Interactions Within Ecosystems
Date: 3/12/13
P. 100-101 in ILL
Sustaining Ecosystems
• Ecosystems are destined to change, gradually,
over time. Sadly, human induced changes
often leave ecosystems unable to replenish
resources and the delicate balance of life is
upset. Terrestrial and aquatic ecosystems
each have a unique set of limiting factors and
challenges that threaten their sustainability.
Terrestrial Ecosystems
• Terrestrial ecosystems are limited by four major abiotic
factors:
1. Soil: Provides nutrients for all plants that grow on land.
Poor quality soil is an important limiting factor in many
ecosystems
2. Available Water: Since water is essential to all life water
can easily become a limiting factor for a population. Plants
are able to adapt to changing availability of water by
directing their roots deeper underground to reach
groundwater during droughts or periods of low
precipitation.
3. Temperature: Many plants and animals adapt
to a specific range of seasonal temperatures. A
variety of strategies such as hibernation,
migration, shedding leaves, a winter coat and
dormancy are used to help these organisms
survive.
4. Sunlight: has an effect on all terrestrial
ecosystems. The amount of sunlight usually
varies with the geographical location and with
the canopy plants that are growing in a specific
area.
Aquatic Ecosystems
• Aquatic ecosystems are often very diverse and
are important to the earth’s ecological state.
These ecosystems are affected by three major
abiotic factors:
– chemical environment (level of dissolved
oxygen)
– light levels (this is the most important
abiotic factor)
– Water temperature
Relationships within
an Ecosystem
Interdependence
What is interdependence?
• There are several different complex
relationships that exist among organisms
in an ecosystem. Organisms can be
interdependent, meaning their
population size or lives would be greatly
affected without the other’s presence.
Relationships like predation and
mutualism can help to regulate
populations.
Symbiosis—any relationship between two species
that live in the same ecosystem.
1. Mutualism—both species benefit (WIN-WIN)
a. Ex: insects and flowers the insects get food and the flowers
could not pollinate and reproduce without the insects help
Can you think of any other examples?
2. Commensalism—one member of the relationship
benefits and the other is neither
helped nor harmed.
(WIN-0)
Example: barnacles on a whale
the barnacles have a place to live
and the whale is not harmed or
helped by their presence
3. Parasitism—one organisms lives on or inside
another organism (the host) and harms it.
The parasite obtains all or part of its nutritional
needs from the host. (WIN-LOSE)
Example: fleas on a dog the fleas depend on the
dog to survive, the dog is harmed by their
presence
Predation—one organism captures and feeds on another
organism
1. Predator—one that does the killing
2. Prey—one that is the food
Who wants to be in a symbiotic relationship?
For the next 6 slides determine whether the
relationships shown are mutualism,
commensalism, parasitism, or predation.
Parasitism
Mutualism
Lobster and Sea Turtle– the sea
turtle is about to eat the lobster as
crunchy little snack!
Rhino and Oxpeckers—Oxpeckers (also
known as tickbird) will feed off ticks,
horsefly larvae and other parasites in the
rhino’s ears.
Aerophytes (epiphytes)—plants that grow
high up on another plant to obtain nutrients
and moisture from the air but cause no
harm to that plant
Shark and Remora—the remora fish will
attach to the shark, get a free ride and feed
off scraps left behind as it eats or that get
dropped as it tears the flesh from its prey
Female mosquito biting a human—
mosquito will feed off the blood and the
human will be harmed.
Ant, Acacia and Caterpillar-The caterpillars
have nectar organs which the ants drink
from, and the acacia tolerates the feeding
caterpillars. The ants appear to provide
some protection for both plant and
caterpillar.-
Ecological Interactions Between Organisms
Competition—when two organisms of the same or different
species attempt to use an ecological resource in the same
place at the same time.
Ex: food, water, shelter, mates
Cooperation—necessary to provide for young, escape
predators, and protect/ preserve the territory
Cooperation among competitors promotes coexistence
Monkeys compete
with each other and
other animals for food.
Rams compete with
each other for mates.
National Geographic Clip
http://education.nationalgeographic.
com/education/activity/ecologicalrelationships/?ar_a=1
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Energy Flow Through an
Ecosystem
Food Chains, Food Webs, Energy Pyramids
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Nearly all of Earth’s energy begins with
the sun!
• Sunlight is necessary for organisms to produce
their own energy.
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Organisms that make their own energy
(glucose) during photosynthesis are called
PRODUCERS.
Producers use most of the energy they
make for themselves for cellular
respiration which releases the energy
needed for all life processes.
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Photosynthesis
•Chemical reaction in chloroplasts of producers
that uses energy from the sun to transform water
and carbon dioxide into glucose and oxygen
•ENERGY is stored in glucose
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CELLULAR RESPIRATION
Chemical reaction in the mitochondria of all
cells to convert glucose and oxygen into usable
energy that allows organisms perform the
necessary life processes.
6O2 + C6H12O6  6H2O + 6CO2 + energy
It’s a cycle! The O2—
CO2 cycle or
photosynthesis/
respiration cycle.
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The energy that is not used by producers can be
passed on to organisms that cannot make their
own energy.
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Organisms that cannot make their
own energy are called CONSUMERS.
Consumers that eat producers to get energy…
•Are first order (1st)/trophic
level or primary consumers
•Must be herbivores
(plant-eaters) or omnivores
(plant and meat eaters)
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Most of the energy the primary
consumer gets from the producer is
used by the consumer.
Some of the energy moves
into the atmosphere as heat.
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Some energy in the primary
consumer is STORED & not lost to
the atmosphere or used by the
consumer itself.
This energy is available for another
consumer (predator).
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A Consumer that Eats Another
Consumer for Energy:
•Is called a secondary or
2nd order consumer
•May be a carnivore or a
omnivore
•May be a predator
•May be a scavenger
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Most of the energy the secondary
consumer gets from the primary
consumer is used by the secondary
consumer.
Some of the energy is lost as heat,
but some energy is stored and can
passed on to another consumer.
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A consumer that eats a consumer that
already ate a consumer:
•Is called a 3rd order or tertiary
consumer
•May be a carnivore or a
omnivore
•May be a predator
•May be a scavenger
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Consumers that eat other dead
consumers are called
scavengers
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All dead and decaying matter at each
trophic level is broken down by
decomposers such as bacteria and fungi.
The recycling of raw materials and
nutrients back into the soil after
decomposition—a process call
biodegradation, is vital to all ecosystems.
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The transfer of energy from the sun to
producer to primary consumer then to
higher order consumers can be shown in a
FOOD CHAIN.
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Another way of showing the
transfer of energy in an
ecosystem is the
ENERGY PYRAMID
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Energy Pyramids Show
•Amount of available energy
decreases for higher order
consumers
•It takes a large number of
producers to support a small
number of primary
consumers
•It takes a large number of
primary consumers to
support a small number of
secondary consumers
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Remember: Every chemical process that happens
in your body releases heat as a byproduct (ex:
burning calories).
Rule of 10—only about 10% of the available
energy within a trophic level is transferred to the
next higher trophic level
Biomass Pyramid—represents the amount of
living organic matter at each trophic level
0.1%
1%
10%
100%
Energy Pyramid
Biomass Pyramid
Food Webs:
•Are
interconnected
food chains
•They show the
feeding
relationships in an
ecosystem
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Identify the Producers, Consumers, & Decomposers:
Count the
Food
Chains!
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