Bio 112: Phylum Annelida

Coelom

A body cavity

Complete digestive tract

A digestive tube with two openings, a mouth and an anus.

Body cavity

A fluid or air space that holds the organs and protects from internal injury

Prostomium

A small fleshy projection over the mouth

Clitellum

A thick cylindrical collar

Nephridia

A tubule open to the exterior that acts as an organ of excretion or osmoregulation. It typically has ciliated or flagellated cells and absorptive walls.

How might an earthworm manipulate its body to prevent a predatory bird from pulling it from its burrow?

An earthworm an manipulate its body by relaxing the circular muscles and contract longitudinal muscles to shorten itself. It can also extend setae to try and attach itself to other surroundings to try and pull away.

Hydrostatic skeleton

An exoskeleton that maintains its form due to the pressure of fluid inside the skeleton.

Coelomates

An organism with a true coelom, where the coelomic space is surrounded on all sides by mesoderm.

Septa

Between segments

Closed circulatory system

Blood circulates within a series of blood vessels at all times.

Setae

Bristle like hairs

Gastrulation

Cells move and form two or three embryonic tissue layers

Which muscle layer is directly under the epidermis?

Circular muscle

How are protosomes and dueterostomes distinguished?

Differences in cleavage, how the coelom is formed, and the fate of the blastopore

What is the function of blood vessels in the intestine?

Diffusion of nutrients

Metamerism

Division of the body into similar segments that are arranged linearly along the anterior-posterior axis.

Oligochaetes

Earthworm

What are the three embryonic tissue layers?

Ectoderm, endoderm, and mesoderm.

What effect would contraction of the circular muscle layer have on the length and width of the earthworm?

Elongates the worm and shrinks the width

True or false: Earth worms are single gender organisms (male or female)

False, they are hemaphroditic

What role does coelom play in locomotion of the earthworm?

Fluid transfer

What is the advantage of having a prominent fold in the intestine (typhlosole)?

Increase surface area to be able to absorb more nutrients

Lumen

Inside space of the intestine, derived from embryonic endoderm

Discuss possible reasons for the evolution of the circulatory system in annelids. Relate your answer to body plan and size.

It would evolve into a closed circulatory system because it needs to circulate blood everywhere. If they were to have an open circulatory system blood would not be necessarily able to "flow" through the worm through a vessel or vein.

How does segmentation play into the process?

Lengthens and contracts allowing for movement similar to a slinky.

Which muscle layer is feathery looking and towards the middle?

Longitudinal

What are the two different muscle layers in a Annelida?

Longitudinal and circular

Polychaetes

Marine worms

From which embryonic tissue is the peritoneum derived?

Mesoderm

What is the function of the two muscle layers?

Movement

Name a pseudocoelomate

Nematode

Pseudocoelomates

Organisms that contain a body cavity but this space is lined by mesoderm tissue on the body wall but there is no mesoderm tissue associated with the intestine side of the body cavity

Acoelomates

Organisms that lack a body cavity

Oviducts

Place where eggs are discharged

Name an acoelomate

Planarian

Name a coelomate

Polychaete

What are the names of the two groups coelomates are distinguished into?

Protostome and deuterostome

What effect would contraction of the longitudinal muscle layer have on the length and width of the earthworm?

Shrinks the length but widens width

Seminal vesicles

Spem is discharged

Seminal receptacles

Sperm is received

Parapodia

Structures that function in gas exchange and locomotion

Compare the level of cephalization in earthworms to that of flatworms

The earthworm has a small simple brain at the anterior end of the body and cephalization occurs with the nerve cells at one part of the body. This is much like the flatworms where they also concentrate their sense organs towards the front of their bodies. (Mouth and pharynx location too)

Peritoneum

The innermost layer of the body wall in the adult earthworm

Cephalization

The nervous system is concentrated in a ganglionic mass at the anterior end of the organism

Typhlosole

The prominent in-folding of the intestine

Mesenteries

The tissue that supports organs in a coelomate animal

The crop is an adaptation which facilitates temporary food storage. Why would the ability to store food be advantageous to these organisms?

This is advantageous because if they are not able to obtain food for a while, the extra food stored will keep them alive until then. With areas that are low in detritus they are able to conserve more in their storage.

Triploblastic

Three tissue layers

Chloragogen tissue

Tissue that makes up the outermost layer of the intestine

True or false: Annelids have a fluid filled body cavity separating the digestive tract from the body wall.

True

Diploblastic

Two tissue layers

What role does setae play in locomotion of the earthworm?

Used to anchor themselves

Hemoglobin

What makes the blood red