Annelida: Characteristics and Classification

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Questions and Answers

What is the primary reason palolo worms detach their lower halves?

To escape predators

To find food in the water column

To regenerate their bodies

To release eggs or sperm during mating season (correct)

Which of the following is NOT a characteristic feature of Oligochaeta?

They do not have parapodia

They have few chaetae

They possess a distinct head (correct)

They can live in marine environments

Which of the following organisms is a representative of the subclass Oligochaeta?

Nereis virens

Palolo viridis

Eisenia fetida

Tubifex tubifex (correct)

How quickly can a palolo regenerate its detached portion?

Within a week Signup and view all the answers

Which of the following statements about Oligochaeta is false?

They primarily inhabit marine environments Signup and view all the answers

What characteristic feature distinguishes Annelida from other phyla?

They are metamerically segmented Signup and view all the answers

Which statement correctly describes the segments of Annelida?

They have a fixed number of segments all of the same age Signup and view all the answers

What is one of the defining features of Class Polychaeta?

Presence of chaetae on parapodia Signup and view all the answers

Which of the following organisms is a representative of Class Polychaeta?

Nereis (ragworm) Signup and view all the answers

What is the likely ecological role of Polychaeta in marine environments?

They contribute to the aeration of sediments. Signup and view all the answers

Which characteristic is not a feature of Annelida?

They have a notochord during their larval stage. Signup and view all the answers

During which event do Samoan families typically harvest Palolo worms?

Seven days after the full moon Signup and view all the answers

What flavor profile is commonly associated with Palolo worms when consumed?

Salty and fishy Signup and view all the answers

What feature differentiates the locomotion of Polychaetae from Oligochaetae?

Use of parapodia Signup and view all the answers

Which anatomical feature is found in the circulatory system of Oligochaetae?

Dorsal and ventral blood vessel Signup and view all the answers

Which reproductive characteristic is unique to Oligochaetae compared to other Annelida classes?

Hermaphroditic with cocoon production Signup and view all the answers

What is the primary function of metanephridia in Oligochaetae?

Waste removal Signup and view all the answers

Which of the following features is NOT characteristic of Hirudinea?

Presence of parapodia Signup and view all the answers

Which of the following sense organs are commonly found in Polychaetae?

Palps and chemoreceptors Signup and view all the answers

What is the mode of gas exchange in Oligochaetae?

Diffusion through skin Signup and view all the answers

Which developmental process is characteristic of Polychaetae?

Indirect development with a trochophore larval stage Signup and view all the answers

Study Notes

Annelida (Segmented Worms)

Annelida, meaning "little rings" in Latin, refers to segmented worms.
Segmented body plan
Triploblastic (three germ layers)
Bilaterally symmetrical
Coelom throughout their lives

Characteristic Features of Annelids

Segmented bodies: Each segment is similar in structure and contains similar internal organs.
Metameric segmentation: Each segment is a metamere, and segments are essentially repeated units along the body.
Triploblastic: Having three germ layers
Bilaterally symmetrical: Body can be divided into mirror-image halves along a single plane.

Annelida Classification

Polychaeta (Many bristles): Many bristles (chaetae) on parapodia (lateral projections) which help them to burrow. Primarily marine.
- Representatives: Nereis (ragworm), Palolo viridis (Palolo)
Oligochaeta (Few bristles): Few bristles (chaetae), no parapodia. Mostly terrestrial or freshwater.
- Representatives: Lumbricus terrestris (earthworm), Tubifex tubifex, Megascolides australis (giant earthworm)
Hirudinea (Leeches): No bristles, no parapodia, anterior and posterior suckers. Mostly freshwater or terrestrial.
- Representatives: Hirudo medicinalis (medicinal leech)

Characteristic Features of Polychaeta

Bristles (chaetae) present on parapodia (projections).
Primarily marine.
Most have a distinct head.

Characteristic Features of Oligochaeta

Few or no chaetae.
No parapodia
No distinct head
Mostly terrestrial or freshwater

Characteristic Features of Hirudinea

No chaetae or parapodia.
No distinct head
Suckers on anterior and posterior ends
Mostly ectoparasites or predators

Annelida Reproduction

Mostly hermaphrodites (both male and female reproductive organs)
Some species have separate sexes.
Polychaetes may have a larval stage (trochophore).
Many Annelids have direct development.

Annelida Locomotion

Two types of muscles—circular and longitudinal—used for locomotion.
Parapodia in Polychaetas—lateral projections on each body segment—aid in movement.
Few chaetae in Oligochaeta and no parapodia in Hirudinea
Suckers are used by leeches for movement.

Annelida Habitats

Polychaetes are mostly marine.
Some Polychaetes are found in freshwater or brackish areas.
Oligochaeta: Primarily terrestrial or freshwater.
Hirudinea: Primarily freshwater or terrestrial.

Other Key Features of Oligochaeta

Digestive System: Mouth, salivary glands, pharynx, esophagus, crop, gizzard, intestine, and anus.
Circulatory System: Closed system with dorsal and ventral blood vessels.

Other Key Features of Polychaeta

Nervous system (ladder-like)
Sense organs: (Palps, tentacles, antennae, and eyes)
Excretory system: Metanephridia (pair per segment)

Annelida Benefits

Earthworms improve soil structure and fertility.
Certain species (e.g., polychaetes) are food sources.
Some are used medicinally (e.g., leeches).

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Description

Explore the fascinating world of Annelida, the segmented worms, known for their unique body structure and classification. This quiz covers essential features, such as segmentation, symmetry, and the two main classes: Polychaeta and Oligochaeta. Test your knowledge of these intriguing organisms and their characteristics.