Zoology - Phylum Annelida

metamerism

serial repetition of body structures - all into integrated into functional whole

how is the evolutionary advent of metamerism significant (because it made possible much greater complexity in structure and function) WHAT IS THE COMPEXITIES (3)

1. increase burrowing efficiency

2. sophisticated nervous system

3. redundancy - safety factor

euryhaline polychaetes

tolerated a range of salt concentrations

what are the primary distinctive features of Polychaeta

1. well developed head - specialized sensory structures

2. no clitellum

3. paired appendages - parapodia (for anchoring and locomotion)

   b. bundles of setae on parapodia (for anchoring and locomotion)

predatory polychates

eversion of proboscis to sieze prey (feeding)

herbivores and scavengers

jaws tear food into smaller pieces (feeding)

deposit feeding polychaetes

extracts organic nutrients from ingested sediment (feeding)

sedentary and tube dwelling polychaetes

filter feeding; ciliary motion creates water currents (feeding)

how are respiratory gasses exchanged

diffusion across body wall

how is oxygen carried around the body

respiratory pigments dissolved in blood

asexual reproduction of polychaetes

1. budding

   1. transverse fission

how are gametes released

gonad → coelum → nephridiop (worm ruptured and dies)

epitoky

formation of reproductve individual (epitoke )

separates from nonproductive individual (atoke)

what are the advantages of reproductive swarming of epitopes of species

1. increased fertilization rate

2. atoke safe from predation

3. predator swamping

what type of locomotion occurs in this group polychaetes

antagonism of circular and longitudinal muscle results in contraction waves

what is the function of the clitellum

forms a cocoon c

cocoon formation

site of fertilization;hatching

typhlosole

increase surface area of nutrient absorption

how do earthworms enrich soil

1. add nitrogen to soil

2. aerate soil

3. mix subsoil and topsoil

why do oligochaetes excrete large amounts of dilute urine

freshwater or moist soil - hypertonic to soil