L8 Annelids

Question 1

What type of body cavity do they have?

Answer 1

Coelom - are coelomates

Question 2

What are the advantages of having a coelom?

Answer 2

Transport substances
Gut can move independent of the body wall
Site for gamete maturation
Acts as a hydrostatic skeleton

Question 3

How does the coelom act as a hydrostatic skeleton?

Answer 3

Filled with fluid - incompressible. Circular muscles go around the animal, and longitudinal muscles run down it, they can move antagonistically, which allows the animal to move by peristalsis

Question 4

What is metameric segregation?

Answer 4

Functioning units that form the animal, most are similar

Question 5

What is the proliferation zone?

Answer 5

Where new segments occur

Question 6

How is segmentation modified?

Answer 6

Structures may be restricted to a particular segment
Some segments develop specialised structures
Segments fuse

Question 7

What is the prostomium?

Answer 7

the first body segment in an annelid worm’s body in the anterior end

Question 8

What is the pygidium?

Answer 8

Terminal segment of certain invertebrates

Question 9

What forms the brain in annelids?

Answer 9

The ventral nerve cord ends in a cone of nerves at the anterior end

Question 10

What are septa?

Answer 10

Divisions internally between the segment - depends on group how well formed they are, or if present at all

Question 11

What are nephridium?

Answer 11

Used in excretion - is a tubule opening to the exterior of the animal at each segment

Question 12

What are the three classes of annelids?

Answer 12

Polychaetas
Oligochaetas
Hirudinea

Question 13

Which class is most diverged?

Answer 13

Hirudinea

Question 14

What are the general characteristics of the polychaetes?

Answer 14

Lots of setae

Parapodia

Question 15

How many species of polychaetes are there?

Answer 15

around 8000, mostly marine segmented worms e.g. fan worms, tube worms

Question 16

What are setae?

Answer 16

a stiff structure resembling a hair or a bristle, especially in an invertebrate

Question 17

What are parapodia?

Answer 17

A number of paired muscular bristle-bearing appendages used in locomotion, sensation, or respiration

Question 18

Give an example of a sessile form

Answer 18

Fan worm, has a head specialised for collecting food

Question 19

Give an example of an errant (mobile) form

Answer 19

ragwort, move around a lot, so have developed parapodia. Are active hunters so require jaw like structure

Question 20

Give an example of a sedentary form

Answer 20

Arenicola, lugworm. Used as fishing bait parapodia are reduced, as are burrowers. Are deposit feeders, living in u shared burrows. essential to ecosystem as they ensure the movement and recycling of organic material in the sand

Question 21

how do polychaetes reproduce?

Answer 21

Dioecious
External fertilisation
Spawning may be synchronous 
Epitoky 
Produce trochophore larvae 
Swarming

Question 22

What is epitoky?

Answer 22

A transformation undergone before reproduction, that occurs in many species. Requires a lot of energy,

Question 23

What are the clitellata?

Answer 23

The hirudineans and the oligochaetes

Question 24

What are the general features shared by the clitellata?

Answer 24

No parapodia
Produce clitellum
Hermaphrodite
Gonads are restricted

Question 25

What are the oligochaete, and what are their general characteristics?

Answer 25

eg. Earth worms, have different ecotypes
are terrestrial and freshwater
Few setae, but have very well developed septre
Peristaltic locomotion
deposit feeder
Gas exchange across the skin so vulnerable to predation
mutual sperm transfer

Question 26

What did Darwin show in his earthworm studies?

Answer 26

Are an essential part of soil nutrient cycling, Bunged burrow with leaves, worms dragged the leaves down the burrow from the narrow end, displaying some sort of intelligence

Question 27

What are the Hirudineans and what are their general characteristics?

Answer 27

Leeches, are the most advanced annelids
no setae
restricted to 34 segments
Mutual sperm transfer
Have a sucker on first and last segments
Suckers and longitudinal muscles used to move
Predacious, of insects and vertebrates, penetrate with a proboscis - can take up to 10 times body weight in blood