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A c a d e m ic M o d u le — P ractice Test 6 207READING PASSAGE 1
You should spend about 20 mimms on Questions 1 -14 , which are based on
Reading Passage 1 below.
Pollination
Plants have evolved a wide variety of methods to reproduce themselves. Some
plants reproduce asexually by splitting off new roots or bulbs (e.g., garlic, lilies) or
even branches, stems, or leaves (e.g., mangroves, spider plants). Plants that repro
duce asexually are essentially reproducing clones of themselves. This is a simple and
direct method of reproduction, producing new plants more quickly and with less
energy than plants using sexual reproduction. The majority of plants, however,
reproduce sexually. The advantages from an evolutionary perspective include more
genetic variety and better dispersal than the colonies of clones formed by asexual
reproduction. In flowering plants, pollen (male) grains are moved from the anther
to the stigma, where the pollen fertilizes1 the ovaries (female), resulting in seeds.
A few flowering plants such as peas, beans, and tomatoes pollinate themselves,
but more commonly, pollination occurs between separate plants, either through
pollen being borne by the wind (most conifers and many grasses) or by pollina
tors, animal species that plants rely on to help move the pollen from one plant to
the ovaries of another. Most pollinators are insects, but some species of bird and
bats also play an important role.
Plants have evolved a variety of methods to entice pollinators to do their work.
Many produce nectar, a sugary substance that pollinators use as food. A well-
known example is the honeybee, which collects nectar as well as pollen for food.
When a bee enters one flower, it brushes against the anther, and pollen grains are
picked up by the surface of its body. When the bee enters a second flower and
brushes against the stigma, some of that pollen comes in contact with the ovaries
of the second plant, thus fertilizing it, resulting in seeds that contain genetic mate
rial from the male gametes of the first plant combined with the female reproduc
tive organs of the second plant. Most bees, butterflies, and moths, as well as certain
species of bats and birds, are attracted to nectar-producing flowers. d
Flowering plants have evolved a variety of methods for signaling2 their usefulness
to pollinators or for otherwise making their work easier. Butterflies are attracted to
Academic Module-Practice Test G
flowers that are open during the day, are bright—typically red, yellow, or orange—
and have a “landing platform.” In contrast, many moths are active at night and thus
are attracted to flowers that are pale or white, have a strong fragrance, but also have
broad areas to land on. Both butterflies and moths have long tongues and have co
evolved with plants that have developed deep sources of nectar that are available
only to certain species. Hummingbirds are also attracted by color3 especially by
bright reds, and flowers that attract these tiny birds also have strong stems and are
designed for pollen to be brushed on the hummingbirds’ heads as they sip nectar.
1British: fertilises
2British: signalling
3British: colour
, 208 A c a d e m ic M odule
Bees do not see red; thus, flowers that attract bees tend to be blue, yellow, pur
ple, or other colors. Many bee attractors also have nectar guides, which are spots
near the center1 of each flower that reflect ultraviolet light, making it easier for
the bees to find the nectar. Bees are also attracted to flowers with a mintlike or
sweet smell. Snapdragons not only attract bees visually, they are adapted to
appeal to certain bee species: snapdragons have a landing platform that, if the bee
is the correct weight, opens— allowing access to the nectar and pollen.
Pollinators play a major role in agriculture. While many staple crops such as
rice, corn, canola, and wheat are self-pollinating or pollinated by the wind, farm
ers are dependent on pollinator species for many fruit, vegetable, nut, and seed
crops. Over 30 percent of the world’s crops require the work of pollinator species.
Bees are the most "common agricultural pollinators, with crops including fruit
trees such as apples and cherries; vegetables such as squash, beans, tomatoes, and
eggplant; flowering shrubs and annual and perennial flowers; forage crops such
as clover and alfalfa; and fiber2 crops such as cotton. Other pollinators include
midges (cocoa), wasps (figs), moths (yucca, papaya), butterflies (asters, daisies,
marigolds), and even a few species of bats (agave, palms, durians) and humming
birds (fuchsia).
Recent declines in honeybees and in other pollinator species around the world
have raised concerns about future food production, and many scientists have
called for increased study of the role of pollinators, the agricultural and environ
mental changes involved in the declines, as well as the economic and environ
mental effects and ways to prevent further declines.
Academic Module-Practice Test G
1British: centre
2British: fibre
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