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Ecology
Biology 20
Study of the interactions between
organisms and their physical environment
and with each other.
Equilibrium in the Biosphere
Biosphere
the part of the earth that is inhabited by organisms .
3 parts:
1 Lithosphere
Land
2 Hydrosphere
water
3 Atmosphere
The gasses that surround the Earth.
Living vs. Non-living
There are two factors which make
up the biosphere.
 Biotic Factors
Living components of the biosphere
plants and animals…
 Abiotic Factors
Non-living components
of the biosphere
minerals, water, weather...
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Interactions Within the Biosphere
Levels of Organization
 Abiotic vs Biotic
 When a non-living factor affects a living factor.
 i.e. The weather affecting a living organism
 Biotic vs. Biotic
 When a living factor affects another living factor.
 i.e. Two organisms fighting for the same food.
 Biotic vs. Abiotic
 Abiotic vs. Abiotic
Levels of organization
Cell
Tissue
Organ
System
Hierarchical Levels within the Biosphere
Biosphere
World
Ecosystem
Lake or River
Organism
Population
Community Lots of different species of organisms
Ecosystem
Community
Population
Lots of same species of fish
Organism
Fish
Biome
Biosphere
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Important Definitions
Population:
group of individuals of the same: species,
place & time
Community:
populations of all species in an area
Ecosystem: community and its biotic and abiotic factors
 Interactions
Biome: large scale ecosystems
 Can be found around the world  tundra, grassland
General Terms
Autotroph
Producer
Photosynthesis
 Light energy used to make organic compounds (glucose)
 Done by chloroplast containing organisms (plants, algae)
Chemosynthesis
 Energy released by chemical reactions to make a sugar
 Oxidizing hydrogen sulfide or methane
 Done by bacteria in extreme environments (deep sea
vents, hot springs)
More General Terms
More General Terms
Heterotroph
Herbivore
Consumer
 A Primary consumer eats a producer
 A Secondary consumer eats a primary consumer
 A Tertiary consumer eats a secondary consumer…
An organism that only eats plants.
 Rabbit, squirrel
Carnivore
An organism that only eats animals.
 Wolf, Lion, Tyrannosaurus Rex
Omnivore
An organism that eats both plants and
animals.
 Bear, Human
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More General Terms
Scavenger
An organism that feeds on dead organisms or the
wastes of organisms.
 Vulture, Seagull,
Decomposer
An organism that breaks down organic wastes and
the remains of dead organisms into simpler
compounds such as:
 carbon dioxide
 ammonia
 Water
Food chains
Input energy
Biogeochemical
Ecosystems are
OPEN SYSTEMS.
Energy and matter
can flow in and out
of system
Food Chain
 A linear illustration that represents the step sequence of who eats
whom in the biosphere.
 used to show:
energy transfers
 Two Types
Cycles
 Grazer: plant, herbivore, carnivore
 Detritus: organic waste, scavengers, decomposers
Energy Lost
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Food chains
Food Chain
Characteristics:
 Energy is transferred from organism to organism
 Each time energy is transferred about 90% is lost as
heat or used for life processes
 Lost as heat during cellular respiration, stored in an
unusable form, metabolized by the organism itself for ATP
to live
 Note that:
 the arrow points at the eater
 the arrows separate trophic
(eating) levels
Trophic Levels
 Trophic level: how far an organism is from the original
energy source
 Plants – first trophic level
Original energy is from the sun
 When an organism is ingested by another, energy is
transferred
 Plant – mouse – owl
 Producer – primary consumer – secondary consumer
(top carnivore)
 T1 – T2 – T3
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Food Webs
 What would happen if we relied on deer for our food?
 In reality, a consumer relies on more than one food source
 If one source is scarce, consumer can eat more of something else
 Food web:
 a series of interlocking food chains
Food Web
 ABCD represent
different trophic
levels.
 Level D represents the
decomposers
 more accurately represents energy pathways
who eats whom… really
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Laws of Thermodynamics
Biosphere requires a constant
flow of energy
Energy flows one way through
the biosphere following basic
scientific principles called the
laws of thermodynamics
Laws of Thermodynamics
First Law
Second Law
Energy can be changed in form,
but not created or destroyed.
(Law of conservation of energy)
Any energy change results in loss of
energy as heat
Energy input = Energy Output
Energy input  desired energy +
waste energy
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Energy Flow
 About 10% of the energy is transferred from one trophic level to
the next.
 During any change, some of the energy is lost as waste
energy or heat.
 Applied to an ecosystem, as energy flows through the
community there is energy loss at each trophic level.
 Much of this loss is in the form of heat which is lost
when food molecules are broken down in the cells.
 There would be less energy loss in the community if
consumers only fed on producers
Ecological Pyramids
 Ecological pyramids illustrate the energy loss through the trophic
levels
 Solar radiation transformed in plants
 Plants create chemical energy
 Plant eaten by consumer
 Energy lost at each transformation
 Higher trophic level = less energy available
 Number of trophic levels limited b/c of loss of energy
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Ecological Pyramids
In ecological pyramids,
Base -the producer populations
Next Level - the primary consumers
Higher levels and above -the
secondary, tertiary etc.
Ecological Pyramids
Energy Pyramids
 Three types:
 Numbers: total number of organisms in each trophic
levels
 Biomass: mass of dry tissue of organisms at each
trophic level
shows how mass decreases as you move up the food
chain
 Energy: based on energy produced at each trophic
level
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Pyramid of Numbers
Pyramid of Biomass
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Human Interference in
the Ecosystem
Pesticides
used to kill pests
mosquitoes - malaria
 Example
 DDT: dichloro diphenyl trichloroethane
 developed as a biological weapon in WWII
 1950’s - used as a pesticide for insects
pesticides in food chain accumulate
at each level
causes loss of diversity.
 DDT also affects human populations
 found in breast milk
 came from sprayed crops
animals that ate crops
 Banned in Canada and US in 1970’s
 Not banned in other areas - Mexico, Central America
 Continues to be produced as a cheap pesticide in
poorer nations
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Biological amplification
Pesticide concentration builds up at
the top level of the pyramid
toxins accumulate in fatty tissue
not released in wastes
Magnifies each time you move up
higher trophic level - higher
concentration
Biogeochemical Cycles
Cycling of Organic Matter
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Cycling of Organic Matter
 The materials used in building the bodies of
living organisms are limited to the atoms and
molecules that make up the planet.
 There is no alternative source of matter.
 Therefore, to maintain life on Earth, matter
must be recycled.
Cycling of Organic Matter
 Food is organic matter. Every time you eat, organic matter
that was once part of other living things passes into your
body.
 Through the process of digestion, complex organic
molecules are broken down into simpler molecules.
 Cells use these simple molecules to build the complex
molecules that become part of your own structure.
Cycling of Organic Matter
 Decay
 After death, decomposer organisms make the
materials available to other living things.
 Decomposers break down the organic matter
in dead bodies and feces into small, inorganic
molecules
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Properties of Water

All living things need water

Water can be found in the biosphere in three
states
Properties of Water
1. Solid (snow or ice)
2. Liquid
3. Gas ( vapour)

Water is continuously entering and leaving
living systems
Properties of Water
Water: a Polar molecule
Water molecules have a
positive pole and a negative
pole causing water
molecule to be a polar
molecule
Properties of Water
 The attraction between
opposing charges of
different molecules create a
special hydrogen bond.
 Hydrogen bonds pull water
molecules together
 Polar molecule – a molecule
that has a positive and a
negative end
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Biogeochemical Cycles
 Matter can neither be created or destroyed
 It cycles through the biosphere.
 As it cycles, it follows certain characteristic pathways
 These pathways are called “Biogeochemical
Pathways”
Biogeochemical Cycles
 A biogeochemical
pathway can be defined as
 the complex cyclical transfer of nutrients ...
 from the environment to an organism and back to the
environment.
 There are 3 major cycles to understand
 Carbon/Oxygen Cycle
 Bio = Life
 Nitrogen Cycle
 Geo = Earth
 Phosphorus Cycle
The Carbon Cycle
 Also called the Carbon-Oxygen Cycle.
Refers to the flow of CO2 through the biosphere.
The Carbon Cycle
The main part of this cycle involves the
interrelation between cellular respiration and
photosynthesis.
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Photosynthesis
Cellular Respiration
The Carbon Cycle
 Carbon dioxide is also released by the activities
of :
Volcanoes
Glucose + O2
CO2 + H2O
Automobiles
Combustion of any source
Uplifting and weathering
The Carbon Cycle
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Reservoirs for Carbon
Organic Carbon
- Organic carbon is held in the bodies of all living
things.
- All living things die, and decomposition eventually
returns the carbon to the cycle in inorganic form.
- There is one important exception to this rule:
Some ecosystems such as bogs, store huge
quantities of carbon in organic form.
Reservoirs for Carbon
Inorganic Carbon
 When Carbon is not in organic form it
may be found in three main reservoirs.
1.
The Atmosphere
2.
The Ocean
3.
Earth’s Crust
- Peat
Human Impact on the Carbon
Cycle
 Human have modified the global carbon cycle by:
 Mining fossil fuels and burning them, releasing
carbon from organic reservoirs faster than
normal.
 Humans are also increasing the amount of carbon
dioxide in the inorganic reservoir by clearing
away vegetation in order to build or farm.
The Nitrogen and
Phosphorus Cycles
 Oceans can hold only so much carbon dioxide
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The Nitrogen Cycle
 The complex cycling of nitrogen between organisms
and the environment.
 The air is 79% nitrogen.
 The main component of most fertilizers is a nitrogen
compound.
Nitrogen and Animals
 Nitrogen is also needed for the
construction of proteins and nucleic
acids
 Muscle tissue
 Hair
 Bones
Nitrogen and Plants
 Nitrogen is a chemical that plants
need to grow well.
 Nitrates are a group of nitrogen
containing compounds that are readily
absorbed by the roots of plants
Nitrogen Usage
 Nitrogen is usually utilized in life in the form of nitrates.
 There are 2 main ways atmospheric nitrogen can be
converted into useful forms.
1) Lightning
2) Bacteria
 Cell parts
 DNA
 RNA
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Method #1 -- Lightning
 Lightning can force nitrogen and oxygen together to form
nitrates
 these will fall with precipitation and be absorbed by
plant roots.
 The plants will change these into their own proteins.
 Animals eat the plants and reorganize those proteins
into the ones they need.
Method #2 -- Bacteria
 These can convert atmospheric
nitrogen into nitrates.
 Nitrogen-fixing bacteria can
also be found in small lumps
called nodules on the roots of
legumes.
 Legumes can utilize atmospheric
nitrogen
 Legumes are members of the
bean family and include:
Clover and Alfalfa…
Legumes
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Nitrogen and decomposers
 After an organism dies, it decays.
 Decaying matter which contains nitrogen produces
ammonia.
 Ammonia will degrade into nitrites.
 Nitrites will degrade into nitrates.
 The nitrates will now re-enter the cycle.
Bacteria
 Some bacteria will actually convert the nitrates
back into atmospheric nitrogen.
Denitrifying bacteria.
These bacteria do not need oxygen -- anaerobic
respiration.
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Denitrification
Atmospheric pool of
nitrogen
Lightning
the process in which nitrates are
converted to nitrites and then to
nitrogen gas
Fertilizers
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Nitrogen-fixing
bacteria in root
nodules of legumes
Atmospheric pool of nitrogen
Nitrogen-fixing bacteria in root nodules of legumes
Fertilizers
Soil nitrate
Nitrate take up by plant roots
Plant and animal proteins
Dead organisms
Decomposers
Nitrate bacteria
Nitrate bacteria
Denitrifying bacteria
Lightning
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a Atmospheric nitrogen
b Lightning causes oxygen to react with nitrogen
c Rain dissolves the oxides of nitrogen that are formed
d Fertilizer
e Soil
f Nitrogen-fixing plants (legumes)
g Plants use nitrate to make protein
h Plants are eaten by animals
i Excretion
j Death
k Bacterial decomposition of nitrates to nitrogen
Phosphorus Cycle
 Phosphorus is a nutrient required by all living things.
 Component of bones and teeth
 DNA
 ATP
 Phosphorus Cycle is simpler than the carbon or nitrogen
cycles because it does not involve movement through the
atmosphere.
The Phosphorus Cycle
 Phosphorus is used in only one important inorganic
form…
 Phosphate Ion (PO43-)
 Plants absorb this through their roots.
 After plants incorporate phosphorus...
 it is transferred through the food chain
 it is eventually returned to the soil.
 excretions of animals
 actions of decomposers.
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The Phosphorus Cycle
Two methods of P recycling:
geological (abiotic Long-term cycle)
living organisms (biotic short-term
cycle)
Long Term Cycle
 Most common form: a part of rocks
 Properties:
 soluble - dissolve in water
 Phosphates dissolve in water—erosion (weathering)
carries them from land to streams and rivers and then
finally to the oceans
 Oceans  sediments may be thrust upward (uplifting) and
once again form land through geological activity
The Phosphorus Cycle
Long Term Cycle
The weathering of rocks gradually adds
phosphorus to the soil and to the
waterways.
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Short Term Cycle
Short Term Cycle
 Phosphates in water also enter the food chain
through photosynthetic organisms
 Decomposition of dead organisms  soluble
phosphates are absorbed by plants and used
during photosynthesis
 Plants are eaten by animals
Phosphorous Cycle
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Roles in Ecosystems
 Each organism has its own place within an
ecosystem.
 Ecological niche – an organism’s role in an
ecosystem, consisting of its place in the food
web, its habitat, its breeding area and time of
day at which it is most active.
Roles in Ecosystems
 Each species in an ecosystem tends to have a
different niche, a different role to play. This
helps to reduce competition between species.
 E.g. Even if two species eat the same food they
are not in competition because they may:
 Live in different places
 Eat at different times
Roles in Ecosystems
 E.g. Owls and hawks feed on many of the
same organisms, but occupy distinctly
different niches.
Owls hunt down prey with in forests
Hawk hunt down prey in grassland and open fields
Owls are active during dusk and at night
Hawk hunt by daylight
Competition is further reduced because owls and
hawks nest in different areas.
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Competition for Niches
 When a new species enter an ecosystem, it
causes a disturbance because it comes into
competition for a niche with one or more of
the species already in the ecosystem.
 Exotic species – species that are not native
to an ecosystem
 The introduction of new species happens
naturally. Animals are mobile and can move
from one ecosystem to another.
Introduction of Exotic
species
 The introduction of new species by humans to an
ecosystem is one of the main causes of species
depletion and extinction, second only to habitat loss.
 Problems with introducing Exotic Species:
 No natural population controls ( predators or diseases)
 Native species may not be able to compete for space, food or
reproductive sites.
 Prey organisms may not have defense mechanisms.
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Introduction of Exotic
species
 The actual number of introduced species that have established
themselves in Canada is well over 300 species.
Supporting Biodiversity in
Terrestrial Ecosystems
Limiting Factors in
Terrestrial Ecosystems
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Limiting Factors
 Terrestrial ecosystems are ecosystems that are found
anywhere on Earth that is not covered by water.
 Despite their many differences in each terrestrial
region biotic and abiotic factors are interdependent.
 These factors can limit the size of populations and can
also determine the number of species that survive in
each ecosystem.
 Abiotic Factors that can limit
Terrestrial ecosystems:
1. Soil
2. Available Water
3. Temperature
4. Sunlight
Soil
The quality and amount of soil
are critical factors in determining
the size and health of the plant
community and the biodiversity
of an ecosystem.
Soil
 Soil pH
 Humans have been contributing to higher levels of
acidity in many soils by burning fossil fuels.
 Burning of fossil fuels release sulphur dioxide and
nitrogen oxides into the air which fall to earth as acid
deposition.
Acid deposition – the process by which sulphur
dioxide and nitrogen oxides in the atmosphere
form acidic compounds and fall to Earth’s surface.
(Acid rain is an example of acid deposition)
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Available Water
 The amount of available water in an ecosystem
help determine the size and health of
populations and the biodiversity of an
ecosystem.
Sunlight
 The amount of sunlight determines what
plants will grow in an ecosystem.
 In ecosystems around the equator receive
more or less the same amount of daily
sunlight.
 Regions at more southern or northern
latitudes experience changes in the amount of
sunlight during different times of the year.
Temperature
 Temperature affects both biotic and abiotic
factors.
 Temperature can vary significantly throughout
the year in an ecosystem.
Taiga
 In a forest, the amount of sunlight varies from
the top of the canopy to the forest floor.
 In Taiga biomes, the mature trees are mostly
conifers like spruce and pine
 These trees can only support certain types of
birds that have tough beaks for cracking open
cones and nuts
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Taiga
Taiga
 Year-round, these trees block the sunlight
from reaching the forest floor
 This determines the types of plants that can
grow below the canopy
 In the Taiga, we see shade loving plants like
shrubs, mosses and ferns
 Due to the low growth on the forest floor,
nesting animals are only successful if they are
suitably camouflaged
 These plants then determine which primary
consumers exist in this ecosystem
Deer and moose
Deciduous Forests
 Have higher temperatures and precipitation
than Taiga
 Also have more humus
 Decaying plant and animal matter
 These conditions lead to a richer soil and
support growth of deciduous trees
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Deciduous Forests
 Spring: sun can reach all the way to forest floor
 Summer: Canopy is full, so very little sun gets
to the understorey.
 This is ok, because the understorey had the chance to
grow in the spring and is already mature
 Resulting in support for a diverse range of
organisms
Deciduous Forests
 Lots of leaf litter
 Many different insects
 Full understorey
 Moose and deer
 Leafy canopy
 Variety of birds and climbing mammals
Limiting factors of
Aquatic Ecosystems
Limiting Factors in
Aquatic Ecosystems

Like terrestrial ecosystems, aquatic
ecosystems are limited by abiotic factors:
1.
Chemical environment
2.
Light levels
3.
Temperature
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Chemical environment
1. The type of water:
 Freshwater
 Saltwater
Chemical environment
2.
Chemical environment
The amount of oxygen dissolved in the water.
 The amount of dissolved oxygen depends on:
 Temperature (warmer water holds less)
 Pressure (more oxygen dissolved at sea level
than mountain streams)
3. Any other dissolved substance
E.g., Naturally occurring minerals,
and organic pollutants.
 And the amount of salt and other substances
dissolved in the water (more salt, less oxygen)
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Light Levels and Temperature
 Light and temperature in an aquatic ecosystem may
vary over the course of the year (seasonal changes),
But these factors are also affected by the depth of the
water.
 Depending on the depth of the body of water the amount
of light available, the temperature and oxygen levels can
all vary. This will have a significant impact on what
organisms you can find.
Littoral Zone
 the area extending out from the lakeshore to
the point where you can no longer find plants
rooted.
 Most productive part of the lake.
 High amount of sunlight.
Zones within Aquatic
Ecosystems
Littoral
Limnetic
Profundal
Limnetic zone
 the area of a lake or pond in which there is
open water and sufficient light for
photosynthesis to occur.
 Most common form of organism in the zone is
plankton (small autotrophic and heterotrophic
microorganisms.
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Profundal zone
 the region of a lake beneath the limnetic zone,
in which there is insufficient light for
photosynthesis to occur.
 Most of the time only sources of nutrients in the zone
are dead plants and animals that fall from the limnetic
zone.
 Low oxygen due to bacteria decomposing dead organic
matter.
 No sunlight, no photosynthesis.
Lake Ecosystems
1. Oligotrophic
Changes in Lake
Ecosystems
 Lakes are typically deep and cold.
 Nutrient levels are low limiting size of
producer populations.
 Limited numbers of only a few kinds
of organisms.
 Water usually very clear.
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Lake Ecosystems
2. Eutrophic
Eutrophication
 Lakes are generally shallow and
warmer.
 In general oligotrophic lakes gradually become
eutrophic over time and eventually filling in
and becoming dry land.
 Very good supply of nutrients.
 This process is call eutrophication.
 Many species of photosynthetic
organisms.
 Water is often murky.
Eutrophication
Eutrophication
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Eutrophication
Eutrophication
 Human sometimes accelerate eutrophication
by adding nutrients to lakes:
Human wastes
Fertilizers
Household and Industrial products
Thermal energy
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