energy_pyramid_example

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					    Energy pyramid example




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To summarize: In the flow of energy and inorganic nutrients through the
ecosystem, a few generalizations can be made:

   1. The ultimate source of energy (for most ecosystems) is the sun
   2. The ultimate fate of energy in ecosystems is for it to be lost as heat.
   3. Energy and nutrients are passed from organism to organism through
      the food chain as one organism eats another.
   4. Decomposers remove the last energy from the remains of organisms.
   5. Inorganic nutrients are cycled, energy is not.



The diagram above shows how both energy and inorganic nutrients flow
through the ecosystem. We need to define some terminology first. Energy
"flows" through the ecosystem in the form of carbon-carbon bonds. When
respiration occurs, the carbon-carbon bonds are broken and the carbon is
combined with oxygen to form carbon dioxide. This process releases the
energy, which is either used by the organism (to move its muscles, digest
food, excrete wastes, think, etc.) or the energy may be lost as heat. The dark
arrows represent the movement of this energy. Note that all energy comes
from the sun, and that the ultimate fate of all energy in ecosystems is to be
lost as heat. Energy does not recycle!!

The other component shown in the diagram are the inorganic nutrients. They
are inorganic because they do not contain carbon-carbon bonds. These
inorganic nutrients include the phosphorous in your teeth, bones, and
cellular membranes; the nitrogen in your amino acids (the building blocks of
protein); and the iron in your blood (to name just a few of the inorganic
nutrients). The movement of the inorganic nutrients is represented by the
open arrows. Note that the autotrophs obtain these inorganic nutrients from
the inorganic nutrient pool, which is usually the soil or water surrounding
the plants or algae. These inorganic nutrients are passed from organism to
organism as one organism is consumed by another. Ultimately, all organisms
die and become detritus, food for the decomposers. At this stage, the last of
the energy is extracted (and lost as heat) and the inorganic nutrients are
returned to the soil or water to be taken up again. The inorganic nutrients are
recycled, the energy is not.

Many of us, when we hear the word "nutrient" immediately think of calories
and the carbon-carbon bonds that hold the caloric energy. IT IS VERY
IMPORTANT that you be careful in your use of the word nutrient in this
sense. When writing about energy flow and inorganic nutrient flow in an
ecosystem, you must be clear as to what you are referring. Unmodified by
"inorganic" or "organic", the word "nutrient" can leave your reader unsure of
what you mean. This is one case in which the scientific meaning of a word is
very dependent on its context. Another example would be the word
"respiration", which to the layperson usually refers to "breathing", but which
means "the extraction of energy from carbon-carbon bonds at the cellular
level" to most scientists (except those scientists studying breathing, who use
respiration in the lay sense).

           1.   A community is an association of interacting populations of
                different species living in a particular habitat.
           2.   Five factors shape the structure of the community:
                     a. Interactions between climate and topography
                           dictate rainfall, temperature, soil composition, and
                           so on.
                     b. Availability of food and resources affects
                           inhabitants.
                     c. Adaptive traits enable individuals to exploit
                           specific resources.
                     d. Interactions of various kinds occur among the
                           inhabitants; these include competition, predation,
                           and mutualism.
                     e. Physical disturbances, immigration, and episodes
                           of extinction affect the habitat.



           3.   Interactions can occur between any two species in a
                community and between entire communities.
           4.   There are several types of species interactions:
                     a. Neutral relationship: neither species directly
                          affects the other (example: eagles and grass).
                     b. Commensalism: one species benefits and the other
                          is not affected (example: bird’s nest in tree).
                     c. Mutualism: there is a symbiotic relationship where
                          both species benefit.
                     d. Interspecific competition: both species are harmed
                          by the interaction.
Predation and parasitism: one species (predator or parasite) benefits




                                    COMMUNITIES

 II.   Factors That Shape Community Structure
        A.     A habitat is a place where an organism lives; it is characterized by
               distinctive physical features, vegetation, and the array of species living in
               it.
            1.     A community is an association of interacting populations of different
                   species living in a particular habitat.
            2.     Five factors shape the structure of the community:
                         a.    Interactions between climate and topography dictate
                               rainfall, temperature, soil composition, and so on.
                         b.    Availability of food and resources affects inhabitants.
                         c.    Adaptive traits enable individuals to exploit specific
                               resources.
                         d.    Interactions of various kinds occur among the inhabitants;
                               these include competition, predation, and mutualism.
                         e.    Physical disturbances, immigration, and episodes of
                               extinction affect the habitat.
            3.     Several community properties are the result of the factors above.
                        a.    Varying numbers of species are found in feeding levels
                              from producers to consumers.
                        b.    Diversity tends to increase in tropical climates, creating
                              species richness.
                        c.    Relative abundance refers to the number of individuals of
                              each species; dispersion describes how the individuals are
                              dispersed through the habitat.



        B.      The Niche Concept
             1.    The niche of each species is defined by the sum of activities and
                   relationships in which it engages to secure and use the resources
                   necessary for its survival and reproduction.
             2.    The potential niche is the one that could prevail in the absence of
                   competition; the realized niche results from shifts in large and small
                   ways over time as individuals of the species respond to a mosaic of
                   changes.



        C.      Species Interactions
             1.    Interactions can occur between any two species in a community and
                   between entire communities.
             2.    There are several types of species interactions:
                         a.   Neutral relationship: neither species directly affects the
                              other (example: eagles and grass).
                         b.   Commensalism: one species benefits and the other is not
                              affected (example: bird’s nest in tree).
                         c.   Mutualism: there is a symbiotic relationship where both
                              species benefit.
                         d.   Interspecific competition: both species are harmed by the
                              interaction.
                         e.   Predation and parasitism: one species (predator or
                              parasite) benefits while the other (prey or host) is harmed.



III.   Mutualis m
       A.    The yucca moth feeds only on the yucca plant, which is completely
             dependent on the moth for pollination–classic example of mutualism.
        B.   This example is a form of symbiosis which implies an intimate and rather
             permanent interdependence of the two species on one another for survival
             and reproduction.
IV.   Competitive Interactions
       A.    Categories of Competition
          1.    Competition within a population of the same species (intraspecific) is
                usually fierce and may result in depletion of a resource.
          2.    Interspecific competition is less intense because requirements are less
                similar between the competitors.
          3.    There are two types of competitive interactions regardless of whether
                they are inter- or intraspecific:
                      a.    In exploitation competition, all individuals have equal
                            access to a resource but differ in their ability (speed or
                            efficiency) to exploit that resource.
                      b.    In interference competition, some individuals limit others’
                            access to the resource.
       B.    Competitive Exclusion
          1.    Competitive exclusion suggests that complete competitors cannot
                coexist indefinitely.
          2.    When competitors’ niches do not overlap as much, the coexistence is
                more probable.
          3.    Differences in adaptive traits will give certain species the competitive
                edge.
       C.    Resource Partitioning
          1.    Similar species share the same resource in different ways.
          2.    Resource partitioning arises in two ways:
                      a.    Ecological differences between established and competing
                            populations may increase through natural selection.
                      b.    Only species that are dissimilar from established ones can
                            succeed in joining an existing community.



V.    Predation
       A.     Predation Versus Parasitism
           1.    Predators get their food from prey, but they do not take up residence
                 on or in the prey.
           2.    Parasites get their food from hosts, and they live on or in the host for a
                 good part of their life cycle; they may or may not kill the host.
       B.     Dynamics of Predator-Prey Interactions
           1.    Many of the adaptations of predators and their victims arose through
                 coevolution.
           2.    The dynamics, ranging from stable coexistence to recurring cycles,
                 depend on:
                       a.    the carrying capacity of prey population in the absence of
                             predation,
                       b.    the reproductive rates of the prey and predator,
                       c.    the behavioral capacity of the individual predators to
                             respond to prey density.
             3.    Stable coexistence results when predators prevent prey from
                   overshooting the carrying capacity.
             4.    Fluctuations in population density tend to occur when predators do not
                   reproduce as fast as their prey, when they can eat only so many prey,
                   and when carrying capacity for prey is high.



 VI.    Predator/Prey Interactions - Evolutionary Results
         A.   Camouflage is any adaptation in form, color, patterning, or behavior that
              allows a prey or predator to blend with its surroundings.
         B.   Warning coloration in toxic prey offer bright colors or bold patterns that
              serve as a warning to predators.
         C.   In mimicry, prey not equipped with defenses may escape predators by
              resembling toxic prey.
         D.   Moment-of-truth defenses allow prey animals defend themselves by
              startling or intimidating the predator with display behavior.
         E.   Adaptive responses to prey are adaptations used by predators to counter
              prey defenses.



VII.    Parasitic Interactions
         A.     Kinds of Parasites
             1.    Parasites may live on the surface of the host (ectoparasites) or within
                   the host’s body (endoparasites).
             2.    Microparasites include bacteria, viruses, and protistans; macroparasites
                   include flatworms, nematodes, and small arthropods.
             3.    Social parasites depend on the social behavior of another to complete
                   the life cycle; for example, cowbirds lay their eggs in the nest of other
                   birds, which unknowingly incubate and hatch the cowbirds’ eggs
         B.     Evolution of Parasitism
             1.    Natural selection tends to favor parasite and host adaptations that
                   promote some level of mutual tolerance and less-than- lethal effects.
             2.    Usually death results only when a parasite attacks a novel host or when
                   the number of parasites overwhelm the host’s defenses.
         C.     Parasitoids
             1.    Parasitoids are a type of insect larvae that kill other insect larvae by
                   feeding on their tissues.
             2.    This provides natural control of insect populations.



VIII.   Community Stability and Change
         A. Succession
           1.   Ecological succession is the predictable developmental sequence of
                species in a community.
                       a.    Pioneer species are the first to colonize an area, followed
                             by more competitive species.
                       b.    A climax community is the most persistent array of species
                             that results after some lapse of time.
          2.    Primary succession happens in an area that was devoid of life.
                       a.    Pioneer species help to improve soil fertility; they are
                             usually small, low-growing plants with a short life cycle
                             and an abundance of seeds.
                       b.    Gradually other, usually larger, species join or replace the
                             pioneer species.
          3.    In secondary succession, a community reestablishes itself to a climax
                state after a disturbance that allows sunlight to penetrate.
       B.    The Climax-Pattern Model
          1.    It was once thought that the same general type of community would
                always develop in a given region because of constraints imposed by
                climate.
          2.    According to the climax-pattern model, a community is adapted to a
                total pattern of environmental factors–climate, soil, topography, wind,
                fires, etc.–to create a continuum of climax stages of succession.
       C.    Cyclic, Nondirectional Changes
          1.    Community stability may require episodes of instability that permit
                cyclic replacement of equilibrium species, thus maintaining the climax
                community.
          2.    A good example are the necessary fires in the forests of California that
                rid the areas of underbrush.
       D.    Restoration Ecology
          1.    Natural restoration of the climax community takes a long time.
          2.    Active restoration involves human intervention to speed the re-
                establishment of a damaged ecosystem.



IX.   Community Instability
       A.    How Keystone Species Tip the Balance
          1.   A keystone species is a dominant species that can dictate community
               structure.
          2.   For example, when sea stars (keystone predator on mussels) were
               removed from a habitat, mussels increased in number and in turn
               preyed on enough other species to reduce the community from 15 to 8.
       B.    How Species Introductions Tip the Balance
          1.   Geographic dispersal of species can occur in three ways:
                     a.   A population might expand its home range by slowly
                          moving into outlying regions that prove hospitable.
                       b.   During the course of a lifetime, individuals may be rapidly
                            transported across great distances (jump dispersal), as in
                            bilge water of large ships.
                       c.   A population may move out from its home range over
                            geologic time, as by continental drift.
           2.    Some introduced species have proved beneficial: soybeans, rice,
                 wheat, corn and potatoes; others are notoriously bad: water hyacinth,
                 kudzu, rabbits in Australia, gypsy moths, zebra mussels, and
                 Africanized bees.



X.   Patte rns of Biodiversity
      A.      Mainland and Marine Patterns
           1.     The number of species increases from the Arctic regions to the
                  temperate zone to the tropics.
           2.     Diversity is favored in the tropics for three reasons:
                         a.    More rainfall and sunlight provides more food reserves.
                         b.    Species diversity is self-reinforcing from herbivores to
                               predators and parasites.
                         c.    Traditionally, the rate of speciation has exceeded the rate of
                               extinction.
      B.      Island Patterns
           1.     Islands distant from source areas receive fewer colonizing species
                  (distance effect).
           2.     Larger islands tend to support more species (area effect).
           3.     Species numbers increase on new islands and reach a stable number
                  that is a balance between immigration rate for species new to the
                  island and the extinction rate for established species.

				
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