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Symbiosis
Notes #11
Symbiosis (notes)
• Symbiosis is the close interaction of two species which benefits at
least one of them
• Literally translated symbiosis means together (sym) life (bio)
The bird cleans the croc’s mouth of
residual food and parasites.
Everybody wins: the croc gets
cleaned, the bird gets a meal.
Types of Symbiosis (notes)
• There are three types of symbiosis: mutualism, commensalism, and
parasitism
Clownfish are immune to the
stings of anemones, living
among them as protection.
The anemones receive
nothing for their services.
Mutualism (notes)
• Mutualism is when both organisms benefit
• Mutualisms are very common in nature
(Non-note examples)
Ants “herd” aphids like cattle, protecting them from predators
The aphids produce a sweet “honeydew” which the ants eat
Pollinators get pollen (protein) and nectar (sugar) from plants
The plants get fertilized so they can reproduce
Mutualism Video
• https://www.youtube.com/watch?v=Xm2qdxVVRm4
Commensalism (notes)
• Commensalism is when one organism benefits and another is
unaffected
• This is often from one organism changing the environment
Elephants knock down trees to eat the leaves, creating grassland
Organisms that rely on grasslands have a place to live
Trees grow tall to maximize the amount of sunlight they receive
Birds create nests in these trees which are safe from predators
Commensalism Video
• https://www.youtube.com/watch?v=Qqa0OPbdvjw
Parasitism (notes)
• Parasitism is when one organism benefits while another is harmed
• Parasite species outnumber non-parasite species on the planet
Cuckoo birds lay their eggs in the nests of other birds
The other birds raise the chicks as their own, at the expense of
their own brood
Intestinal parasites live safely inside vertebrate digestive systems
The vertebrates lose valuable nutrients the worms absorb
Parasitism videos
• https://www.youtube.com/watch?v=eg5xe3zffHk
• https://www.youtube.com/watch?v=UrAAnUiBQVo
Symbiosis Summary (not notes)
“Sym” = together
“Bio” = life
3 types of symbiosis
1. Mutualism: both partners benefit
• Very common in nature
• Examples include flowers and their pollinators, legumes and nitrogen-fixing bacteria, humans and their crops
• Video: https://www.youtube.com/watch?v=Xm2qdxVVRm4
2. Commensalism: one benefits, the other is unaffected
• Often a result of one organism changing the environment and another benefitting from this change
• Examples include cockroaches and humans, elephants and various plains animals
• Video: https://www.youtube.com/watch?v=Qqa0OPbdvjw (first half)
3. Parasitism: one benefits, the one is hurt
• Parasites are more numerous species-wise than non-parasites
• The reason for this is because parasites specialize, so every time a new species arises a whole new set of
parasites also evolves to focus on it
• Examples include ticks and mammals, various types of internal worms
• Video: https://www.youtube.com/watch?v=eg5xe3zffHk