Principles of Ecology
• Ecology – study of
relationships between living
and nonliving parts of the
world
• Ernst Haeckel (1866) – first
to use the word to name the
study of how organisms fit
into their environment
Exam Need to Know Material
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Levels of organization from molecules to biosphere:
How do ecologists study the living world around them?
Members of food chains – trophic levels (ie: producers, decomposers, detritivores etc…)
Biomagnification, carrying capacity, limiting factors
Food Chains vs Food Webs
Ecological pyramid types
Autotrophs vs heterotrophs- different types
Water cycle
Nitrogen cycle
Phosphorous cycle
Carbon cycle
Abiotic vs biotic
Symbiotic relationships – parasitism, commensalism, mutualism
Predator vs prey
Biodiversity benefits
Characteristics of Minnesota Ecosystems
Parts of the Environment
• Abiotic factors – non-living parts
of an organism’s environment
– Air currents, temperature,
moisture, light, soil
• Biotic factors – all the living
things that inhabit the
environment
Levels of Organization
Organism
Population
Community
Ecosystem
Biome
Biosphere
Niche vs. Habitat vs. Ecosystem
• Ecosystem – all the organisms in a given area and the
abiotic factors that affect them
• Habitat – place an organism lives out its life
• Niche – role and position a species has in its
environment
– Includes all biotic and abiotic interactions as an organism
meets its needs for survival
– If two species are competing for the same niche, one will
most likely drive the other out and take control of the niche.
• What is your niche?
Niche vs. Habitat vs. Ecosystem
An egret lives around Lura Lake which is part of
the Maple River Watershed. The egret and its
mate eat fish, frogs, salamanders, snakes,
crayfish, mice, aquatic insects, crickets,
grasshoppers, and a variety of other insects in
Lura Lake and build a nest in a tree along side
the lake.
• What is the egret’s habitat?
• What is the egret’s niche?
• What is the egret’s ecosystem?
Relationships
• All living things form
relationships with other
living things
• Symbiotic Relationship –
a relationship between
organisms of two
different species that live
together in direct contact
Commensalism
• One organism benefits – The other is not affected
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Examples
Spanish moss on a tree
Barnacles on a whale
Burdock seeds on a passing animal
Mutualism
• Both organisms benefit
– Acacia tree and ants (Pseudomyrmex sp.) – tree provides food
for the ants and the ants protect the tree from animals that
would eat the leaves
– Lichens: algae and fungus living together.
Algae provides food (photosynthesis)
and the fungus provides protection and
attaches the lichen to the rock or
wood where it lives.
Parasitism
• One organism benefits,
the other is harmed
– Some live with in the host
• Tapeworms
• Heartworms
• Bacteria
– Some feel on the external surface of the host
• Ticks
• Fleas
• Mistletoe
– Most do not kill their host
(at least not quickly)
Ecosystem Requirements
• #1 - Continuous supply of Energy
• #2 – A flow of energy from one population to
another
Obtaining Energy
• Autotrophs - use energy from the
sun or energy stored in chemical
compounds to produce energy
• Heterotrophs – must consume
their energy
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Herbivores
Carnivores
Omnivores
Detritivores
Scavengers
Decomposers
Herbivores
• Eat plants (autotrophs)
Carnivores
• Eat other heterotrophs
– Predators – kill their own food
– Scavengers – eat animals that are already dead
Omnivores
• Eat both autotrophs and heterotrophs (plants
and animals)
Detritivore
• A type of decomposer – eats decaying matter
and return nutrients to soil, water, and air
– Ex. worms, millipedes, woodlice, dung flies, and
slugs
Decomposers
• They break down the dead organisms through
decomposition and return nutrients to soil,
water, and air -Ex. Fungus and bacteria
Energy Flows through an Ecosystem in a Complex
Network of Feeding relationships called a FOOD WEB.
Food Chain
Energy Pyramid
• The energy pyramid is made of several trophic levels
• A Trophic Level (or feeding level) is a group of
organisms whose feeding source is the same number of
steps from the Sun.
– Primary Producers (Autotrophs) are the First Trophic
Level.
– Primary Consumers (Herbivores) are the Second Trophic
Level.
– Secondary and Tertiary Consumers (Carnivores and
Omnivores) are the Third and
Fourth Trophic Levels.
– Most Animals feed at more
than one Trophic Level.
Trophic Levels
• Energy is Lost or Used as it Flows through the
Trophic Levels of an Ecosystem.
• Producers (Plants) absorb Energy from the Sun, but
only about ½ of the Energy capture from the Sun
becomes part of the Plants Body. The other ½ is used
for Living and Growing or Lost as HEAT.
• At each Trophic Level, the Energy stored in an
organism is about 1/10 that of the Level Below it.
(10%).
Trophic Levels
• Because Energy diminishes at each successive
Trophic Level, Few Ecosystems can contain
more than 4 or 5 Trophic Levels.
• Organisms at Higher Trophic Levels, Large
Carnivores, tend to be Fewer in number than
those at Lower Trophic Levels, Producers.
Number and Biomass Pyramids
• The number of
organisms at each
trophic levels
decreases as you
step up the
pyramid.
• Biomass (living
organic matter) is
reduced at each
trophic level as
well
Bioaccumulation/ Biomagnification
• Energy is not the only thing that is passed along through the food
web.
• If contaminants are introduced at any level, those organisms that
consume the contaminated food, will absorb the contaminants as
well.
• Because the amount of energy required gets higher at each level,
those organisms have to consume more and thus can accumulate
higher levels of the contaminants in their bodies – bioaccumulation.
• Example – A pesticide that you put of your yard is consumed by the
grasshoppers that live there. The partridge eats
10 grasshoppers. The hawk eats 3 partridges.
– If the grasshopper consumed 1 mg of the pesticide,
the partridge ingested 10mg, and the hawk
consumed 30mg.
Geochemical Cycles
• Geochemical Cycles are the movement of a particular form of
matter through the living and nonliving parts of an ecosystem
• Since Earth is a closed system, it must continually cycle its
essential matter.
• Matter changes form but is neither created nor destroyed; it is
used over and over again in a continuous cycle.
• Organisms are an important part of this cycling system.
• Matter placed into biological systems is always
transferred and transformed. Matter, including
carbon, nitrogen, and water, gets cycled in and
out of ecosystems.
Carbon Cycle
• Carbon is one of the major components of the biochemical
compounds of living organisms (proteins, carbohydrates,
lipids, nucleic acids).
• Carbon is found in the atmosphere and also in many minerals
and rocks, fossil fuels (natural gas, petroleum, and coal) and in
the organic materials that compose soil and aquatic sediments.
• Organisms play a major role in recycling
carbon from one form to another in the
following processes:
– Photosynthesis
– Respiration
– Decomposition
– Conversion of biochemical
compounds
Carbon Recycling Processes
• Photosynthesis:
Autotrophs take in
carbon dioxide from
the atmosphere and
convert it to simple
sugars.
• Respiration: Organisms
break down glucose and
carbon is released into
the atmosphere as
carbon dioxide.
Carbon Recycling Processes
• Decomposition: When organisms die, decomposers break down
carbon compounds which both enrich the soil or aquatic
sediments and are eventually released into the atmosphere as
carbon dioxide.
• Conversion of biochemical compounds: Organisms store
carbon as carbohydrates, proteins, lipids,
and nucleic acids in their bodies.
When animals eat, those
compounds can be:
– used for energy
– converted to compounds that are
suited for the predator’s body
– released to the atmosphere as methane
and other gases
Carbon Recycling Processes
• Other methods of releasing stored carbon may be:
– Combustion: When wood or fossil fuels (which were formed
from once living organisms) are burned, carbon dioxide is
released into the atmosphere.
– Weathering of carbonate rocks:
Bones and shells fall to the bottom
of oceans or lakes and are
incorporated into sedimentary rocks
such as calcium carbonate. When
sedimentary rocks weather and
decompose, carbon is released into
the ocean and eventually into the
atmosphere.
Nitrogen Cycle
• Nitrogen is the critical component of amino acids
which are needed to build proteins in organisms.
• Nitrogen is found in the atmosphere as elemental
nitrogen (N2), in living organisms (in the form of
proteins and nucleic acids), or in organic materials that
compose soil and aquatic sediments.
• Organisms play a major role in recycling nitrogen from
one form to another in the following processes:
– Nitrogen-fixation
– Intake of nitrogen into the
organisms
– Decomposition
– Denitrification
Nitrogen Recycling Processes
• Nitrogen-fixation: Nitrogen-fixing bacteria, which are found
in the soil, root nodules of plants, or aquatic ecosystems, are
capable of converting nitrogen found in the air or dissolved in
water into the forms that are available for use by plants.
• Intake of nitrogen into the organisms: Plants take in the
nitrogen through their root
systems in the form
of ammonia or nitrate
and in this way,
nitrogen can enter
the food chain.
Nitrogen Recycling Processes
• Decomposition: When an organism dies or from
animal waste products, decomposers return nitrogen to
the soil.
• Denitrification: Denitrifying bacteria break down the
nitrogen
compounds in
the soil and release
nitrogen into the
atmosphere.
Water Cycle
• Water is a necessary substance for the life processes of all living
organisms.
• Water is found in the atmosphere, on the surface of Earth and
underground, and in living organisms.
• The water cycle, also called the hydrologic cycle, is driven by the
Sun’s heat energy, which causes water to evaporate from water
reservoirs (the ocean, lakes, ponds, rivers), condense into clouds,
and then precipitate back to water bodies on Earth.
• Organisms also play a role in recycling
water from one form to another by:
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Intake of water into the organisms
Transpiration
Respiration
Elimination
Percolation
Water Recycling Processes
• Intake of water into the organisms: Organisms take in water and
use it to perform life functions (such as photosynthesis or
transport of nutrients).
• Transpiration: Plants release water back into the atmosphere
through the process of transpiration (the evaporative loss of
water from plants).
• Respiration: All organisms metabolize
food for energy and produce water as
a by-product of respiration.
• Elimination: Most organisms need
water to assist with the elimination
of waste products.
Phosphorus Cycle
• a) It is the main constituent of
energy rich compounds like ADP
(Adenosine diphosphate) and ATP
(Adenosine triphosphate)
• b) It’s a major constituent of cell
membrane, nucleic acid, cellular
energy transfer systems.
• c) Essential for metabolic reactions
releasing energy.
• d) Required for encoding of the
information in genes (as it is the
component of nucleotides and
nucleic acids).
• Phosphorus has no gaseous phase
and hence forms a part of
sedimentary cycle
Maintaining Ecosystems
• All of the Earth’s processes help ecosystems
maintain our biosphere
• Our biosphere is the inhabited portion of our
planet made up of three parts:
– Atmosphere
– Hydrosphere
– Geosphere
• Each of these systems must interact efficiently
for each ecosystem to be maintained
Atmosphere
• Our atmosphere is primarily composed of materials
from life’s processes.
• Oxygen
– Plants and other autotrophs produce enough oxygen for
themselves and other organisms through photosynthesis
– The oxygen from photosynthesis is also responsible
for the ozone layer which prevents the sun’s UV
radiation from reaching the Earth’s surface
• Carbon Dioxide
– Oxygen is used by plants and animals for cellular respiration
which releases carbon dioxide into the atmosphere
– The processes of photosynthesis and cellular
respiration help keep the concentrations of
oxygen and carbon dioxide balanced.
Atmosphere
• Nitrogen
– Nitrogen in the atmosphere is
maintained by the Nitrogen cycle
• Water
– Water vapor in the atmosphere is
maintained by the water cycle
– As water vapor condenses in the
atmosphere, impurities (dust, particulates, etc) are
removed from the atmosphere and fall to Earth with
precipitation. Thus, the air is cleaned after a rain or
snow fall.
Atmosphere Imbalance
• The greenhouse effect is the normal warming effect when gases
(such as carbon dioxide, oxygen, methane, and water vapor) trap
heat in the atmosphere.
• The amount of carbon dioxide in the atmosphere cycles in
response to how may plants and other photosynthetic organisms
cover Earth and how much carbon dioxide they absorb.
• The amount of carbon dioxide in the atmosphere also cycles in
response to the degree to which oceans cover Earth. The salt
water of oceans acts as a sink for carbon dioxide, absorbing what
plants do not use and converting it to various salts such as
calcium carbonate.
Hydrosphere
• The hydrologic cycle is maintained by the energy of the
Sun and the effect of weather.
• The hydrologic cycle purifies water in several ways:
– Evaporated water is pure water containing no impurities.
– As water seeps down through the soil and rock it is physically
filtered of impurities.
– As water flow slows, heavier
particles of sediment settle out,
leaving purified water to travel
toward the oceans.
Geosphere
• As part of the geosphere, the soils on Earth
are constantly being generated and eroded.
• All soils are composed of four distinct
components – inorganic minerals, organic matter, water, and air.
• As the weathering of inorganic materials from wind, water, and
ice and the decaying of organic materials continue, more soil is
produced.
• Soil erosion and deposition are natural processes that move soil
from one location to another due to water, wind, ice and other
agents.
• In most areas, the presence of plants allows the process of soil
production to be consistent with the process of soil erosion so
that the overall amount of soil remains constant.
• The presence of soil in an ecosystem allows for succession to
take place.