Phylum Annelida and Its Classes

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Questions and Answers

What is the primary method of gas exchange in oligochaetes?

Through diffusion across a moist body wall (correct)

Through pores on the body surface

Through specialized respiratory organs

Through gills

Which of the following is a defining characteristic of the class Oligochaeta?

Presence of a clitellum (correct)

Lack of setae

Predatory feeding habits

Presence of parapodia

Which of the following statements accurately describes the feeding habits of polychaetes?

Polychaetes only feed on detritus and decaying matter.

Polychaetes primarily feed on algae and other aquatic plants.

Polychaetes exhibit a diverse range of feeding strategies, including predation, scavenging, and suspension feeding. (correct)

Polychaetes are exclusively carnivorous predators.

What is the primary mode of locomotion in oligochaetes?

Through muscle contractions generating peristaltic waves (C) Signup and view all the answers

How do the setae of polychaetes differ from those of oligochaetes?

Polychaete setae show greater variation in morphology among different species. (B) Signup and view all the answers

Which of the following statements accurately describes the reproductive characteristics of oligochaetes?

Oligochaetes are hermaphroditic and reproduce sexually, exchanging sperm between individuals. (B) Signup and view all the answers

Which of the following characteristics is NOT typically found in the class Polychaeta?

Presence of a clitellum (A) Signup and view all the answers

Which of the following is a significant difference between the two main groups of polychaetes, Errantia and Sedentaria?

Errantia are generally mobile, while Sedentaria live in protective tubes. (A) Signup and view all the answers

Which of the following is a defining characteristic of the phylum Annelida?

A segmented body with repeating organ systems (A) Signup and view all the answers

What is the primary function of setae in annelids?

Locomotion (B) Signup and view all the answers

Which class of annelids is primarily characterized by the presence of parapodia?

Polychaeta (A) Signup and view all the answers

What is the primary role of the cuticle in annelids?

Protecting the body from predators (B) Signup and view all the answers

How do polychaetes typically respire?

Through modified parapodia (A), Through gills (B), Through the skin (D) Signup and view all the answers

What is the primary function of nephridia in annelids?

Excretion of waste products (B) Signup and view all the answers

Which of the following statements about polychaetes is TRUE?

Polychaetes possess a brain and sensory appendages on their anterior end (C) Signup and view all the answers

Which of the following is a differentiating feature between the classes Oligochaeta and Polychaeta?

Presence or absence of parapodia (B) Signup and view all the answers

What is the primary method of reproduction observed in freshwater oligochaetes?

Asexual reproduction through transverse division (A) Signup and view all the answers

How do leeches primarily feed on their hosts?

With three toothed jaws that make incisions in the host (A) Signup and view all the answers

Which of the following statements accurately describes the larval stage in oligochaetes?

They develop directly into miniature worms without a larval stage. (C) Signup and view all the answers

What is a defining characteristic of the Class Hirudinea?

A posterior sucker for locomotion and feeding (D) Signup and view all the answers

What type of fertilization occurs in leeches?

Internal fertilization via spermatophore penetration (C) Signup and view all the answers

How do leeches move across solid substrates?

Utilizing suckers as temporary anchors (D) Signup and view all the answers

Which statement about oligochaete development is true?

The embryos develop in a nurturing environment provided by the clitellum. (D) Signup and view all the answers

What is a common habitat for most leech species?

Freshwater and terrestrial habitats (B) Signup and view all the answers

Study Notes

Phylum Annelida

Annelids are a phylum of segmented worms
Number of described species is approximately 12,400
Defining characteristic: One or more pairs of chitinous setae (chaetae)
Body structure: Soft-bodied, reasonably circular in cross-section, and longer than wide
Metamerism: Series of repeating segments with repeating organ systems (skin, musculature, nervous system, and excretory system)

Class Polychaeta

Defining characteristic: Paired lateral outfoldings of the body wall (parapodia); many setae
Distribution: Primarily marine (63% of annelid species)
Body features: Parapodia function in gas exchange and locomotion; setae are siliceous, chitinous, or calcareous bristles
Feeding: Predation, scavenging, suspension feeding, and deposit feeding
Reproduction/development: Includes active, mobile species (errant) and sedentary species that live within protective tubes

Class Oligochaeta

Defining characteristics: Pronounced cylindrical glandular region of the body (clitellum) that plays important roles in reproduction and permanent gonads
Distribution: Primarily freshwater or terrestrial habitats (6.5% of annelid species, with few marine)
Body features: Lack parapodia, protosomium lacks conspicuous sensory structures, setae are less densely distributed, and gas exchange occurs through diffusion across a moist body wall
Movement: Continuous cycles of contraction and relaxation of circular and longitudinal muscles called peristaltic waves
Reproduction: Hermaphrodites, sperm simultaneously exchanged, sperm stored in specialized organs called spermathecae, fertilization occurs externally and embryos develop in a nutritive fluid within a cocoon. Asexual reproduction is more common, involves transverse division of the body into segments and subsequent regeneration

Class Hirudinea

Defining characteristic: Posterior sucker
Distribution: Mostly freshwater and terrestrial habitats with fewer marine species
Body features: Lack parapodia, specialized respiratory structures, and head appendages; the body is often not separated into segments by septa with a continuous coelomic space largely filled with connective tissue (mesenchyme), and the circulatory medium is the coelomic fluid
Locomotion: Move by generating peristaltic waves, using suckers as temporary anchors
Feeding: Ectoparasitic, feeding on the blood of other invertebrates and vertebrates, possess 3 toothed jaws for making an incision on the surface of the host.
Reproduction: Simultaneous hermaphrodites with internal fertilization, the clitellum functions in producing a cocoon and a nutritive fluid, miniature leech emerges from the cocoon after development

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Description

Explore the fascinating world of Annelida, the segmented worms that include both Polychaeta and Oligochaeta classes. Discover their unique characteristics, body structures, and various feeding methods. This quiz will test your knowledge on the defining traits and classifications within this diverse phylum.