Intro to the Invertebrates

What is an Animal?

Basic Definitions What is an animal? –a multicellular eukaryotic heterotroph whose cells lack cell walls. What is an invertebrate? –an animal that does not have a backbone.

What is an Invertebrate?

Simple to more complex

The Phlya of Invertebrates Porifera Cnidaria Platyhelminthes Nematoda Annelida Arthropoda Echinodermata

PhylumExamples Evolutionary Milestone Poriferaspongesmulticellularity Cnidariajellyfish, hydra, coraltissues Platyhelmint hes flatwormsbilateral symmetry Nematodaroundwormspseudocoelom Molluscaclams, squids, snailscoelom Annelidaearthworms, leechessegmentation Arthropoda insects, spiders, crustaceans jointed appendages Echinoderm ata starfishdeuterostomes Chordatavertebratesnotochord

Vocabulary Radial Symmetry: having body parts that repeat about an imaginary line through the center of the body. Bilateral Symmetry: having body parts that repeat on either side of the body. Cephalization (cephalo = head): the gathering of sense organs and nerve cells into the head region. Ganglia- Clusters of nerve tissue Hermaphrodite: having both sexes in one animal.

Symmetry

Embryonic Development: Zygote = fertilized egg Blastula = a hollow ball of cells Blastopore = the blastula folds in creating an opening Protostome = mouth is formed from blastopore Deuterosome = anus is formed from blastopore

Different Body Plans Coelom: body cavity that is completely lined with mesoderm. A coelomate is an animal with a coelom. An acoelomate is an animal without a coelom.

Body Plans

Phylum Porifera Sponges

Sponges (Phylum Porifera) Sponges have no specialized tissues. Many holes called pores, or ostia. Osculum – large opening at the top. Water is taken into the sponge through its many pores and circulated out through the osculum. This is how they ‘breathe’ They have no muscle or nervous system. Sponges are sesslie – which means they do not move. Sponges filter food out of the water as it flows through the ostia. Special cells called collar cells pick up the food and start digestion. Sponges can regenerate lost body parts.

Sponge Anatomy

Phylum Cnidaria Jellyfish, Coral, Hydra, Sea Anemone, Portuguese-man-of-war

Cnidaria “Stinging Cell” animals with raadial symmetry. They have Nematocysts – stinging cells in the tentacles, activated by touch. Provides protection and helps capture food. Some are sessile, some can ‘swim’. They are hermaphrodites (contain both male and female reproductive structures in the same body. They have 3 layers –Ectoderm – outer cell layer –Endoderm – inner cell layer –Mesoglea – jelly-like layer separating ectoderm and endoderm. Within the mesoglea is a nerve net. There is no brain. They contain a central cavity called the gastrovascular cavity, or enteron. Digestion takes place here and the contents are absorbed by the endodermal cells. The undigested food is expelled through the mouth.

2 Body forms in Cnidaria Polyp Form Medusa Form

Phylum Platyhelminthes Planarians, Flukes, and Tapeworms

Platyhelminthes or Flatworms (the simplest bilateral animals) Three classes Planarians are mostly free-living, non-parasitic, and marine Flukes are parasites Tapeworms are parasites (with hooks and suckers that anchor the worm inside the intestines of a host animal)

Anatomy of a Flatworm

Ever see the ALIEN movies?

Phylum Nematoda Roundworms and Rotifers

Nematodes Roundworms can be parasitic (hookworm, pinworm, threadworm) or non-parasitic, they can also be decomposers. They have pointed heads and tapered tails with a complete digestive tract. Rotifers are tiny animals, with a crown of cilia and a complete digestive tract. They are common in freshwater.

Nematode Anatomy

Phylum Annelida Earthworms, Leeches and Polychaetes Christmas Tree Worm

Annelids Segmented bodies; Bilateral symmetry True body cavity (coelom). The organs of the digestive, nervous, and circulatory systems run the length of the body. Complex digestive and circulatory systems. Earthworms are hermaphrodites. Small brain located near the pharynx. A ventral nerve cord extends from the brain and runs the length of the body. In each segment it swells to form structures called ganglia. Their muscular system contains both circular and longitudinal muscles. As these muscles contract and relax they shorten and elongate the body making it move. Setae, small bristle- like hairs, extend from the body walls and act as anchors as the worm moves. They have a hydrostatic skeleton (water-filled tube). No respiratory organs; worms breathe through their moist skin.

Earthworm Anatomy

Phylum Mollusca Clams, Squid, Octopus Can you see the Giant Clam in this photo?

Mollusks Mollusks have bilateral symmetry. Their body is covered with a thin membrane called the mantle. This structure may secrete the shell. Three body parts: head, muscular foot, and the visceral hump (contains the internal organs). Breathing occurs through the gills or the lining of the mantle cavity. Squid and octopus are the most intelligent invertebrates. They are about as smart as a house cat. Reproduction is sexual. They are true coelomates.

Check out the complex anatomy of a clam

Giant squid- an amazing mollusk

Giant squid Head: houses a complex brain. Eyes: largest in the animal kingdom. They can grow to 25 cm (10 in.) in diameter--about the size of a volleyball. Fins: relatively small in this species. They help balance and maneuver the huge animal as it swims. Mantle: the main body. This muscular sac contains most of the organ systems. Arms (8): studded with two rows of suckers. Feeding tentacles (2)two rows of suckers Funnel: a multipurpose tube used in breathing, jetting, squirting ink, laying eggs, and expelling waste.