Ch. 34 - 35 – Sponges, Cnidarians, & Ctenophores What is an invertebrate? An animal without a backbone. What are some examples? Animals are classified by their shape or symmetry. What is symmetry? Arrangement of body parts around a central axis.

Types of Symmetry 1. Asymmetrical – an organism without a definite shape. Ex. Sponge 2. Radial symmetry – an organism that can be divided into similar halves by any plane that passes through its longitudinal axis. Ex. hydra

3, Bilateral symmetry – is an organism that can be divided into similar halves by only one specific plane passing through its longitudinal axis. Ex. Humans, spiders, fish

Parts of an organisms’ surface 1. Posterior – lower end of the organism Ex. Feet of humans 2. Anterior – upper end of the organism. Ex. Head of a human 3. Dorsal – top surface of an organism. Ex. Back on a human 4. Ventral – bottom surface. Ex. Belly of a human

Organisms Development Organism develop from a zygote Then into an embryo Next is a blastula – a hollow ball of cells Final the blastula caves in and forms a depression called a blastopore. Once the blastula forms a blastopore it is now called a gastrula.

3 Germ Layers 1. Ectoderm – outside layer of cells Ex. Skin 2. Endoderm inside layer of cells Ex. Organs 3. Mesoderm – middle layer of cells Ex. Muscles Pg. 704

Porifera (phylum) Sponges No gastrula stage No true organs Sessile – don’t move Very colorful

Features of a sponge Osculum – top opening of a sponge A sponge is hollow in the middle The sponge’s hollow cavity is lined with collar cells, which have flagella. The collar cells are used to filter out food. Water and food enter the sponge through its pores then pass back out its osculum. Sponges are filter feeders.

Amebocytes transport the food from the collar cells to the rest of sponge. Sponges have the ability to reproduce sexually or asexually; sponges carry both egg and sperm cells. Sponges reproduce asexually by producing buds called gemmules.

Sponges have the ability to regrow missing parts. What is this called? Regeneration Most sponges have both sperm and egg cells, some have separate sexes. Hermaphrodite is an organism with both egg and sperm cells.

Cnidaria (phylum) Example: jellyfish, hydra, coral Have endoderm & ectoderm layers All live in water (mainly marine) Have stinging cells called nematocyst Have a hollow gut Have tentacles

2 body shapes of Cnidarians 1. Polyp Sessile and vase-like shape 2. Medusa Swimming and bell shape All cnidarians use their tentacles to capture and paralyze their prey with a coiled stinger called a nematocyst.

3 Classes of Cnidarians 1. Hydrozoa – Hydra Both polyps and medusa shapes 2. Scyphozoa – jellyfish Mostly medusa 3. Anthozoa – corals Only as polyps

Hydrozoa (class) Hydra use their nematocyst to capture prey and engulf the whole prey into their gastro vascular cavity. They only have one opening (mouth and anus). Asexual reproduction of small buds occurs during warm weather. Sexual reproduction occurs mainly in the fall. Hydra are hermaphrodites.

Scyphozoa (class) Mostly medusa Jellyfish have poisonous tentacles with nematocyst, also. Several humans been seriously injured and even killed from jellyfish off the coast of Australia.

Anthozoa (class) Only polyp Sea anemones are polyps along rocks. Clown fish swim around in their tentacles. The clown fish is protected from the tentacles by a chemical in their skin that doesn’t allow the nematocyst to fire.

3 main body cavities of organisms 1. Acoelomate – without a body cavity. Ex. Hydra, planaria 2. Pseudocoelomate – false body cavity. Ex. Roundworm 3. Coelomate – a true body cavity. Ex. Earthworm, insects, humans, ect.

Platyhelminthes (phylum) Flatworms Lacks circulatory system Lacks respiratory system Bilateral symmetry Senses and nerves at the anterior end called cephalization. Three classes: Turbellaria, Trematodes, Cestoda.

Turbellaria (class) Planaria is an organism in this class. 1. Its freshwater 2. Swims with the aid of cilia 3. Its mouth is in the middle of its body. It extents out by a tube called the pharynx. 4. Water and wastes are exited out the planaria through the flame cells.

5. Planaria have the ability to sense light with 2 anterior eyespots. 6. Planaria have 2 anterior nerve cells called ganglia. The ganglia enables the planaria to sense touch, taste, and smell. It is much like a simple brain. 7. Planaria are hermaphrodites. 8. Planaria are able to regenerate.

Trematoda (class) Flukes (hosts) Endoparasites – live inside the host Ectoparasites – live on the external surface of the host.

Lifecycle of the liver fluke Mates inside the liver of a sheep. Eggs enter the intestine and exit. Eggs hatch in water and invade snails as larva form. The larva leave the snails as a free swimmer and form a cyst on grass blades on land. The sheep eat the grass and the cyst hatches in the digestive tract and bore there way into the blood system which leads them to the liver.

Cestoda (class) Tapeworms 1. Parasitic just like flukes. 2. Lack sense organs, mouth, and digestive system 3. Attaches to a host with its hooks and suckers. 4. Head is called scolex. Body segments are called proglottids.

Nematoda (phylum) Roundworms 1 mm to 120 cm Parasites in digestive tract 2 openings – mouth and anus Trichinosis occurs in humans. Become infected by eating undercooked pork with trichina cysts. Causes pain and stiffness as a cyst in muscle cells. Freeze pork for 72 hours.

Rotifera (phylum) Rotifers Free-swimming Marine and freshwater Cilia along its mouth, which is used to sweep food into its mouth. Looks like a spinning wheel as it moves.