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Chapter 145 -- Part 1: Biomes
The distribution of the earth's Biomes depends on the amount of precipitation and temperature in the area.
The dominant vegetation and animal life of each biome.
There are many different types of flora and fauna.
If you travel north from the equator, you will pass through the tropical rainforest, desert, temperate grassland, taiga, and tundra.
Similar to changes in latitude, changes in altitude produce effects.
On the slopes of the Appalachian Mountains in the east and the Rockies and coastal ranges in the west, there is a similar trend.
As elevation increases and temperatures and humidity decrease, one passes through deciduous forests to taigas.
There is an overview of the world's major biomes.
Tropical rainforests are found near the equator with abundant rain, stable temperatures, and high humidity.
The forests cover only 4% of Earth's land surface, but they account for 20% of Earth's net carbon fixation.
Tropical rainforests have a lot of different species.
They may have as many as 50 times the number of trees as a forest.
The floor of the forest is dimly lit at midday because of the dense canopy of the dominant trees.
The canopy keeps rain from falling directly onto the forest floor.
Epiphytes are plants that grow on other trees rather than supporting themselves.
They are not parasites and may kill the trees by blocking the light.
The most diverse animal species in the world are found in tropical rainforests.
Many species are in danger.
Deserts have less than 25 cm of rain per year.
Deserts have the most extreme temperature fluctuations.
The daytime surface temperature can be as high as 70degC.
The heat is lost quickly at night.
After sundown, temperatures plummet.
The characteristic of the desert is that cacti with shallow roots can capture as much rain as possible during hard and short rains.
Other plants include sagebrush and creosote bush.
There are many small annual plants that grow after a hard rain and die within a few weeks.
When the heat is not so intense, most animals are active at night or early morning.
They remain cool during the day by hiding in the shade or burrowing underground.
The cacti can expand to hold more water and have leaves that protect it from animals attacking it for its water.
There are regions hundreds of miles across in the Sahara Desert that are completely barren of vegetation.
Rodents, kangaroo rats, snakes, lizards, arachnids, insects, and a few birds are characteristic animals.
There are huge areas in both the tropics and the tropics.
The conditions for forests are inhospitable because of low total annual rainfall.
The United States and Africa have bison and pronghorn antelope.
Prairie dogs and other rodents are common.
In the northeast of North America, south of the taiga, there are forests characterized by trees that drop their leaves in winter.
There are more plant species in the taiga.
There are species of plants and animals that live on the ground, on the low branches, and on the treetops.
The soil is rich because of leaf litter.
Squirrels, deer, fox, and bears are the principal mammals.
Much of the world's northern regions are located in northern Canada.
They are dominated by conifer forests.
There are lakes, ponds, and bogs in the landscape.
They have very cold winters.
This is the largest area.
Taigas are characterized by heavy snowfall and the trees are shaped with branches directed downward to prevent snow from breaking their branches.
Black bears, moose, and other large mammals are the principal large mammals.
In the summer, flying insects and birds are abundant.
Taigas have more variety in animals than tundras do.
The far northern parts of North America, Europe, and Asia are home to the Tundras.
They are characterized by frozen subsoil found in the farthest point north.
The frozen desert is often referred to as the frozen desert because it gets very little precipitation.
There are many lakes, ponds, and bogs in the tundra.
There are many insects, particularly flies.
The principal mammals are reindeer, caribou,Arctic wolves,Arctic hares, lemmings, and polar bears.
The number of organisms in the tundra is large, but the number of species is small.
A subset of the high Arctic tundra is a strong carbon sink.
The activities of organisms can be affected bybiotic and abiotic factors.
About 75% of Earth is covered by aquatic biomes.
They are not characterized by a single group of organisms.
salinity is the primary distinction among aquatic biomes.
The freshwater, estuary, and marine biomes are related.
There are rivers, streams, ponds, and wetlands that have a salinity of less than 0.1%.
There are some freshwater reserves in the ground.
Less than 4% of Earth's water is freshwater.
Estuaries are located at the mouths of rivers.
Salt marshes and mangrove forests support a lot of animal life.
The marine biome has a salinity of 3% on average.
Three-fourths of Earth's surface is covered by the marine biomes.
Water has a high heat capacity and there is an enormous volume of water, which makes them the most stable of all the biomes.
Most of Earth's food and oxygen is provided by them.
The amount of sunlight received, the distance from the shore, and the water depth are some of the factors that make up the marine biomes.
Chemicals need to be recycled because Earth gets a constant supply of energy from the sun.
The three chemical cycles are the water, carbon and nitrogen.
Living systems depend on the properties of water to function.
Rains and clouds form over the oceans and land.
The rain makes its way back to the sea.
98% of the water in the world is in the oceans.
About 2% of the population is locked in glaciers and polar ice caps.
There is a small amount in the atmosphere.
Carbon moves from the environment to organisms, where it is used to build things.
In all organisms, carbon is used.
The carbon cycle is based on the processes of photosynthesis and respiration.
Organisms need to exchange matter with the environment to grow.
CO 2 is added to the air and O 2 is removed.
CO 2 is added to the air when fossil fuels are burned.
CO 2 is removed from the air by photosynthesis.
Fossil fuels are one of the major carbon sources.
Carbon is found in the soil, in dissolved carbon compounds in the oceans, and in the atmosphere as CO 2 and CO.
Nitrogen moves from the environment to the organisms, where it is used to build things.
Nitrogen enters the air from the ground.
The majority of it enters the environment by way of flora.
Matter is recycled.
Nitrogen-fixingbacteria live in the nodules in the roots of the legumes and convert free nitrogen into the ammonium ion.
The nitrate ion is converted into nitrites and then into nitrates.
Denitrifyingbacteria convert nitrates into free atmospheric nitrogen.
The atmosphere is the main source of nitrogen.
Nitrogen is found in the soil, lake, river, and ocean.
It is also used to make animal and plant fuel.
As the population increases, people waste natural resources, destroy animal habitats, and pollution the air and water.
Here are a few examples.
Humans have disrupted the freshwater environment.
Excess growth of algae and other plants can be caused by runoff from sewage and pastures.
Swimming and boating are not possible in shallow areas because of weeds.
There are two things that happen when large populations of organisms die.
The deeper the lake, the more organic material accumulates on the bottom.
Detritivores use up oxygen to break down the dead organic matter.
Some fish can't live with low oxygen levels.
Oxygen levels continue to decrease as fish die.
The process continues, more organisms die, the oxygen levels decrease, more decomposing matter accumulates on the lake bottom, and ultimately, the lake disappears.
Humans impact the environment at both local and global levels.
Acid rain is caused by pollutants in the air.
Nitrogen and sulfur pollutants in the air cause the rain's pH to be less than 5.6 because they turn into nitric, nitrous, sulfurous, and sulfuric acids.
The ancient stone architecture is damaged by this.
Industry has gotten into the food chain.
Chicken and beef may have serious ill effects on humans if they are fed feed containing antibiotics and hormones.
We occupy the top of the food chain so we accumulate and remain in the human body's fat tissues.
This process is called magnification.
The greenhouse effect is the first thing we need to understand global warming.
Much of the light and heat that comes to Earth from the sun is absorbed and retained by the CO 2 and water vapor in the atmosphere.
The average temperature on the surface of Earth would be much colder if the greenhouse effect did not happen.
During the last 150 years, atmospheric CO 2 levels have increased due to the burning of fossil fuels.
Scientists link increased CO 2 levels to global warming.
The past five years have been the warmest in the modern record, with the fourth highest mean temperature.
Global warming has already had an impact in the far north, which includes the tundra and forests.
As snow and ice melt, they reveal darker and more absorbent surfaces.
Earth is warmed even more because more radiation is absorbed.
The smallest area of sea ice on record was covered in the summer of 2007.
Animals such as polar bears, seals, and seabirds are at risk because of the decrease in habitat.
The likelihood of fires increases with higher temperatures.
More coastal and inland flooding, flash floods, and erosion can be caused by melting polar ice.
Reducing CO 2 emissions by industrialized nations is the only solution to global warming.
CO 2 is absorbed by forests as they grow.
Carbon is stored in wood, leaves, and soil.
The CO 2 is released when the forest is cut down.
Paying countries not to cut down their forests would be a solution to the problem.
This would slow global warming.
The world's population could be affected by global warming.
The level of the seas would be raised due to the melting of the polar ice caps.
Major coastal cities in the United States, including New York, Los Angeles, and Miami, would be under water.
The Great Barrier Reef in Australia is under increased stress due to global warming.
Coral can't build their skeletons because of this stress.
Oysters and sea urchins are suffering because of increased acidification of the oceans due to an increase in CO 2 dissolved in the oceans.
Carbon dioxide from the atmosphere is dissolved in the oceans by combining with H 2 O.
The oceans are becoming more acidic because of increased atmospheric carbon dioxide.
Many marine organisms, including reef-building corals and animals that build shells, need this compound.
Coral reefs provide shoreline protection and support a great diversity of commercial fish species, so their destruction would be a great loss.
Many food chains that include shell-building animals are negatively affected.
The formation of a hole in the protective ozone layer has been caused by the accumulated air of chlorofluorocarbons.
The incidences of skin cancer worldwide have increased due to the increase in UV light reaching Earth.
The introduction of a new species can threaten native wildlife.
Nonnative species can grow, reproduce, and spread without limits.
Invasive species can kill native species.
Invasive species don't have to come from another country.
Lake trout are native to the Great Lakes.
They compete with native cutthroat trout for resources and habitat in Wyoming.
Humans are the main spreaders of invasive species.
Ships carry aquatic organisms.
In crates around the world, insects are carried in wood.
People who are unaware of the consequences release animals they don't want in the wild.
The problem of pythons in the Everglades has become frightening.
They grow as long as 19 feet and hunted native rabbits that were close to extinction.
Billions of dollars are spent each year on removal and/or rehabilitation of invasive species.
The African honeybee is a very aggressive honeybee that was brought to Brazil in 1956 to breed a honeybee that would produce more honey in the tropics than the Italian honeybee.
The African honeybees have been spreading throughout the Americas.
Ten people were killed by bees in the United States by the year 2000.
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