CH 28

Producers (or autotrophs

) make their own food using inorganic nutrients and solar energy from the environment

Detritus feeders and decomposers convert the bodies of dead organisms into simple molecules, such as carbon dioxide, water, and minerals

They recycle nutrients, forming a vital link in the nutrient cycles of ecosystems If detritus feeders were absent, primary productivity would stop for lack of nutrients, and the community would collapse

The nitrogen cycle has its major reservoir where?

in the atmospherre

Micronutrients

including zinc, molybdenum, iron, selenium, and iodine are required in trace amounts

It is absorbed by autotrophs, where it is

incorporated into biological molecules that pass through food webs

Chains of carbons=

the building blocks of life

The amount of life that a particular ecosystem can support is determined by

the energy captured by the producers in that ecosystem

Food chains and food webs describe

the feeding relationships within communities

Aquatic food chains have phytoplankton as

their dominant producers

Plants dominate most communities because

they have the most energy available to them, followed by herbivores and carnivores We can feed more people directly on grain than on meat from animals fed on grain

Carbon dioxide and other greenhouse gases

trap heat in the atmosphere

Reservoirs

are sources and storage sites of nutrients Major reservoirs are usually in the abiotic environment

The water cycle, or hydrologic cycle

, describes the pathway that water takes as it travels from its major reservoir—the oceans—through the atmosphere, to reservoirs in freshwater lakes, rivers, and groundwater, and then back again to the oceans The oceans contain more than 97% of Earth's water Solar energy evaporates water, and it comes back to Earth as precipitation

Global warming

A large and growing body of evidence indicates that human activities have amplified the natural greenhouse effect, producing a phenomenon called

A small percentage of available energy transfers to the next trophic level because:

A robin will only obtain part of the energy trapped in the grasshopper Some energy will have been used up to power the grasshopper's hopping, flying, and gnashing of mouthparts Some energy would go into the indigestible exoskeleton, and a significant amount would be lost as heat

The sun converts hydrogen into helium, transforming a relatively small amount of matter into enormous quantities of energy

A tiny fraction of this energy reaches Earth in the form of electromagnetic waves, including heat, light, and ultraviolet energy Much of the energy reaching Earth is reflected by the atmosphere, clouds, and the Earth's surface, leaving only 1% of the energy available to power life Since only a tiny fraction of this solar energy is captured by plants, life on Earth is supported by less than 0.03% of the energy reaching Earth from the sun

Global warming will have many consequences

A worldwide meltdown is occurring Glaciers and ice sheets have been melting at unprecedented rates

Human activities release almost 10 billion tons of carbon (in the form of CO2) into the atmosphere each year

About half of this carbon is absorbed into the oceans, plants, and soil The other half remains in the atmosphere

Overloading the sulfur and nitrogen cycles causes

Acid decomposition

Many lakes and ponds in the Adirondack Mountains are too acidic to support fish

Acid rain also increases the extent organisms are exposed to toxic metals, such as aluminum, mercury, lead, and cadmium, which are far more soluble in acidified water

As greenhouse gas levels rise, more heat is retained than is radiated back into space, causing the Earth to warm

Although CO2 accounts for most greenhouse emissions, other important greenhouse gases include methane and nitrous oxide

Biological magnification

Because of the inefficiency of energy transfer, certain persistent toxic chemicals become increasingly concentrated in the bodies of animals that occupy increasingly higher trophic levels by a process called biological magnification Mercury taken up by producers can be highly concentrated in carnivores such as swordfish, and are a health hazard to humans as a result

About 60% of atmospheric nitrogen (as nitrogen oxides) and 75% of atmospheric sulfur dioxide are produced from

Burning fossil fuels

Fertilizer factories use energy from fossil fuels and nitrogen from the atmosphere to synthesize ammonia, nitrate, and urea for fertilizers that now dominate the nitrogen cycle

Burning fossil fuels combines atmospheric nitrogen and oxygen, generating nitrogen oxides that form nitrates

Fossil fuels remained untouched until the beginning of the Industrial Revolution

Burning these fuels released it as CO2 into the air

Tertiary consumers

Carnivores that eat other Carnivores

The carbon cycle has major reservoirs in the atmosphere and oceans

Chains of carbon atoms form the framework of all organic molecules, the building blocks of life The carbon cycle describes the movement of carbon from its major short-term reservoirs in the atmosphere and oceans, through producers and into the bodies of consumers and detritus feeders, and then back to its reservoirs

Nitrogen fixation

Converts N2 into ammonia -N2 is converted to ammonia by specific bacteria during a process called nitrogen fixation Some of these bacteria live in water and soil and convert the ammonia into nitrate that plants can directly use Others live in symbiotic associations with plants called legumes, which include alfalfa, soybeans, clover, and peas

Net primary production is a measure of the energy stored in producers

Ecosystems vary in their primary production Deserts lack water and have limited primary production as a result The open ocean has light as a limiting factor in deep water, and nutrients are limiting in surface water Tropical rain forests and estuaries (coastal areas where rivers meet the ocean) have an abundance of resources and have high productivities

Energy moves in a one-way flow through communities within ecosystems

Energy, in contrast, is continuously replenished The energy to drive life's activities comes from the sun It is used and transformed in the chemical reactions that power life It is ultimately converted to heat that radiates back into space

Acid rain decreases productivity of crops and the health of wild plants

Essential nutrients are leeched from the soils and decomposer organisms are killed This results in weakened plants that are more vulnerable to infection and insect attack Since 1965, half of the red spruce and beech trees have died in the Green Mountains of Vermont due to acid rain Atop Mount Mitchell in North Carolina, the pH of fog has been recorded at 2.9—more acidic than vinegar

These two substances combine with atmospheric water and form

Nitric and sulfuric acids The excess production of these two substances has led to acid deposition, or acid rain, in many parts of the world

Global temperature increases have paralleled increases in atmospheric carbon dioxide (continued

Estimates of future climate change predict that average global temperatures will rise by at least 3.2º F (1.8º C) by the year 2100; a high-level emissions scenario projects an increase of 7.2º F (4.0º C) Small global temperature changes can have enormous impacts; for example, during the last Ice Age (20,000 years ago), temperatures were only 5º C lower than at present

How is energy passed?

From one tropic level to the next

Over time, these carbon sources were converted to fossil fuels by _____

Heat and pressure

Global temperature increases have paralleled increases in atmospheric carbon dioxide

Historical and recent temperature records have revealed a global temperature increase that parallels the measured rise in atmospheric CO2 The decade from 1998 to 2008 is the warmest ever recorded

Overloading the nitrogen and phosphorus cycles damages aquatic ecosystems

In farm fields, gardens, and suburban lawns, ammonia, nitrate, and phosphate are supplied by chemical fertilizers to stimulate plant growth Water dissolves and carries away large quantities of these fertilizers that then drain into lakes and rivers and overstimulate the growth of phytoplankton

The phosphorus cycle has its major reservoir where?

In the rock bound to oxygen as phosphate

Much of Earth's carbon is bound up in what?

Limestone rock -formed from calcium carbonate deposited on the ocean floor in the shells of prehistoric phytoplankton

Rising sea levels will flood many coastal cities and wetlands and may increase hurricane intensity

More extreme weather patterns are predicted Warming will alter air and water currents, changing precipitation patterns More severe droughts and greater extremes in rainfall may lead to more frequent crop failures and flooding -Wildlife will be affected Forests may suffer loss of species or be replaced by grasslands Coral reefs may decline due to warming waters

Two basic laws underlie ecosystem function

Nutrients constantly cycle and recycle within and among ecosystems Energy moves through ecological communities (the various populations of interacting organisms that inhabit ecosystems) in a continuous one-way flow

consumers (or heterotrophs)

Organisms that cannot photosynthesize are called _____. They acquire energy and nutrients from molecules in the bodies of other organisms

Transpiration

Plants absorb water through roots, but most is evaporated back to the atmosphere from leaves, through a process called ________ Water is essential for all terrestrial communities because other nutrients must be dissolved in it before they can be used

A second source of added atmospheric CO2 is deforestation, which destroys tens of millions of forested acres annually and accounts for 15% of CO2 emissions Deforestation occurs principally in the Tropics as rain forests are cut and burned

Since 1850, atmospheric CO2 has increased by 37% This increase is from 280 ppm to 383 ppm, with a current annual increase of 2 ppm

Water that has fallen on land takes various paths

Some evaporates from the soil, lakes, and streams Some runs off the land back to the ocean A small amount enters underground reservoirs called aquifers, which are water-permeable sediments such as silt, sand, or gravel that are saturated with water Aquifers are tapped to supply water for irrigating crops

Energy enters communities primarily through photosynthesis

Specific wavelengths of sunlight are captured by photosynthetic pigments such as chlorophyll Solar energy is used in reactions that store energy in chemical bonds Using energy from the sun and inorganic nutrients from the abiotic portions of the ecosystem, plants synthesize sugars, starches, proteins, nucleic acids, and other biological molecules they need to sustain life During photosynthesis, plants release oxygen that other organisms need to generate ATP

The following six factors affect the fate of sunlight entering Earth's atmosphere

Sunlight enters the atmosphere Some of the energy from sunlight is reflected back into space Most sunlight reaches Earth and is converted into heat This heat is radiated back into the atmosphere Most heat is released back into space Carbon dioxide and several other greenhouse gases trap some of this heat in the atmosphere This is a natural process called the greenhouse effect

Many environmental problems that occur in modern society have resulted from human interference with the ecosystem function

The Industrial Revolution increased human reliance on energy stored in fossil fuels, and as a result, has exposed ecosystems to many substances that are foreign to them, such as oil and its spillage into the ocean Reliance on fossil fuels has also disrupted nutrient cycles of nitrogen, phosphorus, sulfur, and carbon

Days later, and often hundreds of miles from the source, the acids fall to Earth dissolved in rainwater

The acid eats away at statues and buildings It damages forests It alters lake communities and can render them lifeless

The phytoplankton die, and their bodies sink into deeper water and provide food for decomposer bacteria

The decomposers use up most of the available oxygen, and other aquatic organisms, such as invertebrates and fish, die, creating "dead zones" in many waters

The energy that photosynthetic organisms store and make available to other members of the community over a given period is called net primary production

The net primary production of an ecosystem is influenced by the amount of nutrients available to producers, the amount of sunlight reaching them, and the appropriate amounts of water and temperature

Studies have documented shifts in species' ranges towards the poles and advancement of springtime events to earlier dates

The range of tropical disease-carrying organisms, such as malaria-transmitting mosquitoes, may expand

Each category of organism is called a

Tropic level

Between 345-280 million years ago, the bodies of many plants and animals were buried, escaping decomposition

UHHUH

With human population growth, freshwater has become scarce

Water scarcity limits crop growth Pumping water from underground aquifers is rapidly depleting many of them

A small percentage of available energy transfers from one trophic level to the next

When a grasshopper (primary consumer) eats the leaves of a plant (producer), only some of the solar energy trapped by the plant is available to the insect Some of the energy was used by the plant for cellular metabolic activities, and some was lost as heat Some of the molecules in plants cannot be digested or absorbed

Carnivores

act as secondary consumers that prey on herbivores Carnivores such as spiders, hawks, cheetahs, and salmon are higher-level consumers Some carnivores eat other carnivores and are called tertiary consumers

Reduced sulfur emissions have improved

air quality and rain acidity in some regions

Overloading the nitrogen and phosphorus cycles damages

aquatic ecosystems

If not eaten, when organisms die, their bodies ____

are broken down by detritus feeders and decomposers

Macronutrients

are required by organisms in large amounts and include water, carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, and calcium

Denitrifying bacteria

break down nitrate, releasing N2 back to the atmosphere

Cellular respiration

by organisms releases CO2 into the atmosphere and oceans

Carbon enters communities through

capture of CO2 during photosynthesis Producers on land get CO2 from the atmosphere Aquatic producers get CO2 dissolved in the water

Energy flows through

communities from photosynthetic producers through several levels of consumers

The nitrogen cycle

cycle is the process by which nitrogen moves from nitrogen gas in the atmosphere to reservoirs of ammonia and nitrate in the soil and water, through producers and into consumers and detritus feeders, and then back again to its reservoirs While nitrogen gas (N2) makes up 78% of the atmosphere, this form of nitrogen cannot be utilized by plants Plants utilize nitrate (NO3-) or ammonia (NH3) as their nitrogen source Nitrogen is a crucial component of proteins, many vitamins, nucleotides (such as ATP), and nucleic acids Some nitrogen is released in wastes and dead bodies Decomposer bacteria convert this back to nitrate and ammonia in the soil or water, which is then available to plants

At each level, excess phosphorus is excreted and

decomposers return phosphate to the soil and water

Nutrient cycles (or biogeochemical cycles

describe the pathways nutrients follow between communities and the nonliving portions of ecosystems

carbon cycle

describes the movement of carbon from its major short-term reservoirs in the atmosphere and oceans, through producers and into the bodies of consumers and detritus feeders, and then back to its reservoirs

phosphorus cycle

describes the process by which phosphorus moves from phosphate-rich rocks to reservoirs of phosphate in soil and water, through producers and into consumers and detritus feeders, and then back to its reservoirs Phosphorus is a crucial component of ATP and NADP, nucleic acids, and phospholipids of cell membranes; it is also a major component of vertebrate teeth and bones

Decomposers

digest food outside of their bodies by secreting digestive enzymes They primarily consist of fungi and bacteria They absorb only needed nutrients, leaving the rest for other organisms Mushrooms in a lawn or the blue-gray fuzz on old bread are fungal decomposers at work

atmospheric nitrogen compounds have shown a small overall increase,

due to increased gasoline burning by automobiles

Primary consumers

eat producers and acquire carbon stored in their tissues These herbivores release some of the carbon through respiration as CO2, excrete carbon compounds in their feces, and store the rest in their bodies, which may be consumed by higher trophic levels

Energy pyramids illustrate

energy transfer between trophic levels -The net energy transfer between trophic levels is roughly 10% efficient and is known as the "10% law"

Primary consumers

feed directly and exclusively on producers These herbivores include animals such as grasshoppers, mice, and zebras, and form the second trophic level

food chain

is a linear feeding relationship with just one representative at each trophic level Different ecosystems have radically different food chains Natural communities rarely contain well-defined groups of primary, secondary, and tertiary consumers Plants form the base of land-based (terrestrial) food chains that support plant-eating insects, birds, and mammals, each of which may be preyed upon by carnivorous consumers

Net primary production

is a measure of the energy stored in producers

Interfering with the carbon cycle

is warming Earth's climate

Detritus feeders

live on dead organic matter, including the bodies of other organisms, fallen leaves and fruit, and wastes Examples include mites, earthworms, protists, nematode worms, centipedes, some insects and snails, and vultures Detritus feeders extract energy stored in organic debris and excrete the rest in small pieces Their excretory products are food for other detritus feeders and decomposers Detritus feeders and decomposers release nutrients for reuse

Phytoplankton are consumed by zooplankton, which consist

of protists and small, shrimp-like crustaceans Zooplankton is consumed by fish, which are eventually eaten by larger fish

In contrast to carbon and nitrogen, phosphorus___

phosphorus does not have an atmospheric reservoir

Throughout its cycle

phosphorus remains bound to oxygen in the form of phosphate

Phosphate may be reabsorbed by autotrophs or

re-incorporated into rock

Since 1990, government regulations have led to

reductions in sulfur dioxide and nitrogen oxide emissions from power plants

food web

shows the actual feeding relationships in a community, including its many interconnecting food chains Food webs show that some animals, such as raccoons, bears, rats, and humans, are omnivores and act as primary, secondary, and tertiary consumers

Fossil fuels

which include coal, oil, and natural gas, are formed when the remains of prehistoric organisms are buried and subjected to high temperatures and pressures for millions of years Burning fossil fuels releases stored energy in hydrocarbons and releases carbon into the atmosphere as CO2

biomass

which is the weight of living material at each trophic level Because the dry weight of an organism's bodies at each trophic level is roughly proportional to the amount of energy stored at that level, a biomass pyramid for a given community has the same shape as its energy pyramid

energy pyramid

which shows maximum energy available at the base and steadily diminishing amounts at higher levels, illustrates the general energy relationships between tropic levels