Focus on the Biota: Metabolism, Ecosystems and Biodiversity

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Chapter 9 Focus on the Biota Metabolism,
Ecosystems and Biodiversity
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Major environmental issues associated with Global
Change on short-time scales Global
Warming Stratospheric Ozone Depletion Deforestat
ion and Loss of Biodiversity
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Components of the Earth system through which
elements (such a C) recycle. Biosphere/biota
plays an important role in interactions and
recycling of elements.
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Fundamental characteristics of life that allow it
to interact with the physical processes that
occur on the planet in such a way that Earth is a
habitable planet. 1. Life spreads
exponentially 2. Life needs energy 3. Life
pollutes 4. Life is versatile Classify life
(in a systems-way) according to processes -
rather than characteristics of organisms
(taxonomy) Processes related to the way life
organisms get and use energy
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Recall that CO2 and CH4 are greenhouse gases -
methanogenous are important as either (a)
autotrophic or (b) heterotrophic (a) CO2
4H2 CH4 2H2O (b) CO3COOH
CH4 CO2 The net result of the
activity of methanogenous and oxygenic
photosynthesizers is to release O2 and CH4 to the
atmosphere Oxygenic photosynthesis 2CO2
2 H2O CH2O 2O2 Fermentation
2 CH2O
CH3COOH Heterotrophic methanogenesis CH3COOH
CH4 CO2 ___________________________
______________________________________ NET
CO2 2 H2O
CH4 O2
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• Structure of the Biosphere
• population all the members of a single species
  that live in a region
• community 2 or more groups of interacting
  species
• biome region with a characteristic plant
  community (desert, boreal forest)
• ecosystem community of different populations
  (animals, microbes, fungi, plants) with the
  physical environment that it supports
• Interactions between ecosystems and the physical
  environment can alter local climate feedbacks

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Possible feedbacks between the boreal forest and
climate - from experiments conducted with a
General Circulation Model change all forest
north of 45N to bare ground and compare to actual
forest equivalent to moving forest line south
Implied by Model Results
positive coupling
Model Results
positive feedback
negative coupling
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• increase in wintertime albedo trees prevent
  snow from covering homogeneously the area less
  trees more snow on bare ground - albedo increased
• decrease in Tair in April about 12 deg C drop
  in T
• colder T in winter leads to increase in sea-ice
  cover which in turn leads to higher albedo of the
  area
• this further higher albedo leads to a decreased
  Tair
• Implied by this results more sea-ice keeps SSTs
  lower decreasing the oceans thermal content
  which keeps high-latitude Tair unusually low and
  so the forest is prevented from re-growing
• We might say that the forest keeps the climate
  that it needs to
• grow healthily it prevents winter T from being
  dangerously low for
• its own survival!

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The figure presents a systems diagram of the
feedbacks involving boreal forest cover, albedo,
temperatures, sea ice, and the oceans. The
diagram helps us see that it is possible for the
northern boreal forest to have a significant
impact on the larger-scale climate. Now use
information you have about the possible impacts
of anthropogenically induced greenhouse climate
change and this diagram to discuss the
implications in terms of climate and forest cover
(Critical-Thinking Problem 1). What do you
already know? That anthropogenically induced
greenhouse change is a warming trend in the
earths climate, and in particular that this
means increased winter temperatures. So the
question can be re-stated now according to the
system diagram of this figure, what are the
implications of increased winter temperatures for
the climate and forest of high latitudes? Warmer
winter temperatures would lead to a decrease in
sea ice, which would lead to a decrease in albedo
and an increase in sea-surface temperatures
(SSTs). The increased SSTs lead to increased
high-latitude summer temperatures, which would
lead to increased boreal forest cover. The
increase in boreal forest cover would lead to a
decrease in albedo. The decrease in albedo
resulting from both increased boreal forest cover
and decreased sea ice would lead to higher winter
temperatures. In sum this would be a positive
feedback cycle that would accentuate the climatic
changes caused by global warming.
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Ecosystems overlap, gradually merge, transitional
boundaries ecotones
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who-eats-whom diagram food chains are
interconnected as food webs Trophic levels
series of feeding levels
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Interactions between species can be cooperative,
mutually supportive bees and trees one gets
food the other reproduces. An extreme form of
this support is symbiosis coral and plant-like
dinoflagellates. Another extreme is complete
competitive coexistence, but less often than one
might think. Disruptions of ecosystems dynamics
is generally followed by a predictable pattern of
rebuilding succession. Unpredictability in
these patterns leads to diversity.
Biodiversity Measures of Biodiversity Diversity
of Interactions
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homogeneous
heterogeneous
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Measures of Biodiversity Simpsons diversity
index measures the likehood (probability) that
two individuals from the same community will be
of different species - quantitatively Sd
Simpsons diversity 1 - (PA)2 (PB)2 (PC)2
... where PA is the proportion of species A
(B, C, etc.) in the community probability that
an individual chosen randomly will be of species
A (B, C, etc.). In this example Sd 1 - (0.99)2
(0.01)2 0.02 Community I Sd 1 - (0.5)2
(0.5)2 0.50 Community II
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• Assignment 1
• Take A Closer Look at Physiology vs Ecological
  Optimal Growth Box, page 178 Read it once to
  understand the basic concepts. Then
• Explain the graphs of figure 9.1
• Describe briefly, but clearly, the two paradoxes
  referred to in the text of the box
• Please read the hand out Lab Report Format,
  provided in
• the website for the course when preparing to
  write this
• 11/2 (suggested length) assignment