CHAPTER 7 ECOSYSTEMS AND NUTRIENT CYCLING ENGINEERING EARTH A desert experiment gone awry

7 ENGINEERING EARTH Learning Outcomes A desert experiment gone awry At the end of this chapter you will know: Environmental factors that affect the makeup and distribution of biomes Tolerance limits and organization structure in ecosystems Nutrient cycling and the organisms responsible for these functions Learning Outcomes

7 ENGINEERING EARTH Main Concept A desert experiment gone awry Case study: Eight scientists spent two years in an artificial environment known as Biosphere 2. Main Concept Ecosystems are complex assemblages of living and non-living components. Many of the roles played by the living organisms in a system are irreplaceable. In addition to wanting to prove that survival in an artificial, self-sustaining habitat was possible, the purpose of this study was to gain a better understanding of the complex interactions on Earth, so we can make better decisions.

7 ENGINEERING EARTH TERMS TO KNOW: Sustainable Economics A desert experiment gone awry We learn from mistakes. More than one-third of the flora and fauna became extinct. Morning glory vines took over agriculture. TERMS TO KNOW: Sustainable Economics Ecosystem services Cockroaches and crazy ants were thriving. Trees failed to develop stress wood since there was no wind. A heavy diet of sweet potatoes left the scientists orange. Oxygen supplies became dangerously low.

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biospheres Ecosystem Habitat Species Niche The scale of interactions between organisms aids human classification of natural systems.

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biospheres Ecosystem Habitat Species Niche The scale of interactions between organisms aids human classification of natural systems.

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biospheres Ecosystem Habitat Species Niche The scale of interactions between organisms aids human classification of natural systems.

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biospheres Ecosystem Habitat Species Niche The scale of interactions between organisms aids human classification of natural systems.

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biospheres Ecosystem Habitat Species Niche The scale of interactions between organisms aids human classification of natural systems. All ecosystems are based on nutrient cycling and energy flow

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biosphere 1 (The Earth) is materially closed but energetically open. This means that energy enters and leaves the system but biomass—the plants and animals—do not. Biomes fall into three broad categories based on climate and determined by predominant plants. Marine, freshwater, and terrestrial biomes are further distinguished as ecosystems based on interactions between specific biotic and abiotic components. To conduct field research in biological systems is difficult due to our lack of control over the interactions. In the Biosphere 2, scientists were able to control and measure environmental variables like oxygen and CO2 balances periodically throughout their stay. TERMS TO KNOW: Energy flow Nutrient cycles Biomass Biome

7 Organisms and their habitats form complex systems TERMS TO KNOW: Biosphere 1 (The Earth) is materially closed but energetically open. This means that energy enters and leaves the system but biomass—the plants and animals—do not. Biomes fall into three broad categories based on climate and determined by predominant plants. Marine, freshwater, and terrestrial biomes are further distinguished as ecosystems based on interactions between specific biotic and abiotic components. To conduct field research in biological systems is difficult due to our lack of control over the interactions. In Biosphere 2, scientists were able to manipulate and measure environmental variables like oxygen and CO2 balances periodically throughout their stay. TERMS TO KNOW: Energy flow Nutrient cycles Biomass Biome

Organisms and their habitats form complex systems 7

Organisms and their habitats form complex systems 7

Organisms and their habitats form complex systems 7

7 Organisms and their habitats form complex systems Biomes are specific types of terrestrial ecosystems with characteristic temperature and precipitation conditions. Temperature decreases when moving away from the equator and with increased elevation.

7 Organisms and their habitats form complex systems Mediterranean scrub Tundra Tropical rainforest Desert Savanna Boreal forest

7 Organisms and their habitats form complex systems Biosphere technology was developed in the 1960s and 1970s as preparation for space exploration. Biosphere 2 remains the largest enclosed ecosystem ever created. Biosphere 2 houses several biomes under one roof, each contributing to overall function.

7 Organisms and their habitats form complex systems Each biome required consideration of the interactions between plant and animal species as well as careful assessment of nutrient requirements for each organism. Biosphere 2 houses several biomes under one roof, each contributing to overall function.

7 Living things survive within a specific range of environmental conditions Each biome required consideration of the interactions between plant and animal species as well as careful assessment of nutrient requirements. Most desert biomes fluctuate from extreme cold at night to high temperatures during the day. By comparison, rainforests need consistently warm temperatures. Each organism must maintain homeostasis within a narrow range. In Biosphere 2, tolerances needed to be maintained within a closed system. TERMS TO KNOW: Limiting factor Range of tolerance

7 Living things survive within a specific range of environmental conditions Populations have a range of tolerance for each environmental factor—light, water, salinity, nitrogen. Each species has an upper and lower limit of tolerances beyond which the organism cannot survive. On the lower end of the spectrum is the absolute minimum for survival of a factor. This is where limiting factors determine survival. The optimal level is somewhere in the middle and will vary somewhat among individuals within a population.

7 Living things survive within a specific range of environmental conditions Populations have a range of tolerance for each environmental factor—light, water, salinity, nitrogen. Each species has an upper and lower limit of tolerances beyond which the organism cannot survive. On the lower end of the spectrum is the absolute minimum for survival of a factor. This is where limiting factors determine survival. The optimal level is somewhere in the middle and will vary somewhat among individuals within a population.

7 Living things survive within a specific range of environmental conditions Populations have a range of tolerance for each environmental factor—light, water, salinity, nitrogen. Each species has an upper and lower limit of tolerances beyond which the organism cannot survive. On the lower end of the spectrum is the absolute minimum for survival of a factor. This is where limiting factors determine survival. The optimal level is somewhere in the middle and will vary somewhat among individuals within a population.

7 Living things survive within a specific range of environmental conditions TERMS TO KNOW: Limiting factor Range of tolerance In the beginning, things went smoothly—carrots, broccoli, spinach, kale, and other vegetables had been planted next to the human habitat, and a few domestic animals provided milk and meat. The scientist got healthier at first. Less light than anticipated led to lower productivity than needed. Pests and disease began to cut production, too. The Biosphere ocean is still used for marine research.

7 Nutrients such as carbon cycle through ecosystems TERMS TO KNOW: Nutrients cycle through and are stored in both biotic (living) and abiotic (non-living) components of a system. Reservoirs for CO2 include plants, oceans, and soil. The producers use the stored CO2 from the atmosphere to produce sugar while releasing oxygen. TERMS TO KNOW: Biotic Abiotic Reservoirs (or sinks) Producer Consumer Cellular respiration The sugar molecule represents stored chemical energy that the producer can use. The consumer eats the plant and, in so doing, releases the energy from the sugar molecules through cellular respiration.

7 Nutrients such as carbon cycle through ecosystems Carbon cycles in and out of living things during photosynthesis and cellular respiration. Carbon is transferred as consumers and decomposers eat other organisms. Some carbon is stored in the bodies of organisms and in oceans, soil, and the atmosphere. Overall, the carbon cycle is balanced between respiration and photosynthesis.

7 Nutrients such as carbon cycle through ecosystems Carbon cycles in and out of living things during photosynthesis and cellular respiration. Carbon is transferred as consumers and decomposers eat other organisms. Some carbon is stored in the bodies of organisms and in oceans, soil, and the atmosphere. Overall, the carbon cycle is balanced between respiration and photosynthesis.

7 Nutrients such as carbon cycle through ecosystems Carbon cycles in and out of living things during photosynthesis and cellular respiration. Carbon is transferred as consumers and decomposers eat other organisms. Some carbon is stored in the bodies of organisms and in oceans, soil, and the atmosphere. Overall, the carbon cycle is balanced between respiration and photosynthesis.

7 Nutrients such as carbon cycle through ecosystems Carbon cycles in and out of living things during photosynthesis and cellular respiration. Carbon is transferred as consumers and decomposers eat other organisms. Some carbon is stored in the bodies of organisms and in oceans, soil, and the atmosphere. Overall, the carbon cycle is balanced between respiration and photosynthesis.

7 Nutrients such as carbon cycle through ecosystems In Biosphere 2, oxygen and carbon were off by such a great amount that the scientists found themselves constantly exhausted. The reason was that oxygen levels had fallen to dangerously low levels—levels too low to extract energy from the food they were eating. The plants in Biosphere 2 were producing oxygen, but the excessive growth of soil microbes used oxygen faster than the plants could replace it.

7 Nutrients such as carbon cycle through ecosystems TERMS TO KNOW: Nitrogen and phosphorus are two additional chemicals that are essential for life. TERMS TO KNOW: Nitrogen fixation Phosphorus cycle 7

7 Nutrients such as carbon cycle through ecosystems Nitrogen is the most abundant element in the Earth’s atmosphere and is needed to make proteins and nucleic acids. Plants cannot use nitrogen directly from the atmosphere but, rather, must convert it into usable forms through the nitrogen cycle. During nitrogen fixation, one form of nitrogen is converted by bacteria to another form that can be taken up by the roots of plants. Nitrogen is needed by all living things to make biological molecules like protein and DNA. It is continuously moved in and out of organisms and the atmosphere in a cycle dependent on soil bacteria.

7 Nutrients such as carbon cycle through ecosystems Nitrogen is the most abundant element in the Earth’s atmosphere and is needed to make proteins and nucleic acids. Plants cannot use nitrogen directly from the atmosphere but rather, must convert it into usable forms through the nitrogen cycle. During nitrogen fixation, one form of nitrogen is converted by bacteria to another form that can be taken up by the roots of plants. Nitrogen is needed by all living things to make biological molecules like protein and DNA. It is continuously moved in and out of organisms and the atmosphere in a cycle dependent on soil bacteria.

7 Nutrients such as carbon cycle through ecosystems TERMS TO KNOW: Nitrogen and phosphorus are two additional chemicals that are essential for life. TERMS TO KNOW: Nitrogen fixation Phosphorus cycle

7 Nutrients such as carbon cycle through ecosystems Phosphorus is needed by all organisms to make DNA. This is a very slow cycle. There is no atmospheric component—it is dependent only on the weathering of rock to release new supplies into the water and soil. Once dissolved in water, the phosphorus can be taken up by organisms. Phosphorus passes from inorganic to organic form through interaction with water and organisms. In Biosphere 2, the phosphorus became trapped in water systems and polluted aquatic habitats. Algal mats absorbed much of the excess phosphorus. Once dried, the minerals could be reclaimed from the algae.

7 Nutrients such as carbon cycle through ecosystems Another Biosphere 2 project is experimentation to predict the effects of climate shifts on trees.

7 Ecosystems are complicated, but learning how they function will help us restore degraded ones Lessons from Biosphere 2 The Earth is far more complicated than we imagined or could plan for. A small change can set off a sequence of events that can degrade a system’s capacity to support life. Negative results can be just as informative as positive results. We gained a greater understanding of carbon cycling. Biosphere 2 is still used by scientists from around the world to study the effects of an atmosphere loaded with CO2.

PERSONAL CHOICES THAT HELP 7

UNDERSTANDING THE ISSUE 7

UNDERSTANDING THE ISSUE 7

ANALYZING THE SCIENCE 7

7 EVALUATING NEW INFORMATION The Smithsonian: http://nationalzoo.si.edu/SCBI/MigratoryBirds/Coffee/default.cfm

MAKING CONNECTIONS 7