Unit 2 – The Biosphere
Ecological Organization
in the Biosphere
Intro to Ecological Organization
• The Biosphere – the layer of life on earth – from
the deepest ocean vent to the upper reaches of
the atmosphere, the zone where life can survive.
• Ecology - combines the Greek words oikos,
meaning “house” or “the place where one lives”
with logos meaning “the study of”  The study
of interactions among organisms and their
environment
Levels of Ecological Organization
Levels of Organization
• Individual Organism - a single individual of a
specific species
• Population - all the members of the same
species living in the same habitat
• Community - a collection of all the
populations of many different species in a
certain area at a certain point in time
Levels of Organization
• Ecosystem - The relationship between living
and non-living components of a biological
community
• Biome - many ecosystems in the same region
that share the same climate and dominant
ecosystems
• Biosphere –the earth's crust, waters, and
atmosphere that supports life
Levels of Ecological Organization
Ecological Methods
•Observing
•Experimenting
•Modeling
Observing
• Observing – the first step to asking ecological
questions
– From basic observations of what species live in an
area, to more complex observations of behaviour
and interactions between individuals and between
species
– Helps to inspire and design experiments and
models.
Experimenting
• Experimenting – required to test hypotheses
– Lab studies: set up artificial environments in the
laboratory, allows more control of conditions
– Field studies: experiments conducted in the
natural ecosystem, harder to control but more
valid
Modeling
• Modeling – models can help us to understand
ecological phenomena
– Particularly useful for process that happen over long
time periods or large spatial scales
– Models are used to study complex issues such as the
impact of climate change on ecosystems
– Consist of mathematical formulas based on data
collected through observation and experimentation
– Predictions made by models are then tested by
additional observation and experimentation
Quick History of Life on Earth
• Take your own brief notes during this video
• https://www.youtube.com/watch?v=sjEPkjp3u4&index=1&list=PL8dPuuaLjXtNdTKZkV
_GiIYXpV9w4WxbX (13:30)
Energy Flow in the Biosphere
• Autotrophs – organisms that can make their
own food from basic nutrients and sunlight or
some other non-living source.
Also called Producers.
– Auto means “self”, and “troph” comes from Greek
word meaning “feeder”. Therefore autotroph
means “self-feeder”
Two Types of Autotrophs
• Energy from the Sun – most producers
harness solar energy through the process of
photosynthesis. During photosynthesis,
plants, algae, and photosynthetic bacteria use
light energy to power chemical reactions that
convert carbon dioxide and water into
energy-rich carbohydrates such as starches
and sugars, plus oxygen as a by-product.
Two Types of Autotrophs
• Life without Light – some autotrophs can
produce food in the absence of light, using
chemical energy instead, through a process called
chemosynthesis. They break down chemicals
such as hydrogen sulphide to produce
carbohydrates. Several types of bacteria can
perform chemosynthesis, and many of them live
in remote places such as thermal vents on the
bottom of the ocean, and in extreme
environments such as the hot springs at
Yellowstone National Park.
Energy Flows in the Biosphere
• Heterotrophs – consumers at any level that
cannot make their own food, and therefore
must obtain their food and energy by
consuming autotrophs or other heterotrophs.
Also called consumers
– (Hetero means different or other – so heterotroph
= “feeds on others”)
Primary Consumer
• Primary Consumer (herbivore): an organism
that eats primary producers.
– Example: grasshopper
Secondary Consumer
• Secondary consumer : an organism that eats
primary consumers.
– Example: a warbler, which eats grasshoppers
Tertiary Consumer
• Tertiary consumer: an organism that eats
secondary consumers.
– Example: peregrine falcon, which eats smaller
birds like warblers
Herbivore
• A herbivore is an organism that only eats
producers.
– Examples: deer, mice, some small birds, squirrels
Carnivores and Omnivores
•
A carnivore is an organism that eats other
animals.
–
•
Examples: wolves, coyotes, lions, tuna, sharks
A omnivore is an organism that eats both
plants and animals.
–
Bears are good examples of omnivores
•
–
Eat fish and other small animals, as well as berries
Can you think of another familiar omnivore?
HUMANS!
Carnivores and Omnivores
Scavengers and Decomposer
•
A scavenger is an animal that feeds off dead or
decaying animals but does not kill them
– Scavengers are also sometimes called detritivores
because they feed on detritus, or dead plant and
animals matter.
– Examples: Vultures, hyenas, earthworms, snails, and
crabs
• A decomposer is an organism that breaks down complex
organic molecules into simpler molecules. This returns
nutrients to the soil.
– Examples: fungi and bacteria
Scavengers
Decomposers
Trophic Level
• Trophic Level – a category of living things defined
by how it gains energy.
-The trophic levels are numbered based on the
number of steps they are away from the energy
source
– First Trophic Level: Producers (autotrophs)
– Second Trophic Level: Primary Consumers
(eat producers)
– Third Trophic Level: Secondary Consumers
(eat primary consumers)
– Fourth Trophic Level: Tertiary Consumers
(eat secondary consumers)
Example Food Chain:
Sun

Role in
Food Chain
Trophic
Level
Steps from
the Sun
grass  mouse  snake 
Producer
Primary
Consumer
1
2
falcon
Tertiary
Consumer
3
4
Example Food Chain:
Sun

grass  mouse  snake 
Primary
Secondary
Consumer Consumer
falcon
Role in
Food Chain
Producer
Tertiary
Consumer
Trophic
Level
Steps from
the Sun
First
Second
Third
Fourth
1
2
3
4
Food Chains
• food chains are a way of showing a one way,
step-by-step, sequence of who eats whom in
an ecosystem.
• we use arrows to show energy flow – that’s
why the arrow always points to the higher
trophic level
Sun  producer  primary consumer 
secondary consumer  tertiary consumer
Food Webs
• food chains are unlikely to include all the
organisms in a natural ecosystem
• each individual organism in an ecosystem is
involved in many food chains
• the chains all interlock to form a feeding
relationship called a food web
Interactive food web creator: http://www.vtaide.com/png/foodwebS.htm
The Role of Producers
• Food webs always begin with autotrophs
– photosynthetic or chemosynthetic organisms at
the first trophic level (ie. plants)
– These processes ultimately provide the energy
required by the entire ecosystem.
Using the Energy
• All organisms (including plants) undergo
cellular respiration in order to use the energy
in their food.
Equation for Cellular Respiration:
glucose + oxygen  carbon dioxide + water + energy
Homework
• Read Pages 62-73 in your text
– Answer questions 1-3 on pg 65, and 1-3 on pg 73
Limits on Energy Transfer
• Every time energy is transferred between the
components of an ecosystem, the amount of
energy available to the next trophic level is
reduced.
• Not all of the energy captured in photosynthesis is
available to the animal that eats the plant because
the plant used most of that energy to carry out its
life processes
• Primary consumers do not digest all of a plant
meal, some is lost in the feces. Of the remaining
energy, some is lost as thermal energy from the
chemical transformations of digestion and through
cellular respiration and the animal’s activity.
The 10% Rule
• Only 10% of the energy plants receive is
stored, and therefore is passed on to the
primary consumers
• Only 10% of the energy that primary
consumers receive is stored and passed on to
Secondary consumers
• the farther up the food chain, the less energy
that is available
• this usually limits the number of trophic levels
in a food chain to about 5
Thermodynamics
• Thermodynamics is the study of energy
transformations
• First Law of Thermodynamics: although
energy can be changed from one form to
another, it cannot be created or destroyed.
• Second Law of Thermodynamics: during any
energy transformation, some of the energy is
converted into an unusable form, (usually
thermal energy) that cannot be passed on.
Human Use of Energy
• Humans are dependent on the energy flow through
ecosystems just like all other living things.
• We are part of many food chains at different levels,
dependent on what we are eating.
Think about it: Are we more efficient when we eat
like Herbivores or Omnivores? Why?
• We also used the energy for fuel for heat or electricity
(example: burning wood)
• Humans have permanently changed many ecosystems
in order to grow and hunt food.
Scientific Models of Energy
• Scientists often construct models to help
them understand how living things work.
• Models are theoretical descriptions or
analogies that help us visualize something
that has not been directly observed.
• They provide a pathway for making
predictions.
Ecological Pyramids
• Ecological pyramids – graphs used to
represent energy flow in food chains and food
webs or the populations of organisms in a
food chain.
– allow ecologists to visualize the relationships in an
ecosystem and compare them.
– NOTE: graphs of natural ecosystems may or may
not look like a pyramid!
Pyramid of Numbers
•
•
•
•
A Pyramid of Numbers can be drawn by
counting the number of organisms at each
trophic level in an ecosystem.
As you move up the trophic levels, the
number of organisms decreases.
That is why there is a ratio of about 100000
grasshoppers to every 2 falcons.
However something strange can happen
with the number of producers…
Pyramids of Numbers
1 large producer can support many smaller
consumers
Pyramid of Biomass
• Biomass is the total dry mass of all the living
material in an ecosystem.
• Since organisms store energy as organic
molecules, biomass is a measure of stored
energy, as well as the size of organisms at
each level.
Biomass Pyramid
Numbers and Biomass
Pyramid of Energy
• A Pyramid of Energy is created by measuring
and graphing the amount of energy available
at each trophic level.
• It allows a better understanding of the
relationships and energy flow at each trophic
level. It is the most realistic of the ecological
pyramids.
• Large mass and the energy demands of
hunting limits the number of consumers that
can be supported at the top of the pyramid.
Crash Course Video
• Links in the Chain:
• https://www.youtube.com/watch?v=v6ubvEJ3
KGM&list=PL8dPuuaLjXtNdTKZkV_GiIYXpV9w
4WxbX (10 min)
Ecological Pyramids Worksheet
• Read the short summary article, and complete
this worksheet for your logbook.
Matter Cycling
• While energy flows through the biosphere in one
direction, eventually leaving it as thermal energy,
matter is recycled within and between
ecosystems. The biogeochemical cycles connect
the biological, geological, and chemical aspects of
the biosphere as elements and compounds are
passed between organisms and from one part of
the biosphere to another.
• Matter is not used up in biological systems, it is
just transferred from one form to another.
Example:
• A single atom of carbon, for example, can start
out in a molecule of carbon dioxide, become
incorporated into a plant via photosynthesis,
the plant is then eaten by a herbivore, and
within a few hours will be expelled as waste.
This waste could be eaten by a scavenging
insect, which is eaten by a small mammal,
which is eaten by a predatory bird, and then
exhaled back into the air as carbon dioxide
again.
Matter Cycling
• In the same way, some of the molecules of
water that you drink today were almost
certainly consumed by a dinosaur millions of
years ago, and have cycled through the water
cycle countless times since then.
Water Cycle
• Energy, mostly from the sun, causes water to
evaporate (changing from liquid to gas), or ice
to sublimate (changing directly from solid to
gas) to become water vapour in the air.
Transpiration also occurs, which is
evaporation of water from the leaves of
plants.
Water Cycle
• As the gaseous water rises and the pressure
and temperature of the atmosphere decrease,
the water vapour condenses (changes from
gas to liquid), into fog, mist and clouds. If the
temperature is low enough, water vapour may
form ice crystals by deposition (changing
directly from gas to solid). Precipitation of
some kind (rain, hail or snow) then falls to the
ground.
Water Cycle
• Once water is on the ground it can either run
along the surface of the ground as surface
runoff to accumulate in streams, rivers, lakes,
and the oceans (surface water); or it can seep
down through the soil into underground
reservoirs of water called aquifers to become
ground water.
Nutrient Cycles
• The chemical substances that an organism
needs to sustain life are called nutrients.
Producers obtain nutrients in simple forms
from their environments. Consumers obtain
nutrients by eating other organisms. All
organisms use these nutrients to build tissues
and carry out essential life functions. The
carbon, nitrogen and phosphorus cycles are
particularly important for ecosystems.
Nitrogen Cycle
• Nitrogen Cycle – the cycle of matter in which
nitrogen atoms move from nitrogen gas in the
atmosphere, to inorganic forms in the soil, to
organic forms in living things, and then back
to inorganic forms in the soil and nitrogen gas
in the atmosphere.
Why Nitrogen?
• Nitrogen is required for cells to make proteins
and DNA
• Although nitrogen gas in abundant in the
atmosphere (79%), in order to be useful to
plants, nitrogen must be in the form of a
nitrate ion (NO3-).
• plants also require nitrates to make
chlorophyll. When lacking nitrates, leaves will
not be a rich dark green colour.
Not enough Nitrogen?
Nitrogen Fixation
• Nitrogen fixation – two processes in which
atmospheric or dissolved nitrogen is
converted into nitrate ions.
– lightning
– nitrogen-fixing bacteria,
found in legumes
Denitrification
• Denitrification – the process in which nitrates are
converted to nitrites and then to nitrogen gas
which is released back into the atmosphere.
– carried out by bacteria that do not need oxygen
(anaerobic)
– speeds up when soil is acidic or water-logged
As a result, gardeners often aerate their lawns to
increase oxygen levels and allow nitrates to
remain in the soil.
• Nitrates can also enter ecosystems through the
application of synthetic fertilizers, which contain
nitrates.
Nitrogen Cycle
Phosphorus Cycle
• Phosphorus is essential to living things because it
is required for DNA and RNA, which make up the
genetic code. While it is very important
biologically, it is still quite rare in the biosphere.
• Unlike water, carbon, and nitrogen, phosphorus is
never found in the atmosphere. Instead, when it
is not in the bodies of organisms, it is found on
land in rocks and in soil minerals, and also in
ocean sediments. It is usually found in the form
of inorganic phosphate.
Phosphorus Cycle
• As phosphate-containing rocks wear down
(weather) slowly over time, the phosphate is
released into the soil, where it can be taken
up by plants and bound into organic
compounds. This allows it to enter the food
web, moving from producers to consumers,
and back to the soil through decomposition.
Phosphorus Cycle
• Some of the phosphate in the soil may be
washed into streams and rivers, and
eventually carried to the ocean. There it can
be used by marine food webs; while some
phosphate is also deposited on the ocean
floor as sediments, which may eventually turn
back into rock.
Phosphorus Cycle
• Another way that phosphorus is added to the
biosphere is through human action. Synthetic
fertilizers contain phosphates, so fertilizer use
adds additional phosphates to the soil. Runoff
of these fertilizers, especially when over-used,
adds additional phosphate to aquatic
ecosystems.
Carbon Cycle
There are four main types of processes that
move carbon through the cycle.
• Biological Processes: photosynthesis removes
carbon from the atmosphere, while cellular
respiration and decomposition release carbon
back into the atmosphere
• Geochemical Processes: erosion and volcanic
activity release carbon dioxide to the
atmosphere and oceans.
Carbon Cycle
• Mixed biogeochemical processes: the burial
and decomposition of dead organisms and
their conversion under pressure into coal and
petroleum (fossil fuels) – this stores carbon
underground
• Human activities: mining, cutting and burning
forests and burning fossil fuels, all release
carbon dioxide into the atmosphere
Summary of Carbon Cycle
• Carbon is found in the atmosphere as carbon dioxide
gas (as well as in other gases such as methane). Plants
take in carbon dioxide and use carbon to build
carbohydrates through photosynthesis.
• The carbohydrates are passed through food webs to
consumers (some of the carbon being exhaled as
carbon dioxide during their lifetimes) and eventually to
decomposers. When organic matter decomposes, the
carbon can either be released into the atmosphere, or
buried underground where over time it can be
converted into fossil fuels.
Summary of Carbon Cycle
• Carbon is also found in the oceans in the form
of calcium carbonate, which is formed by
some marine organisms, and this chalky
substance accumulates in ocean sediments,
which over time are either compacted into
rock, or broken down and the carbon returned
to the atmosphere as carbon dioxide.
Human Impacts
• We release carbon from organic reservoirs
(carbon sinks) by burning fossil fuels
• We also increase the amount of carbon
dioxide in the atmosphere by clearing
vegetation
The Greenhouse Effect
• 1. Greenhouse Effect – atmospheric gases
that surround the Earth (such as carbon
dioxide and methane) trap the heat from the
sun and warm the Earth’s surface.
Global Warming
• 2. Global Warming – the burning of wood and
fossil fuels have caused carbon dioxide levels
to triple over the past 40 years. In that time
global temperatures have increased by 1
degree Celcius.
Global Warming
Problems from Global Warming
• In the Arctic permafrost will thaw, causing
roads & buildings to collapse (releases more
carbon)
• Icecaps and glaciers will melt, rivers will
overflow, and ocean levels will rise causing
cities to flood or be submerged, and some
island nations to disappear completely. This
will create many climate refugees.
Problems from Global Warming
• Changing sea levels will also change ocean
and wind currents, leading to surprising
changes in climates around the world (cooling
in Europe due to the Gulf Stream
disappearing)
• Changing climates will drastically change
ecosystems – plants and animals will need to
shift their habitat ranges to new areas to
survive.
Global Warming Problems
• Many extreme weather events will become more
frequent, severe, and unpredictable.
Nutrient Limitation
• Ecologists are often interested in the primary
productivity of an ecosystem, which is the
rate at which producers create organic matter.
One factor that influences the rate of primary
productivity is the amount of available
essential nutrients. When an ecosystem is
limited by a single nutrient which is rare or
which cycles very slowly, this substance is
called a limiting nutrient.
Human Response
• Since the very first use of agriculture, farmers
have found that crops grown in the same plot
of land every year start to suffer from nitrogen
deficiency. Corn and tomatoes in particular
use up nitrogen (and phosphorus) very rapidly.
One way to address this problem is to use
crop rotation.
Crop Rotation
• Crop Rotation – The practice of growing a
series of different types of crops in the same
area in sequential seasons in order to
replenish soil nutrients such as nitrogen.
– Crop rotation has been used since 6000 BCE by
early farmers in the Fertile Crescent, when they
alternated planting legumes (with their nitrogenfixing bacteria) and their other crops.
– The Romans also used goat, sheep, cattle, and
other dung as a natural fertilizer
Synthetic Fertilizers
• The numbers on a bag of
fertilizer tells you the
Nitrogen, Phosphorus and
Potassium content. These
three nutrients help to
boost the productivity of
the land by helping plants
to grow larger and more
quickly than they would in
unfertilized land.
Synthetic Fertilizers
• In 1784 Henry Cavendish found a way to
synthetically fix atmospheric nitrogen into
nitric acid, and the more modern Haber
process to make ammonia was developed in
the 1910s.
• Since then we have been able to create our
own sources of nitrogen for plants, without
the need for the bacteria found in legumes.
Fertilizers
• Use of some type of fertilizer (natural or
synthetic) can increase yields by 30-50%
• Synthetic fertilizers have become very
important and are often over-used to try to
raise crop yields even higher
Water Pollution
• Ocean ecosystems are considered to be very
nutrient-poor when compared to the land. For
instance, seawater contains about 1/10 000 the
amount of nitrogen that is typically found in soil,
so nitrogen is usually a limiting nutrient in the
ocean. In some regions of the oceans, other
nutrients such as silica or iron may be the key
limiting nutrient. In freshwater ecosystems such
as streams, rivers and lakes, phosphorus is
typically the limiting nutrient.
Water Pollution
• When an aquatic ecosystem receives a large
doses of a limiting nutrient (usually nitrogen
or phosphorus runoff from a heavily fertilized
field), there is often an immediate increase in
the amount of algae and other producers. This
is called an algal bloom.
Algal Blooms and Dead Zones
• If there are not enough consumers around to eat
the excess algae quickly, then the algae can cover
the surface of the water for a large area. This can
cause major disruption to the ecosystem. When
this algae dies and starts to decompose, the
decomposers quickly use up the available oxygen,
and this produces a dead zone (an area of water
where the oxygen levels are too low for most
organisms to survive). Dead zones can become
quite large and last for long periods of time – for
example the huge dead zone in the Gulf of
Mexico.
Nitrogen Article
• Read this article about human impacts on the
Nitrogen Cycle, and highlight important
points. This will go in your logbook
Weekend Homework
• Textbook Pages:
– Read pages 74-80, answer questions 1-4 on pg 80
• Finish that Ecological Pyramids worksheet for
your logbook
• Read that Nitrogen article and highlight it
• Work on your Article Analysis
• We’ll have a Notebook Quiz on Chapter 3 on
Tuesday.
For Review:
• Cycles Review Videos:
– Water & Carbon Cycles:
• https://www.youtube.com/watch?v=2D7hZpIYlCA
– Nitrogen and Phosphorus Cycles:
• https://www.youtube.com/watch?v=leHy-Y_8nRs