" The Big Picture!" by Mr C

Biology 11

Name: ______________ __________________ Date: ________________ Block: ____________

 

 

Phylum Mollusca (Latin: mollis = “soft”)

Pages 329-334

 

I Background:

 

• 10 Classes, 8 of which are still alive today, 2 are just fossils (we will only look at 3 of the Classes):
  • ________________________________: Clams, Oysters, Mussels, Scallops etc. ~ 8000 species
  • ________________________________: Marine-Sea Snails, Limpets, Conchs, Nudibranchs (Sea Slugs), Sea Hares, Sea Angel, Sea Butterfly, Sea Lemon; Terrestiral-Snails and Slugs; Feshwater-Snails etc. ~40000-150000 species
  • ________________________________: Squid, Octopodes, Nautilus, Cuttlefish etc. ~790 species

 

• ~250000 estimated species
• Most Molluscs are marine but some are freshwater and others are terrestrial like the common snail and slug
• The Phylum Mollusca demonstrate incredible diversity from the clam to the giant squid

 

DID YOU KNOW!!!: The Molluscs are the second largest Phylum (abundance of species) next

to the Phylum Arthropoda!!!

 

II Body Plan/Structure: (General Characteristics of all Molluscs)

 

• Molluscs demonstrate a ____________________________ symmetrical body plan
• They have the three true germ layers:
  • __________________________
  • __________________________
  • __________________________

• They have true coeloms
  1. The coelom has been reduced to a special body cavity that just surrounds the organs.       This cavity is called a _______________________ and contains a special type of blood called ____________________________. Since the __________________________________ is not found in __________________________________ of any kind it is considered an _______________________________________________________________
• The Molluscs all have a true ___________________________________ with a _______________, ________________________ and _______________
• The following features are common to all Molluscs:
  1. A muscular ___________________:   The foot is used for locomotion
  2. A ____________________: The shell is largely consisting of ____________________________________. Some Molluscs have very reduced _______________, and others, like slugs have lost their ___________ all together
  3. A ____________________: This is a fold of outer skin which lines the ____________________ and covers the rest of the body
  4. A ________________________________: The internal organs including the gut, kidneys, heart(s), and reproductive organs
  5. _________________:       These are specialized organs used for respiration (and sometimes feeding).
  6. A ___________________: This is a unique to the Phylum Mollusca and is a rasping “______________________” organ with hard ______________. It is very different in all of the Molluscs and serves many functions from __________________ algae off rocks as in the Gastropods, to a _______________________________ as in the Cephalopods

 

Class Bivalvia (Greek: bi = “two”, valvia = “shells”)

Pages 330 & 332

1. Background

 

• Includes many hard shelled creatures including Clams, Oysters, Mussels, Scallops etc.
• ~ 8000 species

 

DID YOU KNOW!!!: The giant clam, Tridacna gigas, is the largest Bivalve in the world. Some

have been measured to weigh up to 227 kg (~500 pounds), as much as 1.2 m across

(~4 feet) and have an average lifespan of ~100 years!!!

 

1. Body Plan/Structure

 

• All Bivalves have a ____________ that is divided into two halves called_____________
• The two _______________ are connected at one edge by a strong _________________________ that holds the two valves _______________
• There are one or two _____________________________________ that connect the two __________________ together and when they are contracted the two valves come _____________________, closing the Bivalve
• In Bivalves the __________________ takes on the form of a thin _______________________ that surrounds the body just underneath the shell. The mantle is responsible for creating the ________________.
• In some bivalves the part of the ___________________ that is exposed to the outside of the body has _______________ to form two __________________ used for filter feeding
• Often there is a large ____________________________ which is where _____________ can be found
• The _______________ are used for respiration and feeding
• Bivalves do have a ________________, but it has been laterally flattened
• They do not have a ________________
• Bivalves lack a head even though they demonstrate __________________ symmetry, and in fact, do not have a ________________
• They have an _____________________________________________ which means that the “blood” just bathes the organs and is not contained within ____________________________

 

III. Feeding:

 

• Bivalves are _____________________________
• Water circulates through the ________________________________ where microscopic food particles are trapped by the ________________
• The gills are ______________________ and the _______________ move the food towards the _____________ where it is taken into the _______________________
• The food is digested in the _____________________ and then passed out through the _____________ into the _____________________________
• Some Bivalves live buried in the sand and have evolved to have two ________________
• In this case one siphon ______________________________ and food is filtered out by the ______________
• Once the water has passed over the gills the Bivalve contracts its ____________________________________ and the water (along with waste from the anus) is passed out of the Bivalve from the other siphon

DID YOU KNOW!!!: The Geoduck (pronounced gooey-duck) is one of the longest living

organisms in the animal kingdom and can live up to 160 years. Scientists believe this is because of their feeding mechanism. They burrow very deep into the sand and send their long siphons to the surface of the sand to collect water and food. This process not only protects them from predators but also helps prevent the wear and tear of having to move!!!

1. Respiration:

 

• Respiration occurs in the same way that feeding does
• Water is taken into the ____________________________ (can be through a siphon) and passes over the _________________
• ______________________ is taken into the ______________ from the water and _________________________________ is released from the __________ into the water

 

1. Internal Transport:

 

• Bivalves have an _____________________________________________
• This means that they do not have any _________________________ which would store the “blood”
• Instead the “blood” (called ________________________) bathes the organs
• As oxygen and food particles are taken up by the ________________ they are passed into the _________________________ which acts to transport the ___________________ and _____________________ to the rest of the body
• A _______________ pumps the ______________________ to ensure that circulation occurs (even if it is not through blood vessels)

 

1. Excretion:

 

• Most of the waste material exits the anus and is then released out of the Bivalve through the __________________________ (or siphon if present)

 

VII. Response:

 

• Though Bivalves demonstrate ____________________symmetry they lack a _________

• Instead they have ______________________________ of very simple ______________________ which control the ______________ and ____________________________________
• Though having such simple _________________________________________ (especially compared to other Molluscs), Bivalves can still sense and respond to the senses of:
  1. ____________________
  2. ____________________
  3. ____________________
  4. ____________________

 

 

DID YOU KNOW!!!: The Scallops have one of the most complex sensory organs of all of the

Bivalves. They have hundreds of eyes on the fringe of the mantle that have lenses and retinas, however, as complex as these eyes are they can still only detect light or dark!!!

 

VIII. Movement:

 

• Bivalves are ______________________, but do have the ability to move
• Most often Bivalves use their muscular _____________ for movement
• The muscular ________________ is used to help the Bivalve ______________________ into the sand or move along the bottom of the ocean
• Other Bivalves such as Cockles have an extremely muscular ____________ which allows them to quickly “leap” from danger
• Razor shells use their ____________ to burrow extremely fast into the sand
• Another form of movement is only seen in the Scallops. They use their incredibly strong _____________________________________ to rapidly open and close their valves to actually swim away from predators

 

DID YOU KNOW!!!: The scallops that we eat at restaurants are actually the adductor

muscles of the organism called a Scallop. The reason that these muscles are so large in Scallops is because they use them to forcefully open and close their valves allowing them to actually swim away from their predators!!!

 

1. Reproduction:

 

• Most Bivalves species contain both _____________ and ____________________ forms that are separate from each other, though some hermaphroditic species do exist
• Most often sexual reproduction occurs by ______________________________________ where ______________ is released by the ______________ into the water and _____________ are released by the _________________ into the water
• The fertilized egg will become a _______________________________ that will grow to become the adult Bivalve

 

 

 

 

 

 

 

 

 

1. Ecological Roles:

 

• There are numerous ecological roles that Bivalves fill
• Many Bivalves are food for thousands of different species of animals (including us)
• They help to recycle sediment back into the environment
• They help to filter the water
• One major harmful ecological role that Bivalves play involves pollution. Since they are filter feeders much of the pollution that they filter feed becomes trapped in their tissues. When other organisms feed on those toxic Bivalves they often become sick and die.

 

DID YOU KNOW!!!: Mussels produce an incredibly strong “superglue” that helps them cling to

surfaces during rough seas. This “superglue” is called byssus. Researchers have discovered the gene that Mussels use to create byssus and have since been able to produce the material using genetically modified yeast cells. This is a great leap in scientific research as byssus could be used for many things including dentistry, medicine and industry.