ACTIVITY 148: You are going to
read a newspaper article about coral reefs. Five paragraphs have been removed from the
extract. Choose from the paragraphs A-G the one which fits each gap 1-6. There is one extra paragraph which you do not need to use.
Then check the correct answers.
GAPS 1-6
AROUND CORAL REEFS
If you're snorkelling around a coral reef, you'll see the local marine
life in all its carnival colours. But the show clearly isn't just a
tourist attraction. For the fish that live on the reef, it's more a
matter of life and death. As with any other creature, the survival of a
fish species depends on two things –
food supplies and breeding success.
Seeing a coral reef in all its
glory, you can't help feeling that fish have completely failed to solve
this dilemma. The picture, however, only comes into focus when you take
the fish's-eye view. For fish, according to Justin Marshall from the
Vision, Touch and Hearing Research Centre at the University of
Queensland in Brisbane, see things differently.
This means that the carnival looks
quite different to the marine life itself. To help him discover exactly
how different it looks, Marshall has designed a unique underwater 'spectrophotometer',
which analyses the colours of things objectively in terms of their
physical reflection. He is also measuring the light available in
different micro-habitats.
The general shift towards the blue end of
the spectrum in underwater light explains why most nocturnal reef fish,
such as the soldierfish, squirrelfish and big-eyes, are mainly red in
colour. According to Marshall, some reef fish might see red, in which
case they could capitalise on the colour blindness of others and use red
markings for private communication. But in most cases, red species are
surprisingly inconspicuous.
As any snorkeller will know, lots of reef
fish display the sort of colour combinations that suggest camouflage is
the last thing on the fish's mind. The bright blues and yellows that are
most common, however, are only conspicuous at a certain range. They fade
to grey at a distance, because the colours are so close together that
they merge.
Wider colour bands will be visible
much farther away, of course, but still the fish's-eye view is different
from ours. Most recently, Marshall has discovered that fish may see
hardly any contrast between the blue of many species, such as tropical
angelfish, and the colour of the water around a tranquil reef. More
surprisingly, says Marshall, a fish with blue and yellow stripes can be
just as well camouflaged, as even this distinct pattern will merge into
some backgrounds. When the fish are all together in a shoal, it's hard
for a predator to spot where one individual starts and another ends.
It's what Marshall calls 'the zebra effect'. If Marshall is correct,
then a fish with bold blue and yellow markings can either advertise or
hide itself by simply adjusting its behaviour.
In other words, one set of colours
can send out very different signals depending on the setting. To
complicate things further, most reef fish can vary their colours, whilst
it is common for species to change colour from night to day or as they
grow older. Colours may even change with a fish's mood -whether it's
fighting or fleeing from predators.
