 Flatworms (Platyhelminthes)  Includes Planaria, tapeworms, flukes  Bilaterally symmetrical  Three embryonic tissues = endoderm, mesoderm, and ectoderm  No body cavity, mesoderm muscle inside  Blind digestive track shown here  Most are parasitic and are economically important

a) Radial, asymmetrical b) Radial, bilateral c) Bilateral, radial d) Asymmetrical, bilateral

 Parasitic – 2 hosts  Whitish in color  Absorbs nutrients through outer body wall  Each reproductive unit can have 100,000 eggs inside  Humans can get by eating under cooked meat

Partial or Pseudocoelom True Coelom

 Very common – 99% of us have been hosts to some sort of round worm in our life time  Bilateral, 3 tissues  Body cavity between mesoderm & endoderm

 In soil, vinegar (eels), rotting fruits & veggies, parasitic  Complete digestive track  Muscles along body wall (from mesoderm) allow for whole body movement back and forth  Range in size -1 mm to > 1 m Body is covered by a cuticle that keeps it from desiccating

 Earthworms, leeches, various marine polychaetes such as fire worm  3 tissues, true body cavity or coelom  Body is segmented into repeating units, which enable the animals to move by stretching and contracting segments  Complete digestive system, brain and nerve chord, circulatory system has 5 pumping tube rings  Polychaetes have a pair of fleshy appendages per segment

Annelid variety – parasites, filter feeders, and taking organic material from soil

 Snails, slugs, clams, scallops, oysters, octopus, squid, cuttlefish, etc.  Good eating!  Bilateral symmetry, 3 true tissues  True coelom – totally surrounded by muscle (mesoderm); internal organs have muscles like gut and circulatory system as well as outer body wall – complete digestive track  Body = head and foot  Some of the most intelligent invertebrates

True body cavity or coelom – muscle surrounds gut, blood vessels, etc. Brain, nerves and sensory organs Snails – hermaphrodites – both are male to each other’s female organs when 2 mate Terrestrial snails and slugs use mucus secretions to keep body surface moist

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A. Nematode B. Flatworm - Platyhelminthes C. Cnidaria D. Sponge - Porifera

 Very large group – about ¾ of all known species  3 tissues, true body cavity or coelom  Brain and ventral nerve cord  tube body is consolidated into different body regions, such as head, thorax and abdomen of insect  Appendages have become modified in different ways during course of evolution 1 st 5 – head & mouthparts, next 3 thorax & legs, last segments – abdomen, ovipositor, penis

 Economically important group  Disease transmission in human, pet, livestock, crop  Predators – lower pest populations  Consume our crops, but also pollinate crops  Source of food for many  Unique level of social organization in some

 Live in groups or colonies  Queen plus her daughters  Cells contain stored pollen and nectar and brood  Trophallaxis and communication  Colony cycle

 3 tissues, true coelom  Their embryological development sets them apart from the other invertebrates.  They develop backwards orientation from other invertebrates – similar to vertebrate animals  So this makes them the most similar to vertebrate animals

A. Nematode B. Annelida – Segmented worm C. Echinodermata D. Sponge - Porifera

a) Mesoderm b) Ectoderm c) Endoderm

Tunicates

Review Two tissues, no coelom no coelom partial coelom true coelom 3 tissues