Visualizing Environmental Science How Ecosystems Work Chapter 5 Chapter Chapter77 [chapter [chapteropener openerimage] image] © 2017 John Wiley & Sons, Inc. All rights reserved. Solving Lake Washington’s Ecological Imbalance • Effluent released into the large freshwater lake raised the levels of the nutrient phosphorus present in the water ― In 1955, scientists linked high phosphorus levels to increased cyanobacterial growth ― Large mats of cyanobacteria had formed a thick green scum on the surface ― This led to explosive growth of bacteria that decompose the cyanobacteria, which, in turn, used up large quantities of dissolved oxygen in the lake ― Larger organisms were then affected by this oxygen depletion, and fish and small invertebrates began to die © 2017 John Wiley & Sons, Inc. All rights reserved. Solving Lake Washington’s Ecological Imbalance • Beginning in 1963, effluent was diverted from the lake, and by 1968, all sewage input into the lake had ceased ― The lake’s condition began to improve, and the water to clear ― No further cyanobacteria overgrowth has occurred since, and the lake remains clear to this day Dissolved phosphorus in Lake Washington from 1955 to 1974. Note that the level of dissolved phosphorus declined in the lake as the phosphorus contributed by sewage effluent (shaded area) declined. Cyanobacterial growth from 1964 to 1975, during Lake Washington’s recovery, as measured indirectly by the amount of chlorophyll, the pigment involved in photosynthesis. Note that as the level of phosphorus dropped in the lake, the number of cyanobacteria (that is, the chlorophyll content) declined. © 2017 John Wiley & Sons, Inc. All rights reserved. What is Ecology? • Ernst Haeckel • The study of the interactions among organisms and between organisms and their abiotic environment • Biotic and abiotic • Linked to geology, chemistry, physics © 2017 John Wiley & Sons, Inc. All rights reserved. What is Ecology? • Levels of organization – Population: A group of organisms of the same species that live in the same place at the same time – Communities: All the populations of different species that live and interact together within an area at the same time – Ecosystem: A community and its physical environment © 2017 John Wiley & Sons, Inc. All rights reserved. What is Ecology? • Levels of organization – Landscape: A region that includes several interacting ecosystems • Landscape ecology studies the connections among ecosystems in a given region – Biosphere: The parts of Earth’s atmosphere, ocean, land surface, and soil that contain all living organisms • Compare atmosphere, lithosphere , hydrosphere © 2017 John Wiley & Sons, Inc. All rights reserved. The Flow of Energy Through Ecosystems • Energy—the ability to do work – Potential energy = stored energy – Kinetic energy = energy of motion • Thermodynamics—the study of energy and its transformations – First and second law of thermodynamics © 2017 John Wiley & Sons, Inc. All rights reserved. The Flow of Energy Through Ecosystems Potential and kinetic energy Potential energy is stored in the drawn bow (a) and is converted to kinetic energy (b) as the arrow speeds toward its target. © 2017 John Wiley & Sons, Inc. All rights reserved. The First Law of Thermodynamics • Energy cannot be created or destroyed • Total energy content of an organism and its surroundings is always the same • However, energy can change from one form to another © 2017 John Wiley & Sons, Inc. All rights reserved. The First Law of Thermodynamics • Photosynthesis – Plants capture light energy from the sun, and convert it into stored chemical energy – This captured energy is then released during cellular respiration, and is used by the organism to do biological work – The chemical equation for photosynthesis is: • 6C02 + 12H2O + radiant energy → C6H12O6 + 6H2O + 6O2 – The chemical equation for cellular respiration is: • C6H12O6 + 6O2 + 6H2O → 6CO2 + 12H2O + energy © 2017 John Wiley & Sons, Inc. All rights reserved. The Second Law of Thermodynamics • The amount of usable energy in the universe decreases over time, as some is lost as heat – Heat: Less usable and more disorganized form of energy • Within living organisms, during each energy transformation some energy is changed to heat – No organism can use this heat energy for biological work • Entropy—a measure of this disordered energy • No process that requires energy is 100% efficient, as much energy is transformed to heat and becomes unusable for work © 2017 John Wiley & Sons, Inc. All rights reserved. Producers, Consumers, and Decomposers • Producers, consumers and decomposers – Three categories based on how nourishment is obtained • Producers manufacture large organic molecules from simple inorganic molecules – Producers are potential food for other organisms – Plants are the most significant producers on land – Algae and certain bacteria are the important producers in aquatic environments This moose is a herbivore, or primary consumer, utilizing the chemical energy stored in grasses © 2017 John Wiley & Sons, Inc. All rights reserved. Producers, Consumers, and Decomposers • Consumers are animals that consume other organisms – Primary consumers, or herbivores, eat producers – Secondary consumers eat primary consumers – Tertiary consumers eat secondary consumers • Secondary and tertiary consumers are carnivores • Consumers that eat both plants and animals are omnivores © 2017 John Wiley & Sons, Inc. All rights reserved. Producers, Consumers, and Decomposers • Detritivores—consumers, such as this crab, that eat waste organic matter • Decomposers—bacteria and fungi that break down dead organisms • Detritivores and decomposers are important for ecosystem health, and work together to prevent a build-up of organic waste © 2017 John Wiley & Sons, Inc. All rights reserved. The Path of Energy Flow in Ecosystems • Energy flow—the passage of energy in a one-way direction through an ecosystem, occurs in food chains • Trophic level—each level in a food chain • Energy is lost as heat along the way, thus the number of steps in a food chain is limited, and less energy is available for organisms at the higher trophic levels © 2017 John Wiley & Sons, Inc. All rights reserved. The Path of Energy Flow in Ecosystems • A food web is a complex of interconnected food chains in an ecosystem • A food web gives a more realistic view of the flow of energy in an ecosystem than the simple path shown in a food chain © 2017 John Wiley & Sons, Inc. All rights reserved. The Path of Energy Flow in Ecosystems • Ecological pyramids graphically represent the relative energy values of each trophic level • Pyramids of numbers show the number of organisms at each trophic level in a given ecosystem • Pyramids of energy illustrate how energy dissipates into the environment as it moves from one trophic level to the next This pyramid of numbers represents 10,000 grass plants supporting 10 mice, which support one bird of prey. © 2017 John Wiley & Sons, Inc. All rights reserved. Ecosystem Productivity • Gross primary productivity (GPP) is the rate at which energy is captured during photosynthesis • Net primary productivity (NPP) is the amount of biomass found in excess of that broken down by a plant during cellular respiration – Only the energy represented by NPP is available as food for an ecosystem’s consumers – Humans use a much higher percentage of global NPP than all other animal species NPP is expressed in grams of dry matter produced per square meter per year for the selected ecosystems © 2017 John Wiley & Sons, Inc. All rights reserved. The Cycling of Matter in Ecosystems • Biogeochemical cycles – Matter—the material of which organisms are composed – Biogeochemical cycles involve biological, geological, and chemical processes – Humans have GREAT influence – Cycling vs. flow • Matter cycles through ecosystem – From abiotic environment to organisms, then back to environment • Energy flows through the ecosystem – From producers to consumers to decomposers, finally to be released as heat energy © 2017 John Wiley & Sons, Inc. All rights reserved. The Cycling of Matter in Ecosystems • Matter cycles between the biotic and abiotic environments as it moves from one part of the ecosystem to another – Carbon, hydrologic, nitrogen, sulfur, and phosphorus are all biogeochemical cycles © 2017 John Wiley & Sons, Inc. All rights reserved. The Carbon Cycle • The global movement of carbon between the abiotic environment (atmosphere, ocean) and organisms – Atmosphere/ocean photosynthesis cellular respiration/combustion/decomposition atmosphere/ocean • Carbon is an essential component of organisms’ molecules • Also essential component of abiotic environment © 2017 John Wiley & Sons, Inc. All rights reserved. The Carbon Cycle • Carbon makes up 0.04% of the atmosphere • Needed to make proteins and carbohydrates • Present in several forms such as CO2, HCO3–, CaCO3 • Photosynthesis fixes carbon from CO2 into carbohydrates • Fossil fuels, coal, oil and natural gas are deposits of carbon compounds © 2017 John Wiley & Sons, Inc. All rights reserved. The Hydrologic Cycle • Water circulates among the ocean, land, and atmosphere • The hydrologic cycle provides a renewable supply of water for terrestrial organisms – Runoff is the movement of water from land to rivers and lakes – Watersheds are areas of land where runoff drains • Climate change and aerosols, a type of air pollutant, weaken the hydrologic cycle © 2017 John Wiley & Sons, Inc. All rights reserved. The Nitrogen Cycle • Nitrogen is an essential component of proteins and nucleic acids • Atmosphere is 78% nitrogen gas • Nitrogen gas molecules must be broken apart before the nitrogen can be used in proteins and nucleic acids • Five steps in which nitrogen cycles between the abiotic environment and organisms – – – – – Nitrogen fixation Nitrification Assimilation Ammonification Denitrification © 2017 John Wiley & Sons, Inc. All rights reserved. The Nitrogen Cycle • Nitrogen fixation converts atmospheric nitrogen gas to a form that organisms can use (NH3) • Nitrogen-fixing bacteria carry out nitrogen fixation in soil and aquatic environments • Photochemical smog and acid deposition are nitrogen-based air pollutants © 2017 John Wiley & Sons, Inc. All rights reserved. The Sulfur Cycle • Bacteria-driven cycle • Sulfur is primarily found underground in sedimentary rocks and minerals, and in the ocean • Available in other forms such as SOx, H2SO4, and H2S • Sulfur gas is a minor part of the atmosphere, but has substantial movement in/out of atmosphere • Sulfur is a necessary component of proteins • Animals get sulfur from plant protein • Burning coal releases sulfur, which causes acid deposition © 2017 John Wiley & Sons, Inc. All rights reserved. The Phosphorus Cycle • No atmospheric component • Phosphorus cycles between land and organisms • Phosphorus in soil is absorbed by plant roots – Necessary to make nucleic acids and ATP • Humans accelerate loss of phosphorus from the land • Phosphorus in fertilizers can cause eutrophication, as in Lake Washington (chapter opener) © 2017 John Wiley & Sons, Inc. All rights reserved. Ecological Niches • Ecological niche – The totality of an organism’s adaptations, its use of resources, and the lifestyle to which it is fitted • Describes the place and function of an organism within the ecosystem • Takes into account all aspects of an organism’s existence • The “way of life of an organism” • Habitat – Part of an organism’s niche, the place where the organism lives © 2017 John Wiley & Sons, Inc. All rights reserved. Ecological Niches • Niches can be expressed as: – Fundamental niche—the potential, idealized niche – Realized niche—the actual niche an organism occupies © 2017 John Wiley & Sons, Inc. All rights reserved. Resource Partitioning • One way species avoid or reduce niche overlap • Serves to reduce competition for resources • Can include timing of feeding, nest sites, and location of feeding © 2017 John Wiley & Sons, Inc. All rights reserved. Resource Partitioning Resource partitioning of five warbler species Each species spends most of their time feeding in different areas of the tree © 2017 John Wiley & Sons, Inc. All rights reserved. Interactions Among Organisms • Organisms of an ecosystem interact and form associations • Three main types of interactions occur between species in an ecosystem – Symbiosis – Predation – Competition © 2017 John Wiley & Sons, Inc. All rights reserved. Symbiosis • Symbiosis—two species living in close association • Symbiosis is the result of coevolution, as seen in this honeycreeper’s curved bill perfectly suited to sip nectar from the tubular flowers of the lobelia plant © 2017 John Wiley & Sons, Inc. All rights reserved. Symbiosis • There are three main types of symbiosis – Mutualism, where both organisms benefit – Commensalism, where one benefits but the other is unaffected—neither harmed nor helped – Parasitism, one benefits at the expense of the other © 2017 John Wiley & Sons, Inc. All rights reserved. Symbiosis • Mutualism – both organisms benefit from their association Most common in Central America, the acacia ant gains shelter and nutrients from the acacia plant, in turn protecting the plant from predators. Photographed in Costa Rica. © 2017 John Wiley & Sons, Inc. All rights reserved. Symbiosis • Commensalism – one organism benefits from the association without either harming or helping the second organism Epiphytes are small plants that attach to the branches and trunks of larger trees. Photographed in Olympic National Park Hoh Rainforest, Washington State. © 2017 John Wiley & Sons, Inc. All rights reserved. Symbiosis • Parasitism – one organism (the parasite) benefits from the other (the host) and harms the host organism Close-up of deer ticks on a human fingertip. Females of the species can transmit Lyme disease while feeding on human blood. © 2017 John Wiley & Sons, Inc. All rights reserved. EnviroDiscovery Bee Colonies Under Threat • Since 2006, major losses to bee colonies have occurred worldwide, referred to as colony collapse disorder (CCD) – CCD is the result of neonicotinoid pesticides, pathogens, parasites, and viruses such as Israeli acuteparalysis virus • Bees are important pollinators and many crops are threatened by bee declines Hand pollination of pear trees in China, in a region where bee populations have vanished © 2017 John Wiley & Sons, Inc. All rights reserved. Predation • Predation—the consumption of one species (prey) by another species (predator) – Coevolutionary “arms race” as predators evolve to better catch prey and prey evolve to better escape predator – The cheetah sprints at high speeds to catch prey – The goldenrod spider uses camouflage to ambush prey © 2017 John Wiley & Sons, Inc. All rights reserved. Predation • Avoiding predation – Social behavior can decrease predation, such as adult meerkats standing guard at their burrow, ready to alert the group of danger – Chemical defense in prey, such as poison glands and bright warning colors – Camouflage to hide from predators, such as this Indian leaf butterfly © 2017 John Wiley & Sons, Inc. All rights reserved. Competition • Competition – The interaction among organisms that vie for the same resources in an ecosystem, such as food or living space – Can be complex • Intraspecific competition – Competition for resources between members of the same species • Interspecific competition – Competition for resources between members of different species © 2017 John Wiley & Sons, Inc. All rights reserved. Keystone Species • Keystone species are crucial to the maintenance and function of an ecosystem – Not the most abundant species, but have influence on entire ecosystem – May be the top predator in an ecosystem – Often affect the available amount of food, water, or other resources The gray wolf is considered a keystone species in its ecosystem. © 2017 John Wiley & Sons, Inc. All rights reserved. Case Study: Global Climate Change: How Does it Affect the Carbon Cycle? • Biggest culprit in climate change is the increasing atmospheric CO2, which has increased 20% in last 50 years – Generated by burning of fossil fuels, clearing and burning forests • ‘Stabilization wedges’ is an approach to reduce carbon emissions; each ‘wedge’ would result in a 1-billion-ton-peryear reduction by 2056 © 2017 John Wiley & Sons, Inc. All rights reserved.