Annelids, Metamerism (8)

Question 1

What is metamerism?

Answer 1

Segmentation of the body into repeated units, both externally and internally

Question 2

What are annelids commonly known as?

Answer 2

Segmented worms

Question 3

Which other phyla exhibit metamerism besides Annelida?

Answer 3

Arthropoda and Chordata

Question 4

What is an evolutionary advantage of metamerism in annelids?

Answer 4

The creation of hydrostatic compartments, lessening the impact of injury, and permitting tagmatization.

Question 5

What is schizocoelous development?

Answer 5

A process in which mesodermal layers split to form body cavities.

Question 6

What is the function of peritoneum in annelids?

Answer 6

It lines the body wall of each compartment and forms mesenteries that cover organs.

Question 7

What are the two main clades within Pleistoannelida?

Answer 7

Errantia and Sedentaria.

Question 8

What is a distinctive feature of Errantia?

Answer 8

Paired parapodia found in most segments used for locomotion and respiration.

Question 9

What is the function of parapodia in Errantia?

Answer 9

Locomotion and, in some species, respiration

Question 10

What is a proboscis in Errantia and what is its function?

Answer 10

An extendable muscular structure used for feeding, often equipped with paired jaws.

Question 11

How does gas exchange occur in Errantia?

Answer 11

Via diffusion across the body wall and parapodia, sometimes with parapodial gills

Question 12

What circulatory system do Errantia possess?

Answer 12

A closed circulatory system with contractile dorsal and ventral aortas

Question 13

What sense organs are present in Errantia?

Answer 13

Eyes (ranging from simple eyespots to image-resolving eyes), nuchal organs (chemoreception), and statocysts (body orientation).

Question 14

What is epitoky in polychaetes like Eunice viridis?

Answer 14

The transformation of part of the body into a sexually mature form (epitoke) during the breeding season.

Question 15

What is the adaptive significance of epitoke swarming behavior in Errantia?

Answer 15

It protects non-reproductive individuals (atokes) and ensures synchronous maturation of epitokes, maximizing fertilization.

Question 16

What distinguishes Sedentaria from Errantia?

Answer 16

Sedentaria are generally burrowers or tube dwellers with reduced parapodia, often used for anchoring or respiration.

Question 17

What is the defining feature of Clitellata?

Answer 17

The presence of a clitellum, a reproductive structure that produces a cocoon for eggs.

Question 18

Which groups are included in Clitellata?

Answer 18

Oligochaeta (earthworms) and Hirudinea (leeches).

Question 19

Do earthworms have parapodia?

Answer 19

No

Question 20

What are setae in earthworms?

Answer 20

Bristle-like structures set in sacs within the body wall, moved by muscles for locomotion.

Question 21

What is the function of the gizzard in earthworms?

Answer 21

To grind food into smaller pieces for digestion

Question 22

How do earthworms exchange gases?

Answer 22

Through their moist skin; they lack specialized respiratory organs

Question 23

What circulatory system do earthworms have?

Answer 23

A closed circulatory system with a dorsal vessel (heart-like), aortic arches, and ventral vessels

Question 24

How do earthworms reproduce?

Answer 24

They are monoecious and exchange sperm during copulation, producing a cocoon where fertilization and development occur.

Question 25

What are leeches classified under?

Answer 25

Class Hirudinea within Clitellata

Question 26

What is unique about the body of leeches compared to other annelids?

Answer 26

They have lost internal metamerism (no septae) and their coelomic cavity is filled with connective tissue and lacunae

Question 27

What do leeches feed on?

Answer 27

They feed on small invertebrates or body fluids of vertebrates, using either a proboscis or chitinous jaws

Question 28

What anticoagulant do leeches secrete while feeding?

Answer 28

Hirudin

Question 29

What muscles allow annelids to contract and extend their bodies for movement?

Answer 29

1. Circular muscles; contract to make the segment longer and thinner
2. longitudinal muscles; contract to make the segment shorter and thicker

Question 30

What are the functions of the suprapharyngeal ganglion in Errantia?

Answer 30

It controls motor and sensory functions related to feeding and forward movement.

Question 31

How do polychaetes reproduce if they have no permanent sex organs?

Answer 31

Polychaetes are dioecious
- gametes develop in the coelomic cavity
- fertilization is external, and early larvae are trochophores.

Question 32

What type of feeding structure do tube-dwelling Sedentaria possess?

Answer 32

Sedentaria often have specialized parapodia that function as gills for feeding while anchored in their tubes

Question 33

In what segments of earthworms are reproductive organs located?

Answer 33

Reproductive organs are found in segments 9 to 15 in Lumbricus species.

Question 34

What is the function of the typhlosole in earthworm digestion?

Answer 34

The typhlosole increases the surface area for digestion and absorption in the intestine

Question 35

What are the four types of muscles found in leeches that aid in their movement?

Answer 35

Oblique, circular, longitudinal, and dorsoventral muscles.

Question 36

How is the coelomic cavity of leeches different from other annelids?

Answer 36

The coelomic cavity is filled with connective tissue and lacunae (fluid-filled spaces) instead of distinct compartments.

Question 37

How much can a leech increase its body mass after feeding?

Answer 37

Leeches can increase their body mass by 2 to 10 times after feeding.