chapter 3Review
In this chapter, we have learned how ecosystems function by looking at how energy moves through an ecosystem and how matter cycles around an ecosystem. This energy and matter form the basis of the trophic groups that exist in ecosystems and they are responsible for the abundance of each group in nature. The typical movement of energy and matter can be altered by ecosystem disturbances, although the magnitude of the impact depends on the resistance of a particular ecosystem and its resilience after the disturbance.
Biosphere Producer Autotroph Photosynthesis Cellular respiration Aerobic respiration Anaerobic respiration Consumer Heterotroph Herbivore Primary consumer Carnivore Secondary consumer Tertiary consumer Trophic levels Food chain Food web Scavenger Detritivore Decomposers Gross primary productivity (GPP) Net primary productivity (NPP) Biomass Standing crop Ecological efficiency Trophic pyramid Biogeochemical cycle Hydrologic cycle Transpiration Evapotranspiration Runoff Carbon cycle Limiting nutrient Macronutrient Nitrogen cycle Nitrogen fixation Nitrification Assimilation Mineralization Ammonification Denitrification Leaching Phosphorus cycle Algal bloom Hypoxic Sulfur cycle Disturbance Resistance Resilience Watershed Restoration ecology Intermediate disturbance hypothesis | An organism that uses the energy of the Sun to produce usable forms of energy. Also known as Autotroph. A nutrient required for the growth of an organism but available in a lower quantity than other nutrients. The process by which cells unlock the energy of chemical compounds. The process by which cells convert glucose and oxygen into energy, carbon dioxide, and water. The successive levels of organisms consuming one another. An organism that specializes in breaking down dead tissues and waste products into smaller particles. An event, caused by physical, chemical, or biological agents, resulting in changes in population size or community composition. The movement of water through the biosphere. The total amount of solar energy that producers in an ecosystem capture via photosynthesis over a given amount of time. The proportion of consumed energy that can be passed from one trophic level to another. A measure of how much a disturbance can affect flows of energy and matter in an ecosystem. The process by which fungal and bacterial decomposers break down the organic matter found in dead bodies and waste products and convert it into inorganic compounds. The total mass of all living matter in a specific area. The study and implementation of restoring damaged ecosystems. A consumer that eats producers. Also known as Primary consumer. The transportation of dissolved molecules through the soil via groundwater. Low in oxygen. The sequence of consumption from producers through tertiary consumers. A consumer that eats producers. Also known as Herbivore. The process by which producers use solar energy to convert carbon dioxide and water into glucose. A consumer that eats other consumers. The rate at which an ecosystem returns to its original state after a disturbance. Water that moves across the land surface and into streams and rivers. An organism that consumes dead animals. The conversion of ammonia (NH4+) into nitrite (NO2–) and then into nitrate (NO3–). The region of our planet where life resides, the combination of all ecosystems on Earth. The release of water from leaves during photosynthesis. The conversion of nitrate (NO3–) in a series of steps into the gases nitrous oxide (N2O) and, eventually, nitrogen gas (N2), which is emitted into the atmosphere. The process by which fungal and bacterial decomposers break down the organic nitrogen found in dead bodies and waste products and convert it into inorganic ammonium (NH4). An organism that is incapable of photosynthesis and must obtain its energy by consuming other organisms. Also known as Consumer. A complex model of how energy and matter move between trophic levels. The combined amount of evaporation and transpiration. All land in a given landscape that drains into a particular stream, river, lake, or wetland. A representation of the distribution of biomass, numbers, or energy among trophic levels. The amount of biomass present in an ecosystem at a particular time. A carnivore that eats secondary consumers. Fungi and bacteria that convert organic matter into small elements and molecules that can be recycled back into the ecosystem. The movements of matter within and between ecosystems. A rapid increase in the algal population of a waterway. The energy captured by producers in an ecosystem minus the energy producers respire. The movement of sulfur around the biosphere. A process by which some organisms can convert nitrogen gas molecules directly into ammonia. One of six key elements that organisms need in relatively large amounts: nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. The movement of phosphorus around the biosphere. An organism that uses the energy of the Sun to produce usable forms of energy. Also known as Producer. An organism that is incapable of photosynthesis and must obtain its energy by consuming other organisms. Also known as Heterotroph. The process by which producers incorporate elements into their tissues. The hypothesis that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels. The movement of nitrogen around the biosphere. A carnivore that eats primary consumers. The process by which cells convert glucose into energy in the absence of oxygen. The movement of carbon around the biosphere. |
Module 6 The Movement of Energy
Explain the concept of ecosystem boundaries.
Ecosystem boundaries distinguish one ecosystem from another. Although boundaries can be well-
Describe the processes of photosynthesis and respiration.
Photosynthesis captures the energy of the Sun to convert CO2 and water into carbohydrates. Respiration, whether aerobic or anaerobic, unlocks the chemical energy stored in the cells of organisms.
Distinguish among the trophic levels that exist in food chains and food webs.
The trophic levels consist of producers that convert solar energy into producer biomass through photosynthesis, primary consumers that eat the producers, secondary consumers that eat the primary consumers, and tertiary consumers that eat the secondary consumers. Omnivores eat individuals from more than one trophic group. Trophic groups that eat waste products and dead organisms are scavengers, detritivores, and decomposers.
Quantify ecosystem productivity.
Ecosystem productivity can be quantified by measuring the total amount of solar energy that producers capture, which is gross primary productivity, or by measuring the total amount of solar energy captured minus the amount of energy used for respiration, which is net primary productivity.
Explain energy transfer efficiency and trophic pyramids.
The energy present in one trophic level can be transferred to a higher trophic level and the efficiency of this transfer is generally about 10 percent. Because of this low energy transfer efficiency, the amount of energy present in each trophic level declines as we move to higher trophic levels. We can represent the energy in each trophic level as a rectangular block in a pyramid, with a size that is proportional to the energy found in the trophic level. Low ecological efficiency results in a large biomass of producers, but a much lower biomass of primary consumers and an even lower biomass of secondary consumers.
Module 7 The Movement of Matter
Describe how water cycles within ecosystems.
In the water cycle, water evaporates from water bodies and transpires from plants. The resulting water vapor cools and forms clouds, which ultimately drop water back to Earth in the form of precipitation. When the water falls onto the land, it can evaporate, be taken up by plants and transpired, percolate into the groundwater, or run off along the soil surface and ultimately return to lakes and oceans.
Explain how carbon cycles within ecosystems.
In the carbon cycle, producers take up CO2 for photosynthesis and transfer the carbon to consumers and decomposers. Some of this carbon is converted back into CO2 by respiration, while the rest is lost to sedimentation and burial. The extraction and combustion of fossil fuels, as well as the destruction of forests, returns CO2 to the atmosphere.
Describe how nitrogen cycles within ecosystems.
In the nitrogen cycle, nitrogen fixation by organisms, lightning, or human activities converts nitrogen gas into ammonium (NH4+) or nitrate (NO3–). Nitrification is a process that converts ammonium into nitrite (NO2–) and then into nitrate (NO3–). Once producers take up nitrogen as ammonia, ammonium, nitrite, or nitrate, they incorporate it into their tissues in a process called assimilation. Eventually, organisms die and their tissues decompose and are converted to ammonium in a process called mineralization. Finally, denitrification returns nitrogen to the atmosphere.
Explain how phosphorus cycles within ecosystems.
The phosphorus cycle involves a large pool of phosphorus in rock that is formed by the precipitation of phosphate onto the ocean floor. Geologic forces can lift these sediments and form mountains. The phosphorus in the mountains can be made available to producers either by weathering or by mining. Producers assimilate phosphorus from the soil or water and consumers assimilate it when they eat producers. The waste products and dead bodies of organisms experience mineralization, which returns phosphorus to the environment where it can be ultimately transferred back to the ocean.
Discuss the movement of calcium, magnesium, potassium, and sulfur within ecosystems.
Calcium, magnesium, and potassium are derived from rock and can be held by soils. Producers can assimilate these elements, and mineralization of waste products and dead organisms returns the elements back to the environment. Most sulfur exists in the form of rocks and is released through the process of weathering, which makes it available for plant assimilation. Some sulfur exists as a gas in the form of sulfur dioxide (SO2), which can be produced by volcanic eruptions and the burning of fossil fuels. In the atmosphere, SO2 is converted into sulfuric acid (H2SO4) when it mixes with water. The sulfuric acid can then be carried back to the ground when it rains or snows.
Module 8 Responses to Disturbances
Distinguish between ecosystem resistance and ecosystem resilience.
The resistance of an ecosystem is a measure of how much a disturbance can affect its flows of energy and matter. In contrast, the resilience of an ecosystem is the rate at which an ecosystem returns to its original state after a disturbance has occurred.
Explain the insights gained from watershed studies.
Because watersheds contain all of the land in a given landscape that drains into a particular water body, experimental manipulations such as logging allow scientists to determine how a disturbance to an ecosystem alters the flow of energy and matter.
Explain the intermediate disturbance hypothesis.
The intermediate disturbance hypothesis states that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels.