Miller Chapter 7 Review

Chapter 7: Climate and Biodiversity
7-1: What Factors Influence Climate?
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.
Climate –the general pattern of atmospheric conditions in a given area over periods ranging from at least three decades to thousands of years.
Climate is the sum of weather conditions in a given area, averaged over a long period of time
Ocean Currents – mass movements of surface water driven by winds blowing over the oceans.
The currents help to determine regional climates and are a key component of the Earth’s natural capital
Global air circulation and ocean currents distribute heat and precipitation unevenly between the tropics and other parts of the world.
Three major factors affect the circulation of air in the lower atmosphere:
Uneven heating of the earth’s surface by the Sun
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
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.
Rotation of the Earth on its axis
The equator spins faster than the regions to its north and south
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
Properties of air, water, and land
Density = Mass per unit of volume (M/V)
Clockwise in the northern hemisphere and counterclockwise in the southern hemisphere
The ocean and the atmosphere are strongly linked in two ways:
Ocean currents are affected by winds in the atmosphere
Heat from the ocean affects atmospheric circulation
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
Earth’s air circulation patterns, prevailing winds, and configuration of continents and oceans are all factors in the formation of six giant convection cells.
Three of them south of the equator
Three of them north of the equator
Cells lead to an irregular distribution of climates and of the resulting deserts, grasslands, and forests
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.
These gases are called greenhouse gases – play a role in determining the lower atmosphere’s average temperatures and thus the Earth’s climate
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.
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
Greenhouse Effect – the process results in a natural warming of the troposphere
Without this natural warming effect, the earth would be vary cold and mostly lifeless planet
The burning of fossil fuels, clearing of forest, and growing of crops release carbon dioxide, methane, and nitrous oxide into the atmosphere
Human activities are likely to enhance the earth’s natural greenhouse effect and change the earth’s climate during this century
Mountains interrupt the flow of prevailing surface winds and the movement of storms
As the drier air mass passes over the mountaintops, it flows down the leeward slopes (facing away from the wind), and warms up.
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)
Results in semiarid and arid conditions on the leeward side of a high mountain range (ex. Death Valley)
Bricks, concrete, asphalt, and other building materials absorb and hold heat, and building block wind flow (ex. Heat Islands)
7-2: How Does Climate Affect the Nature and Location of Biomes?
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
Climate and vegetation vary according to latitude and also according to elevation
Several major BIOMES – large TERRESTRIAL regions, each characterized by a certain type of climate and a certain combination of dominant plant life.
Biomes are not uniform – they consist of a mosaic of patches, each with somewhat different biological communities but with similarities typical of a biome
Three Major Types of Deserts: annual precipitation is low and often scattered unevenly throughout the year
Tropical Deserts – such as the Sahara and the Namib of Africa, hot and dry most of the year
Temperate Deserts – Sonoran Desert in southeastern California, daytime temperatures are high in summer and low in winter, precipitation is more than a tropical desert
Cold Desert – Gobi Desert in Mongolia, vegetation is sparse, winters are cold, summers are warm or hot, precipitation is low
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
Three Major Types of Grasslands:

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
Tropical Grassland (Savanna) – contains widely scattered clumps of trees, usually has warm temperatures year-round and alternating dry and wet seasons
Tropical Savannas in East Africa are home to grazing (grass-eating) and browsing (twig-leaf eating) hoofed-animals
Herds of these grazing and browsing animals migrate to find water and food in response to seasonal and year-to-year variations in rainfall
Two types of temperate grasslands – depend primarily on average rainfall
Short – Grass Prairies
Tall - grass Prairies - get more rain
In all prairies winds blow almost continuously and evaporation is rapid, often leading to fires in the summer and fall
Many of the world’s natural temperate grasslands have been converted to farmland
Cold grasslands (Arctic Tundra) – lie south of the artic polar ice cap
Winters are long with few hours of daylight and the scant precipitation that falls is primarily snow
Permafrost – underground soil in which captured water stays frozen for more than two consecutive years
The Tundra is a fragile biome, usually has nutrient poor soils
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

Three major types of Forest:
Forest – lands dominated by trees, result in varying precipitation levels and varying average temperature
Tropical Rain Forest – found near the equator, where hot, moisture-laden air rises and dumps its moisture, fairly constant warm wet climate is ideal for a wide variety of plants and animals
Tops of trees form a dense canopy which blocks most light from reaching the forest floor
Draped with vines (called lianas)
Have a very high net primary productivity
Have been used as blueprints for making most of the world’s prescription drugs
High species richness
Vegetation layers are structured, according to the plants’ needs for sunlight
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
At least half of these forest have been destroyed or disturbed by human activities such as farming and cattle production
Temperate Deciduous Forest – have cooler temperatures and fewer decomposers than tropical forest have, have a slower rate of decomposition
Degraded by various human activities, especially logging and urban expansion
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
Winters are long and extremely cold, Summers are short with cool to warm temperatures
Most boreal forest are dominated by a few species of coniferous (cone-bearing) evergreen trees
Decomposition is slow due to the low temperatures
Coastal Coniferous Forest (Temperate Rain Forest) – found in coastal temperate areas with ample rainfall or moisture from dense ocean fog
Mountains – most spectacular environments, places where dramatic changes in altitude, slope, climate, soil, and vegetation take place over a very short distance
Mountain soils are easily eroded when vegetation holding them in place is removed by natural disturbances or human activities
Many mountains are islands of biodiversity
Mountains play important ecological roles
Often habitats for species that found nowhere else on earth (endemic species)
Play a critical role in the hydrologic cycle by serving as a major storehouse of water
Some mountaintop snow packs and glaciers are melting earlier in the spring each year
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

7-3: How Have Human Activities Affected the World’s Terrestrial Ecosystem?
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
Many environmentalist are:
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
Restore many of the land areas that have been degraded, especially in areas that are rich in biodiversity
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
The locations and sizes of the world’s biomes are not fixed and they change as the earth’s climate changes
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