Read the passage below. Use the information in the passage and your own
knowledge to answer the questions that follow.
Venus flytraps carry out the process of photosynthesis. The glucose
produced is used as a source of energy. In addition to synthesising glucose,
plants also need to make amino acids, vitamins and other components to
survive. To do this, plants need to absorb minerals.
5 In the bogs where Venus flytraps live the mineral content of the soil is low so
minerals are scarce. Most plants cannot survive in this environment because
they cannot make enough of the building blocks necessary for growth. The
Venus flytrap has evolved the ability to grow well in this habitat by finding
alternate means of getting minerals. Insects provide a good source of the
10 minerals missing from the soil, and they contain additional carbohydrates.
Carnivorous plants attract and capture insects, discriminate between food
and non-food, and digest the insects. They do this using mechanical and
chemical processes. Plants lack the muscles and tendons to eat, chew
and swallow food. The Venus flytrap completes the entire process using
15 specialised leaves that carry out the role of the mouth and the intestines.
Most plants have some mechanism to attract insects. The Venus flytrap does
this by secreting sweet nectar from the leaves of the trap. When an insect
lands or crawls on the trap, it is likely to touch one of six, short, stiff hairs
on the trap’s surface. These are trigger hairs, and they serve as a motion
20 detector for the plant. If two of these hairs are brushed in quick succession,
or one hair is touched twice, the leaves close on the insect.
The mechanism of trap closure is not clearly understood but it involves
changes in the concentration of solution in the cells. The cells expand as
water enters causing the trap to close. Once the trap fully closes, the leaves
25 form a seal so that digestive fluid and insects are kept inside the trap and
bacteria and fungi cannot get in.
To make sure that the insects are kept in the trap, the edges of the leaves
have projections that fit together when the leaves shut. These projections
look like teeth but they are only used to keep the trap shut.
30 The leaf trap now serves as a digestive organ to dissolve the soft tissues and
cell membranes of the food. It produces acid and enzymes. The insect body
is broken down over a period of 5 to 10 days and the products of digestion
are absorbed.