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2016 ‫מועד יולי‬ - 41 - ‫ פרק ראשון‬- ‫ אנגלית‬

Text II (Questions 18-22)

(1) Sunlight is crucial to most of the food chains on Earth. The vast majority of plants
produce food for themselves – and, indirectly, for the animals that feed on them – by a
process called photosynthesis, which is driven by sunlight's energy. Therefore,
scientists had long believed that nothing could survive in the ocean's darkest depths,

(5) beyond the reach of the sun's rays. But in 1977, new technology allowed geologists to
conduct research on the Pacific Ocean floor near the Galapagos Islands, where they
discovered a previously unknown type of ecosystem.

The life forms they observed were found in close proximity to a hydrothermal
vent – an opening from which water heated by volcanic activity beneath the seabed

(10) gushes out into the cold ocean water. The heated water carries hydrogen sulfide and
other chemicals that would be poisonous to creatures living in most environments.
However, life forms around the vent flourish, thanks to the tiniest organisms there:
bacteria. The bacteria convert the toxic chemicals into the food they need in a process
known as chemosynthesis.

(15) The entire ecosystem's food chain relies on this process. The creatures living near
the hydrothermal vents feed on the bacteria. One of the most abundant and remarkable
of these vent-dwelling creatures is the giant tube worm. For sustenance, the tube worm
is completely dependent on the bacteria, which it ingests early in its life. Because it
lacks a digestive system and has a mouth that disappears as it grows older, it relies on

(20) the built-in food supply provided by the bacteria, which live inside its body.

Questions

18. The main purpose of the first paragraph is to -

(1) explain why the 1977 discovery was surprising
(2) define the process of photosynthesis
(3) show how geologists explore the ocean floor
(4) describe the ecosystem near the Galapagos Islands

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