environmental science
biome
a large, relatively distinct terrestrial region with characteristic climate, soil, plants, and animals, regardless of where it occurs; a biome encompasses many interacting ecosystems. Near the poles, temperature is generally the overriding climate factor in determining biome distribution, whereas in temperate and tropical regions, precipitation is more significant.
Tundra
is the treeless biome in the far north that consists of boggy plains covered by lichens and small plants such as mosses; it has harsh, very cold winters and extremely short summers.
Boreal forest
is a region of coniferous forest in the Northern Hemisphere, located just south of the tundra.
Temperate Rain Forest
is a coniferous biome with cool weather, dense fog, and high precipitation.
Temperate Diciduous Forest
is a forest biome that occurs in temperate areas where annual precipitation ranges from about 75 cm to 126 cm
Tropical Rain Forest
is a lush, species-rich forest biome that occurs where the climate is very moist throughout the year.
Chaparral
 is a biome with mild, moist winters and hot, dry summers; vegetation is typically small-leafed evergreen shrubs and small trees.
Temperate Grassland
is a grassland with hot summers, cold winters, and less rainfall than is found in the temperate deciduous forest biome.
Savanna
is a tropical grassland with widely scattered trees or clumps of trees.
Desert
is a biome in which the lack of precipitation limits plant growth; deserts are found in both temperate and tropical regions.
important environmental factors in aquatic ecosystems

salinity, amount of dissolved oxygen, and availability of light for photosynthesis.

 

Freshwater ecosystems include
standing-water, flowing-water, and freshwater wetlands (marshes and swamps).
flowing water ecosystem
is a freshwater ecosystem such as a river or stream in which the water flows in a current.

Standing water ecosystem

 

is a body of fresh water surrounded by land and whose water does not flow, such as a lake or pond
Freshwater wetlands
are lands that shallow fresh water covers for at least part of the year; wetlands have a characteristic soil and water-tolerant vegetation.
estuary
is a coastal body of water, partly surrounded by land, with access to the open ocean and a large supply of fresh water from a river. Water in an estuary is brackish rather than truly fresh. Temperate estuaries usually contain salt marshes, whereas tropical estuaries are lined with mangrove forests.
Evolution

is the cumulative genetic changes in populations that occur during successive generations.

 

Natural Selection
is the tendency of better-adapted individuals—those with a combination of genetic traits better suited to environmental conditions—to survive and reproduce, increasing their proportion in the population.
Natural selection is based on four premises established by Charles Darwin:
(1) Each species produces more offspring than will survive to maturity. (2) The individuals in a population exhibit inheritable variation in their traits. (3) Organisms compete with one another for the resources needed to survive. (4) Those individuals with the most favorable combination of traits are most likely to survive and reproduce, passing their genetic traits to the next generation.
ecological succession

is the process of community development over time, which involves species in one stage being replaced by different species.

 

primary succession
is the change in species composition over time in an environment that was not previously inhabited by organisms; examples include bare rock surfaces, such as recently formed volcanic lava and rock scraped clean by glaciers.
Secondary succession
is the change in species composition that takes place after some disturbance destroys the existing vegetation; soil is already present. Examples include abandoned farmland and open areas caused by forest fires.
population ecology
is the branch of biology that deals with the number of individuals of a particular species found in an area and how and why those numbers change over time.
growth rate (r)
) is the rate of change (increase or decrease) of a population’s size, expressed in percent per year.
growth rate is due to
birth rate (b) and the death rate (d): r = bd.
Emigration (e)
), the number of individuals leaving an area
immigration (i)
the number of individuals entering an area, also affect a local population’s growth rate.
Biotic potential
is the maximum rate a population could increase under ideal conditions.
Exponential population growth

is the accelerating population growth that occurs when optimal conditions allow a constant reproductive rate for limited periods.

 

 Eventually, the growth rate decreases to around zero or becomes negative because of environmental resistance,

environmental resistance
unfavorable environmental conditions that prevent organisms from reproducing indefinitely at their biotic potential.
carrying capacity (K)
is the largest population a particular environment can support sustainably (long-term), assuming there are no changes in that environment.

Human Population Patterns

It took thousands of years for the human population to reach 1 billion (around 1800). Since then, the population has grown exponentially. The United Nations projects the population will reach 7 billion by 2013. Although our numbers continue to increase, the growth rate (r) has declined slightly over the past several years
zero population growth
in which it remains the same size because the birth rate equals the death rate, toward the end of the twenty-first century
Thomas Malthus
was a British economist who said that the human population increases faster than its food supply, resulting in famine, disease, and war. Malthus’s ideas appear to be erroneous because the human population has grown from about 1 billion in his time to more than 6 billion today, and food production has generally kept pace with population. But Malthus may ultimately be proved correct because we don’t know whether our increase in food production is sustainable.
earth’s carrying capacity dependent on..

Estimates of Earth’s carrying capacity for humans vary widely depending on what assumptions are made about standard of living, resource consumption, technological innovations, and waste generation. In addition to natural environmental constraints, human choices and values determine Earth’s carrying capacity for humans.

Demographics
is the applied branch of sociology that deals with population statistics.
;As a country becomes industrialized, it goes through a_________as it moves from relatively high birth and death rates to relatively low birth and death rates.
demographic transition
infant mortality rate
is the number of infant deaths under age 1 per 1000 live births
total fertility rate (TFR)
is the average number of children born to each woman.
Replacement-level fertility
is the number of children a couple must produce to ;replace; themselves
;Age structure
is the number and proportion of people at each age in a population.
;A country can have replacement-level fertility and still experience population growth if the largest percentage of the population is in the prereproductive years. In contrast to developing countries, highly developed countries have low infant mortality rates, low total fertility rates, and an age structure in which the largest percentage of the population isn’t in the prereproductive years.
Four factors are most responsible for high total fertility rates:
high infant and child mortality rates, the important economic and societal roles of children in some cultures, the low status of women in many societies, and a lack of health and family planning services. The single most important factor affecting high TFRs is the low status of women. The governments of many developing countries are trying to limit population growth.

Education of women decreases the total fertility rate, in part by delaying the first childbirth. Education increases the likelihood women will know how to control their fertility. Education also increases women’s career options, which provide ways of achieving status besides having babies.

Urbanization
is the process whereby people move from rural areas to densely populated cities. In developing nations, most people live in rural settings, but their rates of urbanization are rapidly increasing.
Rapid urbanization makes it difficult to provide city dwellers with basic services such as
housing, water, sewage, and transportation systems.
Compact development
is the design of cities so that tall, multiple-unit residential buildings are close to shopping and jobs, and all are connected by public transportation.
Malnutrition

is the impairment of health due to consuming too few or too many calories.

;

Undernutrition

is a serious underconsumption of calories that leaves the body weakened and susceptible to disease.

;

Overnutrition
is a serious overconsumption of calories that leaves the body susceptible to disease.
Food insecurity
;a condition in which people live with chronic hunger and malnutrition, is exacerbated by population growth, environmental problems, and poverty.
slash-and-burn agriculture
patches of tropical forests are cleared to plant crops.
Nomadic herding
carried out on arid land, requires herders to move livestock continually to find food for them.
Intercropping

involves growing a variety of plants simultaneously on the same field.

;

Prime farmland
in the United States is being lost to urbanization and urban sprawl. Global declines in plant and animal varieties have led many countries to collect germplasm, any plant or animal material that may be used in breeding.
Farmers and ranchers strive to increase yields in many ways, including administering
hormones and antibiotics to livestock.
green revolution
introduced modern cultivation methods and high-yield crop varieties to Asia and Latin America. These methods require developing nations to import energy-intensive technologies and to face environmental problems caused by inorganic fertilizers and pesticides.
Environmental problems caused by industrialized agriculture include
air pollution from the use of fossil fuels and pesticides, water pollution from untreated animal wastes and agricultural chemicals, pesticide-contaminated foods and soils, and increased resistance of pests to pesticides
Land degradation
decreases the future ability of the land to support crops or livestock.
Clearing grasslands and forests and draining wetlands to grow crops have resulted in
habitat fragmentation, the breakup of large areas of habitat into small, isolated patches.
Sustainable agriculture
uses methods that maintain soil productivity and a healthy ecological balance while minimizing long-term impacts. Unlike industrialized agriculture, sustainable agriculture relies on beneficial biological processes and environmentally friendly chemicals.
Genetic engineering
is the manipulation of genes to produce a particular trait
Genetic engineering produces;
more productive livestock varieties, more nutritious crops, or crop plants resistant to pests, diseases, or drought.
Concerns about genetic engineering include
its potential to produce harmful organisms and to trigger food allergies.
pesticide
is any toxic chemical used to kill pests
narrow-spectrum pesticide
kills only the intended organism and does not harm other species.
Most pesticides are broad-spectrum pesticides
;which kill a variety of organisms, including beneficial ones, in addition to the target pest.
Pesticides can effectively control disease-carrying organisms and crop pests.
;The abundance of pests in agriculture is partly due to the common practice of monoculture, the cultivation of only one type of plant over a large area.
Pesticide use leads to several problems:
pests evolve genetic resistance, an inherited characteristic that decreases the effect of a given agent (like a pesticide) on an organism; ecosystem imbalances occur when pesticides affect species other than the intended pests; and pesticides exhibit persistence, degrading very slowly.
Bioaccumulation
is the buildup of a persistent pesticide or other toxins in an organism’s body.
Biological magnification
is the increased concentration of toxins, such as certain pesticides, in the tissues of organisms at higher levels in food webs. Pesticides also show mobility, moving to places other than where they were applied.
biological controls
which use naturally occurring disease organisms, parasites, or predators to control pests.
Pheromones
natural substances produced by animals to stimulate a response in other members of the same species, are used to attract and trap pest species.
Integrated pest management
 is a combination of pest control methods that, if used in the proper order and at the proper times, keep a pest population low enough to prevent substantial economic loss.
Which are the crops on from which humans get 50% of all their calories
grain
Why do strawberries turn red?
Because they absorb red yellow and orange light
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