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The Biosphere
I. Introduction
A. For most of life on Earth, the sun is the main source of energy
B. But around hydrothermal vents, life depends on chemoautotrophic sulfur bacteria
C. From the roof of the world to the deepest oceans, Earth’s diverse environments are
bursting with life
II. The Biosphere
A. 34.1 Ecologists study how organisms interact with their environment at several levels
1. Ecology is the scientific study of
2. Organisms can potentially be affected by many different variables, grouped into two
major types
a. Biotic factors include all of the organisms in an area,
b. Abiotic factors are the environment’s nonliving component,
3. An organism’s habitat includes the biotic and abiotic factors present in its
surroundings
4. Ecologists study environmental interactions at the levels of the
a. organism
b. population, a group of individuals of the
c. community, an assemblage of all the populations of organisms
d. ecosystem, both the
5. The biosphere
a. Extends from the atmosphere several kilometers above Earth to the depths of the oceans
b. Includes all of the Earth that is inhabited by life
B. 34.2 The science of ecology provides insight into environmental
problems
1. Human activities affect all parts of the biosphere
a. Cities, farms, and highways have changed Earth’s landscape
b. The widespread use of chemicals such as fertilizers and pesticides poses problems to
people and other organisms
C. 34.3 Physical and chemical factors influence life in the biosphere
1. The most important abiotic factors that determine the biosphere’s structure and
dynamics include
a. the energy source,
b. temperature
c.
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d. nutrients
e. other aquatic factors
f. other terrestrial factors
D. 34.5 Regional climate influences the distribution of terrestrial communities
1. Climate often determines the distribution of communities.
2. Earth’s global climate patterns are largely determined by
a. the input of solar energy and
b. the planet’s movement in space
3. Solar radiation varies with latitude
a. Equatorial regions receive
b. Higher latitudes receive sunlight
4. Most climatic variations are due to the uneven heating of Earth’s surface.
5. Earth’s permanent tilt causes the seasons
a. In June, the Northern Hemisphere of the Earth is
b. In December, the Northern Hemisphere of the Earth is
c. The reverse is true about the Southern Hemisphere, generating opposite seasons
during the same time of year
6. The tropics are the region surrounding the equator between latitudes 23.5° north and 23.5°
south
7. Uneven heating of the Earth causes rain and winds
a. The direct intense solar radiation in the tropics near the equator has an impact on the
global patterns of rainfall and winds
b. The tropics experience
8. As the air rises in the tropics, it
a. cools and releases much of its water content
b. produces abundant precipitation typical of most tropical regions
9. High altitude air masses
a. lose their moisture over equatorial zones and then
b.
10. The air then
a. cools and descends again at latitudes of about 30° north and south or
b. spreads back toward the equator
11. As the air moves back toward the equator, it
a. warms and
b. picks up moisture
12. The temperate zones are between the tropics and
a. the Arctic Circle in the north and
b. the Antarctic Circle in the south
c. The temperate zones have seasonal variations and
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13. Prevailing wind patterns result from the combined effects of
a. rising and falling air masses and
b. Earth’s rotation
c. In the tropics, Earth’s rapidly moving surface deflects vertically circulating air,
d. In temperate zones, the slower-moving surface produces the westerlies,
14. Ocean currents, river-like flow patterns in the oceans, result from a combination of
a. prevailing winds,
b.
c. unequal heating of surface waters, and
d.
e. Ocean currents have a profound effect on regional climates
15. Landforms can also affect local climate; for example, air temperature declines about 6°C
with every 1,000-m increase in elevation
16. Near mountains, rainfall is affected by
a. location of mountains,
b. prevailing winds, and
c.
17. The “rain shadow” of the California coastal mountain range refers to the scarcity of rain on
the eastern side of the mountain (and adjacent lowlands) compared to the western flank of the
mountain range
18. Climate and other abiotic factors of the environment control the global distribution of
organisms
19. The influence of these abiotic factors results in biomes, the major types of ecological
associations
III. Aquatic Biomes
A. 34.6 Sunlight and substrate are key factors in the distribution of marine organisms
1. Aquatic biomes are shaped by the availability of
a. light and
b. nutrients
2. Within the oceans the
a. pelagic realm includes
b. benthic realm which consists of
c. aphotic zone, where there is insufficient light
d. photic zone where light penetration is sufficient for photosynthesis and
phytoplankton can occur
i. Zooplankton are abundant in the pelagic photic zone
ii. Coral reefs also occur in the photic zone
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3. The marine environment includes distinctive biomes where the ocean meets the land or fresh
water
a. Intertidal zones are where the ocean meets the land and the shore is
i. pounded by waves during high tide
ii. exposed to the sun and drying winds during low tide
b. Estuaries are productive areas
c. Wetlands are transitional between
B. 34.7 Current, sunlight, and nutrients are important abiotic factors in freshwater biomes
1. Freshwater biomes
a. cover less than 1% of the Earth
b. contain less than 0.01% of its water
c. harbor 6% of all described species
d. include
2. Freshwater biomes fall into two broad groups:
a. standing water biomes
b. flowing water biomes
IV. Terrestrial Biomes
A. 34.8 Terrestrial biomes reflect regional variations in climate
1. Terrestrial ecosystems are grouped into nine major types of biomes, distinguished
primarily by their predominant vegetation
2. The geographic distribution of plants and thus terrestrial biomes largely depends on climate.
The key climate factors are
a.
b.
3. The same type of biome may occur in geographically distant places if the climate is similar.
4. The current concern about global warming is generating intense interest in the effect of
climate on vegetation patterns
5. Scientists are documenting
a. latitudinal shifts in biome borders and snow and ice coverage
b. changes in
B. 34.9 Tropical forests cluster near the equator
1. Tropical forests
a. occur
b. experience warm temperatures and days that are 11–12 hours long year-round
c. have abundant rainfall (200-400 cm per year)
2. The tropical rain forest is among the most complex of all biomes
a. Tropical rain forests harbor enormous numbers of species
b. Large-scale human destruction of tropical rain forests continues to endanger many species
C. 34.10 Savannas are grasslands with scattered trees
1. Savannas
a. are
b. have 30–50 cm annual rainfall
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c. experience dramatic seasonal variation
d. are dominated by
e. are mostly inhabited by large grazing mammals and insects
D. 34.11 Deserts are defined by their dryness
1. Deserts are the driest of all terrestrial biomes
a. They are characterized by
b. Desertification, the conversion of semiarid regions to desert, is a significant
environmental problem
E. 34.12 Spiny shrubs dominate the chaparral
1. The chaparral is a shrubland with
a. cool, rainy winters
b. hot, dry summers
c. Vegetation is
F. 34.13 Temperate grasslands include the North American prairie
1. Temperate grasslands
a. are mostly treeless,
b. experience precipitation of about 25–75 cm per year, with periodic droughts and cold
winters
c. in North America have historically been grazed by large bison and pronghorn
d. farms have replaced most of North America’s temperate grasslands.
G. 34.14 Broadleaf trees dominate temperate forests
1. Temperate broadleaf forests
a. grow where there is sufficient moisture to support the growth of large trees
b. experience wide-ranging temperatures (-30°C to 30°C) and high annual precipitation (75–
150 cm)
c. nearly all of the original broadleaf forests in North America have been drastically altered
H. 34.15 Coniferous forests are often dominated by a few species of trees
1. Cone-bearing evergreen trees, such as spruce, pine, fir, and hemlock, dominate
coniferous forests.
2. The northern coniferous forest, or taiga, is the largest terrestrial biome on Earth. The taiga is
characterized by
a.
b.
3. Temperate rain forests of coastal North America are also coniferous forests.
I. 34.16 Long, bitter-cold winters characterize the tundra
1. The tundra covers expansive areas of the Arctic between the taiga and the permanently
frozen polar ice
2. The treeless arctic tundra
a. is characterized by permafrost,
b. experiences little precipitation
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J. 34.17 Polar ice covers the land at high latitudes
1. Polar ice covers
a. land
b. much of the Arctic Ocean
c. the continent
2. Temperatures are extremely cold year-round and precipitation is very low
3. The terrestrial polar biome is closely intertwined with the neighboring marine biome
K. 34.18 The global water cycle connects aquatic and terrestrial biomes
1. Ecological subdivisions such as biomes are linked by
a. nutrient cycles and the water cycle
c. water in the form of precipitation and evaporation moves between the land, oceans, and
atmosphere
i. Over the oceans,
ii. Over the land,
2. Human activities affect the global water cycle
a. The destruction of tropical rain forests
b. Pumping large amounts of groundwater to the surface for irrigation increases the rate of
evaporation over land
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