Transcript Ecosystems - Diablo Valley College

Chapter 54
Ecosystems
Overview
Food Chains and Food Webs
Productivity
Ecological Pyramids
Biomagnification
Nutrient Cycles
Global Warming
Ecosystems -The Community along with:
Nutrient Cycling
Energy Flow
Energy Transfer in Ecosystems
Food / Energy Pyramid
Primary Consumers eat producers, incorporating
the energy into the next level.
Only 10 % of energy consumed moves to next
level


Animals loose 90% of the energy at each level
Why are Big Fierce Animals so Rare??
Consumers are Heterotrophs
Limited by Thermodynamcis
Simple
Food Chains
Trophic Levels
Both
Marine and
Terrestrial
Productivity
What is it?
Season effects
varies by ecosystem
Productivity –Amount of food in
an ecosystem
Primary productivity is growth of producers
(Biomass) the baseline for the entire
ecosystem.
Gross productivity is the total amount of
food produced or ingested at that trophic
level.
Net productivity is amount available to
next trophic level, after respiration
Measured by dry weight or calories
Productivity rates:
Kelp beds have highest productivity
Tropical rainforest highest per sq. meter
on land, but only covers 3.3 % of globe
Open ocean, one of the lowest, but
because it covers 65.0 % it equals
rainforest
Marsh lands nearly equal tropical
rainforest productivity
Summary of satellite data on global
primary productivity from 1997 to August
2000
Winter
NORTH
AMERICA
SPAIN
ATLANTIC OCEAN
AFRICA
Spring
Ocean Currents
Upwelling
Wind from the north starts surface ocean
water moving
c. Deep, cold water
moves up to replace
water moving west
Earth's rotational force deflects moving water westward
Fig. 55-7
EXPERIMENT
B
C
D
E
F
G
Shinnecock
Bay
Moriches Bay
Atlantic Ocean
A
Phytoplankton density
(millions of cells per mL)
RESULTS
30
Ammonium
enriched
24
Phosphate
enriched
18
Unenriched
control
12
6
0
A
B
C
D
E
Collection site
F
G
Table 55-1
Food Webs
Energy transfer follows trophic levels
Many animals eat at several trophic levels
Omnivores: like most of us


At salad bar you’re a herbivore
Eating a burger makes you a carnivore
marsh hawk
Higher
Trophic
Levels
Sampling of connections in a
Tall grass prairie food web
crow
upland
sandpiper
garter snake
frog
weasel
spider
Second
Trophic
Level
sparrow
earthworms, insects
First
Trophic
Level
badger coyote
prairie vole
grasses, composites
pocket gopher
ground squirrel
Energy Transfer in Ecosystems
Food / Energy Pyramid
Only 10 % of energy consumed moves to
next level
Why are Big Fierce Animals so Rare??
Consumers are Heterotrophs
Limited by Thermodynamics
Laws of Thermodynamics
Energy = ability to do work
1st Law = Total amount of energy is a
constant
2nd Law = Some energy is lost in every
transfer, not 100% efficient



Most energy lost as heat
Autotrophs about 1% efficient (light–sugar)
Heterotrophs about 10% efficient
Energy Pyramid
Pyramid of Numbers
Nutrients Cycle
Elements change form, but are not lost

No more carbon now than when the dinosaurs
lived !!
May be trapped in bio-inactive forms

Ice, fossil fuels
Held together in chemical bonds


Breaking bonds – releases energy
Uses energy to form bonds
Cycles:
Nutrient cycles to learn:
Water
Carbon
Nitrogen
Carbon Cycle
Large reservoirs in rocks (99%), fossil
fuels
Associated with Greenhouse Effect



Build up of CO2 , CH4 etc. in atmosphere
Raise sea levels – flooding islands, coasts
More severe weather ??
Food chain moves through Carbon cycle
Nitrogen Cycle
Largest pool is in atmosphere (80%) a generally
bio-inactive form



Nitrogen fixing bacteria capture it from air
Many native plants have nitrogen fixing root nodules
After water the most growth-limiting nutrient
Nitrogen important for Autotrophs to make
protein
Protein breakdown releases it back to
environment in urine
Nitrogen Cycle
Always need to replenish agriculture fields
with fertilizer.
Denitrifying bacteria release it back to
atmosphere
Tightly cycled in Ecosystems
Needed to make amino acids
Nitrogen Metabolism
In amino acids, nucleotides
Nitrogen fixing bacteria (N2 ->NH3)

In soil, and some plant root nodules
Nitrifying bacteria convert NH3 -> NO2

In soil, or biotower in treatment plant
Denitrifying bacteria N02 -(Nitrite) or
N03 (Nitrate) to atmospheric N2

In soil, counter-act fertilizers
Forests and Nitrogen Cycle
Most of nitrogen tied up in a tree’s
Biomass
Soils tend to be nutrient poor
Often highest in later stages of succession
Burning trees releases nutrients



Soil fertility only lasts a few seasons
Nitrogen is leached out with rains
Classic problem with Slash and Burn
Fig. 31.8
Hubbard
Brook
Loss of Nitrate from a forest
after clear cutting
1620
1850
1850 (pocket only)
1990
Remaining virgin forest
Extent of deforestation in the United States
Bioaccumulation &
Biomagnification
Bioaccumulation Build-up of substance within
body


Lead in humans
Calcium from milk to already strong bones
Biomagnification build up of of substance along
food chain


DDT and birds
Rachel Carlson’s Silent Spring
Build up
of DDT
along
Food Chain
Bioaccumulation
Biomagnification
Fig. 34.1
Peregrine falcon
DDT Residues (ppm wet weight of whole live organism)
Ring-billed gull fledgling (Larus delawarensis)
Herring gull (Larus argentatus)
Osprey (Pandion haliaetus)
Green heron (Butorides virescens)
Atlantic needlefish (Strongylira marina)
Summer flounder (Paralychthys dentatus)
Sheepshead minnow (Cyprinodon variegatus)
Hard clam (Mercenaria mercenaria)
Marsh grass shoots (Spartina patens)
Flying insects (mostly flies)
Mud snail (Nassarius obsoletus)
Shrimps (composite of several samples)
Green alga (Cladophora gracilis)
Plankton (mostly zooplankton)
Water
Data for a Long Island, NY estuary in 1967
75.5
18.5
13.8
3.57
2.07
1.28
0.94
0.42
0.33
0.30
0.26
0.16
0.083
0.040
0.00005
Greenhouse Effect
Gasses trap heat in atmosphere

Carbon dioxide, methane, CFC’s
Anthropogenic use of these gasses is
increasing
Earth’s temperature appears to be
warming

Hard to measure a world temperature
Greenhouse Effect
Sun’s rays penetrate
atmosphere. Enters
as light not as heat.
Hitting the earth,
light changes to
heat.
Surface radiates heat.
Greenhouse gases absorb
some heat and radiate it
back toward Earth.
Increased greenhouse
gases trap more heat
near Earth’s surface.
Correlation in changes in atmospheric CO2 with ice ages and interglacials
Fig. 55-21
14.9
390
14.8
380
14.7
14.6
370
Temperature
14.5
360
14.4
14.3
350
14.2
340
14.1
CO2
330
14.0
13.9
320
13.8
310
13.7
13.6
300
1960
1965
1970
1975
1980 1985
Year
1990
1995
2000
2005
Satellite image of an iceberg roughly the same size as Connecticut
Antarctica 2000
National Snow and Ice
Data Center
Fig. 34.6
Fig. 55-24
Chlorine atom
O2
Chlorine O3
ClO
O2
ClO
Cl2O2
Sunlight
Fig. 55-24
Chlorine atom
O2
Chlorine O3
ClO
O2
ClO
Cl2O2
Sunlight
“Tragedy of the Commons”