Transcript 12_CommEcosys - life.illinois.edu

Announcements
September 25, 2006
One exam down, two to go…
(unless you need to take the final).
Should have results in this week.
Communities and Ecosystems
Lecture Objectives:
1. Differentiate between a community and an
ecosystem
2. Learn to classify organisms based on their
position in the food chain/food web
Ecosystem
Community
Population
Individual
• Community — Assemblage of all interacting
populations of organisms in an area.
• Ecosystem — System of all interacting
organisms, including their non-living
surroundings.
– biotic and abiotic
Can classify organisms by how they interact
with one another
Predator versus prey
Host versus parasite
But can also classify organisms by how they
obtain nutrients
Trophic Pyramid
Atom — Fundamental unit of matter.
92 kinds of atoms (elements) in nature (plus several
others that have been synthesized)
The elements that we care most about are:
Carbon - C
Nitrogen - N
Phosphorus - P
Oxygen - O
Hydrogen - H
Molecules — Atoms bonded together into stable
units.
Water molecule: H2O
Roles of Organisms in the trophic pyramid
Producers — Organisms able to use sources of
energy to make complex organic molecules from
simple inorganic molecules in the environment.
Organic – biological—
contains multiple carbon
atoms (e.g., sugars)
Inorganic – non biological
Photosynthesis:
Process used by plants to convert inorganic material
into organic material using light.
Carbon Dioxide + Water (in the presence of
sunlight) produces Glucose + Oxygen.
sunlight
6CO2 + 6H2O
Carbon dioxide,
inorganic form of carbon
C6H12O6 + 6O2
Glucose,
organic form of
carbon
Photosynthesis
happens on
land…
…and in lakes and
oceans
• Consumers — Consume organic matter to
provide themselves with energy and
organic matter necessary for growth and
survival.
– Primary Consumers
• Herbivores (eat plants)
– Secondary Consumers
• Carnivores (eat other animals)
• Omnivores (eat plants and other animals)
Roles of Organisms
• Decomposers
– Digest organic molecules from dead organisms
into simpler organic compounds, and absorb the
nutrients. (Bacteria and fungi)
• Use non-living organic matter as source of energy.
*without
decomposers,
dead things
would pile up
Energy Flow
Each step in the
flow of energy
through the food
chain known as
a trophic level.
Energy Flow
As energy moves from one trophic level to the
next, most of the useful energy (90%) is lost
as heat.
2nd Law of Thermodynamics (remember
what a law is?)
When matter is converted from one
form to another, energy is lost
Food Chains and Food Webs
• Food Chain
— Passage
of energy
from one
trophic level
to the next
due to one
organism
consuming
another.
Not very realistic…what about all those other
interactions we talked about?
Food Web —
Series of multiple
food chains.
Energy is not the only thing moving up the food chain
Bioaccumulation - an accumulation of a contaminant
in an organism at a higher trophic level
PCBs – Polychlorinated biphenyls
Chlorodanes
methyl - mercury
PCBs
A group of more than 200 man-made chemicals that were used as
insulating fluid for electrical equipment like capacitors and
transformers.
More than 1 billion pounds of PCBs were manufactured in the United
States.
Because of the health effects associated with exposure, commercial
production of PCBs ended in 1977.
In 1979, the U.S. Environmental Protection Agency (USEPA) banned
all use of PCBs; however, PCB removal or replacement is not required
for equipment that already contained these chemicals.
PCBs accumulate in the fat of people and animals.
Fish Consumption advisories
PCB Concentration (parts per million)
below 0.05
0.05 - 0.2
0.2 - 1.0
1.0 - 2.0
above 2.0
Advisory Category
unrestricted
1 meal per week
1 meal per month
6 meals per year
no consumption
www.idph.state.il.us/envhealth/fishadv/fishadvisory03.htm
Chinook Salmon
Coho Salmon
Rainbow Trout
Brown Trout
Less than 30"
1 meal/month
All Sizes
1 meal/month
Less than 17"
1 meal/week
Less than 22"
1 meal/month
Larger than 17"
1 meal/month
Larger than 22”
6 meals/year
Larger than 30”
6 meals/year
Channel Catfish
All Sizes
Do Not Eat
Lake Trout
Less than 23"
1 meal/month
23" to 27”
6 meals/year
Larger than 27”
Do Not Eat
Yellow Perch
All Sizes
1 meal/week
Carp
All Sizes
Do Not Eat
Nutrient Cycles in Ecosystems
• Organisms are composed of molecules
and atoms that are cycled between living
and non-living portions of an ecosystem.
• Biogeochemical Cycles
– Carbon
– Nitrogen
– Phosphorus
Nutrient Cycles
• Consuming prey, excretion, and decomposition
all contribute to cycling of major nutrients
• Three of the most important elements:
– Carbon, Nitrogen, Phosphorous
• Cycles describe how inorganic forms are
converted to organic forms, used by organisms,
and released as inorganic forms
Why care about Carbon?
Life as we know it is
Carbon based
Most of our energy comes
from carbon-based
compounds
CO2 is a greenhouse gas
CO2 is a greenhouse gas one that absorbs infrared
radiation and warms surface air
Carbon Cycle
• Carbon and Oxygen combine to form
Carbon Dioxide (CO2).
• Plants use Carbon Dioxide during
photosynthesis to produce sugars.
• Plants use sugars for plant growth.
Carbon Cycle
• Herbivores eat plants, and incorporate
molecules into their structure.
• Respiration breaks down sugars releasing
CO2 and water back into the atmosphere.
Why care about Nitrogen?
Nitrogen is also
important in
biomolecules
Amino acid
Nitric Acid (HNO3) is a component of acid rain
Nitrogen is often limiting for plants, esp. crops
Nitrogen cycle
• Nitrogen often a limiting resource for
plants
– Farmers try to increase nitrogen
availability
– Can use fertilizer
• Runoff then can pollute aquatic systems
– Or rotate crops
• Soy has symbiotic nitrogen-fixing bacteria
Why care about P
Phosphorus is vital to life (ATP, phospholipid
membranes, etc.)
Phosphorus is often a limiting nutrient for algae
Phosphorus pollution has been responsible for
algal blooms in many lakes
Phosphorous cycle
•
•
•
•
Main source is weathering of rocks
Dissolved in water
Plant uptake, animals consume plants
Decomposers use dead organic matter,
waste products
• Some waste products become dissolved in
water and lost as deposits
Human Impact on Nutrient Cycles
• Human activities have caused significant
changes in biogeochemical cycles:
– Burning Fossil Fuels.
– Converting forests to agricultural land.
• Fertilizer carried into aquatic ecosystems.
• Increase aquatic plant growth rate.
–Lowered oxygen concentrations.
Points to Know
1.
2.
3.
4.
5.
6.
The difference between populations, communities, and
ecosystems
Characteristics of each trophic level – how does it get its
energy/nutrients? What moves behind different levels?
What is photosynthesis and why does it matter for
organisms besides plants?
How does biomass change as one moves up or down the
food chain? Why?
Major features of the carbon, nitrogen, and phosphorus
cycles
How can humans change nutrient cycles?