Download Mutualism & Parasitism

Symbiosis
Symbiosis: the intimate and prolonged
association between two or more
organisms of different species.
-Parasitism (+, -)
-Mutualism (+, +)
-Commensalism (+, o)
hackberry nipple gall
Symbiosis
Essentially any life form on Earth is a
habitat.
Human beings, sitting in SC-217 for
Ecology lecture are, themselves habitat for
an amazing array of organisms!
A human being is a symbiosis.
Up to 1000 species of microbe live in the
human gut, and nearly as many on the
human skin. Fungal and Bacterial.
Gut flora has about 100x as many genes
as in the human genome!
Good evidence that this is not merely a
commensal relationship…in fact, humans
cannot survive without these microbes.
Too much “sterilization” would kill you!
Parasites
Parasites can have hugely varied life
forms.
Microscopic: viruses, bacteria,
fungal. Associated with “disease”
Bird flu virus
Parasites
Parasites can have hugely varied
life forms.
Macroscopic: flatworms,
roundworms, lice, ticks, smuts
and “plants.”
Mistletoe: a parasite on trees in N. American and
Europe. Can induce kissing for those standing under
during the Yuletide.
Parasites
Parasites can be ecotoparasites or
endoparasite.
They can have intermediate hosts which
may not have any negative consequences.
They often move around using “vectors.”
Relationships can be quite complex.
Ticks carry Lyme disease. Deer carry ticks
Lyme disease is a bacterial parasite that is
transmitted through tick bites. In general,
the ticks are moved around by mammals_
especially white-tailed deer. The ecology of
white-tailed deer, then is directly related to
human health because of disease
transmission.
Parasites
Many parasites/diseases of humans (and other
animals) have very complex ecological
relationships.
Example: Malaria is a disease caused by a
parasitic protozoan. The protozoan is
transferred effectively by mosquitoes.
(particularly Anopheles). Malaria infection kills
~ 1 million people/year.
Parasites
Meningeal worm infection. Snails carry the larvae. Deer
accidentally eat the snails when grazing. Larva escape the
snails, move into the blood stream, infect tissues surrounding
the brain, eventually move into the lungs.
Hosts evolve defenses,
parasites evolve new
mechanisms. Long-term
interplay of selection between
hosts and parasites..
Parasitism can, and often does,
interact with other aspects of an
organism’s ecology.
In this case, the fish is infected
with a parasite, its behavior
changes, and then more of those
individuals are eaten by birds.
Mutualism
Mutualisms are extremely varied,
influencing virtually every living
organism (and, thus) ecosystem on
Earth.
As mentioned before, humans are a
mutualistic assemblage.
Some organisms are very clearly
mutualists.
Lichens are a fascinating example
Mutualism
The mutualism is so tight for lichens
that they are sometimes called
“composite organisms!” They consist of
an intimate mingling of fungus and
algae.
Fungal piece is the “mycobiont” and
provides nutrients.
An algea- generally green algae is the
“photobiont” and provides energy
through photosynthesis.
If you think about it, that is a wicked
combination! Lichens are extremely
hardy organisms_ able to survive in
very extreme conditions. (Example- on
the shingles of your roof!).
If you grow the fungus and algae
separate from one another, they take on
a very different form from the symbiosis.
Mutualism
Corals are another interesting mutualism. In
this case an animal (the coral “polyp”) is
associated with an algae. The algae
provides energy via photosynthesis. The
coral provides protection and substrate to the
algae.
Mutualism
Rhizobium is a genus of bacteria that forms a
mutualistic relationship with plants in the family
Fabaceae (Legumes…think “peas”). When the
bacteria are free in the soil, they act like bacteria.
When they encounter root hairs of a legume plant they
form a mutualism in which “nodules” are formed.
Within these nodules, the bacteria can “fix” gaseous
nitrogen to ammonia. This can have huge impacts on
soil nitrogen availability.
Mycorrhizae is the name for a mutualism that occurs between
plants and fungi. The fungi attach to root hairs of plants and can
vastly increase the extent of the roots and increase the plants
capacity for “foraging” for nutrient and water. The fungi, in turn,
receives access to the produces of photosynthesis (energy!).
There is a cost to forming the relationship for the plant (giving up
energy) and these relationships are often associated with poor
growing environments. Practically all plants do this!
“cleaning” mutualisms,
are relatively common.
Defensive mutualism
http://www.youtube.com/watch?v=s3blzcbll7Q
Pollination syndromes:
Evolutionary evidence of
long-term mutualistic
relationships
Hammer orchid
https://www.youtube.com/watch?v=Hv4n85-SqxQ
Orchid mimic
https://www.youtube.com/watch?v=-h8I3cqpgnA
Symbiosis