Is it Alive?
CELLULAR RESPIRATION IN YEAST
• Yeast (the living organisms in soil sample C of the “It’s
Alive” activity) are facultative aerobes.
• Undergo aerobic respiration when O2 is present – as was
the case during the activity – sugar molecules, CO2 (what
caused the bubbling in the sample), water, and a high
yield of ATP
C6H12O6 + 6O2  6CO2 + 6H2O + ATP (hi yield)
• Undergo alcoholic fermentation when O2 is absent –
sugar molecules broken down into ethanol, CO2 and a low
yield of ATP
C6H12O6  6C2H5OH + 2CO2 + ATP (low yield)
ENERGY FLOW & CHEMICAL CYCLING
IMSS BIOLOGY ~ SUMMER 2012
LEARNING TARGETS
•
To distinguish the abiotic & biotic factors that compose an ecosystem.
•
To understand the roles of photosynthesis & cellular respiration on an
ecological scale (review).
•
To understands what characterizes the major ecosystems on Earth.
•
To describe the flow of energy and cycling of matter through an ecosystem
(food webs).
•
To describe the major biogeochemical cycles that are components of an
ecosystem.
•
To demonstrate how the global carbon cycle is impacted by human activity.
OVERVIEW OF THE BIOSPHERE
• The biosphere is the global ecosystem which includes all of
life and their interactions, with other life as well as with
the physical elements (atmosphere, hydrosphere,
lithosphere)
• Recall that the living and physical factors making up the
biosphere are categorized into
• Abiotic factors
• Biotic factors
REVIEW: ABIOTIC FACTORS OF THE BIOSPHERE
• Non-living (physical, chemical, non-biological)
environmental factors that primarily affect the
distribution patterns of organisms (where they
live), e.g.
•Energy source
•Temperature
•Water
•Nutrients
•Other aquatic factors
•Other terrestrial factors
ENERGY SOURCE (A REVIEW)
•
Recall that all organisms require a source of energy (the energy contained in ATP) to
sustain cellular metabolism (aka cellular respiration).
•
The power for most ecosystems is solar energy captured by chlorophyll (photosystems)
during photosynthesis. Thus, solar energy is used to convert (fix) atmospheric CO2 into
usable chemical energy (ultimately, sugars) by primary producers (i.e.,
photoautotrophs)
• Sunlight is used to fix CO2 into sugars. These sugars are available for use as “fuel” by
the producers themselves (e.g. plants) AND the consumers (e.g. herbivorous animals)
biologycorner.com
•
Map of global primary productivity over both ocean (sea surface) and land, as
measured by NASA Terra & Aqua satellites that are equipped with devices capable
of measuring chlorophyll densities.
A cool resource: http://earthobservatory.nasa.gov/GlobalMaps/
TEMPERATURE
•
Key abiotic factor because of its influence on metabolic processes.
•
With a few exceptions (extremophiles), organisms cannot sustain
active metabolism outside of the 0 – 45°C range, due to
• disruption of protein folding, thus functionality
• disruption of cell membrane fluidity, thus functionality
• freezing of body fluids (disrupts water & solute balance inside and
around cells)
An example of an extremophile: Thermophilic (“heat
loving”) bacteria in volcanic zone of New Zealand’s North
Island. Temperatures here exceed 80°C (176°F).
WATER
•
Recall that water is an
essential molecule of life.
•
Water availability and
body water balance are
critical to sustaining life in
both terrestrial and
aquatic environments
• On land: risk of desiccation
(drying out)
• In sea: risk of body fluids
becoming too salty
• In freshwater: risk of body
fluids becoming too dilute
Behavior of cells in different osmotic conditions.
(B) Analogous to what a freshwater organisms
face. (C) Analogous to what a marine organisms
face. (A) Cell in isotonic environment or cell
capable of regulating its volume to maintain
homeostasis.
NUTRIENTS
•
Recall that in addition to carbon, life requires many other inorganic
nutrients, e.g. nitrogen, phosphorus, calcium, potassium,
magnesium, iron, zinc, etc.
•
Nutrient availability in the soil, water, etc. will determine growth of
primary producers, thus the types and biomass of consumers that
can be sustained in a given environment.
Soil pH can affect nutrient availability to
plants. Width of each band indicates
relative availability of each nutrient at
the various pH levels.
How would rising levels of atmospheric
CO2 affect soil nutrient availability?
OTHER AQUATIC FACTORS
•
Other abiotic factors that may be
limiting for an organism living in
aquatic environments
• Dissolved oxygen levels (also
affected by temperature – higher
the temperature, the lower the O2
solubility)
• Salinity
• pH (largely determined by
atmospheric CO2 levels)
• Water movement, e.g. currents
and tides
OTHER TERRESTRIAL FACTORS
•
Frequency of fires
•
Wind patterns &
severity
•
Storm events
•
Flooding events
Summer monsoon activity (June–September) in central India
has changed significantly in the past 50 years. The extremes
have increased.
REVIEW: BIOTIC FACTORS OF THE ENVIRONMENT
• All the organisms living within a specific
environment (habitat) make up the biotic part of
that habitat; any living component that affects
another organism, e.g.
• ???
•Predator-prey interactions
•Competition
•Symbiotic relationships
TERRESTRIAL ECOSYSTEMS
• The biosphere can be thought of the sum of all
ecosystems on Earth.
• Terrestrial ecosystems (biomes) are distinguished by their
vegetation pattern, which is ultimately determined by
abiotic factors, namely
• Precipitation
Climate
• Temperature
• Other important influences on these climatic factors
• Altitude (elevation)
• Latitude
Fig. 18.27
•
An example of the effect of altitude on vegetation patterns in Sonora
Desert of southwestern N. America.
•
Air temperature decreases with increasing elevation.
ECOSYSTEM PROCESSES
•
Two major processes sustain all ecosystems
• Energy flow: passage of energy through the components of the ecosystem
• Chemical cycling: use & reuse of chemical elements, e.g. carbon & nitrogen,
within the ecosystem
• A simple terrarium is a microcosm that exemplifies these two ecosystem
processes
• Energy flows through
& out of ecosystems
• Chemicals are
recycled within &
between ecosystems.
ENERGY FLOW IN ECOSYSTEMS
•
All organisms require energy for
• Growth
• Maintenance
• Reproduction
• Movement (in many)
• What actually powers cellular work?
•
Where does this energy ultimately come from?
•
What other details do you need to answer these questions
adequately?
•
http://earthobservatory.nasa.gov/Features/WorldOfChange/biosphe
re.php …
PRIMARY PRODUCTION
•
Each day, Earth receives ca. 1019 kcal of solar energy (ca. 100 x 106 atomic bombs)
• Most absorbed, scattered, or reflected by atmosphere or Earth’s surface
• Ca. 1% converted to chemical energy by photosynthesis
•
Biomass: mass of living organic material in an ecosystem
•
The rate at which an ecosystem’s producers use solar energy to fix inorganic CO2 into
chemical energy that eventually goes into biomass is primary production.
• Yields ca. 165 billion tons of biomass/year
• Ecosystems vary considerably in their primary production.
Primary production: amount of biomass produced by producers over given time in
various ecosystems (blue – aquatic; green – terrestrial). Note that algal beds/coral
reefs are the most productive ecosystems on Earth.
BASIS FOR ECOLOGICAL PYRAMIDS
•
When energy flows as organic matter through the trophic levels of an ecosystem,
most of it is not transferred to every link in a food chain.
• E.g. caterpillar: Of the total amount of energy consumed by this primary
consumer, only ca. 15% will be stored as biomass, thus available to the next link in
the food chain (i.e., a secondary consumer)
PYRAMID OF PRODUCTION
•
Depicts the cumulative loss of energy with each transfer in a food chain
• Each tier represents all organisms in one trophic level
• Width of ea. tier indicates how much of the chemical energy of tier below is
actually incorporated into biomass of that trophic level
• Producers convert only ca. 1% of solar energy, otherwise ca. 10% (actual, 5-20%)
of energy available transferred as biomass in next trophic level (net energy loss of
80-95%)
• Key implications of this
stepwise decline of energy as
go up trophic levels
– Top-level consumers
require more geographic
area
– Less biomass can be
sustained at higher
trophic levels
– Most food chains are
limited to 3-5 levels
APPLICATION TO HUMAN CONSUMERS
•
Humans are generally omnivores, so feed in different trophic levels
• When we eat plant matter – primary consumers
• When we eat primary consumers, e.g. beef, chicken – secondary consumers
• When we predatory fish, e.g. tuna, trout, salmon – tertiary consumers
• Eating at any level higher than primary consumer is more “expensive”
economically and energetically/environmentally
BIOGEOCHEMICAL CYCLES
• We model Earth as a set of interacting “spheres” (biosphere,
atmosphere, hydrosphere, lithosphere) which are open systems in
which energy & mass are constantly flowing & cycling
• The transport & transformation of substances through Earth’s
systems are collectively known as biogeochemical cycles, which
include
•
•
•
•
•
•
Hydrologic (water) cycle
Nitrogen cycle
Oxygen cycle
Carbon cycle
Phosphorus cycle
Except for the hydrologic cycle, biogeochemical cycles follow a
general scheme…
• Abiotic reservoir: where the chemical
accumulates or is available outside of
living organisms, e.g. atmospheric CO2
for carbon
• Generalized steps:
• 1. Producers incorporate chemicals
from abiotic reservoir into organic
compounds, e.g. CO2 transformed into
sugars or fats.
• 2. Consumers feed on producers,
incorporating some of the chemicals
into their own bodies, e.g. proteins,
carbohydrates, lipids.
• 3. Producers & consumers create
wastes which return some of the
chemicals back into environment.
• 4. Decomposers, e.g. bacteria, fungi,
break down complex organic molecules
in detritus  return back to abiotic
reservoir
HYDROLOGIC (WATER) CYCLE
• How can we redraw this diagram to prevent perpetuation
of the misconceptions?
NITROGEN CYCLE
•
Most abundant gas (78.1%) in atmosphere; major abiotic reservoirs: atmosphere & soil
•
Important component of proteins
(1), (2) Must be “fixed” by soil bacteria living in association with roots of certain plants, e.g.
legumes, clover, alfalfa, peas, to produce ammonium (NH4+)
(3) Some NH4+ taken up & incorporated by plants (4) Nitrifying bacteria convert NH4+ 
nitrate, which is more readily assimilated by plants to make proteins (5)  eaten &
assimilated by herbivores (6) whose waste products & death contribute to release of NH4+
for decomposers (7) & nitrifying bacteria. Under low O2, denitrifying bacteria convert
nitrates  N2(g).
OXYGEN CYCLE
•
The 2nd most abundant gas in Earth’s atmosphere & essential element of most
organic molecules
•
Major abiotic reservoirs: silicate & oxide minerals of Earth’s crust/mantle
•
Main source of atmospheric O2 is photosynthesis
•
O2 removed from atmosphere primarily by respiration & decay
http://en.wikipedia.org/wiki/Oxygen_cycle
CARBON CYCLE
•
Abiotic reservoir: most C stored in geologic deposits – carbonate rock, petroleum,
& coal, formed by burial/compaction of dead organic matter on sea bottoms;
normally released by rock weathering
•
Atmospheric C: ¼ used for photosynthesis  sugars, ¼ absorbed by oceans via
direct air-water exchange  calcifying organisms
•
Sugars consumed via cellular metabolism (all living organisms)  C returned to
atmosphere via respiration
•
Sugars also oxidized and returned
to atmosphere via soil microbes
decomposing dead plants,
animals
•
Burning of wood & fossil fuels is
adding increasing levels of CO2 to
the atmosphere which contributed
to global climate change.
•
In this context, what major “piece
of this cycle is missing?
Where’s the
input???
glob
http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle4.html
CARBON CYCLE AND CLIMATE CHANGE
• http://educypedia.karadimov.info/library/globalcarboncy
cle.swf
• http://www.sciencemuseum.org.uk/educators/classroom
_and_homework_resources/resources/carbon_cycle_cap
er.aspx
A Carbon Cycle Story
• Use each cycle component card in your storyboard.
• Consider using arrows and connecting words to give
“flow” to your story. Explain your story – visually, verbally.
•
•
•
•
•
•
•
•
Photosynthesis
Respiration
Decomposition
Combustion
Release
Die
Eat
Absorption
PHOSPHORUS CYCLE
•
Phosphorus is required for nucleic acids, phospholipids, ATP, & vertebrate bones &
teeth.
•
No atmospheric component
•
Major abiotic reservoir: rock
NUTRIENT POLLUTION
•
Growth of algae & cyanobacteria in aquatic ecosystems limited by
low nutrient levels, esp. phosphorus & nitrogen
•
Nutrient pollution (eutrophication) occurs when human activities
add excess amounts of these chemicals into aquatic ecosystems via
runoff from fertilizers or sewage effluent  “blooms” in
phytoplankton populations
• Eutrophication can be anthropogenic or natural
• Major negative impacts primarily to fish & shellfish
• Oxygen depletion due to increased numbers of algae/bacteria
consuming oxygen (primarily at night)
• Some algae (dinoflagellates) are toxic  harmful algal blooms
(HABs)
http://maps.grida.no/go/graphic/increasing-frequency-and-area-of-harmful-algal-blooms-habs-in-the-east-china-sea
THE DEAD ZONE
•
E.g. Nitrogen runoff carried by rivers from Midwestern farm fields has been linked
to an annual summer dead zone in Gulf of Mexico
• Covers ca. 5800 mi2
• Bloom in phytoplankton  die  lots of food for bacteria which deplete O2
A dead zone the size of the state of New
Jersey lies in the Gulf of Mexico near the
mouth of the Mississippi River. Here water
from the Mississippi, laden with sediments,
organic material, nutrients, & pesticides,
enters the Gulf of Mexico (Photo: EPA/N.
Rabalais, Louisiana Universities Marine
Consortium)
Red & orange indicate hi levels of phytoplankton.