how ecosystems work - palm beach state college · chapter 5 copyright © 2014 john wiley &...
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Visualizing Environmental Science
How Ecosystems Work
Chapter 7
[chapter opener image]Chapter 7
[chapter opener image]
Chapter 5
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
What is Ecology?
• The study of the interactions among organisms and between organisms and their abiotic environment
• Biotic and abiotic
© 2014 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; note the tidal pool community
– Ecosystem: community and physical environment
© 2014 John Wiley & Sons, Inc. All rights reserved.
What is Ecology?• A landscape is a region
that includes several interacting ecosystems
• Biosphere– layer of Earth that contains all living organisms
– Compare atmosphere, lithosphere , hydrosphere
© 2014 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
© 2014 John Wiley & Sons, Inc. All rights reserved.
The First Law of Thermodynamics
• Energy cannot be created or destroyed
• Total energy content always the same
• Energy can change from one form to another
– Photosynthesis—solar energy converted to chemical energy
© 2014 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
disorganized form of energy
• Entropy—a measure of this disorder
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Producers manufacture large organic molecules from simple inorganic molecules– Producers are potential food for
other organisms– This moose is an herbivore or a
primary consumer, feeding on the chemical energy stored in grasses
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Consumers are animals that consume other organisms
• Detritivores—consumers such as this crab eat organic matter called detritus
• Decomposers—bacteria and fungi that break down dead and decaying organisms
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through 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
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Ecological pyramids graphically represent the relative energy values of each trophic level
• Pyramids of energy illustrate how energy dissipates into the environment as it moves from one trophic level to the next
© 2014 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
– NPP is expressed in grams of dry matter per square meter per year for the selected ecosystems
© 2014 John Wiley & Sons, Inc. All rights reserved.
• Biogeochemical cycles
– Matter—the material of which organisms are composed
– Humans have GREAT influence on them
The Cycling of Matter in Ecosystems
© 2014 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
The Cycling of Matter in Ecosystems
© 2014 John Wiley & Sons, Inc. All rights reserved.
Carbon Cycle
• 0.04% of the atmosphere
• Needed to make proteins and carbohydrates
• Present in several forms such as CO2, HCO3
-, and CaCO3
• Fossil fuels, coal, oil and natural gas are deposits of carbon compounds
• Photosynthesis fixes carbon from CO2 into carbohydrates
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Hydrologic Cycle
• Water circulates among the ocean, land, and atmosphere
• Creates a renewable supply of water for terrestrial organisms
– Runoff is water from land to rivers and lakes
– Watersheds are areas of land where runoff drains
© 2014 John Wiley & Sons, Inc. All rights reserved.
• Nitrogen is an essential component of proteins and nucleic acids
• Atmosphere is 78% nitrogen gas
• Five steps in which nitrogen cycles between the abiotic environment and organisms– Nitrogen fixation
– Nitrification
– Assimilation
– Ammonification
– Denitrification
The Nitrogen Cycle
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Cycling of Matter in Ecosystems• Nitrogen-fixing bacteria
carry out nitrogen fixation in soil and aquatic environments
– This bacteria is fixing nitrogen in the nodules of a pea plant’s root
• Photochemical smog and acid deposition are nitrogen-based air pollutants
© 2014 John Wiley & Sons, Inc. All rights reserved.
• Most sulfur is underground in sedimentary rocks and minerals
• Animals get sulfur from plant protein
• Sulfur gas is a minor part of the atmosphere, but movement of sulfur is substantial
• Bacteria-driven cycle• Burning coal releases sulfur,
which causes acid deposition
The Sulfur Cycle
© 2014 John Wiley & Sons, Inc. All rights reserved.
• No atmospheric component
• Cycles between land and organisms
• Phosphorous in soil is absorbed by plant roots– Necessary to make nucleic acids
and ATP
• Phosphorus in fertilizers can cause eutrophication, as in Lake Washington (chapter
opener)
• Anthropogenic loss of terrestrial phosphorus
The Phosphorous Cycle
© 2014 John Wiley & Sons, Inc. All rights reserved.
Ecological Niches• 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
• The “way of life of an organism”
• Habitat
– Part of an organism’s niche, the place where the organism lives
© 2014 John Wiley & Sons, Inc. All rights reserved.
Ecological Niches
• Fundamental niche—the potential, idealized niche
• Realized niche—the actual niche an organism occupies
• While the fundamental niches of these two lizards initially overlap, the brown anole out-competed the green anole, restricting is realized niche
• Generalists vs. specialists
© 2014 John Wiley & Sons, Inc. All rights reserved.
Resource Partitioning• One way species avoid or
reduce niche overlap
• Serves to reduce competition for resources
• Resource partitioning of five warbler species
– Each species spends most of their time feeding in different portions of the tree
© 2014 John Wiley & Sons, Inc. All rights reserved.
Interactions Among Organisms
• 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
© 2014 John Wiley & Sons, Inc. All rights reserved.
Interactions Among Organisms
• There are three main types of symbiosis
– Mutualism, where both organisms benefit• The ant obtains food and shelter
from the plant and in turn, protects the plant from predators
– Commensalism, where one benefits but the other is unaffected—neither harmed nor helped
– Parasitism, one benefits at the expense of the other
© 2014 John Wiley & Sons, Inc. All rights reserved.
EnviroDiscoveryBee Colonies Under Threat
• Since 2006, major losses to bee colonies, referred to as colony collapse disorder (CCD)
– CCD is the result of pesticides, pathogens, parasites, and viruses such as Israeli acute-paralysis virus
• Bees are important pollinators and many crops are threatened by bee declines
– Pear trees in China being hand pollinated
© 2014 John Wiley & Sons, Inc. All rights reserved.
Interactions Among Organisms
• 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
© 2014 John Wiley & Sons, Inc. All rights reserved.
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
© 2014 John Wiley & Sons, Inc. All rights reserved.
Competition• The interaction among
organisms that vie for the same resources in an ecosystem, such as food or living space
– Intraspecific competition
– Interspecific competition
© 2014 John Wiley & Sons, Inc. All rights reserved.
Competition• Keystone species, such as the
gray wolf, is crucial to the maintenance of the ecosystem
– Not the most abundant, but have influence on entire ecosystem
– Note the reintroduction of the wolf in 1995 affected the elk population
© 2014 John Wiley & Sons, Inc. All rights reserved.
Keystone Species• Another keystone species,
the sea otter exerts their influence by changing competitive relationships.
• They help maintain balance in an ecosystem.
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