Annelids

Question 1

Define annelids

Answer 1

Segmented worms with a metameric body plan

Question 2

Define metamerism

Answer 2

Segmented arrangement of body, each segment has excretory, nervous and circulatory structures

Question 3

What are some pros of metamerism

Answer 3

Pros: Creates hydrostatic compartments, Lessens impact of injury, permits tagmatization- which helps with specialization of the parts

Question 4

How is metamerism developed?

Answer 4

Mesodermal layers split to form body cavity
Peritoneum lines the compartment walls and cover organs

Question 5

What are setae?

Answer 5

Bristle like structures used for locomotion, sensory and respiratory depending on the organism

Question 6

What are the 3 clades within Phylum annelid

Answer 6

Errantia
Sedentaria
Clitella

Question 7

Summarize clade errantia

Answer 7

Motile worms
~5-10cm long but can be shorter or longer
diverse environments
Paired parapodia

Question 8

Define prostomium, peristomium, and pygidium

Answer 8

The fleshy lobe
First body segment
Terminal segment with anus

Question 9

What is the function of the aciculum?

Answer 9

A chitinous rod that supports the parapodium and setae which extend from parapodia

Question 10

How does feeding work for class errantia?

Answer 10

A simple digestive tract runs from mouth to anus, Anterior region has been modified into a proboscis that is an extendable muscle used for feeding

Question 11

How do class errantia perform gas exchange

Answer 11

Diffusion typically, but some larger organisms may have gills
Closed circulatory system

Question 12

What are the main pieces of the errantia nervous system?

Answer 12

Supra and Sub pharyngeal ganglions connected by the circumpharyngeal ganglion
the ganglia contain small fibres for movement and giant fibres for escape reactions

Question 13

What is unique about errantia eyes?

Answer 13

Can be very simple or very developed, similar to a vertebrate

Question 14

What is the process of epitoky

Answer 14

The sexually immature atoke of a worm grows a sexually mature epitoke, which breaks off in mating seasons and swims to the surface

Question 15

Name a pro and con of epitoky

Answer 15

Pros: protects the atokes, and is efficient in fertilizing eggs
con: etokes make easy prey

Question 16

What is the key difference between errantia and sedentaria?

Answer 16

Sedentaria is more sedentary and tends to burrow more, so are adapted to that
otherwise very similar

Question 17

What are the two groups found in clitellata

Answer 17

Oligochaeta and hirudiniea

Question 18

What is the distinguishing feature of clade clitellata?

Answer 18

The reproductive structure known as the clitellum which forms a cocoon

Question 19

What are some unique features of oligochaeta?

Answer 19

Few setae - 4 pairs per segment- ish
No parapodia
a prostomium located before the mouth

Question 20

How are oligocheata setae moved?

Answer 20

The protractor and retractor muscles

Question 21

What does digestion look like for oligocheata?

Answer 21

The food enters the pharynx then esophagus, can be stored in the crop, the gizzard grinds it into small pieces then deposits into the intestine

Question 22

What is important about the oligocheata intestine?

Answer 22

Folded dorsally to form typhlosole, which increases surface area

Question 23

What is important about the oligocheata circulatory system?

Answer 23

Closed
Heart like structure called a dorsal vessel
Have blood made of hemoglobin and amoeboid cells
Aortic arches help maintain pressure
ventral vessels deliver blood

Question 24

What is important about the oligocheata nervous system?

Answer 24

Basic “brain” called the paired cerebral ganglia
Solid ventral nerve cord acts as a main nerve pathway
No eyes, but sense organs present over body

Question 25

Are oligochaeta mono or di oecious? and explain reproduction briefly

Answer 25

Mono, sex organs found anteriorly; The sperm is exchanged and kept just before the oviduct, then the clitellum slides down the worm, acquiring eggs and then sperm and eventually falls off to form cocoon

Question 26

Do oligocheata have a larval form?

Answer 26

No, they are dirrectly developed

Question 27

Summarize class hirudiniea

Answer 27

Leeches, they have no parapodia, head or appendages, suckers have evolved on both ends

Question 28

What is unique about hirudinea?

Answer 28

No metamerism instead a coelomic cavity with spaces called lacunae, and 4 categories of muscle; oblique, circular, longitudal and dorsoventral

Question 29

What is hirudin?

Answer 29

An anticoagulant secreted by hirudinea members to prevent blood clotting while feeding