Week 9
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General attributes of Annelida
segmented” worms Most marine Body metameric Paired epidermal setae Closed circulatory system Ventral nerve cord with dorsal suprapharyngeal ganglia Protonephridia or metanephridia
What are setae
Hairlike, bristle structures that are associated with the body wall in annelids
Differentiate between metamerism and tagmatization
metamerism: segmented body tagmatization: specialization of the segments
What is the peritoneum in the annelid body
• Thin sheet of cells lining the body cavity • Shiny smooth • A few cells thick
What are parapodia
in annelids, lateral extensions of the body wall - Setae are the bristle like structures on them can be used to walk by contracting longitudinal muscles
What is the prostomium in annelids
• Dorsal extension on most anterior part, kind of makes a mouth • Contains structures ○ Sensory - eyes ○ Antennae - chemosensory ○ Palps - feeding structure
Describe the circulatory system of annelids
Closed circulatory system Dorsal blood vessel (above gut) - Flows back to front Ventral blood vessel - Flows front to back Parapod: have setae that break into capillary beds
Because ammonia is water soluble, marine annelids
can simply diffuse the nitrogenous waste through their body walls
How do terrestrial annelids excrete ammonia
as urea
Features common to Ecdysozoans
Ecdysis: They undergo periodic shedding of their outer covering. Cuticle: They have a protective external cuticle. Segmented body: Many possess a segmented body plan. Bilateral symmetry: Their bodies are bilaterally symmetrical. Nervous system: They have a centralized nervous system. Complete digestive system: Most have a complete digestive tract. Excretory organs: They possess specialized organs for waste removal. Reproductive strategies: They display diverse reproductive methods.
Features of nematodes (round worms)
unsegmented, pseudocoelomate layered cuticle lack cilia typically muscles run longitudinally to maintain its circular shape dioecious renette cells in excretory system
renette cells
glandular or tubular cells that absorb excess salts and move them to the excretory pore
define eutely
strict determined number of cells in its body
4 key features that lead to evolutionary success of arthropods
exoskeleton segmentation and appendages molting and growth diverse reproductive strategies
Describe the process of ecdysis
1st Hypodermis secretes enzymes that degrades the upper layers of the exoskeleton - underlying epithelium becomes separated 2nd Secrete new material to be the base of the new exoskeleton 3rd Old exoskeleton breaks up or animal crawls out New exoskeleton takes a while to harden up - animal is quite soft and vulnerable to predation