Ecosystems
Important Terms
• Ecosystem = a group of organisms and
how they interact with their living and
nonliving environment
• Niche = an organisms role
• Biotic = living or having lived recently
• Abiotic = nonliving, long dead
• Producer = converts energy from the sun,
also called an AUTOTROPH
• Consumer = eats other living things, also
known as a HETEROTROPH
– Primary, Secondary, Tertiary, Quaternary
• Body of water = lake, river, pond, etc
• Food chain = each organism feeds on the
one below it
• Food web = overlapping food chains in a
community
• Types of heterotrophs
– Herbivores = eat plants
– Carnivores = eat animals
– Omnivores = eat both plants and animals (omni =
all)
– Detritivores = eat dead matter (called “detritus”)
– Decomposers = break down organic matter
• Decomposer
– Organic matter = was or is living, made
mainly out of carbon
– Inorganic matter = non living, not made out
of carbon
• Biodiversity = diversity of life
• Biosphere = the part of the earth where life
exists
• Environment = all the external factors
influencing the life of organisms, such as light
or food supply
• Photosynthesis = to convert energy from the
sun (more details to come later)
• Population = the number of individuals in a
species in one ecosystem
• For the following slides, write in your notes
whether the picture is a food web or food
chain
• List the producers and consumers in the
pictures and what they eat.
Biogeochemical Cycles
• What is a Biogeochemical Cycle?
– Only so much matter on earth because it is acts
as a closed system.
• Energy enters as sunlight, but no matter usually
exits or enters.
• Open system: Energy AND matter are exchanged.
– These cycles act as a way to recycle matter
within the biosphere from one form to another.
Energy Vs. Matter
• Energy is TRANSFERRED
– One-way flow of energy through food-chains and food
webs.
• Energy from sun goes to plants, which then goes to consumers.
– Each trophic level loses ~90% of energy as heat.
– Only 10% of energy is used for life processes.
• Matter is TRANSFORMED
– This is why we have biogeochemical cycles.
– Only have a given amount of matter because Earth is a
closed ecosystem.
Nutrient Cycles
• Carbon - key ingredient in living tissue
– “Carbon-based” life forms
• Nitrogen - required for amino acids used in
protein synthesis
– What are our sources of protein?
– What do we use proteins for?
• Phosphorus - required for DNA and RNA
– Why is this important?
Water Cycle
• Water is required by all living things on
Earth, including us.
• Cycles through atmosphere, ocean, and land
Water Cycle
• Major processes that bring water into the
atmosphere
– Evapotranspiration
• Evaporation - water heats up, forming water vapor,
which then moves into atmosphere.
• Transpiration - water from plant leaves evaporates.
– Condensation
• Cloud formation as water vapor in atmosphere
cools, condensing into the small droplets that form
clouds.
Water Cycle
• Major process that brings water out of the
atmosphere:
– Precipitation
• Droplets that formed clouds become to large and are
released as snow, sleet, hail, or rain.
Water Cycle
• Processes on land:
– Runoff
• Precipitation “runs” along land until it reaches a
body of water, such as a lake, river, or ocean.
– Seepage (aka infiltration)
• Precipitation “seeps” (moves into) soil to form
ground water below the soil’s surface.
– Root uptake
• Plants absorb ground water from soil via their roots.
Water Facts
• 390,000 cubic kilometers of water evaporates and
enters atmosphere each year.
– Equivalent to 185,000,000,000,000,000 bottles of 2 litre
soda pop.
• Most evaporates from and precipitates back into
the oceans… Why is this?
– Ocean makes up nearly 75% of Earth’s surface.
– Water that precipitates on land runs back through
streams and rivers.
Carbon Cycle
• How is carbon taken up and released?
– Photosynthesis, respiration, decomposition
– Erosion, volcanic activity, and other geological
activity
– Fossil fuel formation (deposition)
– Human activity
• All these activities transfer carbon dioxide.
Carbon Facts
• 71% of world’s carbon is in the oceans.
– Mostly as carbonate and bicarbonate (dissolved ionic
forms of carbon dioxide).
• 22% exists as fossils.
• 3% contained in dead organic matter and
phytoplankton.
• 3% held in terrestrial ecosystems.
• Only 1% within the atmosphere as carbon dioxide.
Carbon Cycle
• How can carbon get into the ocean?
– Respiration by ocean animals
– Precipitation that contains dissolved carbon
dioxide
– Erosion of carbonate rocks formed from animal
skeletons and shells
Phosphorus Cycle
• Where is a majority of phosphorus located?
– On land in rock and soil minerals.
– In the ocean as sediment.
– Small amount in living organisms, bound
within organic molecules such as DNA and
RNA as well as in skeletons of animals.
– Unlike other nutrients, it DOES NOT enter the
atmosphere.
Phosphorus Cycle
• What is the major form that phosphorus is
found in?
– Phosphate compounds (PO43-)
Nitrogen Cycle
• What form does most nitrogen exist in?
– Nitrogen gas in the atmosphere (N2)
• Why is this a bad thing?
– This form is not readily usable by most
organisms and is often considered inert.
– “Inert” because of a triple covalent bond, which
is a very strong chemical bond.
Nitrogen Cycle
• How do we get to a usable form?
–
–
–
–
Bacterial nitrogen fixation
Atmospheric nitrogen fixation
Decomposition and excretion
Haber-Bosch process = synthetic fertilizer
• What are these usable forms?
– Ammonia (NH3), Nitrate (NO3-) and nitrite
(NO2-).
Nitrogen Cycle
• What can “fix” nitrogen to
a usable form?
– Bacteria
• On root nodules of
legumes such as beans;
convert nitrogen gas to
ammonia.
• In soils, convert ammonia
to nitrates and nitrites
– Enzyme necessary for this
requires that no oxygen be
present.
Nitrogen Cycle
• What process removes usable nitrogen?
– Denitrification
• Bacteria convert nitrates back into nitrogen gas
How Nutrients Effect an
Ecosystem
• Nutrient limitation
– Similar to when a person has a deficiency in a
vitamin or necessary nutritional component
(like iron or calcium), ecosystems can have a
deficiency in a given nutrient.
– This nutrient is called the limiting nutrient,
because it limits the primary productivity of
an ecosystem.
How Nutrients Effect an
Ecosystem
• What is primary productivity?
– The rate at which organic material is created by
producers, such as plants on land or
phytoplankton in the ocean.
• What happens when a limiting nutrient no
longer becomes limiting?
– In the ocean, this creates an algal bloom.
How Nutrients Effect an
Ecosystem
Limiting Nutrients
• A limiting nutrient limits the amount of
primary productivity an ecosystem is
capable of…
– In the ocean, nitrogen is limiting.
– In freshwater, phosphorus is limiting.
• An increase in a limiting nutrient can lead
to algal blooms…
Algal Blooms
• Increase in algae as a result of increased nutrient.
– Step 1: Algae grow and reproduce rapidly.
– Step 2: Algae die.
– Step 3: Decomposers (bacteria) in the water take up all
the oxygen via respiration as they break down the dead
algae.
– Step 4: Limited to no oxygen left for other animals in
the water column.
– Step 5: Other animals such as fish, die due to lack of
oxygen.
Harmful Algal Blooms
• Chemicals released from bloom can be dangerous
– Paralytic shellfish poisoning (picture on right - Alexandrium tamarense)
– Ciguatera (picture on left - Gambierdiscus toxicus)
– Neurotoxic shellfish poisoning (Gymnodinium breve)