Exercise 7. Put the words given in the brackets in the correct word-form

Gene Study Suggests Early Evolution of Land Plants and Fungi Changed Earth's Climate

By Harald Franzen

Land plants and fungi may have arisen far earlier than previously thought, according to a study published today in the journal Science. The gene-based research suggests that the (1)_________ (to emerge) of these organisms may have led to major climate and animal (2)_________ (to evolve) events.

The Pennsylvania State University research team, led by (3)__________ (to evolve) biologist Blair Hedges, based their (4)___________ (to find) on the so-called molecular clock. Genes (5)___________ (to know) to accumulate (6)____________ (to mutate) at a constant rate, much like a ticking clock, can be used to determine when a species originated. To figure out when land plants and fungi originated, the team analyzed 119 such molecular clock genes common to (7)___________ (to live) species of animals, plants and fungi. Their (8)_________ (to result) proved startling. In contrast to fossil-based studies that place the (9)__________ (to appear) of land plants and fungi at around 480 million years ago, the genetic findings indicate that land plants and fungi evolved approximately 700 million and 1,300 million years ago, respectively.

The early (10)______________ (to present) of plants and fungi on land would have reduced the amount of carbon dioxide in the atmosphere, producing a (11)____________ (to cool) effect, the authors note. At the same time, the plants boosted atmospheric oxygen levels, thus paving the way for the (12)__________ (to evolve) of complex animals. (From Scientific American Online, August 10, 2001)

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