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Text 21
I. Read the text and say what information it carries.
DOHJG WITHOUT THIHKIHG
A set of cells in the mouth is stimulated and starts impulses in the
neighbouring nerve cells that keep going until they reach the brain stem. From
there the impulses start back along another set of nerve cells to the cells of the
stomach. As a result, the stomach secrete juices. These actions that we do
without thinking are called reflexes.
Reflexes are caused by things outside the body as well as by things that
happen inside.
Perhaps you have wondered how fish and frogs can get along with such
small, undeveloped brains. Now you can begin to figure it out. You have seen
how very useful are the reflexes which go on as a result of activity, not on the
cerebrum, but of the nerve cells in the brain stem and spinal cord. For example,
a shadow approaches a frog. And because of reflexes the frog's leg muscles react
and it jumps into the pond - just as your finger and arm muscles react to the heat
of a stove.
Still, you may say, reflexes can't be responsible for many • of the things
animals do. How do frogs have sense enough to find a winter home where they
won't freeze to death? Aren't birds pretty smart to fly south in the fall? And what
about ants that actually use other ants as "slaves" to do their work and other
insects as "cows" to supply them with food?
All of these seem like very thoughtful things for creatures to do« But in
reality they are done without thinking. They are what we call instinctive
behaviour. The only real difference between a reflex and an instinct is this: a
reflex is a simple response to a stimulus - a frog's muscle contracts when a
shadow falls on its eye. An instinct, however, is a very complicated set of
responses that involves the whole animal.
An instinct is a way of behaving that living creatures are born with.
Instincts are not learned and can hardly be changed. If you know what the
instinctive behaviour of the parents is like whether they are ante, or frogs, or fish
- you know how their offspring will act.
II. Remember the following words and word combinations, consult a dictionary
about the way they are pronounced:
stem ствол
juice сок
to cause вызывать
get along жить
figure out понимать
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