Chapter 33: Invertebrates (Part II)
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Phylum Rotifera aka...
Characteristics of Phylum Rotifera:
- "wheel animals" for the corona at anterior end
- Bilateral symmetry
- Spiralian Platyzoa
- Complex internal organs
- Adhesive toes help to cling to surface
- most live in freshwater and survive 1-2 weeks
- corona used for locomotion
This phyla is often referred to as the "wheel animals"... which phylum and why?
- Phylim Rotifera
- corona (ring of cilia) at anterior end
Rotifers use their ____ for locomotion and food gathering. Food is crushed by complex jaw in ____.
- complex jaw in the pharynx
Explain reproduction in rotifers
- Females produce more females
Lophophorates include 2 types:
What is common between Bryozoa and Brachiopoda in the Lophophorates?
Both have a lophopore = U-shaped ridge around mouth bearing ciliated tentacles used for gas exchange and guiding food to the mouth.
What is a lophopore?
U-shaped ridge around mouth bearing ciliated tentacles used for gas exchange and guiding food to the mouth.
Phylum Bryozoa... aka?
- Phylum Ectoprocta"moss animals"
____ are only exclusively colonial animals.
Main traits of Bryozoans:
- very small; "moss animals"
- marine & freshwater
- U-shaped digestive system w/ anus outside the ring of lophophore
- Each zooid (individual) secretes a zoecium of chitin and calcium carbonate or some other substance.
- Zoecia may be specialized for feeding, reproductioin, or defense
In phylum Bryozoa, each _____ secretes a ______ made of ____ and ____ or some other substance.
- made of chitin and calcium
In Bryozoans, ____ may be specialized for feeding, reproduction, or defense.
Phylum Brachiopoda... aka?
This phylum looks superficially like a clam but their shells are dorsal/ventral and not lateral as in the bivalves.
_______ and ______ are solitary lophophorates.
Brachiopods and phoronids
- attached to rocks by pedicle or one shell (valve) is cemented to rock
- Lophophore located between shells
- U-shaped gut in some; other have no anus
Phoronoid... aka ?
- worm secretes chitinous tube
- withdraws into tube when disturbed
- some buried in sand, other attached to rocks
Brachiopods are (protostomes/deuterostomes) and phoronids are (protostomes/deuterostomes).
Coelomate invertebrates include vertebrates that have ________?
Both sides surrounded by mesoderm
Phylum Mollusca aka...
Characteristics of Mollusks:
- 93,000 described species (second only to arthropods)
- Occupy every habitat on Earth
- Includes snails, slugs, clams, scallops, octopus, cuttlefish, oysters, mussels, squid, chambered nautilus, etc.
- Size range from mm to giant squid (over 15m long)
- Evolved in the ocean
- Economic imporance: food, mother of pearl
- Mollusks can damage boats, docks, pillings, and wood exposed to the sea
- Zebra mussels are invading freshwater ecosystems
- Some slugs and snails damage flowers, vegetables, other crops
- some snails are intermediate hosts to larval stages of parasites such as flukes
Snails, slugs, clams, scallops, octopus, cuttlefish, oysters, mussels, squids and chambered nautilus are all part of what phylum?
_____ are extremely diverse and important to humans.
This type of mollusk is invading freshwater ecosystems
What is the intermediate host to larval stages of parasites such as flukes?
Describe the body of a mollusk
- Bilateral symmetry
- Mantle = thick epidermal sheet surrounding the mantle cavity, secretes calcium carbonate shell
- Foot- primary means of locomotion (except for octopus, chambered nautilus, and squid)
- Foot also used for attachment, capturing food, digging
- Head may be well-developed or not
Describe the internal organs of Mollusks:
- Coelom is very reduced in size
- visceral mass contains digestive, excretory and reproductive organs
- ctenidia=gills (in aquatic mollusks) have much surface area for gas exchange
- Gills of bivalves also filter out food
- secreted by mantle; protects against predators and adverse environmental conditions
- some have reduced, internalized or no shell at all
- shell has two layers of calcium carbonate; inner layer is mother-of-pearl or nacre
- Pearls form when a grain of sand or other irritant lodges between inner shell layer and mantle-layers of nacre reduce the irritation.
Feeding and Prey Capture in Mollusks:
- Some radular structures are modified for drilling, others work like a harpoon along with a venom gland
- Bivalves are the only mollusks without a radula
Removal of wastes in Mollusks:
- Nephridium = removes nitrogenous waste (somewhat like a kidney)
- waste dumped into mantle cavity
- sugars, salts, water and other materials are reabsorbed by nephridal walls and returned to animal's body
Circulatory system of Mollusks:
- Hemocoel: made of several sinuses and vessel network in gills (All mollusks except for cephalopods have an open circulatory system.)
- Hemolymph-equivalent of blood
- heart-most mollusks have three-chambered heart
Reproduction in Mollusks:
- Most mollusks have separate sexes
- Few bivalves and many freshwater and terrestrial gastropods are hermaphroditic
- some oysters can change sex
- marine mollusks have external fertilization
- most gastropods have internal fertilization
- trochophore larva is free-swimming
- veliger larva is 2nd free-swimming stage
How big are mollusks?
Range from few mm to 15m squid!
What type of symmetry do mollusks exhibit?
thick epidermal sheet surrounding the mantle cavity in mollusks. Secretes calcium carbonate shell (for mollusks that have a shell).
Do all mollusks have a shell?
No, most but not all
What is the primary means of locomotion for most mollusks?
What are the exceptions?
- The feet
- Octopuses, chambered nautilus, and squid
What is significant about the coelom in mollusks?
The coelom is very reduced in size
What is the purpose of ctenidia in mollusks?
What is their additional purpose in Bivalves?
gills that have surface area for gas exchange
gills of bivalves also filter out food
The shells of mollusks are secreted by the ____ made of ______. It protects against predators and adverse environmental conditions.
- made of calcium carbonate
Which of the following mollusks have reduced shells?
Which of the following mollusks have no shell?
substance secreted by the inner mantle in mollusks, forms mother-of-pearl lining and pearls within shells.
Rasplike structure with rows of chitinous teeth used to scrape food off surfaces
The radula in mollusks is made out of ___.
Some radular structures are modified for ____. Others work like a ____ along with a ____ gland.
____ are the only mollusks without a radula.
- structure in mollusks that removes nitrogenous waste
- Somewhat like a kidney
The nephridium removes _____ waste in mollusks.
Where is waste dumped in mollusks?
What substances are reabsorbed by nephridial walls and returned to the animal's body to maintain osmotic balance?
Sugars, salts, water, etc
circulatory system made of several sinuses and vessel networks in the gills.
All mollusks except ____ have open circulatory systems.
equivalent to blood
Most mollusks have a _____ chambered heart.
True or False: most bivalves have separate sexes
A few _____ and many freshwater and terrestrial ______ are hermaphroditic.
What is unique about oysters in relation to reproduction?
Some oysters can change their sex
Marine mollusks have (internal/external) fertilization.
Most gastropods have (internal/external) fertilization.
____ larva is free swimming.
____ larva is 2nd free-swimming stage
Name four classes of Mollusks (PGBC):
- 1. Bivalves
- 2. Gastropoda
- 3. Polyplacophora
- 4. Cephalopoda
Characteristics of Class Polyplacophora:
- Marine only
- 8 overlapping dorsal plates
- body is NOT segmented
- most are grazing herbivores living in shallow marine habitats
Class Polyplacophora... aka ?
Class Gastropoda... aka?
Snails and Slugs
Characteristics of class Gastropoda:
- Primarily marine (40,000 species)
- There are freshwater species also
- The only terrestrial mollusks are gastropods
Most _____ have a single shell, but some have lost their shell.
Most _____ creep on their foot. But some have modified it for swimming.
The head of _____ has a pair of tentacles used for ______ or _____ -receptioin. Eyes are located ________. Some have second set of tentacles with eyes on end of tentacles.
- Chemo- or Mechanoreception
- Located at the base of their tentacles.
What is a unique feature of gastropods?
What is torsion?
Twisting of the body during larval growth so mantle cavity and anus are moved to the front of the body.
(Gastropods/Polyplacophora) are herbivores.
(Gastropods/Polyplacophora) are predators.
What purpose does the mantle cavity serve in terrestrial gastropods?
It serves as a lung
Class Bivalvia includes which species?
Clams, Mussels, Cockles
Class cephalopoda includes which species?
Octopus, squids, nautilus
Characteristics of Bivalves:
- Most 10,000 species are marine
- Some are freshwater
- No radula or head
- Two half shells (valves)
- Inhalant siphon is where water enters bringing food and oxygen
- Exhalant siphon is where water exits
Characteristics of Cephalopoda:
- More than 600 species
- Marine only
- very active predators
- Only mollusks with closed circulatory system
- Foot evolved into arms with suction cups, adhesive devices, and hooks for capturing prey.
- Highly developed nervous system
- Complex behavior patterns: Highly intelligent
- Cephalopod eyes similar to vertebrate eyes
- Ink Sac
____ are the only mollusks with a closed circulatory system
What is unique about the 3rd arm in an Octopus?
Used as the reproductive organ in males
____ have the largest brain size among invertebrates.
True or False: Cephalopods have a highly developed nervous system
True or False: Cephalopod eyes are developed just like vertebrate eyes
True BUT cephalopod eyes evolved separately!
Explain the shells found in the following cephalopods: Octopus, Squid, Chambered nautiluses, cuttlefish
- Octopus: No shell
- Squid and Cuttlefish: Internal shell
- Chambered nautiluses: External shell
How do cephalopods move?
Via jet propulsion when water that entered the mantle is forced out through siphon
- means to bear color
- found in the skin of cephalopods that allows cephalopods to change colors for camouflage or communication
What type of development to cephalopods have?
- Direct development
- The is no larval stage!
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