练习说明
句子填空 题目要求：阅读文段，从文中挑选原词补全句子，每道题目都有特定的字数要求，以黑体加粗字标示。请把答案填到每题空缺处。
Choose ONE WORD ONLY from the passage for each answer.
第 1 题
Volkov's experiments reveal that the electric charge travels down fluid-filled tunnels in a leaf, which opens up pores in cell membranes. Water rushes from the cells on the inside of the leaf to those on the outside, causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens. As the leaves flip, they snap together, trapping an insect inside.
The charge enters tunnels, causing _______________ in the cell walls to open.
第 2 题
The bladderwort plant has an equally sophisticated way of setting its underwater trap. It pumps water out of tiny air sacs or bladders, lowering the pressure inside. When a water flea or some other small creature swims past, it bends hairs on the bladder, causing a flap to spring apart. The low pressure sucks water in, carrying the creature along with it. In one five-hundredth of a second, the flap swings shut again. The cells in the bladder then begin to pump water out again, creating a new vacuum.
When water is pumped out of bladder cells, a _______________ builds up inside.
第 3 题
Many other species of carnivorous plants act like living flypaper, catching animals on sticky tentacles. Pitcher plants use yet another strategy, growing long tube-shaped leaves into which insects fall. Some of the largest have pitchers up to 30cm deep and can consume whole frogs unlucky enough to fall into them. Sophisticated chemistry helps make the pitcher a death trap.
Some plants are big enough to capture and eat _______________.
第 4 题
Both of these 1/ 14 colors came from animals; the mucus found in certain species of shellfish produced the deep rich Tyrian purple and cochineal was extracted from insects. Two other natural sources of color were saffron and indigo. Saffron, the base of yellow dyes, comes from the flowers of a particular kind oi crocus which is thought to have first been cultivated on Crete in the eastern Mediterranean. The leaves of a plant native to India were used to produce indigo, which was the main source of the color blue.
Tyrian purple is made of mucus from _______________ found in the Mediterranean.
第 5 题
They had always used local plants as food, and many of these plants were also used as medicines and in some cases as sources of dyes. Home dyers used any plants they could find that would give a good color. People who picked blackberries to make jam soon recognized this wild fruit as a source for a blue dye.
Dyes made by country people: _______________ had two uses — jam and blue dye.
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