60 Questions
What is the characteristic of Annelids that differentiates them from other phyla?
Metamerically segmented body
What is the purpose of parapodia in Polychaeta?
Locomotion
What is the term for the thickened glandular and non-segmented section of the body wall near the head in Clitellata?
Clitellum
What is the main component of the exoskeletons of insects and certain hard structures in invertebrates?
Chitin
What is the reproductive mode of all species within Clitellata?
Hermaphroditic
What is the unique feature of Polychaeta that enables them to tolerate extreme temperatures and pressure?
No specific feature
What is the term for the process of gastrulation in which the mouth forms first?
Protostomy
What is the phylum to which the peanut worm was previously classified?
Annelida
What is the characteristic of Clitellata that distinguishes them from Polychaeta?
Absence of larval stage
What is the function of photoreceptor cells in the dorsal skin of Clitellata?
Sensory perception
What is the primary function of the chemicals injected by medical leeches?
To stop blood clotting and widen blood vessels
Which of the following characteristics is unique to Annelids?
Segmentation
What is the estimated number of species in the phylum Platyhelminthes?
25,000
What is the primary difference between Turbellaria and Monogenea?
Turbellaria are free-living while Monogenea are parasitic
What is the term for the process of secretion of exoskeletons and endoskeletons?
Biomineralization
What is the characteristic feature of Brachiopods that allows them to anchor themselves to sediment?
Pedicle
What is the estimated percentage of life that disappeared during the Permian mass extinction?
95%
What is the phylum to which Molluscs belong?
Iophotrochozoa
Which of the following is a subgroup of the Sedentaria in Annelids?
Clitellata
What is the term for the ability of some Platyhelminthes to regrow lost body parts?
Regeneration
What is the unique molluscan stage that follows the Trochophore larvae?
Veliger
What is the function of the velum in the Veliger stage?
Feeding and swimming
What is the primary function of the radula in most molluscs?
Scraping food
What is unique about the radula of limpets?
Coated with goethite
What is characteristic of the Class Gastropoda?
Single, often coiled shell
What is the function of the calcium arrow in the mating process of some snails?
Delivering a hormone
What is a characteristic of Nudibranchs?
Loss of shells
What is the primary function of the ctenidia in Bivalvia?
Filter feeding
What is unique about the foot of Cephalopods?
Modified into at least 8 arms
What is a distinctive feature of Mollusca?
External mantle and some form of large muscular foot
What is the primary function of chitin in Annelids?
Structural support and exoskeleton formation
What is the characteristic of Polychaeta that distinguishes them from Clitellata?
Presence of chitin bristles
What is the function of the sucker in leeches?
Feeding on blood
What is the characteristic of Annelida that is not shared with other phyla?
Metamerically segmented body
What is the estimated percentage of Annelids that belong to Class Polychaeta?
70%
What is the function of longitudinal and circular muscles in Annelids?
Movement and locomotion
What is the characteristic of Clitellata that distinguishes them from Polychaeta?
Direct development with no larval stage
What is the primary component of the exoskeletons of insects and certain invertebrates?
Chitin
What is the characteristic of Annelids that is not shared with other protostomes?
Closed circulatory system
What is the function of photoreceptor cells in the dorsal skin of Clitellata?
Light detection
What is the primary reason for the decline of articulate Brachiopods post-Permian era?
Over competition with other species
What is the characteristic feature of the Clitellata that distinguishes them from Polychaeta?
Non-segmented, glandular region near the head
What is the primary function of the chemicals injected by medical leeches?
To widen blood vessels
What is the estimated number of known species of Platyhelminthes?
25,000
What is the phylum to which the flatworms belong?
Platyhelminthes
What is the primary function of the pedicle in Brachiopods?
To anchor themselves to sediment
What is the term for the process of regeneration in Platyhelminthes?
Regeneration
What is the estimated percentage of life that disappeared during the Permian mass extinction?
95%
What is the primary characteristic of the phylum Mollusca?
Diverse body plan
What is the term for the process of secretion of exoskeletons and endoskeletons?
Biomineralization
What is the primary function of the mantel in Molluscs?
to secrete calcium carbonate crystals and conchiolin
Which of the following molluscan classes is characterized by the possession of a radula with an iron-based mineral called goethite?
Limpets
What is the adaptive significance of hermaphroditism in some molluscan species?
it reduces the energy expenditure of males during mating
Which of the following defense mechanisms is unique to Nudibranchs?
all of the above
What is the primary function of the ctenidia in Bivalvia?
to filter feed on plankton and small organisms
Which of the following molluscan classes is characterized by the possession of a modified radula with a parrot-like beak?
Cephalopoda
What is the unique feature of the foot in Cephalopoda?
it is modified for swimming and jet propulsion
What is the estimated number of species in the Class Gastropoda?
around 62,000
What is the primary function of the calcium arrow in the mating process of some snails?
to deliver a hormone to the female reproductive organ
What is the unique feature of the heart cockles (Cardium cardissa)?
they live with zooxanthellae and have translucent shells
Study Notes
Phylum Annelida
- Bilaterally symmetrical, triploblastic, with a full body coelom, and metamerically segmented
- Protostomes: first gastrulation becomes mouth
- Closed circulatory system, excretory system, and a brain
- Longitudinal muscles, circular muscles, and parapodia (stumpy leg-like appendages) with setae (bristle-like hair)
Class Polychaeta
- 70% of Annelids in this class
- Bristle worms with chitin bristles
- Parapodia for locomotion
- Can tolerate extreme temperatures and pressure: found near thermal vents and in deep oceanic trenches
- Dioecious
- Most species within Polychaeta are marine
Class Clitellata (Earthworms and Leeches)
- Thickened glandular and non-segmented section of the body wall near the head (clitellum)
- All hermaphrodites
- No larval stage - direct development
- No parapodia
- No eyes, replaced by photoreceptor cells in the dorsal skin
- Leeches - bloodsuckers with suckers at each end of the body
Annelida Characteristics
- 'True worms'
- Most Annelids are segmented
- Hydrostatic skeletons
- Flatworms - thought to have evolved around 550 million years ago (Ediacaran)
Phylum Platyhelminthes
- Worm-like, dorsoventrally flattened (ribbon-like)
- 25,000 known species, divided into four classes
- Up to 200,000 people die a year from one platyhelminth parasite
Classes of Platyhelminthes
- Turbellaria - free living species
- Monogenea - fish, ectoparasites
- Trematoda - flukes, internal parasites of vertebrates and molluscs
- Cestoda - tapeworms, internal parasites of many vertebrates
Platyhelminthes Characteristics
- Hermaphrodites
- No coelom, no through gut, and no circulatory/respiratory system
- Nervous system present
- Parasitic flatworm life cycles are often complicated, involving numerous hosts and life stages
Biomineralization
- Secretion of exoskeletons and endoskeletons
- Shells, mouthparts, bones, and teeth
- Important in the Cambrian Explosion
Phylum Brachiopoda
- Two shells are not always the same size/shape
- Hole in one shell for the pedicle
- Pedicle, a structure used to anchor themselves to sediment
The Great Dying
- 252 million years ago: The Permian era ended with the largest mass extinction the planet has ever experienced
- Around 95% of all life disappeared over a period of 10,000-60,000 years
- Pangea hot and inhospitable
- Volcanic activity, spewing super-heated sulphur into the air and generating acid rain
- Volcanic dust blocked sunlight, leading to loss of vegetation
Phylum Mollusca
- Protostomes, in the clade Iophotrochozoan
- 110,000 described species
- Diverse phylum with some of the largest body plan disparity
- Seven classes, but no agreement on how they are related
Classes of Mollusca
- Gastropoda (snails and slugs)
- Bivalvia (clams, oysters, mussels)
- Cephalopoda (squid, octopuses, nautiluses)
- Polyplacophora (chitons)
- Scaphopoda (tusk shells)
- Monoplacophora (monoplacophorans)
- Aplacophora (aplacophorans)
General Molluscan Body Plan
- Tough integument/skin called a mantle on their upper and lateral surfaces
- Singular muscular foot used for locomotion
- Mantle can secrete calcium carbonate crystals and a protein called conchiolin to bind them
Test your knowledge of Annelida, including their characteristics, classification, and uses in medicine. Learn about leeches and their role in plastic surgery, as well as the evolution of flatworms.
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