Chapter 17: Annelids Flashcards Preview

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Flashcards in Chapter 17: Annelids Deck (25):
1

-Annelids exhibit segmentation or metamerism. This means that their body is composed of ?
-Each unit contains what?

- serially repeated units
- components of most organ systems

2

The evolution of metamerism allowed for what in regards to structure and function?

- greater complexity

3

Evolution of metamerism pros:
- It increased burrowing efficiency by doing what?
- Regards to the NS?
- Safety factor?

- permitting independent movement of segments
- more sophisticated NS
- if one segment fails others will function perfectly fine

4

-The type of cleavage they undergo is ?
- The coelom forms via?
- They share a ___ as the ancestral larval form
- The habitats they inhabit? (3)

- spiral mosaic
- schizocoely
- trochophore
- marine, freshwater and moist terrestrial habitats

5

-Within the annelid phylum _/_ are marine worms.

2/3

6

Body segments marked by circular grooves are called what?

- annuli

7

Metamerism :
- Repetition of organs in segments is called what?

- metamere or somites

8

What separates the segments?

- septa

9

Segmentation is found in ___, probably homologous with __, and in ___ where it evolved independently.

- arthropods
- annelids
-vertebrates

10

Describe Setae!
- composition
- absent in what animals of this phylum?
-short setae?
- long setae?

- tiny chitinous bristles
- absent in leaches
- short setae: anchor segments in earthworms, prevent it from slipping backwards
- long: help aquatic worms swim

11

Habitats of the following classes:
- Polychaetes
- Oligochaetes
- Hirudinea

- primarily marine and usually benthic (bottom dwelling)
- freshwaters, or terrestrial soils….many leaches are predators

12

Body wall:
- the head is composed of what? (2)

- prostomium
-perstonium

13

Body wall:
- The terminal portion bearing the anus is called ?

- pygidium

14

Body wall:
- Are the head and pygidium considered metameres?

no

15

Body wall:
- New metameres form where?

- just in front of the pygidium

16

Body wall:
- The surface of an annelid is covered with what?(2)

- epidermis and a thin outer layer of non-chitinous cuticle

17

Body wall:
What underlies the body wall?? (2)

- strong circular and longitudinal muscles

18

Coelom?
- forms by?
-What lines body wall and forms dorsal and ventral mesenteries ?
- _____ of adjacent segments meet's to form the septa
- What two things extend through the septa?

- schizocoely
- Peritoneum (mesodermal epithellium)
- Peritonea
- gut and longitudinal blood vessels

19

Hydroskeleton:
- what organisms do not a coelom filled with fluid that serves as a hydrostatic skeleton?
- ____ remains constant
-Contractions of the longitudinal muscles does what?
- Contractions of the circular muscles does what?
-By separating this force into sections what occurs?
-Alternate waves of contractions or ___ allow efficient burrowing
- swimming annelids use ___movements

- leeches
- fluid volume
- causes body to shorten and expand
- causes body to narrow and lengthen
-widening and elongation moves the animal
-peristalsis
-undulatory

20

Origins of Metamerism and the Coelom :
- There is ___ satisfactory explanation for origins of metamerism and coelom has gained acceptance.

no

21

Origins of Metamerism and the Coelom :
-The coelom may have been advantageous as a ____.
- The coelomic fluid would have acted as ____ and reduced need for female cells everywhere.
-The coelom could store ___ for timed release but would require nervous and endocrine control.

-hydrostatic skeleton
-circulatory fluid
-gametes

22

Origins of Metamerism and the Coelom :
- It is unlikely that segmentation is homologous among ___, ___ and ___.

arthropods, annelids and chordates

23

Origins of Metamerism and the Coelom :
- Current evidence supports the hypothesis that segmentation arose how?

- independently multiple times

24

-Selective advantage of a segmented body for annelids appears to lie in the efficiency of ____.
-However this does not explain segmentation in ___ given the rigidity of the ___.

- burrowing
- arthropods, exoskeleton

25

Annelids share many developmental features with what other phylum and are presumed to be closely related?

- Molluscs

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