PSAT Reading Practice Test 6

Questions 1-9 refer to the following information.

Passage 1 is adapted from "Tardigrades become first animals to survive vacuum of space" by Ed Yong ? 2016. Passage 2 is adapted from "These 'Indestructible' Animals Would Survive a Planet-Wide Apocalypse" by Casey Smith, NG Image Collection. Published 2018.

Passage 1
In September last year, a team of scientists launched
a squad of tiny animals into space aboard a Russian
satellite. Once in orbit, the creatures were shunted into
ventilated containers that exposed them to the vacuum of
05space. In this final frontier, they had no air and they were
subjected to extreme dehydration, freezing temperatures,
weightlessness and lashings of both cosmic and solar
radiation. It's hard to imagine a more inhospitable
environment for life but not only did the critters survive,
10they managed to reproduce on their return to Earth.
Meet the planet's toughest animals – the tardigrades.
Tardigrades are small aquatic invertebrates that are
also known as "water bears", after their impossibly cute
shuffling walk. They also happen to be nigh-invincible and
15can tolerate extreme environments that would kill almost
any other animal. They can take temperatures close to
absolute zero, punishing doses of radiation and prolonged
periods of drought. And now, they have become the only
animals to have ever survived the raw vacuum of space.
20Their stellar adventure began with Ingemar Jonsson
from Kristianstad University, who really wanted
to test the limits of their resilience. To that end, he
launched adults from two species (Richtersius coronifer
and Milnesium tardigradum) into space aboard the
25FOTON-M3 spacecraft, as part of a mission amusingly
known as TARDIS (Tardigrades In Space). The
tardinauts spent ten days in low Earth orbit, about
270km above sea level. The tardigrades were sent into
orbit in a dry, dormant state called a "tun" and it's this
30dessicated form that is the key to their extraordinary
levels of endurance. By replacing almost all of the water
in their bodies with a sugar called trehalose, they can
escape many of the things that would otherwise kill
them. Jonsson says, "Environmental agents that rely
35on water or the respiratory system don't work. You can
put a dry tardigrade in pure alcohol and expose them to
poisonous gases without killing them."
The ability to dry out completely is an adaptation to
the tardigrades' precarious environment – damp pools
40or patches of water on moss or lichen that can easily
evaporate. They have evolved to cope with sporadic
drought and can stay dormant for years. All it takes to
revive them is a drop of water, and that's exactly what
happened when the TARDIS astronauts returned to Earth.
Passage 2
45The world's most robust animals may very well
survive until the sun stops shining. Tardigrades are tiny
water-dwelling creatures famed for their resiliency. The
eight-legged invertebrates can survive for up to 30 years
without food or water and can endure wild temperature
50extremes, radiation exposure, and even the vacuum of
space. At a minimum, all of Earth's oceans would have
to boil away to completely wipe out all life on the planet.
Although tardigrades are only known to survive high
temperatures when dry—and those species living in the
55sea would likely die before the waters boiled—tardigrades
are still expected to avoid extinction until our sun swells
up and becomes a red giant roughly six billion years from
now, according to researchers who investigated the effects
of various doomsday scenarios, and who described the
60results in the journal Scientific Reports.
Astrophysical events such as asteroid strikes have
been fingered as the causes of past mass extinctions on
Earth. Such violent cataclysms could easily wipe out
humans: We belong to a sensitive species, and subtle
65changes in the environment impact us dramatically,
notes study co-author Rafael Alves Batista of the
University of Oxford.
Intrigued by the resilience of tardigrades, Alves
Batista and his colleagues wanted to explore the effects
70of potential astrophysical catastrophes on more than
just human life. There are asteroids out there that do
pose collision risks and are large enough to trigger
an "impact winter," blotting out sunlight and causing
temperatures to drop. This would be catastrophic for
75many life-forms on the surface, but tardigrades would
have a refuge.
Tardigrades can live around volcanic vents at the
bottom of the ocean, which means they have a huge shield
against the kind of events that would be catastrophic
80for humans, Sloan says. In essence, the researchers say,
only the death of the sun will ultimately lead to the total
extinction of life on Earth, including tardigrades.
Tardigrades are as close to indestructible as it gets
on Earth," Alves Batista says, "but it's possible that
85there are other resilient species examples elsewhere
in the universe."