Mollusca

__**Mollusca**__
By:Reeyannah Quinto, Brandon Carter, Jalilah Smith & A'janae Lyles

What is it?
It is phylum that has many classes and species underneath it. Some of the most common being snails, clams, squid and slugs. Snails: The snail belongs to the Gastropoda class and are made up of different variety’s such as sea snail, land snails, and freshwater snails. Creatures without a shell are called slugs. The marine snails are the most popular although most people are used to seeing the land snail. The marine snail has much more diversity and biomass. Most snails are herbivores and eat algae or plants. They have microscopic razor like teeth that help shred the food to pieces.

Slug: Like the snail the slug is very much the same in a odd kind of way. Unlike the snail, slugs do not have shells in which they can recoil into. There are also land slugs, marine slugs, and fresh water slugs. Just like the snail the marine water slug takes up most of the population. They too are a part of the Gastropoda class.

Clams: Clams are originally known as freshwater mussels. The clam is normally found buried in mud or sand is actually edible. The example "clam chowder" refers to shellfish soup. A clams shell usually consist of two equal halves which can be connected by a joint or a ligament and it can be either internal or external. Clams have no head and no eyes, but do have a heart, mouth, kidney, and an n anus. Clams eat plankton by filter feeding which is when they draw in water that is contained with food.

Squid: The squid is mainly made up of the mantle which contains a fin on the side used for swimming. The squid is covered in mainly chromatophores which helps the squid blend in with its surroundings making it easier to hide from its predator. The mantle cavity contains the gills that help the squid to breathe. The squid consist of 8 arms and 2 tentacles. It also ejects a black ink from the ink sac when it feels it is in danger.

Classes & What it is a member of
In the Mollusca phylum there are three classes underneath it and they are Gastropoda, Bivalvia, and Cephalopoda (squid). The most common animal in the Gastropoda class are snails and slugs. Gastropoda’s are a major part of the phylum Mollusca and are the most highly diversified class in the phylum. There are 611 families of gastropods and out of the 611, there are 202 families are extinct. Bivalves have flattened bodies from side to side and are completely surrounded by two shells called valves. One of the most common animals in this class are clams. Inside the valves is the body surrounded by the mantle. The mantle holds digestive and reproductive organs and a muscular foot. The last class is the Cephalopoda; these exclusive marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles. Squids are the most common animals in the Cephalopoda class. In the Mollusca phylum the members of the phylum are pseudocoelomate and a coelomate. Coelomates are organisms that have a fluid filled body cavity, an example of an animal that is a coelomate is a squid. Pseudocoelomates are organisms that have a fully functional body cavity, an example of a pseudocoelomate would be a snail, and clam. There are no Acoelomates in the phylum Mollusca.

Characteristics of Mollusca
There are many characteristics that classify the phylum Mollusca. Some of the biggest and most dominant characteristics of Mollusca are: bilateral symmetry, more than two cell layers, tissues and organs, body without cavity, have a pair of kidneys, open circulatory system with a heart and aorta, gaseous exchange organs called ctenidial gills , a nervous system with a circum-oesophagal ring, ganglia and paired nerve chords, Body possesses a through gut with mouth and anus, however the most well-known is having a dorsal or lateral shells of protein.

The symmetry of Moluccas defines the characteristics of the species. It defines how the length and size of the other half is exactly the same as the other meaning that the phylum Mollusca is bilaterally symmetrical. The central axis between the left and right arrange how the two images are the same in the phylum. The body of symmetry of Mollusca is a figure of the same bilateral appearance is when if you were to cut the organism in half it would be equal and exactly alike one another. Bilateral symmetry is when the organism can only be cut in one direction and be identical.

Why are they evolutionarily successful ?
You can tell the phylum Mollusca is very evolutionary successful because there are over 600 different types of classes underneath this phylum. There are also many types of organisms that have evolved from one under this phylum for example the snail. The snails evolved and adapted to different environments for various reason such as geographic isolation. There is a great diversity in every population of each class. Mollusca have made it so that all of the chordate to become an evolutionary foot-note as opposed to the dominant life forms. This took place over 200 million years ago, after mollusks first progressed from the ocean to land. That also shows they have evolved because we can find many of the species under the phylum in more than one place; for example the ocean and land. Mollusca are still very present in our ecosystem today, as well as the structures and characteristics they carry. Many of these common characteristics are found in many phyla now, and it is all because of natural selection, homologous structures and evolution.

Cites Used:
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//<span style="color: #001bff; font-family: Cambria,serif; font-size: 18pt;">General Information //

it’s one of the Largest Phylum. They have about 50,000 living species however; some ever estimate that it could be around 200,000. This Phlyum has been around for about 550 million years.This phylum has many different animals in it that include but are not limited to clams, octopi, oyster, scallop, snail, and squid. There are a couple of different classes under thing Phylum, some examples of this is the following. Class Gastropoda, Class Bivalvia, Class Cephalopoda, Class Polyplacophora, Class Scaphopoda

We as, humans use the whole phylum mollusca and its animals inside this phylum a lot; we eat them and make jewelry out of them. <span style="color: #000099; font-family: Arial,sans-serif; font-size: 10pt;"> One example of this is that there are less than 100 white abalone left after. Due to the fact that in the 1970’s when a whole bunch of people started collecting them and eating them in mass quantities.

Some of the characteristics are that they have a fluid filled sack; they have a soft body coming from a Latin root. They also have a protective inside, which is a hard outside that helps protect their innards. The Coeldom is to help protect the Intestines and other things. The Coeldom is the hard part that helps protect there innards. They have three different parts of their bodies. They also have a line of symmetry that’s only one. Phylum Mollusca animals have a complete Nervous system along with an open circulatory system.They also usually have a tooth tongue.



o Class Ceplapod Octopuses are one of the most intelligent of all the invertebrates. They are one of the one of the most evolutionarily advanced animals to be found the entire invertebrate. They shot ink, that’s why some people call them ink fish. The Sperm whales are there biggest predators.

Some of the animals in this class include squids, octopi, and Cuttlefish. They have been around for about 500 million years. In 1861 they found a squid that was 6 meters long! The animals in this phylum that have shells they are often filled with air. The reason for this is to help them float around. Squids do have a shell but they are small and we now call them the Pen. Cuttlefish also have a shell but it is also small. Octopuses don’t have a shell at all.

There are about 17000 named species of fossil Ceplapods, and about 800 living species that we are aware of at this current moment. For this class they either have a shell, a reduced shell, or none at all. They often use jet propulsion to swim around What the other classes’ call the foot is their tentacles.

They are the type of animals that fight over females: the stronger one ends up getting to mate with the females. The fertilization for these animals happened inside the body just like for us humans. They unlike some other animals have two different sexes. For this class the males use special tentacles in order to fertilize the females. The Mother Octopus lays the eyes in a cave and lays her eggs on the roof of the cave. She watches over then for a while, but she dies shortly after watching the eggs.



Class Gastropoda are one of the fastest growing groups that has hermaphroditism: meaning that all the animals are both male and Female.
 * o **** Class Gastropoda **

Some of the animals in this class include snails, and slugs. This is the largest group of Mullusca with at least 62,000 living species. They make up 80% of the whole Mullesca family! They most likely have a shell but they could also have more than one, or just the opposite were they don’t have any.

There are 3 major subclasses that include Subclass Prosobranchia Subclass Opisthobranchia Subclass Pulmonata ¯ Subclass Prosobranchia For this subclass they have curtain features that make them different from all the rest. They all have gills, and shells. Snails often lay eggs that have a protective covering

¯ Subclass Pulmonata For this subclass it is customary that they have lungs.



Some of the animals in the class are clams, oysters, and scallops. They are also the 2nd largest class in this phylum. They have and open circulatory system, and they also have two different sexes Class Bivalvia have two parts of their shells. They have an oblong shell. More of the fresh water ones have a move roundish shell. Shells are often lopsided. They will most often close the shells in times of danger.They also move by clapping their shells together. They don’t have eyes, or any noticeable head.
 * o **** Class Bivalvia **