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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


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


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


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


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


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



• 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



• 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



• 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


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


• Biogeochemical cycles

– Matter—the material of which organisms are composed

– Humans have GREAT influence on them

The Cycling of Matter in Ecosystems


• 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


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


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


• 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


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


• 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


• 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


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


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


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


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



• 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


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



• 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


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


Competition• The interaction among

organisms that vie for the same resources in an ecosystem, such as food or living space

– Intraspecific competition

– Interspecific competition


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


Keystone Species• Another keystone species,

the sea otter exerts their influence by changing competitive relationships.

• They help maintain balance in an ecosystem.

3-31

Monterey Bay, California

Keystone Species

how ecosystems work - palm beach state college€¦ · •the carbon cycle –the global movement...

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