Transcript Document 7538362

ENVIRONMENTAL SCIENCE
CHAPTER 3:
Ecosystems: What Are
They and How Do
They Work?
Core Case Study:
Tropical Rainforests Are Disappearing
• Found near the equator
• At one time covered 14% land surface, now
covers only 2%
• ~50% world’s known terrestrial plant and animal
species
• ≥50% destroyed or disturbed by humans
– Cutting trees
– Growing crops
– Grazing cattle
– Building settlements
Core Case Study:
Tropical Rainforests Are Disappearing
• Consequences of disappearing tropical
rainforests
1. Decreased biodiversity as species become
extinct
2. Accelerated global warming: fewer trees to
remove carbon dioxide from the atmosphere
3. Changes regional weather patterns: can lead
to increase in tropical grasslands
Sect. 3.1:What Keeps Us and Other
Organisms Alive?
• Concepts to learn in 3.1:
1. The four major components of the earth’s
life-support system are the atmosphere (air),
the hydrosphere (water), the geosphere (rock,
soil, sediment), and the biosphere (living
things).
2. Life is sustained by the flow of energy from
the sun through the biosphere, the cycling of
nutrients within the biosphere, and gravity.
Earth Has Four Major LifeSupport Components
1. Atmosphere: Thin layer of gases, surrounding
earth’s surface. Consists of:
a. Trophosphere: contains the air we breathe
(look up mixture) & greenhouse gases
b. Stratosphere: contains ozone, which filters
UV rays, allowing for life to exist
2. Hydrosphere: contains all of the water on or
near the earth’s surface
a. Which water source makes up the largest
component?
Earth Has Four Major LifeSupport Components
3. Geosphere: 3 parts:
a. Core (extremely hot, mostly liquid rock)
b. Mantle (mostly rock)
c. Crust (thin outer layer)
4. Biosphere: includes all the parts of the
atmosphere, hydrosphere & geosphere where
life is found.
a. “ecology” focuses on this area
b. It is a very thin layer of the earth &
atmosphere
Three Factors Sustain Life on
Earth
1. One-way flow of high-quality energy
from the sun
2. Cycling of matter or nutrients through
parts of the biosphere
3. Gravity
Solar Energy Reaching the
Earth (one way energy flow)
• Sun’s energy reaches us as
electromagnetic waves, seen as:
1. Visible light
2. UV radiation
3. Heat
• Natural greenhouse effect: What
effect does it have on the earth’s
energy?
Solar Energy Reaching the
Earth (one way energy flow)
• The flow of energy in from the sun will equal
the flow of energy out into the environment /
atmosphere
1. Group discussion:
a. How does this happen?
b. Is this energy recycled?
Sect. 3.2: What Are the Major
Components of an Ecosystem?
• Some organisms produce the
nutrients they need.
• Some get the nutrients they need by
consuming other organism.
• Some recycle nutrients back to
producers by decomposing the
wastes and remains of organisms.
Ecology
• Ecology: How organisms interact with biotic
(living) and abiotic (non-living) environments
• Ecology focuses on levels of matter ranging from
the atomic level to the entire biosphere. 5 levels:
1. Organisms
2. Populations
3. Communities
4. Ecosystems
5. Biosphere
Nonliving Components of
Ecosystems
• Abiotic: non-living components of
ecosystems, which includes:
– Water
– Air
– Nutrients
– Solar energy
– Rocks
– Heat
Living Components of Ecosystems
• Biotic: living components of
ecosystems, including:
– Plants
– Animals
– Microbes
– Dead organisms
– Waste products of dead organisms
– Waste products of living organisms
Trophic Levels
• Trophic Levels: “feeding” levels assigned to
every organism in an ecosystem
1. Producers- called autotrophs
a. Produce food thru photosynthesis
2. Consumers – called heterotrophs
a. Primary consumers – herbivores (eat
plants)
b. Secondary consumers – carnivores that eat
herbivores
– Third-level consumers – carnivores that eat
carnivores
Additional Trophic Levels
• Decomposers:
– Release nutrients from the dead bodies
of plants and animals
• Detrivores:
– Feed on the waste or dead bodies of
organisms
Production and Consumption of
Energy
• Photosynthesis
• Carbon dioxide + water + solar
energy glucose + oxygen
• Aerobic respiration
• Glucose + oxygen  carbon dioxide
+ water + energy
Energy Flow and Nutrient
Recycling
• Ecosystems are sustained through:
1. One-way energy flow from the sun
2. Nutrient recycling
Science Focus: Invisible
Organisms
• Microorganisms/Microbes
– Bacteria
– Protozoa
– Fungi
– Phytoplankton
Science Focus: Invisible
Organisms
• Microbes can cause disease
– Malaria
– Athlete’s foot
• Microbes are also beneficial
– Intestinal flora
– Purify water
– Phytoplankton remove carbon dioxide
from the atmosphere
Sect. 3.3: What Happens to Energy
in an Ecosystem?
• As energy flows through ecosystems
in food chains and webs, the amount
of chemical energy available to
organisms at each succeeding
feeding level decreases.
Energy Flow in Ecosystems
• The chemical energy stored in all organisms flows thru
ecosystems from one trophic level to another
• Food chain
1. Sequence of organisms, each of which serves as a
source of food for the next
2. Includes food production, feeders, and decomposition
• Food web
1. A more complex network of interconnected food chains.
2. Consumers feed on more than one organism
3. Organisms are eaten/decomposed by more than one
organism
Usable Energy by Trophic Level
• Energy flow thru food webs follows the second law
of thermodynamics – energy lost as heat
• Biomass: The dry weight of all organic matter
contained in its organisms
1. Each trophic level has one, but biomass
decreases with increasing trophic level
• Ecological efficiency – of energy transferred thru
food chains is typically 10%.
• See “Pyramid of energy flow”, fig. 3-10 pg 47
1. shows variable energy transfer efficiency
between trophic levels
Ecosystem efficiency in
producing plant matter
• The amount of biomass an ecosystem is
capable of producing is determined by it’s
efficiency in capturing solar energy and
converting it to chemical energy in food.
• Gross Primary Productivity (GPP): rate at
which an ecosystems producers (mostly
plants) convert solar energy into chemical
energy (stored in biomass of their tissues)
1. plants do use some of their produced
energy for their own respiration
Two Kinds of Primary
Productivity
• Net primary productivity (NPP): rate at which
producers use photosynthesis to produce &
store chemical energy minus the rate at
which they use some energy thru aerobic
respiration.
• Planet’s NPP limits number of consumers
• Humans use, waste, or destroy between 1055% of earth’s total potential NPP
• Human population is less than 1% of total
biomass of earth’s consumers
3-4 What Happens to Matter in
an Ecosystem?
• Concept 3-4 Matter, in the form of
nutrients, cycles within and among
ecosystems and in the biosphere, and
human activities are altering these
chemical cycles.
Biogeochemical Cycles
• Also called “Nutrient cycles”
• All cycles have a place where the
nutrients accumulate, called reservoirs
• These nutrient cycles connect all
organisms through time!
• Cycles are all driven by:
1. solar energy
2. gravity
Hydrologic Cycle
• Water cycle is powered by the sun.
Involves 3 processes:
1. Evaporation (from bodies of water)
2. Precipitation (rain, snow, sleet)
3. Transpiration – water evaporation from plant
surfaces
• Over bodies of water: most water vapor
comes from the oceans – 84%
• Over land: ~90% of water reaching the
atmosphere comes from transpiration
The Water Cycle
• As water moves thru its cycle, some will
temporarily stored in:
1. Living parts of the ecosystems:
a. EX: Plants roots pull water into plants,
which is stored in chemical compounds, then
moved thru the ecosystem by transpiration
and by plants being consumed
2. glaciers
3. Aquifers: stores of groundwater under
layers of rock, sand & gravel
The Water cycle
• An important feature of the water cycle is
that as water passes thru, there is a natural
renewal of water quality.
1. In a sense, it is like a “water filter” which
filters out impurities.
• Lots of water is visible. How much of it is
available to us as freshwater, usable for
consumption?
* about 0.024% of the total volume of water
Science Focus: Water’s Unique
Properties
• Holds water molecules together
(called hydrogen bonding)
• Water is liquid over a wide
temperature range
• It changes temperature slowly
• Requires large amounts of energy to
evaporate
Additional Unique Properties of
Water
• Dissolves a variety of compounds
• Filters out UV light from the sun
• Adheres to a solid surface – allows
capillary action in plants
• Expands as it freezes
Carbon Cycle
• Based on carbon dioxide (CO2)
• It circulates thru the biosphere, hydrosphere &
atmosphere
• CO2 makes up 0.038% of atmosphere’s volume
• Major cycle processes that carbon cycles thru:
– Aerobic respiration
– Photosynthesis
– Fossil fuel combustion and deforestation (both
can lead to a build-up of CO2)
• Fossil fuels add CO2 to the atmosphere will cause
an increase in temperature (and a decrease in CO2
will decrease surface temperatures)
Nitrogen Cycle
• Multicellular plants and animals cannot directly
absorb and use atmospheric nitrogen (N2), which
makes up most of the atmosphere (78%)
1. Nitrogen is extremely important to the building of
proteins, vitamins & nucleic acids
2. Bacteria are our friends, because they convert
N2 to a form which can be absorbed
3. There are 2 processes involved with this
conversion: Nitrogen Fixation and Nitrification
4. There are 2 additional processes in the nitrogen
cycle: Ammonification and Denitrification
Nitrogen Cycle
• Nitrogen fixation: specialized bacteria in soil
and green algae in aquatic environments
combine N2 with H2 to produce ammonia
(NH3)
1. Some is converted to NH4+ ions, and is
absorbed by plants
• Nitrification: NH3 and NH4+ is converted by
special bacteria into nitrate ions (NO3-)
1. plants will use it to make proteins (amino
acids) & nucleic acids & vitamins
Nitrogen Cycle
• Ammonification: The process that
decomposer bacterias accomplish when they
eat decaying plants & animals, converting
their nitrogen-containing compounds into
ammonia or ammonium ions.
• Denitrification: A specialized process of
bacteria in watery soil & sediments of lakes &
oceans, that convert ammonia & ammonia
ions back into N2 gas, to be returned back
into the nitrogen cycle again.
Phosphorus Cycle
• Does not cycle through the atmosphere
• Its obtained mostly from terrestrial rock formations
& ocean floor sediments
1. water runs over rocks, slowly eroding off
phosphorus salts (containing phosphate ions PO43-)
• It is the slowest moving of all the cycles
• The presence of phosphorus is a limiting factor on
land and in freshwater ecosystems
• Biologically important for producers and consumers
1. part of energy transfer molecules ADP & ATP
2. part of nucleic acids
Sulfur Cycle
• Most sulfur stored in rocks and minerals,
& in ocean sediments
• Enters atmosphere through:
1. Volcanic eruptions and processes
2. Anaerobic decomposition in swamps,
bogs, and tidal flats
3. Sea spray
4. Dust storms
5. Forest fires
Sulfur Cycle
• Biologically important to producers &
consumers
1. sulfur is an essential part of proteins
2. It is absorbed by plants thru their roots
3-5 How Do Scientists Study
Ecosystems?
• Scientists use field research,
laboratory research, and
mathematical and other models to
learn about ecosystems.
Field Research
• Collecting data in the field by scientists
that are actively in “the mud”
• Remote sensing devices are also used
to detect/scan the earths surface
• Geographic information systems (GIS):
used to interpret & display the
information obtained thru remote
sensing devices.
Laboratory Research
• Simplified model ecosystems
– Culture tubes
– Bottles
– Aquariums
– Greenhouses
– Chambers with controllable abiotic factors
• How well do lab experiments correspond with
the greater complexity of real ecosystems?
• Is best for doing controlled experiments!
Scientific Studies of
Ecosystems
• Models can be used
1. Mathematical
2. Computer simulations
• Models need to be fed real data collected
in the field- baseline data before any
meaningful interpretations can take
place.
• Models must also determine
relationships among the key variables
Baseline Data to Measure
Earth’s Health
• A “baseline of data is needed in order
to monitor any changes over time
• Many ecosystems lack this baseline
data
• Call for massive program to develop
baseline data