Ch. 11 Aschelminthes

7 different Phyla

Characteristics

• Has a pseudocoel-

fluid filled body cavity.

• Microscopic to 1

meter long.

Characteristics

• Round.

• Tough external

cuticle.

• Mostly in fresh water.

• Complete digestive

system. Mouth,

intestine, anus.

Myxozoa

Arthropoda Annelida

Mollusca

Lophophores

Hemichordata

Chordata

Other

pseudocoelomates

Nematoda

Porifera

Ctenophora

CnidariaPlacozoa

Platyhelminthes

Nemertea

Ciliophora

Sarcomastigophora

Microspora

Apicomplexa

Mesozoa

Echinodermata

CrustaceaChelicerata

Uniramia

Other Chordata

Phylum Nematoda (Roundworms)

• Eat organic material.

• Up to several meters

long.

• Many are parasites of

plants or animals.

• Live in water or soil.

1st land animals.

Reproduction of Ascaris

• Separate sexes.

• Internal fertilization.

• Release up to

200,000 eggs daily.

• 4 molts (stages of life

cycle).

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Nematode Reproductive Systems

Movement of Roundworms

• Longitudinal muscles

contract, forcing wave

motion of hydrostatic

skeleton.

• This stretches the

cuticle on other side.

• Causes a thrashing

motion.

• No circular muscles

for crawling.• Roundworm moving

• https://www.youtube.com/watch?v=tp-

O3LME3OU

Nematodes and crops

• Negative impacts

• https://www.youtub

e.com/watch?v=Zr

ogAKO3dhI

• Positive impacts

• https://www.organi

ccontrol.com/produ

ct/38/beneficial-

nematodes

The End