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Chapter
35 Mollusks and Annelids Section 2
Annelida
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Chapter
35 Section 2 Annelida
Identify
the structures that provide the basis for dividing annelids into three classes.
List
the advantages of body segmentation.
Describe
the structural adaptations of earthworms.
Compare
the three classes of annelids.
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Chapter
35 Section 2 Annelida
The phylum Annelida is made up of bilaterally symmetrical, segmented worms.
This phylum includes common earthworms, feather-duster worms, and bloodsucking leeches. They are called
annelids,
which means “little rings” and refers to the many body segments.
Annelids have a true coelom that is divided into separate compartments by partitions.
Most annelids have external bristles called
___________
(singular, seta), and some have fleshy protrusions called
______________
(singular, parapodium).
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Chapter
35 Section 2 Annelida
Annelids of the class ________________ generally live in the soil or in fresh water and have no parapodia.
Oligochaeta means “few bristles”; these annelids have a few setae on each segment. The most familiar member is the ______________________.
Structure and Movement
An earthworm’s body has over 100 nearly-identical segments.
Circular and longitudinal muscles line the interior body wall.
Locomotion is made possible by segmentation.
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Chapter
35 Section 2 Annelida Feeding and Digestion
Earthworms ingest soil as they burrow through it.
Soil is moved through these structures: ___________ ____________
______________ __________
___________
___________ includes the
______________
__________ Earthworms play an important role in the condition of soil.
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Chapter
35 Section 2 Annelida Circulation
Contractions of the
____________________
and the dorsal blood vessel force blood through the closed circulatory system.
Respiration and Excretion
Oxygen and carbon dioxide diffuse through the skin, which contains many small blood vessels and must be kept moist.
Cellular wastes and excess water are excreted through _______________.
Neural Control
The nervous system of an earthworm consists of a chain of ganglia connected by a ventral nerve cord. Sensory structures are found in all segments but are concentrated at the anterior end.
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Chapter
35 Section 2 Annelida Reproduction
Earthworms are ____________________, but an individual worm cannot fertilize its own eggs.
During mating, earthworms press their ventral surfaces together.
They are held together by their setae and by a film of mucus secreted by each worm’s _______________.
The sperm from each worm move through the mucus to the seminal receptacle of the other. The clitellum secretes a tube of mucus and __________.
Fertilization occurs inside the tube, which forms a protective case for the young worms.
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Chapter
35 Section 2 Annelida
Most annelids are members of the class Polychaeta, which means “many bristles.” Polychaetes differ from other annelids in that they have antennae and specialized mouthparts.
They are the only annelids that have a trochophore stage. Hirudinea is the smallest class of annelids, consisting of about 500 species of ______________. Leeches have no setae or parapodia. Many leeches are carnivores but some are parasites that suck blood from other animals.
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Chapter
35 Section 2 Annelida Chapter menu Resources
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Chapter
35 Standardized Test Prep
1. Why do terrestrial snails and slugs need an environment with a high moisture content?
A. to avoid drying out B. to see and hear better C. to swim more efficiently D. to avoid being eaten by birds
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Chapter
35 Standardized Test Prep
1. Why do terrestrial snails and slugs need an environment with a high moisture content?
A. to avoid drying out B. to see and hear better C. to swim more efficiently D. to avoid being eaten by birds
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35 Standardized Test Prep
2. Which of the following are the only mollusks with a closed circulatory system?
F. snails G. bivalves H. gastropods J. cephalopods
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35 Standardized Test Prep
2. Which of the following are the only mollusks with a closed circulatory system?
F. snails G. bivalves H. gastropods J. cephalopods
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35 Standardized Test Prep
3. Annelids are divided into three classes based partly on the number of which of the following?
A. setae B. segments C. nephridia D. aortic arches
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35 Standardized Test Prep
3. Annelids are divided into three classes based partly on the number of which of the following?
A. setae B. segments C. nephridia D. aortic arches
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35 Standardized Test Prep
4. Parapodia are distinguishing characteristics of which class of annelids?
F. Bivalvia G. Hirudinea H. Polychaeta J. Oligochaeta
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35 Standardized Test Prep
4. Parapodia are distinguishing characteristics of which class of annelids?
F. Bivalvia G. Hirudinea H. Polychaeta J. Oligochaeta
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35 Standardized Test Prep
The diagram below shows the internal structure of a bivalve. Use the diagram to answer the questions that follow.
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35 Standardized Test Prep
5. Which of the structures is involved in respiration and feeding?
A. A B. B C. C D. D
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35 Standardized Test Prep
5. Which of the structures is involved in respiration and feeding?
A. A B. B C. C D. D
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35 Standardized Test Prep
6. What is structure B?
F. a gill G. a siphon H. the mantle J. an adductor muscle
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6. What is structure B?
F. a gill G. a siphon H. the mantle J. an adductor muscle
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35 Standardized Test Prep
7. Nephridium : excretion :: clitellum : A. digestion B. circulation C. respiration D. reproduction
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Chapter
35 Standardized Test Prep
7. Nephridium : excretion :: clitellum : A. digestion B. circulation C. respiration D. reproduction
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35 Standardized Test Prep
The diagram below shows the mouth structure of a class of organisms. Use the diagram to answer the question that follows.
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35 Standardized Test Prep
8. In which class of organisms is the mouth structure shown above most likely to be found?
F. bivalves G. hirudines H. gastropods J. polychaetes
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35 Standardized Test Prep
8. In which class of organisms is the mouth structure shown above most likely to be found?
F. bivalves G. hirudines H. gastropods J. polychaetes
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Chapter
35 Standardized Test Prep During larval development, gastropods undergo a process called torsion. Describe the outcome of torsion.
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Chapter
35 Standardized Test Prep During larval development, gastropods undergo a process called torsion. Describe the outcome of torsion.
Answer: snail.
Torsion is a developmental process in which the visceral mass twists around 180 degrees in relation to the head, bringing the mantle cavity to the anterior end of the Chapter menu Resources
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Chapter
35 Standardized Test Prep Base your answers to parts A & B on the information below.
Earthworms have three main structural features that enable movement.
Part A Describe these features.
Part B Explain how they work together to enable movement.
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Chapter
35 Standardized Test Prep Answer:
Part A
Circular muscles and longitudinal muscles line the interior body wall of an earthworm. Setae, or external bristles, line the ventral surface of the earthworm. Coelomic fluid is found in individual segments.
Part B: Contractions of the circular muscles increase the pressure of the coelomic fluid. This increased pressure causes the animal to elongate and pushes the anterior end forward. The animal then uses its setae to grip the ground as the longitudinal muscle contracts, pulling the posterior end forward. Chapter menu Resources
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