Annelids Flashcards

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Questions and Answers

What is the major defining characteristic of the Annelids?

One or more pairs of chitinous setae

What are the general characteristics of the annelids?

Bilaterally symmetric 2) At least one pair of chitinous bristles called setae or chetae 3) All are eucoelomate and triploblastic, with organ-level complexity 4) Vermiform, reasonably circular in cross-section, soft-bodied 5) Metamerism 6) Repetition of musculature; excretory, nervous, and reproductive systems 7) Thin, flexible outer wall plays role in locomotion and gas exchange but must remain moist

What does metamerism mean?

It means conspicuous segmentation

What are the advantages of metamerism?

<ol> <li>Decreases risks from injury 2) Allows for compartmentalization 3) Regional specialization 4) Burrowing theory</li> </ol> Signup and view all the answers

Septa are derived from what set of tissue in the annelids?

Mesoderm Signup and view all the answers

What are the two openings per segment referred to as, and are connected with the term nephridia?

Metanephridium Signup and view all the answers

Describe how the metanephridium system is alike to our excretory system.

The blood vessels of the worm surround a nephridium to absorb nutrients that are useful and anything that is not is secreted out of the nephridiopore. Signup and view all the answers

Describe the movement of annelids and the special name for the movement of swimming annelids.

Contraction of longitudinal muscles causes the body to shorten and expand. Contraction of circular muscles causes the body to narrow and lengthen. Swimming annelids use undulatory movements to swim. Signup and view all the answers

What is the defining characteristic of Class Polychaeta?

Paired lateral outfoldings of the body wall called parapodia Signup and view all the answers

What class has 8500 species and makes up 70% of annelids?

Polychaeta Signup and view all the answers

What is the importance of parapodia in annelids?

They are highly vascularized for gas exchange. Signup and view all the answers

Where are the longitudinal and circular muscles located in a Polychaete/annelid?

The circular muscles are located right under the epidermis of the worm while the longitudinal muscles are right below the circular muscles and are comprised of 4 bundles. Signup and view all the answers

Name the segments around the head region and their basic functions.

<ol> <li>Prostomium - houses sensory organs such as tentacles, eyes, and nuchal organ (chemosensory) 2) Peristomium</li> </ol> Signup and view all the answers

What is the mouth of the worm called, and how many of these chitinous jaws are there?

The technical name for the mouthpart is the Pharynx, and there are two chitinous jaws. Signup and view all the answers

What is the dorsal and ventral half of the Parapodia called?

Top is the Notopodium and the bottom is the Neuropodium. Signup and view all the answers

What does the adjective Macrophagous refer to?

Macrophagous refers to the raptorial Polychaetes that eat large particles. Signup and view all the answers

Describe setae when they are in a power stroke vs a recovery stroke.

Setae are protruded during the power stroke and next to the body during the recovery stroke. Signup and view all the answers

How are some ways the sedentary polychaetes different from the non-sessile kinds?

The sedentary kind live in burrows in sediment or bore into calcareous substrates, or live in rigid protective tubes. The parapodia are greatly reduced, and they lack a protrusible pharynx or proboscis. Signup and view all the answers

Sedentary Polychaetes are what two types of Microphagous?

<ol> <li>Nonselective deposit feeding 2) Selective deposit feeders</li> </ol> Signup and view all the answers

What are radioles and are they found in sedentary or motile Polychaetes?

Radioles are ciliated food grooves that sort particles, and they are only found in the sessile polychaetes. Signup and view all the answers

Describe Chaetopterus variopedatus (Parchment tube worm). How many holes does it have in its burrow? What is the use of the mucous bag?

It has two holes. The mucous bag captures food and other debris that the tube brings into it and sorts for food. Signup and view all the answers

Study Notes

Major Characteristics of Annelids

Defined by one or more pairs of chitinous setae.
Bilaterally symmetric body structure.
Eucoelomate and triploblastic with organ-level complexity.
Vermiform and soft-bodied, approximately circular in cross-section.
Exhibit metamerism, or conspicuous segmentation, resulting in repetitive organ systems.
Thin, flexible outer body wall aids in locomotion and gas exchange, requiring moisture.

Metamerism

Represents segmentation, allowing for increased protection and functional specialization.
Contributes to organ compartmentalization and enhances movement efficiency.

Septa and Nephridia

Septa, important for body compartmentalization, are derived from mesodermal tissue.
Each segment contains two openings connected to the excretory system, termed metanephridia.

Movement in Annelids

Movement involves contraction of longitudinal and circular muscles.
Swimming species employ undulatory movements for locomotion.

Class Polychaeta

Characterized by paired lateral structures known as parapodia, serving functions in locomotion and gas exchange.
Represents approximately 70% of annelid species with around 8,500 species.

Anatomical Features

Circular muscles are situated just beneath the epidermis; longitudinal muscles lie beneath these in four bundles.
The head comprises segments: the prostomium (housing sensory organs) and the peristomium.

Feeding Mechanisms

The mouth (pharynx) has two chitinous jaws for capturing prey; classified as macrophagous when consuming large particles.
Setae function differently during the power and recovery strokes of movement.

Sedentary Polychaetes

Adapted for life in burrows, tubes, or calcareous substrates; reduced parapodia and lack a protrusible pharynx.
Two feeding strategies: nonselective and selective deposit feeding.

Specialized Structures

Radioles are ciliated structures found in sessile polychaetes, used for particle sorting.
Chaetopterus variopedatus has two burrow openings and utilizes a mucous bag for food capture.
Arenicola marina (Lungworm) has modifications for burrow ventilation and feeds via parapodia adaptations.

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Description

Test your knowledge on annelids with these flashcards! This quiz covers key characteristics and defining features of annelids, including their anatomy and classification. Perfect for students studying biology or anyone interested in this fascinating group of organisms.