ACT Reading Jun. 2017 74C - Passage IV

Questions 31-40 are based on the following passage.

NATURAL SCIENCE: This passage is adapted from the article "The Asphalt Jungle" by Peter Del Tredici (©2010 by Natural History Magazine, Inc.).

The ecology of the city is defined not only by the
cultivated plants that require maintenance and the pro-
tected remnants of natural landscapes, but also by the
spontaneous vegetation that dominates. the neglected
5 interstices. Greenery fills the vacant spaces between
our roads, homes, and businesses; lines ditches and
chain-link fences; sprouts in sidewalk cracks and atop
neglected rooftops. Some of those plants, such as box
elder, quaking aspen, and riverside grape, are native
10 species present before humans drastically altered the
land. Others, including chicory, Japanese knotweed,
and Norway maple, were brought in intentionally or,
unintentionally by people. And still others - among
them common ragweed, path rush (Juncus tenuis), and
15 tufted lovegrass (Eragrostis pectinacea) - arrived on
their own, dispersed by wind, water, or wild animals.
Such species grow and reproduce in many American
cities without being planted or cared for. They can pro-
vide important ecological services at very little cost to
20 taxpayers, and if left undisturbed long enough they may
even develop into mature woodlands.

There is no denying that most people consider
many such plants to be "weeds". From a utilitarian per-
spective, a weed is any plant that grows on its own
25 where people do not want it to grow. From the biologi-
cal perspective, weeds are opportunistic plants that are
adapted to disturbance in all its myriad forms, from
bulldozers to acid rain. Their pervasiveness in the urban
environment is simply a reflection of the continual dis-
30 ruption that. characterizes that habitat-they are not its
cause. In an agricultural context, the competition of
weeds with economic crops is the primary reason for
controlling them. In an urban area, a weed is any plant
growing where people are trying to cultivate something
35 else, or keep clear of vegetation altogether. The com-
plaints of city dwellers are usually based on aesthetics
(the plants are perceived as ugly, or as signs of blight
and neglect) or on security concerns (they shield human
activity or provide habitat for vermin).

40 From a plant's perspective, it is not the density of
the human population that defines the urban environ-
ment, but the abundance of paving (affecting access to
soil and moisture) and prevalence of disturbance. In
other words, a sidewalk crack is a sidewalk crack
45 whether it is in a city or a suburb. Urbanization is a
process, not a place-a process that tends to leave the
soil in a compacted, impoverished, and often contami-
nated state.

The plants that grow and survive in derelict urban
50 wastelands are famous (or infamous) for their ability to
grow under extremely harsh conditions. Through a
quirk of evolutionary fate, they developed traits in their
native habitats that seem to have "preadapted" them to
flourish in cities. One study, by biologist Jeremy T.
55 Lundholm of St. Mary's University in Halifax, Nova
Scotia, and his then student Ashley Marlin, concluded
that many successful urban plants are native to exposed
cliffs, disturbed rock outcrops, or dry grasslands, all of
which are characterized by soils with a relatively high
60 pH. Cities, with their tall, granite-faced buildings and
concrete foundations, are in a sense the equivalent of
the natural limestone cliff habitats where those species
originated. Similarly, as the British ecologist and
"lichen hunter" Oliver L. Gilbert noted in his classic
65 book The Ecology of Urban Habitats, the increased use
of deicing salts on our roads and highways has resulted
in the development of microhabitats along their margins
that are typically colonized by calcium-loving grass-
land species adapted to limestone soils or by salt-loving
70 plants from coastal habitats.

In general, the successful urban plant neeqs to be
flexible in all aspects of its life history, from seed ger-
mination through flowering and fruiting; opportunistic
in its ability to take advantage of locally abundant
75 resources that may l:!e available for only a short time;
and tolerant of the stressful growing conditions caused
by an abundance of pavement and a paucity of soil. The
plants that grow in our cities managed to survive the
transition from one land use to another as cities devel-
80 oped. The sequence starts with native species adapted
to ecological conditions before the city was built. Those
are followed, more or less in order, by species
preadapted to agriculture and pasturage, to pavement
and compacted soil, to lawns and landscaping, to infra-
85 structure edges and environmental pollution-and ulti-
mately to vacant lots and rubble.

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