Chapter 17: Annelids Flashcards Preview

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Flashcards in Chapter 17: Annelids Deck (25)
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1
Q
  • Annelids exhibit segmentation or metamerism. This means that their body is composed of ?
  • Each unit contains what?
A
  • serially repeated units

- components of most organ systems

2
Q

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

A
  • greater complexity
3
Q

Evolution of metamerism pros:

  • It increased burrowing efficiency by doing what?
  • Regards to the NS?
  • Safety factor?
A
  • permitting independent movement of segments
  • more sophisticated NS
  • if one segment fails others will function perfectly fine
4
Q
  • The type of cleavage they undergo is ?
  • The coelom forms via?
  • They share a ___ as the ancestral larval form
  • The habitats they inhabit? (3)
A
  • spiral mosaic
  • schizocoely
  • trochophore
  • marine, freshwater and moist terrestrial habitats
5
Q

-Within the annelid phylum / are marine worms.

A

2/3

6
Q

Body segments marked by circular grooves are called what?

A
  • annuli
7
Q

Metamerism :

- Repetition of organs in segments is called what?

A
  • metamere or somites
8
Q

What separates the segments?

A
  • septa
9
Q

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

A
  • arthropods
  • annelids
  • vertebrates
10
Q

Describe Setae!

  • composition
  • absent in what animals of this phylum?
  • short setae?
  • long setae?
A
  • tiny chitinous bristles
  • absent in leaches
  • short setae: anchor segments in earthworms, prevent it from slipping backwards
  • long: help aquatic worms swim
11
Q

Habitats of the following classes:

  • Polychaetes
  • Oligochaetes
  • Hirudinea
A
  • primarily marine and usually benthic (bottom dwelling)

- freshwaters, or terrestrial soils….many leaches are predators

12
Q

Body wall:

- the head is composed of what? (2)

A
  • prostomium

- perstonium

13
Q

Body wall:

- The terminal portion bearing the anus is called ?

A
  • pygidium
14
Q

Body wall:

- Are the head and pygidium considered metameres?

A

no

15
Q

Body wall:

- New metameres form where?

A
  • just in front of the pygidium
16
Q

Body wall:

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

A
  • epidermis and a thin outer layer of non-chitinous cuticle
17
Q

Body wall:

What underlies the body wall?? (2)

A
  • strong circular and longitudinal muscles
18
Q

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?
A
  • schizocoely
  • Peritoneum (mesodermal epithellium)
  • Peritonea
  • gut and longitudinal blood vessels
19
Q

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
A
  • leeches
  • fluid volume
  • causes body to shorten and expand
  • causes body to narrow and lengthen
  • widening and elongation moves the animal
  • peristalsis
  • undulatory
20
Q

Origins of Metamerism and the Coelom :

- There is ___ satisfactory explanation for origins of metamerism and coelom has gained acceptance.

A

no

21
Q

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.
A
  • hydrostatic skeleton
  • circulatory fluid
  • gametes
22
Q

Origins of Metamerism and the Coelom :

- It is unlikely that segmentation is homologous among ___, ___ and ___.

A

arthropods, annelids and chordates

23
Q

Origins of Metamerism and the Coelom :

- Current evidence supports the hypothesis that segmentation arose how?

A
  • independently multiple times
24
Q
  • 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 ___.
A
  • burrowing

- arthropods, exoskeleton

25
Q

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

A
  • Molluscs

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