Unit 2:
Ecosystems
Environmental Science
What is an ecosystem?
System
= regularly interacting
and interdependent
components forming a unified
whole.
Ecosystem = an ecological
system;
= a community(living) and its
physical(non-living) environment
treated together as a functional
system.
Ecosystem
 Unit
of biosphere consisting of interacting
biotic and abiotic factors.

Biotic Factors: Living physical factors of an
environment.
 Organisms,

parasites, predation, etc.
Abiotic Factors: Non-living physical factors
of an environment.
 Air,
sunlight, water, pressure, etc.
 Habitat:
The physical location in
which an organism lives.
 Niche: The way of life of an
organism (species).
Includes: Habitat, feeding
habits, reproductive behavior,
etc.
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Parts of the Biosphere
1.
Species – a group of organisms that
can reproduce (Ex – humans).
2.
Population – The number of a species
in a given area (Ex – all the humans
living in Dresden).
3.
Community – All the species in a
given area (Ex – the humans, trees,
grasses, bacteria, squirrels, mice…..
Living in Dresden.)
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Parts of the Biosphere
4.
5.
6.
Ecosystem – The community and all the
nonliving things in an area (Ex – all the
plants, animals, bacteria, fungi and protists,
plus the air, water, and climate of Dresden).
Biome – An area of land characterized by a
particular climate and organisms.
Biosphere – The area on the Earth that
supports life (includes the bottom of the
oceans to the upper atmosphere).
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Parts of the Ecosystem
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Competition

Since resources will eventually run out,
organisms have to compete for it.

Can be between members of the same
species (Ex – Polar Bears have to compete for
fish to eat). Intraspecific competition

Can be between members of a different
species (Ex – a robin and a woodpecker
might compete over a tree to build a nest in.)
Interspecific competition
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Niche
 Niche
– the role an organism plays in the
environment (Ex – The Great White Shark is
the top consumer in some marine
ecosystems.)
 If two organisms occupy the same niche
they will compete for resources until one
species is forced out.
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Carrying Capacity
 The
maximum number of individuals an
ecosystem can support is the carrying
capacity.
 Once the carrying capacity is met,
limiting factors (such as space, food,
shelter) keeps the population size near this
carrying capacity.
Carrying Capacity
# Of Individuals
Time
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Predator – Prey Relationships
Predators Can Control the Prey Population
 Predators help control the prey
population (Since there are few predators
of Deer left in New York State, their
population size is out of control).
 If there are no natural predators the prey
become overpopulated.
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Predator – Prey Relationships
Prey Populations Can Control the Size of
Predator Populations
 If there are few prey in an area, a small
number of predators can survive.
 If there are many prey in an area, more
predators can survive.
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Predator-Prey Relationships
The Predators and Prey May Have No
Relationship
 If the predators rely on many sources of
food, one disappearing may have little
effect (Ex – If cows go extinct we might
have to eat more chicken, but humans
would still survive.)
Predator-Prey Relationship
Example
Moose
Wolves
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Food Chains
Parts of the Food Chain
1.
2.
Producers – (Autotrophs) make their own food
from abiotic factors (Ex – Green plants make
glucose by photosynthesis.)
Herbivores – Consumers that eat only plants. (Ex
– rabbits eat crops and other plants)
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Food Chains
3.
4.
5.
Carnivores – Eat only other consumers
(Ex – lion).
Omnivores – Eat plants and animals (Ex
– Humans).
Detrivores – (Decomposers) Feed off of
and break down dead organisms.
These are usually bacteria and fungi.
Energy Pyramid
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Food Pyramid Relationships
Biomass Pyramid
 Measures the amount of material at each
trophic level.
 Like
the Energy Pyramid, the larges
biomass is at the base (producers) and it
decreases as you move up the pyramid.
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Biomass Pyramid
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Food Pyramid Relationships
Pyramid of Population Size
 The
third pyramid shows the number of individuals
at each trophic level.
 Like
the other two pyramids, the largest population
is at the base (producers) and decreases as you
move up the pyramid.
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Pyramid of Population Size
Summary of the Pyramid
Relationships
Energy Pyramid
Shows the relative amount of energy
available at each trophic level.
Organisms use about 10 percent of
this energy for
life processes. The rest is lost as heat.
Biomass Pyramid
Represents the amount of
living organic matter at each
trophic level. Typically, the
greatest biomass is at the
base of the pyramid.
Pyramid of Numbers
Shows the relative
number of individual
organisms at each
trophic level.
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Trophic Levels






A trophic level is the position occupied by an
organism in a food chain.
Trophic levels can be analyzed on an energy
pyramid.
Producers are found at the base of the
pyramid and compromise the first trophic
level.
Primary consumers make up the second
trophic level.
Secondary consumers make up the third
trophic level.
Finally tertiary consumers make up the top
trophic level.
Antarctic
Food
Web
Trophic Levels Found on an
Energy Pyramid
 The
greatest amount of energy is found at
the base of the pyramid.
 The least amount of energy is found at
top of the pyramid.
Trophic Structure Reminder
 Eltonian
pyramids
 Number of individuals per species
 Is this pyramid stable?
Trophic Structure Reminder
 What
if we transformed each species into
biomass instead of absolute numbers?
Biomass




Energy is sometimes considered in terms of
biomass, the mass of all the organisms and
organic material in an area.
There is more biomass at the trophic level of
producers and fewer at the trophic level of
tertiary consumers. (There are more plants on
Earth than there are animals.)
Bio=life
Mass=weight
Bio + Mass = Weight of living things within an
ecosystem.
Trophic Structure Reminder
•Express trophic structure as energy transfer
•Energy pyramids can never be inverted
•Is there room for anyone else
at the top of this food chain?
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Biological Magnification
 If
a poison is introduced into an ecosystem, it will
affect each level of the food chain more
severely.
 Each
level of the food chain will have more
individuals affected.
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Biological Magnification
Accidental Introductions
 Zebra
Mussel – from Caspian Sea to Great Lakes
(1986) from a ship
 Now
they are everywhere!!!
 Problem: clogs water pipes, smothers native clams,
consumes plankton, no natural predators
 Killer
Bees – genetically altered to make more
honey
 Africanized
bees escaped and took over Brazilian
honeybees
 Problems arose: they are more aggressive, can travel
longer distances, swarm, attack people
 The real threat? Agriculture
More Invasive Species
 Asian



Carp
Introduced in 1970s
No natural predators
Out compete native fish
and mollusks for food
 Snakehead




Fish
Early 2000s
No natural predators
Eat mostly other fish
Can breathe air
4
days out of water
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Nutrient Recycling
Water Cycle - Earth’s water supply is
constantly recycled throughout the
biosphere:
 Evaporation – water vapor leaves the
oceans and joins the atmosphere.
 Transpiration – water vapor evaporates off of
plant leaves.
 Condensation – water vapor in the
atmosphere forms clouds.
 Precipitation – water vapor in the
atmosphere falls to the ground (rain.)
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Nutrient Recycling
CO2 and O2 Cycle
 Photosynthesis and Cellular Respiration work
together to recycle carbon dioxide and oxygen
in the atmosphere.
 Photosynthesis – in plants, uses up CO2 and
produces O2 as a waste.
 Cellular Respiration – in consumers, uses O2 and
produces CO2 as a waste.
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Nutrient Recycling
Nitrogen Cycle
 The Nitrogen in the atmosphere is made
usable for living things through Nitrogen
Fixation. (Legumes- Plants w/ N fixing
bacteria in roots: Beans/alfalfa)
 Plants use this nitrogen in the soil to make
proteins. This process is called assimilation.
 Once the plants and organisms that eat the
plants die, decomposers break down the
remains and return the nitrogen to the soil
and the atmosphere.
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Ecological Succession
 As
organisms live in a given area, they
change their environment.
 As
the environment changes, so do the
organisms that can live there.
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Ecological Succession
 Primary
Succession – a pioneer organism first grows
on a bare rock surface (Ex – Hawaiian Islands)
 Secondary
Succession – after a disaster (fire,
drought) succession begins again at an
intermediate stage (Ex – Pine Barrens of Long
Island).
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Human Effects on the
Environment
Negative Effects:
1.
Urbanization
2.
Industrialization
3.
Agriculture
4.
Exploitation of Wildlife
5.
Deforestation
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Greenhouse Effect
Carbon Dioxide and
other Greenhouse
gases trap the suns
energy in our
atmosphere to keep
the earth within a
range of suitable
temperatures for the
survival of the present
organisms
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Global Warming
 By
burning fossil fuels (use of automobiles, electricity,
home heating) carbon dioxide is released as a waste
gas.
 At the same time we are cutting down trees which
would have used up the Carbon Dioxide.
Global Warming
As a result, Carbon
Dioxide levels increase,
trapping MUCH MORE
heat from the sun and
gradually causing the
Earth to warm up.
 Global Warming could
cause sea level to rise,
habitats to be destroyed,
draught, and mass
extinction.

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Acid Rain
 Air
pollution in the atmosphere combines
with rain water, lowering the pH of the
rain.
 The
resulting acid rain damages
freshwater ecosystems, and there is
evidence linking it to extinctions of many
amphibian species.
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Ozone Layer Depletion
 The
ozone layer is part of the upper
atmosphere and blocks harmful rays of the
sun.
 The release of CFC’s from aerosol cans and
other sources of air pollution interact with the
atmosphere and deplete the ozone layer.
 If the ozone layer is destroyed, harmful rays
from the sun would cause catastrophic
mutations and would threaten all life on Earth.
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Positive Human Influences
 Conservation
of Resources
 Recycling
 Pollution
Controls
 Decreasing our dependence on fossil
fuels.