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What is metamerism
internal segmentation and external segmentation
What are the advantages of metamerism?
- 1. Safety and redundancy: if one metamere dies it's not fatal
- 2. Varied and precise body movements: allows for powerful digging
- 3. More refined nervous system: able to move all somites or just one
- 4. Specialized parts
What does it mean to be schizocoelous?
the coelom develops embryonically as a split in the mesoderm on each side of the gut.
What is the similarities between Annelida and mollusks?
They have trochopore larvae
What do Annelida share with Arthropoda?
- 1. Outer, secreted cuticle
- 2. Similar nervous system, ganglia, ventral nerve cord
- 3. Lateral appendages
- 4. Metamerism
What important ecological role do the common earthworms have?
- Their burrowing increases the drainage and aeration of soils.
- Their migration mixes up the soil, distributing organic matter into deeper layers
What gives rise to the anus in or the terminal portion of the Annelida?
What is peritoneum?
Layer of mesodermal epithelium, lines body wall, surrounding each compartment within a segment
Is the prostomium the oldest or youngest part of the annelida body plan?
In general, the setae for Annelida is made up of what substance?
Identify the 4 major parts to the body wall.
- 1. Longitudinal muscles
- 2. Circular muscles
- 3. Epidermis
- 4. Non-chitinous cuticle
What are Peristaltic contractions?
alternating waves of contraction by longitudinal and circular muscles passing down the body
What does having a septum allow for?
elongation or widening in restricting areas.
What are mesentaries?
- double membrane partitions supporting the gut
- run length of organism
Which class of Annelida does not have a hydrostatic skeleton?
What is the role of a hydrostatic skeleton?
Why does a hydrostatic skeleton result?
Coelom is filled with fluid
True or false. Class Polychaeta has clitellum for reproduction.
FALSE. Oligochaeta and Hirundinea have clitellum but not Polychaeta
Explain the parapodia in class Polychaeta. What are parapodia? What is/are the function?
- Special sense organs
- used for crawling, swimming, anchoring in tubes
- chief respiratory organ
- much more developed in Polychaeta: eyes and statocysts, notopodium and neuropodium
True or false. The fertilization in Polychaeta is internal.
- FALSE: Fertilization is external.
- Polychaeta have no permanent sex organs
Explain the difference between Atokes and Epitokes.
- Atokes have no sex organs
- Epitokes have sex organs, only for a period of time, they go to surface and release gametes
What species has atokes and epitokes?
What is a typhisole?
chlorogogen cells, outer layer function like the liver
What is the role of chlorogogen cells?
- synthesis glycogen and fat
- distribute nutrients to coelom
Explain the circulatory system of the Oligochaeta.
- has 4 arotic arches that pump blood into dorsal blood vessel
- blood has ameboid cells and hemoglobin
How does reproduction occur in Oligochaeta?
- Moneoicious or hermaphroditic
- have glandular structure midway down
- Have clitellum but not until sexually mature
- get in opposite positions (69) for mating
- anchor setae into one another and after copulation, the clitellum breaks, slides over the worm to form a cacoon.
- Eventually the cacoon slips off and a worm emerges from it.
What makes the class Hirundinea different from other classes of Annelida?
- No parapodia or setae!
- coelom: no distinct compartments, instead filled with connective tissue and muscle
- Have fixed # of segments= 34!
What is the role of the posterior sucker of hirundinea?
- for attachment and locomotion
- holds organism in place
What is the role of the anterior sucker of the Hirundinea?
- Attach to prey
- NOTE: smaller than posterior sucker
Explain how the Arenicola (lugworm) lives and how it retrieves food.
- Lives in L-shaped burrow in mudflats
- Uses proboscis to burrow
- peristaltic movements keeps water coming in
- Water filters through the sand at the head end and worm ingests food-laden sand
Identify class and species.
- Class: Oligochaeta
- Lumbricus terrestris
What is a clitellum?
thickened, saddlelike protion of certain midbody segments of many oligochaetes and leeches
What characteristics do we use to divide Phylum Annelida into its classes?
- distribution of setae
- presence or absence of clitellum
What are setae?
- thin, chitinous bristles or rods that are secreted by certain cells in the body wall
- used in locomotion and feeding
What is the function of the cuticle?
- Protective body covering
- reduces water loss
What are nephridiopores?
small pair of excretory pores
Function of a gizzard?
Ground up food into smaller pieces
In Huridinea, the function of the crop is...?
to store blood (storage)
How do polychaetes, oligochaetes, and hirudineans move?
- Polychaetes and oligochaetes move by setae and their hydrostatic skeleton
- hirudineans have muscular body to move