Download Phylum Annelida - Mr. Lesiuk

Phylum Annelida
the segmented worms
The Higher Animals - two lineages
• Higher animals have a coelom and a
mouth/anus
• The infolded blastopore of the forming
gastrula can become either a mouth or anus
• If it becomes: a mouth -> called protostomes
anus -> deuterostomes
blastopore
True Coelom
• Peritoneum (from mesoderm) lines the body
wall and all organs- Totally enclosed by
mesoderm.
• WHAT ARE THE BENEFITS
OF DEVELOPING A
COELOM?
• the ‘solid’ mesoderm of lower animals
becomes inefficient as body size
increased
• Body cavity = fluid + space for
specialized organs needed in circulation
of waste / food
Segmentation
• Repeated body units (seperated by septum)
with similar structures
• Permits specialization of units
Annelid Diversity
Class – Oligochaeta (earth worms)
Oligo = Few
Chaeta = Bristles
• Movement
– circular and longitudinal muscles work together to
produce “inching” wave-like movement called
peristalsis
– chitinous bristles (setae) on each segment help
to anchor worm in soil
• Feeding
– Eat soil / decayed matter
– Muscular pharynx sucks food through mouth then
pushes it down to the esophagus and crop (storage)
to a grinding organ (gizzard) then onto the intestine.
– Blood transports nutrients digested in intestine
– Wastes pass out anus
– *** MPECGI ***
http://www.ncsu.edu/scivis/lessons/earthworm/Overview.html
Closed Circulatory System
• Simple diffusion does not work for large animals.
• Anterior muscular vessels (Aortic Arches) act as ‘hearts’ (5
Pairs)
• Blood carries nutrients and gases through closed vessels
to capillary beds
• No lungs; gases diffuse across moist skin
Excretory System
• Paired nephridea pass through septum
(partition) into posterior segment. Waste out
pore.
Nervous System
• dorsal, anterior ganglion (primitive brain)
• Ventral nerve cord; nerves to each segment
• Can sense chemicals, light, touch
Reproductive System
• Hermaphroditic, but reproduce by copulation
• Clitellum has gland cells which secrete cocoon
to protect developing eggs
Class - Polychaeta
• Many-bristles
• Marine worms
• Each segment has
parapodia (side-feet)
– movement / gas exchange
Class - Hirudinea
• Leeches
• parasites who bite into skin to feed
• Can fast for up to one year
Questions
1. What is the significance of MPECGI ?
2. What is the function of the clitellum?
3. What function do cetea/bristles? Explain.
4. For each class give a member:
Hirudinea :
Oligochaeta
Polychaeta