Focus on the biota: Metabolism, Ecosystems, and Biodiversity

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Focus on the biota Metabolism, Ecosystems, and
Biodiversity
Life on Earth- the earth is the only place in the
solar system that has documented proof of life.
Characteristics of life
Life spreads exponentially- the rate of
population growth depends on the number of
individuals reproducing at any time. If each pair
produces 4 offspring, the number of organisms
increases exponentially.
Life needs energy- photosynthesizers use solar
energy, chemosynthesizers use chemical energy,
most other organisms use the energy stored as the
bodies of the these two.
Life pollutes- every organism has a metabolism
that releases waste products. Other organisms may
use these waste products, or they may accumulate
in the environment.
Life is versatile- organisms react with their
environment in many ways. Microbes are
particularly inventive, such that they occupy an
incredible range of environments from glaciers to
hot springs. Their activities are incredibly
important for all life on Earth.
Autotrophs and Heterotrophs
For our purposes it is more useful to classify
organisms based on the way that they obtain their
energy and metabolize than by the traditional
taxonomic classification system.
Autotrophs- organisms that grow by using a source
of energy to reduce CO2. These are also known as
primary producers.
Plants, algae and photosynthetic microbes
(cyanobacteria, purple and green sulfur bacteria)
are the most common autotrophs, while
chemosynthetic bacteria make up most of the
remainder of the pack (colorless sulfur
bacteria).
These organisms produce organic matter from
inorganic carbon sources either using the Suns
energy or that of energy-releasing chemical
reactions.
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Chemosynthesis is the basis of the mid-ocean
ridge food chain.
The Base of the Food Web Sulfur-Oxidizing
Bacteria Compared to the surrounding sea floor,
upon which organic matter rains from above,
hydrothermal vents boast a community of organisms
that is 10,000 to 100,000 times denser.
The reason for this the presence of
sulfur-oxidizing bacteria as a food source either
directly or through a kind of cooperative
"agreement" between the bacteria and a particular
vent organism.
Sulfur-oxidizing bacteria and other forms of
bacteria that gain energy from the metabolism of
inorganic compounds are chemoautotrophs.
These bacteria are able to oxidize (remove
electrons) compounds such as hydrogen sulfide and
store energy in the form of ATP (adenosine
triphosphate), which is the universal "energy"
molecule in all organisms, including humans.
These bacteria use this energy to transform
carbon dioxide into simple sugars and other
molecules, just like plants.
Thus, these bacteria function much in the same
way as plants, creating organic matter at the
base of the food web for other organisms.
Nowhere is the importance of symbiosis better
demonstrated than in the giant tube worm, who has
the scientific name Riftia pachyptila. When these
worms were collected and examined in greater
detail, some important parts were missing.
These worms have no mouth, no gut, and no anus.
They are completely devoid of any digestive
system whatsoever. How do you get to be four-feet
tall without eating?
This mystery was solved by a graduate student at
Harvard University, Colleen Cavanaugh, who
realized that inside the body of the tubeworm is
an organ called a trophosome.
The trophosome is highly vascularized and
contains specialized cells packed full of
chemoautotrophic sulfur bacteria (285 billion per
ounce of tissue).
The tubeworm provides all the chemicals necessary
for the bacteria to make food, including sulfur,
oxygen, and carbon dioxide, and the bacteria
manufacture sugars or some other form of
energy-rich molecules that provide nutrition to
the tubeworm.
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Autotrophs and Heterotrophs
Heterotrophs- organisms that grow by using
organic matter produced by other orgamisms. These
are also known as secondary producers.
Basically, heterotrophs use autotrophs by
breaking them down (and using their stored
energy) at a higher rate than they would
abiotically.
Structure of the Biosphere
Species are all closely related organisms that
can potentially interbreed and produce fertile
offspring. Species represent the smallest subunit
of the biosphere
Population- all members of a single species that
live in a given area.
Community- characteristic assemblage of two or
more groups of interacting species. May include
any combination of plants, animals, fungi, and
microbes.
Biome- a region with a characteristic plant
community (boreal forest and prairies of
Saskatchewan are two examples).
Ecosystem- a community of plants, animals, fungi,
and microbes coupled with the environment
(climate, soil and rock type, etc.). Coral reef,
tropical cloud forest, and arctic desert are
examples.
Ecosystems
The physical environment (climate, soil type,
topography, etc.) plays a strong role in
establishing an ecosystem.
However, the organisms present may also play a
strong role in altering the physical environment
in a number of ways (creating soil, decreasing
albedo, etc.).
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Feedbacks between the boreal forest and climate
in Northern Saskatchewan and Manitoba.
Models predict that April temperatures might be
12C (21.6F) colder and even July temperatures
may decrease by 5C (9F) if the forest
disappeared.
Physiology vs. Ecology for maximum growth
Species Interactions- primary producers (algae,
plants) are consumed by primary consumers
(zooplankton, rodents) that are eaten by
secondary consumers (fish, hawks), while
decomposers (bacteria and fungi) and detritus
feeders consume the organic matter of primary and
secondary producers and consumers.
Ecotone- a diffuse boundary between ecosystems.
An ecotone may contain an assemblage of species
that is not found in either adjacent ecosystem.
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Polar biomes are characterized by very low
temperatures throughout the year, with the
permanent presence of snow and ice.
Major terrestrial biomes
This eliminates the possibility of significant
terrestrial vegetation, although microscopic
algae, known as cryovegetation, may develop
temporarily on the ice or snow. This lack of
terrestrial producers results in very low
diversity in polar biomes.
Tundra biomes develop in regions where MAT is
low, but where a short summer season permits
development of terrestrial vegetation
Boreal Forest or Taiga biomes form where winters
are long and cold, but the growing season is long
enough to eliminate permafrost, extensive,
conifer-dominated forests develop.
Landscapes tend to be flat, as a consequence of
earlier glacial activity, and bogs, ponds, and
lakes are common, often as a result of beaver
activity in damming streams.
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"Short-grass" prairie biome along the eastern
front of the Rocky Mountains.
Cold desert biome is typically dominated by
dry-adapted shrubs, such as sagebrush
(Artemisia), rabbit-bush (Chrysothamnus), and
arid grasses.
Temperate deciduous forest biome dominated by
trees that drop their leaves during the winter
(cold) months of the year. Temperate deciduous
forest covers much of the United States, east of
the Mississippi River.
Tropical Rainforest Biome- form where rainfall is
abundant throughout the year
Tropical Deciduous Forest Biomes form where
generally rainy areas have a distinct dry season.
Thorn forest scrub, savanna, and tropical
grassland biomes form in the semi-arid tropics,
where available rainfall will no longer support
true forest vegetation, leading to the
development of a mosaic of open biomes.
In very dry deserts like the Namib of Africa or
the Atacama of South America, vegetation may be
virtually absent, except following very rare
rains.
Warm desert biome. This is the particularly rich
warm desert flora of Sonoran Desert.
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Food chain- charts which organisms feed on which.
Food web- interconnected food chains that can be
ordered as trophic levels.
Biomass- the total combined weight of organic
material in each trophic level. Biomass decreases
with each increase in trophic level. In
terrestrial ecosystems, the biomass decreases by
90-99 for each level. The exchange of biomass
can be thought of as exploitation efficiency.
Symbiosis- a relationship where two species
benefit from living together in intimate contact.
Niche- describes an animals lifestyle (where,
when, and what it eats, where it lives, where and
when it nests, etc.)
Ecosystem Disturbance and Succession
Disturbance of an ecosystem generates a
predictable sequence of response called
succession.
In the example of a forest fire the first species
to appear are called opportunists or pioneer
species. These spread fast by reproducing rapidly
and are tolerant of disturbed environments.
Return to original conditions may take hundreds
of years (ex. New England forests, Mt. St.
Helens). This is the biospheres way of healing
after being wounded.
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Biodiversity
Biodiversity is the number of species in a given
area. However, there are other ways to look at
biodiversity too.
Biodiversity is the same in both plots.
Community II is much more heterogeneous and
therefore diverse.
Simpsons diversity index measures the likelihood
that two individuals drawn from the same
community will be of different species.
SDI 1- (proportion of species A)2
(proportion of species B)2
SDI for community I (1- (0.992 0.012) 0.02
SDI for community II (1- (0.52 0.52) 0.5
An Gorta Mór- implications for low diversity
Monocultures- famine, disease, and social
breakdown