Deck 3: Ecosystems: What Are They and How Do They Work

Question 1

What are the two key concepts for this section? Define and distinguish among the atmosphere , troposphere , stratosphere , hydrosphere , geosphere , and biosphere. What three interconnected factors sustain life on the earth? Describe the flow of energy to and from the earth. What is the greenhouse effect and why is it important?

Answer 1

The two key concepts are that there are four major components of the earth's life-support system. These key concepts are the atmosphere, the hydrosphere, the geosphere and the biosphere. Air, water, soil and all living things are made up of the earth's life-support system.
Secondly another key concept is that life is sustained by the flow of energy that comes from the sun. This occurs in the biosphere, which is the cycling of nutrients within the biosphere and gravity.
The first major component of earth's life-support system is the atmosphere. The atmosphere is a thin layer of gasses surrounding the earth's surface. Within the atmosphere there are five specific layers.
•Troposphere , which is the inner layer, reaches approximately 11 miles above sea level at the tropics and 4 miles above sea level at the poles, north and south. The troposphere contains most of the nitrogen and oxygen that humans breathe.
•Stratosphere is the next layer of atmosphere. It reaches from 11-31 miles above the earth's surface. The lower portion of the stratosphere contains enough ozone gas to filter out approximately 95% of the ultraviolet radiation from the sun.
•Hydrosphere consists of all of the water on or near the earth's surface. It is also known as water vapor, liquid vapor and ice (polar ice, icebergs, glaciers and permafrost).
•Geosphere consists of the earth's hot core. It is the mantle (rock and a thin outer crust). The upper portion of the geosphere consists of fossil fuels, which are the nonrenewable resources used by humans at a rapid rate.
•Biosphere consists of parts of the atmosphere, hydrosphere and geosphere. This is also where life is found. The biosphere is roughly the thickness of an apple skin. This area contains the air, water, soil and organisms.
There are three factors that sustain life on earth. For life to continue to be maintained, these three interconnected factors must exist.
•The one-way flow of high-quality energy. This states that energy flows from the sun through living things. There is only one way for the energy to flow and it does not circle around for another pass. This solar energy interacts with carbon dioxide and other gases, warming the troposphere, known as the greenhouse effect. Without the natural process of the greenhouse effect, the earth would be too cold to support any life form.
•The cycling of nutrients (atoms, ions and molecules needed for survival) through the biosphere. The fixed supply of nutrients must be recycled to support life.
•Gravity is the third factor. It allows the planet to hold onto its atmosphere and helps with the movement of chemicals through air, water, soil and organisms.

Question 2

Distinguish between gross primary productivity (GPP) and net primary productivity (NPP) , and explain their importance. What are the two most productive land ecosystems and the two most productive aquatic ecosystems?

Answer 2

Following is the distinction between gross primary productivity (GPP) and net primary productivity (NPP) and their importance:
Gross primary productivity (GPP):
•Gross primary productivity is the degree at which an ecosystem's producers transform solar energy into chemical energy deposited in compounds present in their tissues.
•In order to remain alive, sustain, grow, and reproduce, producers need some of their stored chemical energy for their respiration.
Net primary productivity (NPP):
•The net primary productivity is the degree at which producers utilize photosynthesis to produce and consume stored chemical energy minus the degree at which they consume some of this stockpiled chemical energy via aerobic respiration.
•NPP estimates the quickness with which producers can make the chemical energy that is stored in their tissues and that is potentially accessible to other organisms in an ecosystem.
•The two most important productive land ecosystems are (1) swamps and marshes and (2) tropical rain forest as they have a very high net primary productivity.
•The two most important productive aquatic ecosystems (1) estuaries and (2) lakes and streams as they have a very high net primary productivity.

Question 3

Explain (a) why the flow of energy through the biosphere depends on the cycling of nutrients, and (b) why the cycling of nutrients depends on gravity.

Answer 3

a) Flow of energy is dependent on the cycle of the nutrients. The chemical energy is stored into some biomass in every organism. When the energy flows from one level to another level then it degrades because of losses. According to second law of thermodynamics whenever there is flow of energy from one system to another system then there is loss of energy occurs. This is called as degradation of energy. Organism has certain weight according to the volume and which is called as biomass. Flow of energy is dependent on the biomass and how much solar energy is converted to the chemical energy is the form of biomass.
b) Cycle of nutrients depends on the gravity because the nutrients filter through to the system and reaches to the soil. From soil plants takes up the nutrients which helps to consist the other important activities.

Question 4

For each of the earth's nine major planetary boundaries (Figure 3.A), describe how our exceeding that boundary might affect (a) you, (b) any child you might have, and (c) any grandchild you might have.

Question 5

Recall that net primary productivity (NPP) is the rate at which producers can make the chemical energy that is stored in their tissues and that is potentially available to other organisms (consumers) in an ecosystem. In Figure 3.15, it is expressed as units of energy (kilocalories, or kcal ) produced in a given area (square meters, or m 2) over a period of time (a year). Look again at Figure 3.12 and consider the differences in NPP among various ecosystems. Then answer the following questions:
Early in the 20th century, large areas of temperate forestland in the United States were cleared to make way for agricultural land. For each unit of this forest area that was cleared and replaced by farmland, about how much NPP was lost?

Question 6

What is the key concept for this section? What happens to matter in an ecosystem? What is a nutrient cycle ? Explain how nutrient cycles connect past, present, and future life. Summarize the unique properties of water. Describe the hydrologic cycle , or water cycle. What three major processes are involved in the water cycle? What is surface runoff ? Define groundwater. What is an aquifer ? What percentage of the earth's water supply is available to humans and other species as liquid freshwater? Explain how human activities are affecting the water cycle. Explain how clearing a rain forest can affect local weather and climate. Describe the carbon , nitrogen , phosphorus , and sulfur cycles , and explain how human activities are affecting each cycle.

Question 7

WATER'S UNIQUE PROPERTIES
Water (H₂ O) is a remarkable substance with a unique combination of properties:
•Forces of attraction, called hydrogen bonds (see Figure 6, p. S8, in Supplement 3), hold water molecules together and are the major factor determining water's distinctive properties.
•Water exists as a liquid over a wide temperature range because of the hydrogen bonds between its molecules. If liquid water had a much narrower range of temperatures between freezing and boiling, the oceans might have frozen solid or boiled away long ago.
•Liquid water changes temperature slowly because it can store a large amount of heat without a large change in its own temperature. This high heat storage capacity helps to protect living organisms from temperature changes, moderates the earth's climate, and makes water an excellent coolant for car engines and power plants.
•It takes a large amount of energy to evaporate water because of its hydrogen bonds. Water absorbs large amounts of heat as it changes into water vapor and releases this heat as the vapor condenses back to liquid water. This helps to distribute heat throughout the world and to determine regional and local climates. It also makes evaporation a cooling process-explaining why you feel cooler when perspiration evaporates from your skin.
•Liquid water can dissolve a variety of compounds (see Figure 3, p. S6, in Supplement 3). It carries dissolved nutrients into the tissues of living organisms, flushes waste products out of those tissues, serves as an allpurpose cleanser, and helps to remove and dilute the water-soluble wastes of civilization. This property also means that water-soluble wastes can easily pollute water.
•Water filters out wavelengths of the sun's ultraviolet radiation that would harm some aquatic organisms. This helps to sustain aquatic ecosystems on which many land animals, including humans, depend.
•Unlike most liquids, water expands when it freezes. This means that ice floats on water because it has a lower density (mass per unit of volume) than liquid water has. Otherwise, lakes and streams in cold climates would freeze solid, losing most of their aquatic life. Because water expands upon freezing, it can break pipes, crack a car's engine block (if it doesn't contain antifreeze), break up pavement, and fracture rocks. Thus water plays a major role in shaping landscapes and forming soil.
Critical Thinking
Pick two of the special properties listed above and, for each property, explain how life on the earth would be different if it did not exist.

Question 8

What is the key concept for this section? Describe three ways in which scientists study ecosystems. Explain why we need much more basic data about the structure and condition of the world's ecosystems. Distinguish between the Holocene and Anthropocene eras. List nine planetary boundaries that scientists have identified. Which three of these boundaries have already been exceeded, according to these scientists? What are this chapter's three big ideas ? How are the three scientific principles of sustainability showcased in tropical rain forests?

Question 9

What is the key concept for this section? Define ecology. Define organism , population , community , and ecosystem , and give an example of each.

Question 10

Explain why microbes are so important. What are two ways in which they benefit your health or lifestyle? Write a brief description of what you think would happen to you if microbes were eliminated from the earth.

Question 11

Recall that net primary productivity (NPP) is the rate at which producers can make the chemical energy that is stored in their tissues and that is potentially available to other organisms (consumers) in an ecosystem. In Figure 3.15, it is expressed as units of energy (kilocalories, or kcal ) produced in a given area (square meters, or m 2) over a period of time (a year). Look again at Figure 3.12 and consider the differences in NPP among various ecosystems. Then answer the following questions:
Why do you think deserts and grasslands have dramatically lower NPP than swamps and marshes?

Question 12

Distinguish between the living and nonliving components in ecosystems and give two examples of each.

Question 13

Make a list of the foods you ate for lunch or dinner today. Trace each type of food back to a particular producer species. Describe the sequence of feeding levels that led to your feeding.

Question 14

Recall that net primary productivity (NPP) is the rate at which producers can make the chemical energy that is stored in their tissues and that is potentially available to other organisms (consumers) in an ecosystem. In Figure 3.15, it is expressed as units of energy (kilocalories, or kcal ) produced in a given area (square meters, or m 2) over a period of time (a year). Look again at Figure 3.12 and consider the differences in NPP among various ecosystems. Then answer the following questions:
About how many times more NPP do estuaries produce, compared to lakes and streams? Why do you think this is so?

Question 15

What are three harmful effects of the clearing and degradation of tropical rain forests?

Question 16

What is a trophic level ? Distinguish among producers (autotrophs) , consumers (heterotrophs) , decomposers and detritus feeders (detritivores) , and give an example of each. Summarize the processes of photosynthesis. Distinguish among primary consumers (herbivores) , carnivores , secondary consumers , tertiary consumers , and omnivores , and give an example of each.

Question 17

How would you explain the importance of tropical rain forests ( Core Case Study ) to people who think that such forests have no connection to their lives?

Question 18

Use the second law of thermodynamics (see Chapter 2, p. 35) to explain why many poor people in lessdeveloped countries live on a mostly vegetarian diet.

Question 19

Recall that net primary productivity (NPP) is the rate at which producers can make the chemical energy that is stored in their tissues and that is potentially available to other organisms (consumers) in an ecosystem. In Figure 3.15, it is expressed as units of energy (kilocalories, or kcal ) produced in a given area (square meters, or m 2) over a period of time (a year). Look again at Figure 3.12 and consider the differences in NPP among various ecosystems. Then answer the following questions:
What is the approximate NPP of a tropical rain forest in kcal/m2/yr? Which terrestrial ecosystem produces about one-third of that rate? Which aquatic ecosystem has about the same NPP as a tropical rain forest?

Question 20

Explain the importance of microbes. What is aerobic respiration ? What two processes sustain ecosystems and the biosphere and how are they linked?

Question 21

Visit a nearby terrestrial ecosystem or aquatic life zone and try to identify major producers, primary and secondary consumers, detritus feeders, and decomposers. Take notes and describe at least one example of each of these types of organisms. Make a simple sketch showing how these organisms might be related to each other or to other organisms in a food chain or food web. Think of two ways in which this food web or chain could be disrupted. Write a report summarizing your research and conclusions.

Question 22

How might your life and the lives of any children or grandchildren you might have be affected if human activities as a whole continue to intensify the water cycle?

Question 23

Search for Nitrogen Cycle and look for information on how humans are affecting the nitrogen cycle. Specifically look for impacts on the atmosphere and on human health from emissions of nitrogen oxides, and look for the harmful ecological effects of the runoff of nitrate fertilizers into rivers and lakes. Make a list of these impacts and use this information to review your daily activities. Find three things that you do regularly that contribute to these impacts.

Question 24

What is the key concept for this section? Define and distinguish between a food chain and a food web. Explain what happens to energy as it flows through food chains and food webs. What is a pyramid of energy flow ?

Question 25

MANY OF THE WORLD'S MOST IMPORTANT ORGANISMS ARE INVISIBLE TO US
They are everywhere. Trillions can be found inside your body, on your body, in a handful of soil, and in a cup of ocean water.
These mostly invisible rulers of the earth are microbes, or microorganisms, catchall terms for many thousands of species of bacteria, protozoa, fungi, and floating phytoplankton. They play key roles in the earth's life-support system. Bacteria in our intestinal tracts break down the food we eat, and microbes in our noses help to prevent harmful bacteria from reaching our lungs. Other microbes help to purify the water we drink by breaking down plant and animal wastes in the water. Bacteria and fungi in the soil decompose organic wastes into nutrients that can be taken up by plants that are then eaten by humans and many other plant eaters. Without these tiny creatures, we would go hungry and be up to our necks in waste matter.
Some microorganisms, particularly phytoplankton in the ocean, provide much of the planet's oxygen, and help to regulate the atmosphere's average temperature by removing some of the carbon dioxide produced when we burn coal, natural gas, and gasoline. Other microbes help us to control diseases that affect plants and to limit populations of insects that attack our food crops. In short, microbes are a vital part of the earth's natural capital.
Critical Thinking
What are two advantages that microbes have over humans for thriving in the world?

Question 26

What would happen to an ecosystem if (a) all of its decomposers and detritus feeders were eliminated, (b) all of its producers were eliminated, and (c) all of its insects were eliminated? Could a balanced ecosystem exist with only producers and decomposers and no consumers such as humans and other animals? Explain.