Ecosystems: What Are They
and How Do They Work?
Chapter 3.4 and 3.5
What Is Biodiversity and Why Is It Important?
The biodiversity found in the earth’s genes,
species, ecosystems, and ecosystem processes
is vital to sustaining life on earth.
Soil is an important component of biodiversity
that supplies most of the nutrients needed for
plant growth and helps purify and store water
and control levels of carbon dioxide in the
atmosphere.
Biodiversity – a vital renewable resource
• Genetic diversity
• The total variety of genes in a species or a
population
• Allows for adaptability
• Gene banks and corn leaf blight (1970s)
• Svalbard Global Seed Vault, Norway
Species Diversity
• The number and distribution of species
in a given area
• Also known as species or taxa richness
• Often species diversity and biodiversity are
interchangeable terms
Biodiversity – a vital renewable resource
• Ecosystem (ecological) diversity
• The Earth’s variety of ecosystem
types
• Storehouse of genetic and species
diversity
• Terrestrial ecosystems - soil
Science Focus: Soils
• Base of life on land
• Eroded rock, mineral nutrients, decaying
organic matter, water, air, and organisms
• Key component of biodiversity
Soil Profiles and Soil Maturation
Soil Profile
Animations/soil_profiles.html
• Ecological diversity – variety of terrestrial and aquatic
ecosystems within a given area. Example…
• Functional diversity
Variety of processes of matter cycling and energy flow
Each species has a functional role that may or may not be
replaceable.
Which is more important – functional or species diversity?
Functional Diversity
The biological and chemical processes such as energy
flow and matter recycling needed for the survival of species,
communities, and ecosystems.
Ecological Diversity
The variety of terrestrial and
aquatic ecosystems found in
an area or on the earth.
Biodiversity = Natural Capital
Genetic Diversity
The variety of genetic material
within a species or a population.
Species Diversity
The number and abundance of species
present in different communities
Fig. 3-12, p. 48
Energy in the Ecosystem
As energy flows through ecosystems in
food chains and webs, the amount of
chemical energy available to organisms at
each succeeding trophic level decreases.
Energy Flow in Ecosystems
• Food chain
• Sequence of organisms, each of which serves as a
source of food for the next
• Food web
• Network of interconnected food chains
• More complex than a food chain
Trophic Levels – you are what you eat.
PRODUCERS
• Autotrophs
H2O + CO2 + Light +
Chlorophyll  CH2O+ O2
• Photosynthesis
• Chemotrophs
O2 + 4H2S + CO2 + energy 
CH2O + 4S +3H2O
• Chemosynthesis
CONSUMERS
• Heterotrophs
• Primary (herbivorous)
• Secondary (carnivorous, eat
herbivores)
• Third-level (carnivorous, eat
carnivores)
• Omnivores (herbivorous and
carnivorous)
• Decomposers (absorb nutrients,
primarily bacteria & fungus)
• Detritivores (feed on nonliving
organic matter)
Usable Energy by Trophic Level
• Energy flow follows the second law of
thermodynamics
• Biomass decreases with increasing
trophic level
• Chemical energy (dry weight biomass)
Matter Recycling and Energy Flow
Animations/matter_energy.html
Pyramid of Energy Flow
Ecological efficiency – usable chemical energy = typically 10%
As a consumer, which level is the most efficient?
Are we an efficient species?
Two Kinds of Primary Productivity
• Ecosystems differ in their ability to convert
electromagnetic into chemical energy (biomass)
• Gross primary productivity (GPP)
• Rate producers convert solar into chemical (biomass)
• Energy production per unit area over a given time. (kcal/m2/yr)
• Net primary productivity (NPP)
• Rate producers produce , store and use chemical energy
• NPP = GPP – R (respiration)
• Gives the rate producers can provide for consumers
Ecosystem Productivity
 Greatest amount of biomass production.
Two Kinds of Primary Productivity
• Primary productivity = pay check
• GPP = whole check
• NPP = money left after work bills
• Only NPP is available to consumers
• Therefore, planet’s NPP is a limiting factor to number of consumers
• Humans use, waste, or destroy up to 32% of NPP
• Even though we make up less than 1% off all consumers
• Unsustainbility
Current and Projected Population Sizes by Region
Animations/size_region.html
Demographic Transition Model
Animations/demo_transition.html