Practice Exam 1 - Environmental Science - page 231

13. A Net primary productivity is the rate at which solar energy is converted into biomass, so high net
primary productivity means energy is converted to biomass quickly. Coral reefs, wetlands, and algal
beds also have high net primary productivity.
14. A Water vapor, carbon dioxide, and methane are the most abundant greenhouse gases in the atmo-
sphere. All three gases occur naturally, but their levels have increased in the last century due to human
activity. They all have the ability to trap heat, so the greater the concentration of gases the more heat
that can be trapped within the atmosphere.
15. C In photosynthesis a plant takes in carbon dioxide and water, which react with light energy from the
sun to produce glucose and oxygen. The chemical equation for photosynthesis is:
16. B The golden toad was endemic to the Monteverde cloud forest in Costa Rica. An endemic species is
found in only one location on the planet. Therefore, if it vanishes from this region it becomes extinct.
This is what happened to the golden toad when the climate began to shift in its habitat, drying the
forest. (It was indigenous and native as well, but neither of those conditions contributed to its extinc-
tion.)
17. E A beaver is a keystone species in North America because many other species depend on it for sur-
vival. Beaver dams help to maintain river flow, provide habitat for other organisms, and reduce the ef-
fects of flooding. Also, their dams create wetlands and ponds vital to the maintenance of biodiversity.
18. D Survival in an extremely dry desert environment requires adaptations, including spines to help pro-
tect exposed organisms from being eaten, deep roots to access water, and waxy outer coatings on plants
to prevent water loss.
19. C Boreal forests are dominated by coniferous trees, which are needle-containing trees such as ever-
greens. Coniferous trees are well-suited for the cold, dry climate of this region since their leaves require
less water and sunlight for photosynthesis.
20. A Tundra is found in high latitudes and is very cold through most of the year. Water that remains
frozen in the soil through most of the year is known as permafrost. Unfortunately, in recent years, more
permafrost has been melting and remaining melted for longer periods of time due to climate change.
21. D When using the precautionary principle to assess a newly developed substance, it is assumed that the
substance is harmful until proven otherwise. This process takes a cautious approach so harmful sub-
stances are not introduced to people, wildlife, or the environment.
22. C This example describes a disturbance (volcanic eruption) that completely destroyed all life. This
means that primary succession takes place, with all life in the area essentially starting over. Lichens are
a pioneer species starting the process, followed by the growth of small plants and then the presence of
insects. Eventually larger vegetation develops and, finally, there are mature trees. Over time, this com-
munity remains stable, unaffected by disturbance, and is considered a climax community.
23. C Ice has been accumulating in glaciers and ice caps for millions of years, trapping air bubbles as it
freezes. The composition of these bubbles in an ice core sample tells scientists what was in the atmo-
sphere at the time the ice froze. Concentrations of greenhouse gases, variations in temperature, volcanic
activity, and the composition of the atmosphere can all be determined from ice core samples.
24. D Much solar radiation penetrates the Earth's atmosphere and reflects off of the planet. Some of this
heat escapes back into space and some is reflected back to Earth by greenhouse gases. This double re-
flection, first from the Earth and then from atmospheric gases, is known as the greenhouse effect.