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Q
Phylum Mollusca: (Soft Bodied)
The drive of all life forms is to reproduce, to pass on their genes in a construed way of gaining immortality.
But, we learned in Ecology, that there are a number of things that can stop reproduction and make life very
difficult. These include:
Organisms undergo what we are going to call a “BIOLOGICAL ARMS RACE” via evolution/ natural
selection to combat the factors above.
Reflection: What do you think we mean by Biological Arms Race?
An amazing example of this explosion (over millions of years, if you can call that an explosion) of
diversity as a result of this arms race is Phylum Mollusca.
Some Unifying Characteristics:
Alright, before we hit the rad diversification of mollucs, there are some reasons why all the different
animals from clams, oysters, mussels to octopi, squid, slugs, snails and chitons all belong to the same
Phylum.
1. A muscular “Foot”: Crawling,
2. A Mantle:
3. A mantle cavity:
4. A rough organ called a “Radula”:
5. A calcium shell (apparent, reduced form, or lost):
So how are these put in a body plan: Mollusc Diagram
Most mollusks respire through gills. Land mollusks do not have gills and instead undergo gas exchange
directly through their blood vessels via diffusion. This lining must be kept moist (in order for the gas to
diffuse); hence snails/ slugs must live in moist areas.
Diversity: Many animals belong to Phylum Mollusca and arose due to both biotic and abiotic factors in
their environment. Remember, they live in the ocean, the place of the beginning of life itself. Predator
were a plenty and soft bodies are an easy meal.
Class Gastropoda: the animals included in this class have a single shell or are shell-less and their foot
is located on the bottom of the animal. Animals include: sea slugs, sea butterflies, limpets, nudibranchs,
slugs and snails.
Adaptations:
Class Bivalvia (aka:
).
What are some animals that you think belong to Class Bivalvia?
Adaptations:
Class Cephlopoda
Contrary to bivalves who found greater protection in the form of two shells, cephlapoda uses speed and
smarts to survive.
Adaptations: