Lecture 8 - Annelids

Question 1

what are annelids

Answer 1

segmented worms

Question 2

what body cavity

Answer 2

coelomate - have a coelom

Question 3

4 adv of having a coelom

Answer 3

1 - transport
2 - gut moves independently from body wall
3 - site for gamete maturation
4 - hydrostatic skeleton

Question 4

how do they move

Answer 4

by peristalsis - circular and longitudinal muscles work antagonistically

Question 5

why is advantageous for them to have metameric segmentation

Answer 5

locomotion is more efficient and precise as contraction occurs in segments

Question 6

circulatory system

Answer 6

closed circulatory system with blood vessels

Question 7

3 ways segmentation may be modified by

Answer 7

1 - restriction of structures to particular segments- take on particular roles
2 - some segments develop special structures for particular functions
3 - segments may fuse together

Question 8

what are nephridia

Answer 8

annelids excretory organs - use high pressure to force fluid through and useful substances are absorbed (playthelminthes have protonephridia)

Question 9

what are the 2 groups within annelids

Answer 9

polychaeta and clitellata

Question 10

what are the 2 groups within clitellata

Answer 10

oligochaeta (earthworms)

hirudinea (leeches )

Question 11

what are polychaetes?

Answer 11

marine worms

Question 12

3 features of polychaetes

Answer 12

parapodia - fleshy projections on each segment used for respiration (distinctive feature of polychaetes)
lots of setae (hair like structures)
prostomium (headend) is well developed with elaborate feeding structures

Question 13

what are the 2 big groups of polychaetes

Answer 13

1) errant (active)

2) sedentary e.g fan worms (elaborate heads for collecting food)

Question 14

5 facts about polychaete reproduction

Answer 14

1) dioecious - separate sexes
2) external fertilisation
3) spawning may be synchronus
4) some produce trocophore larva in packets from end of body
5) undergo epitoky

Question 15

what is epitoky

Answer 15

body transformations in order to reproduce - metamorphis into their reproductive form - requires lots of energy - reproductive form has lots of swimming setae

Question 16

what is different about clitellata respiration

Answer 16

they have no parapodia - rely on gas exchange on body surface - produce mucus

Question 17

how do clitellata eggs develop

Answer 17

produce clitellum and cocoons - eggs develop inside with no larval stage

Question 18

clitellata reproduction

Answer 18

hermaphrodite

gonads restricted to a few segments

Question 19

how do earth worms move

Answer 19

peristaltic locomotion

Question 20

whats different about earthworm setae

Answer 20

they only have a few and are very small

Question 21

advantage of earth worm

Answer 21

very good for soil

Question 22

earth worm reproduction

Answer 22

• reproductive organs are found in different segments female in one segment male in the other
• mutual sperm transfer - worms pair up head to head and are bound together by substance produced by clitellum
• no larval stage

Question 23

what is the most advanced and derived of the annelids

Answer 23

hirudineans (leeches)

Question 24

4 features of leeches

Answer 24

• no setae
• restricted number of segments
• hermaphrodites
• no crawl with suckers - well developed longitudinal muscles

Question 25

how do leeches feed

Answer 25

predaceous - blood suckers- symbiotic bacteria in gut break down and absorb the nutrients which is a long process