The document discusses various examples of mutualistic relationships in nature. Mutualism is a positive interspecific relationship where both species benefit. Examples provided include plants and their pollinators, lichens consisting of algae and fungi, cleaner shrimp that remove parasites from fish, ants that protect aphids and collect their honeydew, and nitrogen-fixing bacteria within plant nodules. Many mutualisms involve one organism providing a service like nutrition, protection, or dispersal while receiving shelter or nutrients in return. Mutualisms can be facultative, where the relationship is not strictly required for survival, or obligate, where one or both species depend entirely on the other.

1. Dr. Archana Mantale
Assistant professor
Department of Zoology
Marathwada Shikshan Prasarak Mandal’s
SHRI MUKTANAND COLLEGE, GANGAPUR
Dist. Aurangabad 431109 (MS) India
NAAC Accredited “A” Grade & ISO:9001-2015Certified
MUTUALISM
Dr. A. B. Mantale

2. Mutualism – two species provide
resources or services to each other 
enhances fitness of both species
Both partners benefit from the
relationship (+, +).
MUTUALISM
Dr. A. B. Mantale

3. MUTUALISM
Mutualism is the positive type of interspecific
relationship between two organisms where both of
them benefited from the relationship.
This can involve providing food, protection, a place to
live or even pollination.
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 organisms.
Dr. A. B. Mantale

4. 1. Facultative mutualisms: Mutualisms are not
essential for the survival of either species.
Individuals of each species engage in mutualism
when the other species is present.
 Each species gains a benefit from the presence
of the other, but each can still survive without
the other. “Generalist” mutualisms.
2. Obligate mutualisms: mutualisms are essential
for the survival of one or both species.
 Each species can only live in the presence of the
other. “Exclusive” mutualisms
Facultative vs. Obligate Mutualisms
Dr. A. B. Mantale

5. Examples of Mutualisms:
• Flowering plants and pollinators.
• (both facultative and obligate)
• Parasitoid wasps and polydna viruses.
(obligate)
Ants and aphids. (facultative)
• Termites and endosymbiotic protozoa.
(obligate)
• Humans and domestic animals.
• mostly facultative, some obligate)
Dr. A. B. Mantale

6. Mutualism – clownfish and anemone
The clownfish gets protection from the anemone
and in return protects the anemone from fish that
would eat it (angelfish); the clownfish also keeps
the anemone free of dirt and debris.
Dr. A. B. Mantale

7. Mutualism - Lichens
Lichens consist of a
fungus with an algae
or photosynthetic
bacterium living
inside the fungus.
The alga provides
food for both of them
and the fungus
provides a habitat for
the alga.
Dr. A. B. Mantale

8. Mutualism – cleaner shrimp
These shrimp set up
Large cleaning
stations on the reef
where fish will come
to have parasites
picked from their
skin.
The shrimp gets a
constant food source
and the fish (eel in
this case) gets rid of
potentially dangerous
parasites.
Dr. A. B. Mantale

9. Cleaner Shrimp on a Grouper
Dr. A. B. Mantale

10. Mutualism – Ant and Aphid
Dr. A. B. Mantale

11. The Aphid and the Ant
•Aphids feed on the sap of the plant they are on.
•Ants use their antennae to stimulate the aphids and
cause them to excrete from their abdomen a
substance called honeydew which is rich in the
nutrients ants require.
•Each worker ant goes from aphid to aphid collecting
honeydew which she stores in her abdomen until it's
full; then, she returns to the nest and regurgitates to
feed other members of the colony.
•Ants, in return for the honeydew, protect the aphids
from predators such as flies, wasps, and beetles.
The ants, like human ranchers, sometimes move their
aphids to richer grazing grounds.
Dr. A. B. Mantale

12. Mutualism – sea slug with algae
The algae lives in the
sea slug and makes
food for both of
them – in return it
gets a place to live.
Dr. A. B. Mantale

13. Nitrogen fixing nodules
Bacteria in the
nodules can take
nitrogen gas from
the atmosphere
and turn it into a
form that can be
used by the plant;
in return, the plant
protects the bacteria
from harmful oxygen
and the bacteria get
food from the plant.
Dr. A. B. Mantale

14. Mutualism - pollination
Many plants depend
on pollinators for
their reproduction.
They provide nectar
to attract these
pollinators.
So the pollinator
gets fed and the
plant gets
reproduced!
Dr. A. B. Mantale

15. Another Pollinator – note pollen on back legs
Dr. A. B. Mantale

16. Protozoans in cow’s stomach
These protozoans along
with bacteria help the
cow by digesting
cellulose; cows don’t
have the enzymes to
do this.
The protozoans and
bacteria get a place to
live and a continual
food source. This is a
valuable mutualistic
relationship.
Dr. A. B. Mantale

17. Ants and Acacia Trees
Acacia trees are found in
Central America. Ants
hollow out the large thorns
of the plant for nests and
feed on sweet secretions
from the base of each leaf
and on the protein rich
substance found on the tips
of the leaves, The ants in
return protect the trees
from herbivores that would
eat the leaves. With a
movement of the branch,
ants emerge and release a
nasty odor and attack the
herbivore.
Dr. A. B. Mantale

18. The ants, again
When an
experiment
was done and
the ants Were
poisoned, the
acacia trees died
from Being
overtaken by
other plants and
herbivores.
Dr. A. B. Mantale

19. OxPecker - Mutualism
The oxpecker
Eats parasites
on the mammal –
food for the bird
and removal of
danger for the
mammal
Dr. A. B. Mantale

20. More Ox (?) peckers
Dr. A. B. Mantale

21. Another ox(?)pecker
Dr. A. B. Mantale

22. Caterpillar Ant Mutualism
Dr. A. B. Mantale

23. Flowers and their Pollinators (examples: Bees
and hummingbirds gather nectar and spread
pollen.)
Dr. A. B. Mantale

24. Birds and mammals eat berries and fruits
while the plant benefits by the dispersal of it
seeds.
Dr. A. B. Mantale

25. Algae and Fungi > Lichen - Alga gets water
and nutrients from the fungus and the
fungus gets food from the algae.
Dr. A. B. Mantale

26. Cleaners eat insect pests from the skin of
animals. (ex: Egyptian plover cleans giraffes
and buffaloes)
Dr. A. B. Mantale

27. Many herbivores such as cows, sheep, deer,
horses and rabbits depend on bacteria that live in
their stomachs to break down the plant material.
Dr. A. B. Mantale

28. Coral Reefs- The corals get food and the
algae get protection.
Dr. A. B. Mantale

29. Dr. A. B. Mantale

30. Dr. A. B. Mantale

31. Ants & “Ant Plants”
Ants and bullhorn acacia
Ant plant associations are usually facultative
Dr. A. B. Mantale

32. Nitrogen-fixing bacteria symbionts in plants
Alder (tree)
Root nodules
Obligate (or nearly so), probably specialist or narrow generalist
Dr. A. B. Mantale