Transcript PPT chp 6_edited

Chapter 6:
The Biogeochemical Cycles
Planets near Earth

Inner planets formed by gathering
together of particle by gravitational force
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Would expect Earth, Mars, Mercury and Venus to
have a similar atmosphere - they do not
Planets Near
Earth
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Earth’s unique
atmosphere indicates
that it contains life
Earth has
“environmental
fitness”
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Life evolved in an
environment conducive
for that to occur
Life altered the
environment at a
global level
Rise of Oxygen
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Before 2.3 billion
years ago, the
atmosphere was low
in oxygen
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Evidence - grains of
pyrite in sedimentary
rock (banded iron
formations in figure on
right)
Oceans were filled with
dissolved (unoxidized)
iron
Rise of Oxygen
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Early photosynthesizers included
stromatolites (3.4 billion years old)
Early organisms on earth
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Prokaryotes
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Simple cell structure
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Get energy from fermentation
Low energy yield to organism
 Waste products of
carbon dioxide and
alcohol
Live singly or on end-toend chains
Cannot form 3-D
structures
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Lacked organelles and a nucleus (too much energy to
maintain)
Evolution of Biosphere
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After presence of eukaryotes and
oxygenated atmosphere
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Biosphere started to change drastically
Plants, Animals and Fungi Evolved 700–500
million years ago
They, in turn, continued to alter the
biogeochemical cycles on earth
Life and Global Chemical Cycles
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Micronutrients
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Elements required in small amounts by all life
or moderate amounts by some forms of life
Macronutrients
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24 elements required by all organisms
Include the “Big Six”, which are the building
blocks of life
Carbon, oxygen, hydrogen, nitrogen, phosphorus,
sulfur
 Each plays a special role in organisms
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Biogeochemical Cycles
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A biogeochemical cycle is the complete
path a chemical takes through the four
major components of Earth’s system
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Atmosphere
Hydrosphere
Lithosphere
Biosphere
The Geologic Cycle
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Rocks and Soil
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Continually created, maintained, changed and
destroyed over the last 4.6 billion years
Altered due to physical, chemical, and
biological processes
Geologic cycle - group of cycles
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Tectonic,
Hydrologic
Rock
Biogeochemical
11.1 Pangaea
• Alfred Wegener was a
German climatologist
and arctic explorer who
suggested the concept
of continental drift.
• Continental drift is the
idea that the continents
move around on Earth’s
surface.
11.1 Movement of continents
• Wegener thought that
the continents we
know today had once
been part of an earlier
supercontinent.
• He called this great
landmass Pangaea.
11.1 Movement of continents
• The surface of Earth is
broken into many
pieces like a giant
jigsaw puzzle.
• Plate tectonics
describes how these
pieces move on
Earth’s surface.
11.2 Sea Floor Spreading
• American geophysicist Harry Hess helped
develop the theory of plate tectonics.
• While a Navy officer, Hess helped map the ocean
floor.
11.2 What drives
lithospheric plates?
• Convection cells in
Earth’s lower mantle
drive the lithospheric
plates on the surface.
• Heated lower mantle
material rises toward
Earth’s surface.
11.3 Plate boundaries
•
•
•
Imagine a single plate, moving in one direction
on Earth’s surface.
One edge of the plate—the divergent
boundary—moves away from things.
The opposite edge—called the leading edge or
convergent boundary bumps into anything in
the way.
11.2 Hot spots and island chains
• After the island forms,
the movement of the
plate carries it away
from the mantle plume.
• Scientists determine the
direction and speed of
plate movement by
measuring these island
chains.
11.2 Hot spots and island chains
• A single hot rising
plume, called a mantle
plume, can cause a
volcanic eruption in the
plate above it.
• If the eruption is strong
and lasts long enough,
the volcanic eruption
may form an island on
the plate.
11.3 Mountains and convergent
boundaries
•
Mountain ranges are formed when
continents collide.
11.3 Transform fault boundaries
•
•
A good clue for
locating transform
faults is offsetting.
When seen from
above, the feature
will appear to make
a zig-zag.
The Hydrologic Cycle
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The transfer of water from oceans to the
atmosphere to the land and back to the
oceans
Driven by solar energy
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Evaporation of water from oceans
Precipitation of water on land
Transpiration of water by plants
Evaporation of water from land
Runoff from streams, rivers and subsurface
groundwater
The Hydrologic Cycle
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Total water on earth = 1.3 billion km3
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97% in oceans
2% in glaciers and ice caps
0.001% in atmosphere
The rest in fresh water on land
The Hydrologic Cycle
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At the regional and local level, the
fundamental unit of the landscape is the
drainage basin
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The area that contributes surface runoff to a
particular stream or river
Vary greatly in size
Usually named for main stream or river
The Rock Cycle
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Consists of numerous processes that
produce rocks and soils
Depends of the tectonic cycle for energy
and the hydrologic cycle for water
Rocks classified as
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Igneous
Sedimentary
Metamorphic
The Phosphorus Cycle
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P one of the “big six” required for life
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Often a limiting factor for plant and algal
growth
Does not have a gaseous phase
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Rate of transfer slow
The Phosphorus Cycle
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Enters biota through
uptake as phosphate
by plants, algae and
some bacteria
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Returns to soil when
plants die or is lost to
oceans via runoff
Returned to land via
ocean feeding birds
(guano)
Guano deposits major
source of P for
fertilizers
Nutrient Cycles
Cycling maintains homeostasis
(balance) in the environment.
•3 cycles to investigate:
1. Water cycle
2. Carbon cycle
3. Nitrogen cycle
Water cycle•Evaporation, transpiration,
condensation, precipitation
Water cycle-
Carbon cycle•Photosynthesis and respiration
cycle carbon and oxygen through
the environment.
Carbon cycle-
The Carbon-Silicate Cycle
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The cycling of carbon intimately involved with
the cycling of silicon
Weak carbonic acid falls as rain and weathers
silicate rich rocks
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Releases Ca2+ and HCO3Transferred to oceans and used by marine animals to
construct shells
Shells deposited on sea floor become part of sed rock
layer and return to surface in subduction zones
The Carbon-Silicate Cycle
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Affects the levels of CO2 and O2 in the
atmosphere
Nitrogen cycleAtmospheric nitrogen (N2) makes up nearly
78%-80% of air.
Organisms can not use it in that form.
Lightning and bacteria convert nitrogen into
usable forms.
Nitrogen cycleOnly in certain bacteria and industrial
technologies can fix nitrogen.
Nitrogen fixation-convert atmospheric
nitrogen (N2) into ammonium (NH4+)
which can be used to make organic
compounds like amino acids.
N2
NH4+
Nitrogen cycleNitrogen-fixing
bacteria:
Some live in a
symbiotic
relationship with
plants of the legume
family (e.g.,
soybeans, clover,
peanuts).
Nitrogen cycle•Some nitrogen-fixing bacteria live
free in the soil.
•Nitrogen-fixing cyanobacteria are
essential to maintaining the fertility
of semi-aquatic environments like rice
paddies.
Lightning
Atmospheric
nitrogen
Nitrogen Cycle
Denitrification
by bacteria
Animals
Nitrogen
fixing bacteria
Decomposers
Ammonium
Nitrification
by bacteria
Plants
Nitrites
Nitrates