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Chapter 3
Ecosystems: What Are They &
How Do They Work?
Ecology
• def. Ecology is the study of how organisms
interact with one another and with their
nonliving environment.
• Ecology is the study of the interconnections of nature.
Organisms
• def. Organisms are any form of life, with the cell
being the basic unit of an organism and are
classified into species.
• Approximately 1,412,000 KNOWN species
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Insects ~ 751,000
Prokaryotes ~ 4,800
Protists ~ 57,700
Fungi ~ 69,000
Plants ~ 248,400
Other Animals ~ 281,000
Species
• Groups of organisms with like
characteristics
• Asexual reproduction – one cell that
replicates from the original cell
• Sexual reproduction – combining sex cells
(gametes) from 2 parent cells and have
characteristic traits of both parents
Eukaryotic vs Prokaryotic
•Eukaryotic cells
–Surrounded by a membrane
–Distinct nucleus – DNA is contained
–Several other internal parts called organelles
•Prokaryotic cells
–No distinct nucleus – DNA is not localized
Eukaryotic Cell
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Eukaryotic cell has 5 basic structures:
Nucleus
Organelle’s that lie outside the nucleus
Cytosol, a protein-rich, jelly-like fluid in which
the organelles are immersed in
• Cytoskeleton, an internal scaffolding consisting of
3 types of protein fibers
• Plasma membrane, the outer lining of the cell
Diagram Of Eukaryotic
by Daniel Chiras
•
Animal vs Plant Cells
• Go to the following website for diagrams:
http://sun.menloschool.org/~cweaver/cells/
• http://sun.menloschool.org/~cweaver/cells/
Prokaryotic Cell
• Prokaryotic cells are bacteria and have no
nucleus.
Storage
(inclusion)
granule
Golgi apparatus
Vacuoles
Ribosomes
Mitochondrion
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Endoplasmic
reticulum
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Plasma
membrane
Nucleus
Nuclear
membrane
membrane
Cell wall
Nucleus
Nucleolus
Bud scar
A representation of a yeast cell - Eukaryotic Cell
Chromosome
(nucleoid)
Cytoplasm
Basal body
Hook
Flagellum
Filament
Storage
granules
Ribosomes
Cytoplasmic
membrane
Cell envelope
Cell wall
A representation of a bacterial cell - Prokaryotic Cell
Population
• A group of interacting organisms of the
same species that occupy a specific space at
the same time.
– Genetic diversity – same species with different
genetic differences
– Habitat – the place where the population lives
– Community – population of different species
that occupy the same place
Ecosystems
• def. Ecosystem is a community of different
species interacting with each other and their
non-living environment.
• ex.
Lake Champlain
•
Chazy River
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The Adirondack Mountains
•
New York City
First of Four Spheres of Earth
• Biosphere refers to:
– All of the living parts of the separate
ecosystems of the Earth acting as one unit
– The parts that are organic and self-replicating
– Includes all of the plants and animals of the
Earth
– Includes both living and dead organisms
Other Spheres of Earth
• Lithosphere – Above the core and mantle and
contains the top of the upper mantle and the crust
(which includes all of the soil & rocks)
• Hydrosphere – All of the liquid water on the Earth
and in the ground (groundwater), solid water in
the polar ice, permafrost, & sea ice, and water
vapor in the atmosphere
• Atmosphere – Gaseous envelope that surrounds
the Earth as is comprised of multiple layers
Atmosphere
• Troposphere (layer closest to the Earth and
referred to as the boundary layer) contains most of
the Earth’s air (78% N2 & 21% O2) and is where
all weather is generated.
• Stratosphere contains the ozone layer which
absorbs ultraviolet radiation from the sun.
• Mesosphere is the coldest layer in the atmosphere.
• Thermosphere which includes the:
– Ionosphere contains ions and is responsible for the
absorption of high energy photons from the sun.
– Exosphere is the outermost layer and merges with outer
space.
Our Goal
• The goal of ecology is to develop an
understanding of interactions between the four
spheres and the role that water, air, soil and
organisms plays in our planets life support.
• The goal of environmental science is to use
ecology, chemistry, and all of the sciences to
properly understand the affects on the 4 spheres of
our Earth that we have and to use the sciences to
sustain our planet.
What Sustains Life on Earth?
• One-way flow of high-quality energy (see fig 3-6
on page 39) – the sun’s energy lights and heats the
Earth through various cycles, and allows plants to
undergo photosynthesis
• Cycling of matter – all chemicals, ions,
compounds, nutrients are needed for the survival
of organisms on Earth and must be recycled
through ecosystems
• Gravity – holds the atmosphere close to Earth and
allows downward movement of the matter cycle.
Solar Energy
• See Fig. 3-7 on page 40 and the graphics from An
Inconvenient Truth
• Most of the energy that reaches the Earth from the
sun (1-billionth) is infrared radiation, visible light,
and some ultraviolet with much of the solar energy
reflected back out or absorbed by chemicals in the
atmosphere
• It functions to warm the Earth’s crust and
troposphere, evaporate and cycle water, and
generate winds.
• Green plants uptake solar energy to make food
through the process of photosynthesis.
Photosynthesis
• For the simple version, go to:
http://earthguide.ucsd.edu/earthguide/diagrams/ph
otosynthesis/photosynthesis.html
• For the detailed version, go to:
http://www.cix.co.uk/~argus/Dreambio/photosynth
esis/photosynthesis%201.htm
• For this course we will use the simple version:
•
6CO2 + 6H2O + solar energy  C6H12O6 + 6O2
Solar Energy (continued)
• 34% of solar radiation is reflected back to space
by the atmosphere.
• Most of the UV is absorbed by the stratosphere in
the ozone layer.
• Unreflected solar radiation is generally degraded
into infrared radiation as heat (about 66%)
• Greenhouse gases retain the heat and prevents the
heat from escaping back into space and causes the
Earth to warm (global warming).
Major Biomes
•
Sub-classifications of the biosphere into
separate land units (terrestrial portions)
characterized by specific climate and lifeforms (vegetation) that has adapted to it
– Forests
– Grasslands
– Deserts
Aquatic Life Zones
• Marine and freshwater portions of the biosphere
• Freshwater life zones – examples:
– Lakes
– Streams
• Ocean & marine life zones – examples:
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Estuaries
Coastlines
Coral reefs
Deep ocean
Abiotic vs Biotic
• Abiotic – chemical & physical factors present in
an ecosystem, examples:
– Water
– Air
– Chemicals
• Biotic – biological component– contains all living
organisms, examples:
– Plants
– Animals
– Microbes
Law of Tolerance
The existence, abundance, and distribution of a
species in an ecosystem are determined by
whether the levels of one or more physical or
chemical factors fall within the range tolerated by
that species.
Example: Acid deposition from the mid-west has caused
many lakes in the Adirondacks to become too acidic to
support many different fresh water species because the
acidity fell outside the range of tolerance for those
species.
Classification of Organisms
• Producers (autotrophs) – make their own
food & are the source of all food in the
ecosystem, ex. green plants &
phytoplankton
• Consumers (heterotrophs) – obtain their
energy by feeding off of other organisms
– Decomposers (fungi & bacteria) – organisms
that recycle dead organic material (detritus)
back into the ecosystem
Types of Feeders
• Omnivores – Eat both plants and animals,
– example: humans
• Herbivores – Eat only plants,
– example cows
• Detritivores – Eat dead organic matter
called detritus (debris),
– example: carpenter ant
Aerobic vs Anaerobic Respiration
• Aerobic respiration– uses oxygen to convert
organic nutrients back to carbon dioxide &
water (reverse of photosynthesis)
• C6H12O6 + 6O2  6CO2 + 6H2O + energy
• Anaerobic respiration – occurs in the
absence of oxygen
Biodiversity
• def – Biodiversity is the different forms of life that can
survive the variety of conditions on Earth
• Species Diversity – variety of species that inhabit our
planet
• Genetic Diversity – variety of genes within a species
• Ecological Diversity – variety of biomes and aquatic zones
on Earth
• Functional Diversity – biological and chemical processes
that are needed for the survival of species
• See fig 3-14 on page 45
Biodiversity
www.bhutanabbot.com/aboutbhutan.php
Food Web vs Food Chain
• Food chain – each organism within the
chain is a food source for the next (see fig
3-16 on page 47)
– Trophic – feeding level
• Food web – a series of interconnected for
chains (see fig 3-17 on page 48)
Productivity in an Ecosystem
• Gross Primary Productivity (GPP) = Rate at
which an ecosystem’s producer converts
solar energy to chemical energy as biomass
• Net Primary Productivity (NPP) = Rate at
which producers use photosynthesis to store
energy minus the rate at which they use it
for aerobic respiration
• NPP = GPP - Eused
Importance of Soil
• See figs 3-22 & 3-23 on pages 52 & 53
• Provides most of the nutrients needed for plant
growth and helps purify water via infiltration
• Develops over a long time containing several
layers (horizons) of a variety of materials
– 0 horizon – top layer (mostly undecomposed or
partially decomposed organic matter)
– A horizon – top soil (partially decomposed organic
matter (humus) & inorganic mineral particles
– B horizon – subsoil (combination of soil and rocks)
– C horizon – parent material (mostly rock)
0 & A Horizons
• Most well-developed soils
– The darker the color, the richer the soil is in nutrients
• Supports most of the life in an ecosystem
(bacteria, fungus, worms, and other decomposers
as well as the roots of most plants)
• Holds water well but does lose water through
percolation to lower horizons
– Leaching is the process where nutrients and pollutants
are picked up by the water as it percolates through the
horizons and is deposited in the groundwater
Cycling of Crucial Elements
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Water Cycle
Carbon Cycle
Phosphorous Cycle
Nitrogen Cycle
Oxygen Cycle
Water (Hydrologic) Cycle
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Collects, purifies and distributes the Earth’s fixed water
supply (See fig. 3-24 on page 54)
Evaporation – converts liquid water into vapor
– Transpiration – evaporation from leaves on plants
Condensation- converts water vapor back to liquid
Precipitation – rain, sleet, hail & snow are released from
clouds
Infiltration and percolation – water moves into & through
the soil
Runoff – water moves over the surface and back to the
streams, lakes & oceans
Carbon Cycle
• See fig. 3-25 on page 56-57
• Based on CO2 (carbon dioxide) in the troposphere
and is the key component of heat regulation and
carbonates (CO3-2) in the ocean
• Terrestrial producers remove CO2 from the
atmosphere and aquatic producers remove it from
the water and convert it into simple carbohydrates.
• Decomposition of byproducts (aerobic respiration)
releases CO2 back into the environment for reuse.
• Combustion of fossil fuels such as coal & oil
Human Affect on Carbon Cycle
• Two ways that humans increase CO2 to the
atmosphere are:
– Clear cutting trees and plants that absorb CO2
– Burning fossil fuels and wood produces large amounts
of CO2
• Increased amounts of CO2 could enhance the
greenhouse effect and cause global warming
• Global warming could disrupt and alter the way
our environmental processes take place
Nitrogen Cycle
• See fig. 3-27 on page 58
• Nitrogen fixation – bacteria convert nitrogen (N2)
to ammonia (NH3) which can be used by plants for
growth
• Nitrification – special aerobic bacteria convert
nitrogen (N2) to nitrogen monoxide (NO)
• Both processes add nutrients to plants, that are
eaten by animals, and then either excreted or
discarded
Human Affect on Nitrogen Cycle
• Five ways that humans have had effect on the
nitrogen cycle
– Burning of fossil fuels create NOx which leads to acid
rain
– Anaerobic bacterial action on livestock waste and
commercial fertilizers
– Harvesting of nitrogen rich crops, irrigation of crop
land & burning/clearing grasslands
– Agricultural runoff and discharge of sewage
– Destruction of wetland and forests in large quantities
Phosphorus Cycle
• See fig. 3-29 on page 59
• Phosphates (PO4-3) are the limiting factor
for plant growth
• Much of the phosphorus flows from land to
sea
• Addition of phosphates in aquatic systems
greatly increases their biological activity
Human Affect on Phosphorus Cycle
• Three ways that humans increase phosphorus to
the environment are:
– Commercial production of fertilizers & detergents
– Burning & cutting of forests allow phosphates to be
washed away by runoff
– Runoff and discharge of animal waste, fertilizers from
cropland & municipal sewage
• Human activities have increased the amounts of
phosphates about 3.7 fold
Sulfur Cycle
• See fig. 3-30 on page 60
• Released from the Earth by volcanoes and from
organic material in wetlands as hydrogen sulfide
(H2S)
• Marine algae produce large amounts of dimethyl
sulfide (DMS) which can effect cloud cover and
climate
• Sulfur dioxide (SO2) which comes from volcanoes
and the burning of coal enters the atmosphere and
converts to SOx which leads to acid rain
Human Affect on Sulfur Cycle
• Three ways which humans have altered the
environment with sulfur
– Sulfur containing coal & oil is burned, it
produces about 2/3 the SO2 in the atmosphere
– Refining of sulfur containing petroleum to
make gasoline and heating oil
– Smelting of metals produces large amounts of
SO2 into the environment
System Analysis
• System measurement
– Define objectives
– Identify & inventory variables
– Obtain baseline data
• Data analysis
– Make statistical analysis
– Determine significant interactions
• System modeling
– construct mathematical models
• System simulation
– Run the model with different variables
• System optimization
– Evaluate ways to achieve objectives
Sustainability
• Ecosystems have sustained themselves for
billions of years on Earth by using solar
energy and recycling nutrients. If we take
our lessons from Earth we ca be come more
sustainable by:
– Use renewable energy as our energy source
– Recycle the chemical nutrients needed for
survival, growth & reproduction