Ecology Notes #2
Symbiotic Relationships
Food Webs
Food Chains
SYMBIOTIC
RELATIONSHIPS
Symbiotic Relationships:
An Introduction
 Click on the picture
of the leaf cutter at
the left or on this link
to view a video about
symbiosis.
Leaf cutter video (large version)
Symbiotic Relationships
 Definition: Relationship where 2
species live closely together.
 The word symbiosis can be broken down
into two parts to determine its meaning.
 sym means together (like in the words
sympathy and symphony)
 bio mean life (like in the words biology and
biome)
Types of Symbiosis
Relationship
Type
Species A
Species B
Mutualism
+
+
Commensalism
+
0
Parasitism
+
-
Mutualism
 Relationship where
BOTH species
BENEFIT!
 A + / + relationship.
 Think of a normal
friendship where
both friends gain
something from the
friendship.
Mutualism Example. . .
Sharks are cleaned
by a little fish
known as a
Remora. The shark
never eats them
since they clean
bacteria off of the
shark. Since both
species are helped,
this is mutualism.
Commensalism
 Commensalism is
where one species
benefits while the
second species
remains unaffected.
 A + / 0 relationship
 Think of a friendship
where one of the
friends benefits while
the other doesn’t
change.
Barnacles adhering to the skin of a
whale
Parasitism
 Parasitism is the
situation where one
organism benefits
while the other is
harmed.
 A + / - relationship.
 Think of a friendship
where you might feel
used by your friend.
Video Examples
 Example website
with videos:
http://www.vtaide.
com/png/symbiosi
s.htm
• Predation- an interaction in which one organism
captures and feeds on another organism.
 Competitionoccurs when
organisms attempt to
use an ecological
resource in the same
place.
For Practice
A lichen is a combination of two organisms, an
algae and a fungus. The fungus gets its food
from the algae while the algae gets water from
the fungus. This is an example of which
relationship?
a) Competition
b) Mutualism
c) Parasitism
d) Commensalism
35 Clown fish are small reef fish that seek
protection from predators by sheltering
themselves among the stinging tentacles of sea
anemones. Clown fish are very territorial and
can potentially scare off predators of sea
anemones. This relationship is an example of -A neutralism This is not a type of symbiosis Incorrect
Since both are helped, it
B mutualism
is of mutual benefit or
C parasitism Neither is harmed so this is incorrect
D commensalism
Means only one is being helped and the relationship
has no effect on the other – also incorrect
Beechdrops (Epifagus virginiana) are leafless
plants that lack chlorophyll. Beechdrops get their
nourishment from the roots of beech trees, which
reduces the amount of nutrients available to the
trees themselves. This interaction is best described
as —
A predatory
B parasitic
C commensalistic
D mutualistic
What is helped?
Both the ants and the tree.
This is the definition of:
FOOD WEBS and FOOD
CHAINS
Eat or be eaten
 Here are some important
terms that will help you
describe interactions in a
food web.
1. Producer (autotroph)
 *can make its own food
 *forms the base of the food
web
Mmmmm…delicious.
2. Consumer (heterotroph)
 cannot make its own food
There are several words that describe consumers…
 Prey: the hunted
 Predator: the hunter
 Scavenger: eats dead things
 Herbivore: eats plants
 Carnivore: eats animals
 Omnivore: eats both plants and animals
Hey, you gonna eat that?
3. Decomposer
 Breaks down dead organisms
 Examples: bacteria, maggots, fungi, worms
 They complete the circle of life by returning
nutrients to the soil
4. Detritivore
 Feeds on dead organic material
Food Chain
Producer
Primary
Consumer
Secondary
Consumer
ARROWS represent ENERGY
FLOW!
Tertiary
Consumer
Herbivore
Carnivore
Autotroph
Omnivore
Tertiary Consumer
Secondary Consumer
Primary Consumer
Producers
Food Chain
 Advantage:
 Shows the path of energy
transfer in an ecosystem
 Disadvantages
 Has an endpoint instead of
showing an endless cycle
 Does not show diversity among
the organisms of a community
Food webs
 All organisms need FOOD to survive!
 Food webs show what eats what.
 ARROWS represent ENERGY FLOW!!!
Food Web
 Advantage:
 Shows how energy flows through
an ecosystem
 Shows diversity among the
organisms of a community
 Disadvantage:
 Complex
What is this?
What is this?
What is this?
Trophic Levels
 Group of organisms
whose energy source
is the same number of
steps away from the
sun or the position in a
food chain.
RULE OF 10
 Only 10% of energy is transferred from
one trophic level to the next.
 Example:
 It takes 100 kgs of plant materials
(producers) to support 10 kgs of herbivores
 It takes 10 kgs of herbivores to support 1 kg
of 1st level predator
Carnivores
0.1%
Tertiary Consumers
Carnivores
1%
Secondary Consumers
Herbivores
10%
Primary Consumers
Producers and Decomposers 100%
Biomass
- Dry weight of tissue and other
organic matter found in a specific
ecosystem
- When trophic levels are shown in an energy
pyramid, each higher level on the pyramid
contains only 10% of the biomass found in
the level below it.
18 Energy used by producers in a
Used by producers
grassland food web is provided
byF sunlight
G photosynthesis
H oxygen
J carbon dioxide
This is a process, not
an energy source.
H and J are elements
which are types of
matter, not energy.
So our answer should
be:
F
In this food chain, the
spiders are - A producers
 B primary consumers
 C competitors
 D secondary consumers
In this food pyramid, which
level contains the greatest
amount of energy?





A Tertiary consumers
B Secondary consumers
C Primary consumers
D Producers
About 10% of the energy at one
trophic level is passed to the next
level. What usually happens to the
energy that is not passed to the
next trophic level or used to carry
out life processes?

 A It is given off as heat.
 B It is stored as vitamins.
 C It is used in reproduction.
 D It is used in protein synthesis.
Which organisms in this food web
can be described as both primary
and secondary consumers?





F Hawks
G Weasels
H Raccoons
J Mice
Now, practice making food webs on
the whiteboard.
Label the producers, primary
consumers, secondary
consumers, tertiary consumers,
herbivores, carnivores