JP Keller, Ryan Peterson Invertebrates JP Keller, Ryan Peterson

Sponges Over 9,000 species Simplest creature known to man Live mostly in the oceans and seas Simplest creature known to man Phylum- Porifera Sponges reproduce both ways Sexually- Sperm and Egg released into water Asexually- Budding

Body of a Sponge They are not symmetric They don’t grow from a central point Their cells are not organized into tissues and organs Individual cells can grow through a membrane

How a Sponge Eats Collar cells pump water through sponge One cubic centimeter of sponge can pump 20 liters of water a day The collar cells also trap food The water is filtered to gather tiny animals and protists for food

Cnidarian- Carnivores They have symmetry and are called true animals Also called Eumetazoans Embryonic stage Three different levels of tissue Ectoderm- outer body and nervous system Mesoderm- skeletons and muscles Endoderm- digestive organs Phylum-Cnidaria, includes jellyfish, hydra, corals and anemones Other phylum- ctenophore, includes comb jellies and delicate marine animals

Radially Symmetric Body parts arranged around central point Stinging cells- Cnidicytes, no other organism has these, this is where the phylum name comes from Small barbed harpoon, called a nematocyst

Eating and Reproduction Food trapped by a Cnidadore is introduced by endocytosis and it is digested intracellularly Sexually Larvae find a spot to become a polyp Polyp strobilates Juveniles become mature Asexually They can either bud like sponges or divide themselves

Body Shape Medusa- gelatinous, free floating and umbrella shaped They are the most common Polyps-cylindrical pipe shaped and normally attached to rocks

The Evolution of the Body Cavity Bilateral symmetry Left and right halves are symmetric Top is called the Dorsal Bottom- Ventral Front-Anterior Back-Posterior Definite head Move around head first Sensory organs are here to detect food, mates, and possible danger

Nematodes Pseudocoelom- body cavity between the endoderm and the mesoderm Many advantages circulation- allows for quick movement of fluid Movement-fluid in body cavity makes body rigid for muscle driven boy parts Organ function- organs can function without muscle interference

Key Characteristics Mainly parasitic Includes tape worms Only bilaterally symmetric animals that don’t have a body cavity Reproduce sexually Occurs through the exchange of sperm

Other Important Information One way gut 7 animal phyla have a pseudocoelom Only one has large amount of species Nematode Nematodes- round worms 500,000-600,000 species 13,000 named One spade of dirt- 1 million nematodes

Even More Important Information Phylum- platyhelminthes 20,000 species Mostly flat worms Simplest animal with organs No internal body cavity No circulatory system Only one opening Mouth food enters and exits

More on Nematodes Some can be parasitic, infect humans Layer of muscle extends the length of body Beneath a flexible thick layer of epidermis and cuticle Muscle pushes against the cuticle and pseudocoelom to move worm

Mollusks Largest phylum except for arthropods Over 100,000 species Body cavity called a Coelom Fluid filled cavity in the mesoderm They have primary induction- one layer interacts with another Physical contact of mesoderm and endoderm Least advanced because their bodies aren’t segmented

Other information about the fascinating mollusk They have a circulatory system that move nutrients, oxygen, and waste a circulatory system is a system of vessels that carry fluids to every part of the body The heart(s) power this system They’re called the most successful land animals 35,000 terrestrial mollusk species

Physical Characteristics Three main body parts Visceral mass- central section that contains organs Mantle- heavy fold of tissues around the visceral mass Gills in aquatic snails Simple lungs in terrestrial Every mollusk has a muscular foot!!

Mollusk Reproduction Almost all mollusks reproduce sexually There are both male and female mollusks