Science, Matter, Energy and Ecosystems
Chapter 2
Pages 16-45
Matter and Energy
• Read section 2-2 on Matter and Energy
• Background to many ES issues and future
chapters
• We will discuss some but not all
Science and Critical Thinking
Constructing the Hypothesis
• The goal of science is to discover facts about the
natural world and the principles that explain
these facts.
• How does one “measure” the natural world?
Use senses, see, hear, feel, taste smell, as well as tools
to extend these senses
– Observations
• Can quantify, through statistics can validate
– Scientific Knowledge is ultimately traced to
Observations
Constructing the Hypothesis
The scientific method can be best described
as procedures used to learn about our
world.
Science cannot prove or disprove nonquantifiable factors, such as ESP.
Constructing the Hypothesis
• Must be stated in a way that allows them
to be tested.
• A testable hypothesis is one that at least
potentially can be proved false.
Constructing the Hypothesis
• For example:
– There are no mermaids in the sea
• This is testable and can be proven false by finding
a mermaid
– There are mermaids in the sea
• This cannot be proven false, as the true believer
would say “They are there, you just didn’t find
them”
Constructing the Hypothesis
• Variables are factors that might affect
observations
• Models with variables one can alter – Laboratory
• Ecological models – difficult to alter the
variables. Often only observations to determine
differences based on variability.
• In science, no absolute truths. No hypothesis
can be absolutely proved true.
• Make best decisions with available evidence.
•Scientific hypotheses – an unconfirmed explanation of an
observation that can be tested
•Scientific method – used to test hypotheses – ways scientists
gather data, formulate and test hypotheses.
•Peer review and publication – widely accepted – leads the
scientific theories and laws.
•Scientific theories – description of what we find happening
through repeated observations – verified and credible hypothesis
•Scientific (natural) laws – description of what we find happening,
and is proven over and over
•Frontier science – preliminary results – often subject to news
stories
•Junk Science – no peer review
Levels of organization in nature.
The shaded portion is the five
levels that ecology is based upon.
What is Matter?
• Atoms, ions and molecules
• Anything that has mass and takes up
space.
• Two forms:
– Element – distinctive building blocks of matter
that make up every material substance
– Compound – two or more different elements
held together by chemical bonds
What is Matter?
• Organic compounds
– Compounds containing carbon atoms
combined with each other and with atoms of
one or more other elements such as
hydrogen, oxygen, nitrogen, sulfur,
phosphorus, chlorine, and fluorine.
• Inorganic compounds
– All compounds not classified as organic
compounds.
The Law of Conservation of Matter
• Matter is not destroyed
• It only changes form
• There is no “away” – atoms are not
destroyed, just rearranged.
• What are some examples of matter
changing form?
First Law of Thermodynamics
• Energy is neither created nor destroyed
• Energy only changes form
• You can’t get something for nothing
– Or “There is no such thing as a free lunch!”
• ENERGY IN = ENERGY OUT
Energy
• Kinetic
– Wind
– Electicity
– Flowing water
• Potential
– Water behind a dam
– Gasoline in your car
– Unlit match
Second Law of Thermodynamics
• In every transformation, some energy is
converted to heat
• You cannot break even in terms of energy
quality
Waste energy is
low quality and
cannot be reused
Second Law of Thermodynamics
• What are some other examples of the
Second Law of Thermodynamics?
Water is heated due to energy loss from the flowing water and turbines
20-25% of the chemical energy in gasoline is converted to mechanical energy.
The rest is lost into the environment as low quality heat energy.
5% of electricity is changed into useful light. 95% is lost as low-quality heat.
• Photosynthesis
is the process of
converting solar
energy into
chemical energy
stored in food
• CO2 + H20 --->
C6H12O6 + O2
• Respiration is the process of releasing
chemical energy stored in food to be used by
living things.
• C6H12O6 + O2 ---> CO2 + H20
Ecological Concepts
• Ecology: Study of how organisms
interact with each other and with their
non-living surroundings.
• Eco - is from the Greek word “Oikos” for
house
The Nature of Ecology
Levels of study in Ecology:
• Organisms – single animal
• Populations – same species
• Communities – pop’ns living
together
• Ecosystems – community +
physical environment
• Biosphere – all the earth’s
ecosystems
The Earth’s Life-Support Systems
• Atmosphere
–
Thin membrane of air
– Troposphere
• 11 miles
– Stratosphere
• 12-30 miles
• Lower portion (ozone)
• filters out harmful sun rays
• Allows life to exist on earth
• Lithosphere
– Earth’s crust
• Hydrosphere
– water
• Biosphere
– Living and dead
organisms
Natural Capital: Sustaining Life of Earth
• One-way flow
of energy from
Sun
• Cycling of
crucial elements
• Gravity
Solar Capital: Flow of Energy to and
from the Earth
Greenhouse gasses
water vapor
CO2
Methane
Ozone
Increases kinetic energy,
Helps warm troposphere.
Allows life to exist
(as we know it) on earth.
As greenhouse gasses
increase, temperature of
troposphere increases.
Ecosystem Components
• Abiotic factors
• Biotic factors
• Range of tolerance for each species
– what factors are important for…
Ecosystem Components
• Limiting factors determines distributions
Law of Tolerance
• The existence, abundance and distribution
of a species is determined by levels of one
or more physical or chemical factors.
Common limiting factors
• Limiting factors – more important in regulating
population growth than other factors.
• Terrestrial ecosystems (on land)
– precipitation
– temperature
– soil nutrients
• Aquatic ecosystems
–
–
–
–
–
temperature
sunlight
nutrients
dissolved oxygen
salinity
Biological Components of Ecosystems
• Producers
(autotrophs)
• Consumers
(heterotrophs)
– Herbivores,
carnivores, omnivores
– Decomposers and
detritivores
• detritus = dead organic
material
Biodiversity
• Genetic diversity – variety of genetic material
within a species or a population
• Species diversity – the number of species
present in different habitats
• Ecological diversity – the variety of terrestrial
and aquatic ecosystems found in an area or on
earth
• Functional diversity – biological and chemical
processes needed for the survival of species,
communities and ecosystems
Energy Flow in Ecosystems
• Food chains – sequence of organisms
which is a source of food for the next.
• Food webs – most species participate in
several food chains (they don’t just eat
one thing!).
• Trophic levels
– each step in the flow of energy through an
ecosystem (feeding level)
Food Chains and Energy Flow in
Ecosystems
Ecological Pyramids
• Pyramid of
energy flow
• Ecological
efficiency
• Pyramid of
biomass
• Pyramid of
numbers
Food webs
• reality tends
to be more
complex
than a linear
food chain
Primary Productivity of Ecosystems
• Gross primary productivity (GPP)
• The rate at which an ecosystem's producers capture
and store a given amount of chemical energy as
biomass in a given length of time.
• Net primary productivity (NPP)
• Rate at which all the plants in an ecosystem produce
net useful chemical energy; equal to the difference
between the rate at which the plants in an ecosystem
produce useful chemical energy (gross primary
productivity) and the rate at which they use some of
that energy through cellular respiration.
• (NPP = GPP – Respiration)
Net Primary Productivity comparison
Soils
• Importance
• Provides most of the nutrients for plant life
• Cleans water
• Decompose and recycle biodegradable wastes
• Maturity and Horizons
•
•
•
•
Surface litter layer
Top soil layer (humus)
Sub soil
Parent material
• Variations with Climate and Biomes
• Variations in Texture and Porosity
Soil Profiles in Different Biomes
Matter Cycling in Ecosystems
Biogeochemical cycles – global cycles
recycle nutrients through the air, land and
water
Cycles are driven directly or indirectly by
solar energy and gravity
• Hydrologic cycle (H2O)
• Carbon cycle
• Nitrogen cycle
• Phosphorus cycle
Hydrologic (Water) Cycle
Human Influence on the Water
Cycle
•
•
•
•
•
Water withdraw from lakes and streams
Clear vegetation
Construct impervious surfaces
Fill wetlands
Modify water quality by adding nutrients
The Carbon Cycle (Marine)
Based on Carbon Dioxide
Terrestrial producers remove
CO2 from the air; aquatic
producers remove it from the
water.
Through photosynthesis,
Converts to carbohydrates.
O2 consuming producers
respire,breaking carbohydrates back to CO2.
CO2 not released until burned.
The Carbon Cycle (Terrestrial)
Human Influence on the Carbon
Cycle
• Clear trees and other plants, often times
permanently
• Burning fossil fuels and wood
• Increased CO2 in the troposphere
enhance natural greenhouse effect
• Results in global warming
The Nitrogen Cycle
Atmosphere’s most abundant
element.
Bacteria help recycle nitrogen.
Nitrogen cannot be used by plants
and animals without bacteria’s help.
Waterlogged
soil
Ammonia not taken up by plants
Toxic to plants
Usable by plants
Human Influence on the
Nitrogen Cycle
• Add large amounts of nitric oxide by burning fuel
• Gas converted to nitrogen dioxide gas and nitric
acid (acid rain)
• Add nitrous oxide through anaerobic bacteria
breaking down livestock wastes (global
warming).
• Release nitrogen stored in soils and plants by
destroying forests, grasslands and wetlands.
• Add excess nitrates for agriculture
• Remove nitrogen from topsoils through
harvesting various crops
The Phosphorus Cycle
Slow
Bacteria not a major player
Washes from the land into
streams, then the sea.
Can be deposited as sediment
and remain for millions of
years.
Often a limiting factor for
plant growth on land.
Also limits growth in lakes
And streams because
phosphate salts are only
slightly soluble in water.
Fig. 4-33 p. 82
Human Influence on the
Phosphorus Cycle
• We mine large quantities of phosphate
rock to make inorganic fertilizers.
• We reduce the available phosphate in
tropical soils by clearing tropical forests.
• We disrupt aquatic systems with
phosphates from runoff of animal wastes
and fertilizers, and sewage systems.