Biology: Annelida Class Oligochaeta

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Questions and Answers

What does 'monoecious' mean?

Having both male and female reproductive organs in the same individual. (correct)

Having separate male and female individuals.

Having multiple reproductive organs.

Only reproducing asexually.

What is the prostomium?

That part of the head located in front of the mouth.

Where is the mouth located in an earthworm?

Just behind the prostomium.

What are segments in relation to the body structure?

Each of the parts into which something is or may be divided. Signup and view all the answers

What is the function of the clitellum in earthworms?

Secretes a viscid sac in which eggs are stored. Signup and view all the answers

What are cerebral ganglia?

Considered a rudimentary brain. Signup and view all the answers

What is the role of the subpharyngeal ganglion?

It is the first of five ventral ganglia. Signup and view all the answers

What is the pharynx?

The passage from the mouth to the esophagus. Signup and view all the answers

What is the esophagus in earthworms?

A muscular tube that connects the mouth to the crop. Signup and view all the answers

What do aortic arches do?

Pump blood into the dorsal and ventral blood vessels. Signup and view all the answers

What is the role of calciferous glands?

Excrete excess calcium into the GI tract for elimination into feces. Signup and view all the answers

What are seminal receptacles?

Structures that receive and store sperm from another worm. Signup and view all the answers

What is the function of seminal vesicles?

Produce seminal fluid for sperm cells. Signup and view all the answers

What is the role of testes in earthworms?

Produce sperm for fertilization. Signup and view all the answers

What do ovaries do in earthworms?

Where eggs are laid and stored until they mature. Signup and view all the answers

What is an oviduct?

The tube through which an ovum or egg passes from an ovary. Signup and view all the answers

What is the function of the crop in an earthworm?

Region of the esophagus specialized for storing food. Signup and view all the answers

What is the gizzard?

A modified stomach that grinds food. Signup and view all the answers

What does the dorsal vessel do?

Carries blood toward the anterior end of an earthworm. Signup and view all the answers

What is the ventral nerve cord?

A chain of connected segmental ganglia lying against the body wall. Signup and view all the answers

What is the function of lateral nerves?

Signup and view all the answers

What is the role of the intestine in earthworms?

Location of digestion and absorption. Signup and view all the answers

What is a septum?

A wall between two cavities. Signup and view all the answers

What is a nephridium?

Segmentally arranged, paired excretory tubules of many invertebrates. Signup and view all the answers

How do body segments react when longitudinal muscles contract?

The length of the body is reduced, making the worm short. Signup and view all the answers

How do body segments react when circular muscles contract?

The diameter of the body is reduced, making the worm thin. Signup and view all the answers

What is the most obvious difference between clamworms and earthworms?

Clamworms have many chaetae while earthworms do not. Signup and view all the answers

Know the excretory system and nervous system of an earthworm.

Excretory system: consists of the nephridia; Nervous system: consists of the brain and ventral nerve cords. Signup and view all the answers

Study Notes

Annelida Class Oligochaeta: Earthworm Overview

Earthworms are monoecious, meaning each individual possesses both male and female reproductive organs.
The prostomium is the head segment located in front of the mouth in annelids.

Anatomy and Digestion

The mouth is positioned just behind the prostomium and serves as the intake for food.
Earthworm bodies are made up of multiple segments, each functioning as a distinct unit.
The pharynx connects the mouth to the esophagus, serving as a passageway for food.
The esophagus is a muscular tube that transports food to the crop.
The crop serves as a storage area for food before it moves to the gizzard.
The gizzard is a modified stomach that grinds food with the help of stones.

Circulatory System

Aortic arches act as a primitive heart, with five pairs pumping blood into dorsal and ventral vessels.
The dorsal vessel runs along the worm's back, transporting blood toward the anterior end.

Nervous System

Cerebral ganglia function as a rudimentary brain; they extend into paired ventral nerve cords.
The subpharyngeal ganglion acts as a connection beneath the pharynx, part of the ventral nervous system.

Reproductive Structures

The clitellum is a thickened, saddle-like structure involved in reproduction, secreting a sac for egg storage.
Seminal receptacles store sperm received from other worms, while seminal vesicles produce seminal fluid.
Testes produce sperm, and ovaries are responsible for egg production and maturation.

Excretory System

Nephridia are paired excretory tubules that help in waste elimination and osmoregulation.
Calciferous glands in the esophagus excrete excess calcium for elimination through feces.

Muscular System Functionality

Longitudinal muscle contractions shorten the body, while circular muscle contractions narrow the diameter.

Comparative Anatomy

Oligochaetes like earthworms have few chaetae (bristles), contrasting with the many chaetae found in polychaetes such as clamworms.
Both groups differ in reproductive structures; oligochaetes are hermaphroditic and possess a clitellum.

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Description

Test your knowledge on the Earthworm's anatomy and characteristics through these flashcards focusing on the Oligochaeta class of annelids. Learn definitions of key terms such as 'monoecious' and 'prostomium' to enhance your understanding of these fascinating organisms.