Genes
and Other Things 1
Task 1: The
paragraphs in the text below have been mixed up. With the
other members of the group put them in the correct order in the table
below.
A)
Some are useful and give the creature an advantage which allows it to
have babies which are more likely to be successful. But this process is
entirely accidental. This slow business of trying new body shapes and
styles, some of which work and some of which don't, has been going on
for as long as life. Perhaps you know about it. It's called evolution -
the survival of the fittest.
B) The nineteenth century
naturalist Charles Darwin was the first to realise that all life is
governed by this rule. He found that creatures did indeed adapt though
he didn't know how because, in his time, people didn't know about
genes. It turns out that genes can change. They don't always make
perfect copies when a cell divides. Sometimes a mistake is made. This
is called a mutation. Most mistakes are disasters - the organism dies.
C) Our home
planet is four thousand six hundred million years old. That's
4,600,000,000 years. And life has been around for most of that period.
That's plenty of time to try out a system for making new life to
replace old, and this works just about perfectly. What's more, very
simple life forms - just single cells - long ago began to join together
to make more complicated bodies with thousands or millions of cells.
All these new types of life were natural experiments to see what worked
and what didn't. Many didn't work and died out - they became extinct.
D) Some
worked for hundreds of millions of years like the dinosaurs, but still
ended up extinct. New types of bodies - organisms - generally work when
they happen to be in a part of the planet where there's plenty of food
and few enemies. Too little food, nasty climate or vicious enemies
spells disaster and means extinction unless an organism can adapt in
some way. This is where genes come in.
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Go
on to Genes and other things 2
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