Think About It …
Why would a symbiotic relationship be
beneficial to an organism?
Let’s explore some
By: Kristine Ann B. de Jesus
I. Terms and concepts
C. Degree of dependence: Obligate vs.
D. Types of Mutualism
E. What is a Niche
Biological interactions are the effects
organisms in a community have on one
another. An organism's interactions with
its environment are fundamental to the
survival of that organism and the
functioning of the ecosystem as a whole
In ecology, it can involve individuals of
the same species or individuals of different
species. Species may interact once in a
generation (pollination) or live completely
within another (endosymbiosis).
Effects range from consumption of another
individual (predation, herbivory, or
cannibalism), to mutual benefit (mutualism).
Interactions need not be direct; individuals
may affect each other indirectly through
intermediaries such as shared resources or
Sym: From the greek/latin meaning
Bio: from the greek/latin meaning “to
live” or “living”
Symbiosis: A relationship where two
organisms live together where at least
one of the organisms benefits from the
Symbiosis: “sym” = together, “biosis”= living;
close physical association (e.g., host and
internal symbiont). Could be beneficial or
Symbiosis is the close interaction between
different species of animals. Interactions
vary from one creature living on another to
one creature living inside another.
The fundamental mystery of mutualism is why
one species has apparently evolved to help
“for such could not have been produced through
– Charles Darwin
The answer, of course, is that each species “helps the other” only for the sake of
benefits that it itself accrues.
Most mutualisms probably evolved from originally parasitic interactions
Mutualism is an interspecific interaction
between two species that benefits both
Populations of each species grow, survive
and/or reproduce at a higher rate in the
presence of the other species.
Mutualisms are widespread in nature, and
occur among many different types of
Mutualistic Symbiosis is a type of mutualism in
which individuals interact physically, or even
live within the body of the other mutualist.
Frequently, the relationship is essential for the
survival of at least one member.
Example: Lichens are a fungal-algal symbiosis
(that frequently includes a third member, a
cyanobacterium.) The mass of fungal hyphae
provides a protected habitat for the algae, and
takes up water and nutrients for the algae. In
return, the algae (and cynaobacteria) provide
carbohydrates as a source of energy for the
Bees fly from
flower to flower
which they make
bees. When they
land in a flower, the
bees get some
pollen on their hairy
bodies, and when
they land in the
next flower, some
of the pollen from
the first one rubs
off, pollinating the
The bee and the flower
Spider crabs live in
shallow areas of the
ocean floor, and
algae lives on the
crabs' backs, making
the crabs blend in
predators. The algae
gets a good place to
live, and the crab
The spider crab and the algae.
A certain kind of
bacteria lives in the
intestines of humans
and many other
animals. The human
cannot digest all of
the food that it eats.
The bacteria eat the
food that the
digest and partially
digest it, allowing
the human to finish
The bacteria and the
gets pollinated by
gets food (nectar)
› The raccoon
eats the berries
of the poison ivy
the seeds as it
› Both benefit.
Mushroom and fly
› Fly lands on and
Some of the spores
will adhere to the fly.
› When the fly dies,
(of natural causes)
the spores will be on
new ground and will
allow the mushroom
to grow in a new
Obligate: at least one species could not grow
and reproduce without the other
-The species involved are in close proximity and
interdependent with one another in a way that
one cannot survive without the other.
Facultative: Mutualisms are not essential for the
survival of either species. Individuals of each
species engage in mutualism when the other
species is present.
- both organisms do better with their mutualist,
but can survive and reproduce without it.
1. Facultative mutualisms: Each
species gains a benefit from the
presence of the other, but each
can still survive without the other.
2. Obligate mutualisms: Each
species can only live in the
presence of the other. “Exclusive”
Termites and their Flagellates
Neither organism can survive without
The plant provides food for the ant, as well
as shelter. In return, the ants defend the
plant from other herbivores, or organisms
that eat plants, as well as remove other
plants from the vicinity of their plant so it
can grow better.
live in acacia
as a home for
The tree also
for the ants in
-A relationship where one resource is
traded for another.
corals and the symbiotic algae
The algae get
from the corals, and
the corals get sugars
that are by-products
of photosynthesis from
the algae. When a
coral 'bleaches' it is
actually kicking out
that live in it, so all you
see is the coral's
skeleton, which is
This relationship occurs between two
organisms where one gets a resource,
and the other gets a service.
The honeybee gets
pollen from the flower
(the resource), and
the flower gets its
pollen spread to other
areas (the service)
honeybees and flowers
Flowering plants and pollinators. (both
facultative and obligate)
Parasitoid wasps and polydna viruses.
Ants and aphids. (facultative)
Termites and endosymbiotic protozoa.
Humans and domestic animals. (mostly
facultative, some obligate)
Lichens (fungus and Algae)
Lichens, little non-descript
patches of stuff you see
growing on rocks and tree
bark. This is a symbiosis,
consisting of a fungus and
an alga. The fungus provides
a protective home for the
algae, and gathers mineral
nutrients from rainwater and
from dissolving the rock
underneath. The alga gathers
energy from the sun.
Lichen is really two organisms: algae and fungus.
The fungus needs food but cannot make it. The
algae makes food but needs some way to keep
moist. The fungus forms a crust around the algae
which holds in moisture. Both organisms benefit.
The otters help
the kelp by
eating the sea
endanger it. The
and anchor for
the otters while
Otters and Kelp
The cleaner fish
eats parasites and
food bits out of
the inside of this
moray eel. It gets
a meal and is
predators by the
Each type of Yucca plant
can only be pollinated by a
specific kind of Yucca
That moth can only live on
that kind of Yucca.
Marcgravia evenia has leaves that act
like satellite dishes.
A) Because there are so many different species, they are able to
pollinate a greater variety of flowering plants.
B) Because they have short life cycles, short generation times,
and many offspring.
C) Because they have small brains and therefore cannot learn to
recognize many different plant species.
D) Because they can move quickly from plant to plant and
therefore can remember the last species visited.
•Plant gets its seeds
•Animal gets food
Seed dispersal mutualisms
Whalberg's Epauletted Fruit Bat
(Swollen Thorn Acacia)
•Plants provide ants with nectar
and other resources.
•Ants protect plants from
Protection mutualisms: lycaenid butterflies
produce ‘honeydew’ that
the ants eat.
The ants protect larvae
Protection mutualisms: Heliconius butterflies
• Both species are distasteful to
avian predators (Mullerian mimicry)
• Predators learn to avoid color
patterns more rapidly when color
patterns are prevalent
• Mimicry decreases the likelihood
of predation for each species in this
•Strong convergence of color pattern
Nutrient acquisition mutualisms
•The plant (legumes)
supplies energy to the
•The bacteria ‘fix’ nitrogen
for the plant (convert
atmospheric N2 gas to
ammonium (NH4+) in the
Niche The limits, for all important environmental
features, within which individuals of a species
can survive, grow and reproduce.
The 'occupation' or 'profession' of an organism
› Where it lives?
› Life history?
› Feeding behaviour/times
Co-evolution occurs when two species
interact so strongly with one another that
they are dominant evolutionary forces on
- Obligate, specialist mutualisms
- Specialist predator/prey interactions
(the term was first coined in describing
the “evolutionary arms race” between
plant chemical defenses and insect
herbivores that evolve resistance to those
The flower produces nectar that provides
the perfect nutrition for the bird, and
exists in colors that the bird sees best.
Meanwhile the bird's beak is perfectly
shaped to drink from the flowers. The
flower provides food for the bird, and the
bird, by drinking from several different
flowers spread pollen between flowers.
Not all coevolution
is the result of, or
results in symbiosis.
also occur in a
relationship. Think of
it as a sort of arms
race, as the
predator and prey
each evolve new
either pounce, or
keep from being
garter snake, and the rough skinned
Predator- Prey relationship that has
caused co-evolution. The newt has
evolved an potent toxin in the skin,
while the snake (which eats the newt)
has developed a resistance to this
Neutralism the most common type of
interspecific interaction. Neither
population affects the other. Any
interactions that do occur are indirect or
Example: the tarantulas living in a
desert and the cacti living in a desert
-A type of interspecific interaction, which is the interaction between
species. These interactions may have effects on the species'
populations. In neutralism, interactions are incidental or indirect and
are said to not have an effect on either population. Neutralism
occurs when two populations interact without having an effect on
the evolutionary fitness of each other.
cacti and tarantulas living in
Type of Interaction Sign Effects
both species benefit from
one species benefits, one
populations do not affect
One species is
Directions: Tell whether the relationship is Mutualism, Commensalism Amensalism or
Barnacles create home sites by attaching themselves to
whales. This relationship neither harms nor benefits the
Yucca flowers are pollinated by yucca moths. The moths lay
their eggs in the flowers where the larvae hatch and eat some of
the developing seeds. Both species benefit.
Remoras attach themselves to a shark’s body. They then
travel with the shark and feed on the leftover food scraps from
the shark’s meals. The relationship neither harms nor benefits
Oxpeckers feed on the ticks found on a rhinoceros. The
oxpeckers get a meal and the rhinoceros is helped by the
removal of the ticks.
The stork uses it saw-like bill to cut up the dead animals it
eats. As a result, the dead animal carcass is accessible to
some bees for food and egg laying. The relationship neither
harms nor benefits the stork.
Hermit crabs live in shells made and then abandoned by
snails. This relationship neither helps nor harms the snails.
Wrasse fish feed on the parasites found on the black sea
bass’s body. The wrasse fish get a meal and the black sea
bass is helped by the removal of the parasites.
A sparrow will build its nest under the nest of an osprey.
The smaller birds get protection because other predators
will not mess with the osprey. The osprey are not helped
nor harmed by the sparrow.
Ostriches and gazelles feed next to each other. They
both watch for predators and alert each other to danger.
Because their visual abilities are different, they can
identify threats that the other animal would not see as
Honey guide birds alert and direct badgers to bee hives.
The badgers then expose the hives and feed on the honey
first. Next the honey guide birds eat. Both species benefit.
A cuckoo may lay its eggs in a warbler’s nest. The
cuckoo’s young will knock the warbler’s eggs out of a
nest and the warbler will raise the cuckoo’s young.
As bison walk through grass, insects become active and
are seen and eaten by cowbirds. The relationship neither
harms nor benefits the bison.
Orchids grow inside a bromeliad plant. The orchid
obtains water and nutrients from the bromeliad, but does
not help or harm it.