I.
Miller Chapter 7 Review
Chapter 7: Climate and Biodiversity
a. 7-1: What Factors Influence Climate?
i. Weather – a set of physical conditions of the lower atmosphere, including
temperature, precipitation, humidity, wind speed, cloud cover, and other factors, in
a given area over a period of hours or days.
ii. Climate –the general pattern of atmospheric conditions in a given area over periods
ranging from at least three decades to thousands of years.
1. Climate is the sum of weather conditions in a given area, averaged over a
long period of time
iii. Ocean Currents – mass movements of surface water driven by winds blowing over
the oceans.
1. The currents help to determine regional climates and are a key component of
the Earth’s natural capital
iv. Global air circulation and ocean currents distribute heat and precipitation unevenly
between the tropics and other parts of the world.
1. Three major factors affect the circulation of air in the lower atmosphere:
a. Uneven heating of the earth’s surface by the Sun
i. Heated more at the equator, where the Sun’s rays strike
directly, than at the poles, where sunlight strikes at an angle
and spreads out over a much greater area
ii. The intense input of solar radiation in tropical regions leads to
greatly increased evaporation of moisture from forest,
grasslands, and bodies of water. As a result, tropical regions
normally receive more precipitation than do other areas of the
Earth.
b. Rotation of the Earth on its axis
i. The equator spins faster than the regions to its north and south
ii. Prevailing Winds – major surface winds that blow almost
continuously and help to distribute heat and moisture over the
earth’s surface and to drive ocean currents
c. Properties of air, water, and land
i. Density = Mass per unit of volume (M/V)
ii. Clockwise in the northern hemisphere and counterclockwise in
the southern hemisphere
v. The ocean and the atmosphere are strongly linked in two ways:
1. Ocean currents are affected by winds in the atmosphere
2. Heat from the ocean affects atmospheric circulation
a. El Nino-Southern Oscillation (ENSO) – the large-scale weather
phenomenon occurs every few years when prevailing winds in the
Tropical Pacific Ocean weaken and change direction
3. Earth’s air circulation patterns, prevailing winds, and configuration of
continents and oceans are all factors in the formation of six giant convection
cells.
a. Three of them south of the equator
b. Three of them north of the equator
4. Cells lead to an irregular distribution of climates and of the resulting deserts,
grasslands, and forests
vi. Water Vapor (H2O), Carbon Dioxide (CO2), Methane (CH4), and Nitrous Oxide (N2O),
absorb some of this solar energy and release a portion of it as infrared radiation
(heat) that warms the lower atmosphere.
1. These gases are called greenhouse gases – play a role in determining the
lower atmosphere’s average temperatures and thus the Earth’s climate
2. The Earth’s surface also absorbs must of the solar energy that strikes it and
transforms it into longer wavelength infrared radiation, which then rises into
the lower atmosphere.
a. Some of this heat escapes into space, some is absorbed by molecules
of greenhouse gases and emitted into the lower atmosphere as even
longer wavelength infrared radiation
3. Greenhouse Effect – the process results in a natural warming of the
troposphere
a. Without this natural warming effect, the earth would be vary cold and
mostly lifeless planet
4. The burning of fossil fuels, clearing of forest, and growing of crops release
carbon dioxide, methane, and nitrous oxide into the atmosphere
a. Human activities are likely to enhance the earth’s natural greenhouse
effect and change the earth’s climate during this century
vii. Mountains interrupt the flow of prevailing surface winds and the movement of
storms
1. As the drier air mass passes over the mountaintops, it flows down the
leeward slopes (facing away from the wind), and warms up.
a. This increases its ability to hold moisture, but the air releases little
moisture and instead tends to dry out plants and soil below. (Rain
Shadow Effect)
i. Results in semiarid and arid conditions on the leeward side of a
high mountain range (ex. Death Valley)
b. Bricks, concrete, asphalt, and other building materials absorb and
hold heat, and building block wind flow (ex. Heat Islands)
b. 7-2: How Does Climate Affect the Nature and Location of Biomes?
i. Different combinations of varying average annual precipitation and temperatures,
along with global air circulation and ocean currents, lead to the formation of tropical
(hot), temperate (moderate), and polar (cold), deserts, grasslands, and forests
1. Climate and vegetation vary according to latitude and also according to
elevation
ii. Several major BIOMES – large TERRESTRIAL regions, each characterized by a
certain type of climate and a certain combination of dominant plant life.
1. Biomes are not uniform – they consist of a mosaic of patches, each with
somewhat different biological communities but with similarities typical of a
biome
iii. Three Major Types of Deserts: annual precipitation is low and often scattered
unevenly throughout the year
1. Tropical Deserts – such as the Sahara and the Namib of Africa, hot and dry
most of the year
2. Temperate Deserts – Sonoran Desert in southeastern California, daytime
temperatures are high in summer and low in winter, precipitation is more
than a tropical desert
3. Cold Desert – Gobi Desert in Mongolia, vegetation is sparse, winters are cold,
summers are warm or hot, precipitation is low
4. Desert ecosystems are fragile because they experience slow plant growth,
low species diversity, slow nutrient cycling (due to low bacterial activity in
the soils), and very little water
iv. Three Major Types of Grasslands:
1. Grasslands – occur primarily in the interiors of continents in areas that are
too moist for deserts to form and too dry for forest to grow
a. Tropical Grassland (Savanna) – contains widely scattered clumps of
trees, usually has warm temperatures year-round and alternating dry
and wet seasons
i. Tropical Savannas in East Africa are home to grazing (grasseating) and browsing (twig-leaf eating) hoofed-animals
1. Herds of these grazing and browsing animals migrate to
find water and food in response to seasonal and yearto-year variations in rainfall
b. Two types of temperate grasslands – depend primarily on average
rainfall
i. Short – Grass Prairies
ii. Tall - grass Prairies - get more rain
iii. In all prairies winds blow almost continuously and evaporation
is rapid, often leading to fires in the summer and fall
iv. Many of the world’s natural temperate grasslands have been
converted to farmland
c. Cold grasslands (Arctic Tundra) – lie south of the artic polar ice cap
i. Winters are long with few hours of daylight and the scant
precipitation that falls is primarily snow
ii. Permafrost – underground soil in which captured water stays
frozen for more than two consecutive years
iii. The Tundra is a fragile biome, usually has nutrient poor soils
d. Alpine Tundra – occurs above the line of tree growth but below the
permanent snow line on high mountains, receives more sunlight than
arctic vegetation gets
v. Three major types of Forest:
1. Forest – lands dominated by trees, result in varying precipitation levels and
varying average temperature
a. Tropical Rain Forest – found near the equator, where hot, moistureladen air rises and dumps its moisture, fairly constant warm wet
climate is ideal for a wide variety of plants and animals
i. Tops of trees form a dense canopy which blocks most light
from reaching the forest floor
ii. Draped with vines (called lianas)
iii. Have a very high net primary productivity
iv. Have been used as blueprints for making most of the world’s
prescription drugs
v. High species richness
vi. Vegetation layers are structured, according to the plants’ needs
for sunlight
vii. Lack of fertile soil helps to explain why rain forest are not good
places to clear and grow crops or graze cattle on a sustainable
basis
1. At least half of these forest have been destroyed or
disturbed by human activities such as farming and
cattle production
b. Temperate Deciduous Forest – have cooler temperatures and fewer
decomposers than tropical forest have, have a slower rate of
decomposition
i. Degraded by various human activities, especially logging and
urban expansion
c. Cold or Northern Coniferous Forest (Boreal Forest or Taigas) – found
just south of the artic tundra in northern regions across North
America, Asia, and Europe
i. Winters are long and extremely cold, Summers are short with
cool to warm temperatures
ii. Most boreal forest are dominated by a few species of
coniferous (cone-bearing) evergreen trees
iii. Decomposition is slow due to the low temperatures
d. Coastal Coniferous Forest (Temperate Rain Forest) – found in coastal
temperate areas with ample rainfall or moisture from dense ocean fog
vi. Mountains – most spectacular environments, places where dramatic changes in
altitude, slope, climate, soil, and vegetation take place over a very short distance
1. Mountain soils are easily eroded when vegetation holding them in place is
removed by natural disturbances or human activities
2. Many mountains are islands of biodiversity
3. Mountains play important ecological roles
a. Often habitats for species that found nowhere else on earth (endemic
species)
4. Play a critical role in the hydrologic cycle by serving as a major storehouse of
water
a. Some mountaintop snow packs and glaciers are melting earlier in the
spring each year
i. This is lowering food production in certain areas, because
much of the water needed throughout the summer to irrigate
crops gets released too quickly and too early
c. 7-3: How Have Human Activities Affected the World’s Terrestrial Ecosystem?
i. 60% of the world’s major terrestrial ecosystems are being degraded or used
unsustainably, as human ecological footprint gets bigger and spreads across the
globe
ii. Many environmentalist are:
1. Calling for a global effort to better understand the nature and state of the
world’s major ecosystems and to use the date to protect the world’s
remaining wild areas from development
2. Restore many of the land areas that have been degraded, especially in areas
that are rich in biodiversity
a. Such efforts are highly controversial because of the timber, mineral,
fossil fuels, and other resources found on or under many of the earth’s
remaining wild land areas
iii. The locations and sizes of the world’s biomes are not fixed and they change as the
earth’s climate changes
iv. As the temperature increases this will likely change the sizes and locations of many
biomes, alter the ecological map of the earth’s land areas, wipe out many species,
and degrade important ecosystem services