of

tail [teil] n. tail, trace, braid, tuxedo
socket ["s? kit] n. Socket, nest, hole; tooth bad;
vt. To... with a socket
venom ["ven? m] n. venom, malicious;
vt. to poison, to poison
Practice
1. Why the squirrel waving tail to rattlesnake?

2. Compare the squirrel with ostrich, please share your opinion.

Translation
Say you're an average squirrel, minding your own business, finding seeds to eat, or whatever squirrels like to do.Suddenly, a huge, vicious rattlesnake crawls out of the bushes behind you.It coils itself, ready to attack you.What should you do?

Obviously, you will choose to run away, play dead, and possibly negotiate terms with it.Given that you're a fluffy, docile squirrel and a rattlesnake is a deadly killer, you're not going to stand still and fight it anyway, are you?
you are wrong!Inherited instincts cause the squirrel to charge the rattlesnake, kick sand in its face, try to bite its tail, then turn around and wag its own tail.

You may be wondering, why would a squirrel choose to hit a stone with a pebble?Sand kicking and tail biting might work, but what's the point of wagging your tail?Why would a squirrel provoke a snake with fangs that is already bent over and ready to strike?
As you may have guessed, this seemingly crazy approach of the squirrel actually has its reasons.When encountering a rattlesnake, the squirrel's tail heats up, rising about 4 degrees (Fahrenheit).And through the infrared sensing tissue in the eye socket, what the rattlesnake senses is a large, wiggling red dot.

This chaotic performance, combined with the fact that squirrels are somewhat immune to rattlesnake venom, gives squirrels an instinctive advantage when encountering rattlesnakes.In most cases, the rattlesnake will crawl away in search of less intimidating prey.

Exercise
1.Why do squirrels wag their tails when confronted with rattlesnakes?
2.Compare the behavior of a squirrel and an ostrich when confronted with an enemy, and share your thoughts.

1. To heat up tails, and confused rattlesnake.

(End of this chapter)