Chapter 28 Simple Invertebrates

Sponges- the simplest organisms

Plan for notes:• As we discuss each aspect of simple

invertebrates, complete the spreadsheet you have on your desk titled: Simple Invertebrates

• Your job is to determine what information goes where on the spreadsheet, I am not going to tell you so don’t shout out questions- THINK, READ, LISTEN before you speak!

• If you do not finish the spreadsheet as we are discussing it, look in your textbook pages 617-636 for answers for homework.

Addition to notes•Write page # 617-636 at top of page to help with homework if you don’t finish.

•Please add under the Animal heading the word

EXAMPLES

General Features of Sponges

• They are animals but they completely lack symmetry (asymmetry) and are just a mass of specialized cells

• Sort of like the sand-man in SpiderMan3- if you put the cells through a mesh sieve they would find each other and get back together again making a new sponge.

General Features of a Sponge: Body coverings, Locomotion

• OSTIA - small pores all over the sponge through which water enters.

• OSCULA - larger openings through which water exits.

• SESSILE - they don’t move, they attach themselves to submerged surface and stay there for their lives. (locomotion)

• CHOANOCYTES - collar cells that line the internal cavity of a sponge. Have flagella on them that beats water (and food) into the cavity.

• AMOEBOCYTES - sponge cells that supply the rest of the sponge’s cell with nutrients and carrying away wastes.

Sponge Diversity: Body Covering

• Brillantly colored sponges abound in warm, shallow sea waters.

• Some may contain hundreds of folds that are visible as fingerlike projections.

• The folds increase the sponge’s size and surface area.

Sponges – people like them.

Sponge Skeletons

• Does not have a fixed skeleton like a human

• Composed of SPICLULES tiny needles composed of silica or calcium carbonate.

• Some sponges have SPONGIN a resilient, flexible protein fiber that provides support for the sponge.

Sponges – simple but important

Reproduction

• Sponges can reproduce asexually

• Can regenerate when cut into pieces – each bit of sponge can become a new sponge.

• In freshwater sponges, if life gets rough, they form GEMMULES – clusters of amoebocytes encased in protective coats. When conditions improve, they grow.

Gemmules – how freshwater sponges make it through the winter.

Looks sort of gross, but it is just gemmules…

Can reproduce sexually too.

• Most sponges are hermaphrodites. Since eggs and sperm are produced at different times, self-fertilization is avoided.

• In most species of sponges, fertilization occurs sperm from one sponge enter another sponge through pores.

• Collar cells pass sperm into mesohyl, where egg cells are.

• Fertilized eggs develop into larva and leave sponge• After brief free-swimming stage, the larvae attach

themselves to an object and develop into new sponges.

That’s all for Sponges!

If you were not able to get the 6 columns of information, the movie on Sponges will also give you information, just listen!!!

Cnidarians(nih DAIRians)

Two Body Forms: You may fill in these notes in the

Cnidarians row• Medusa – free floating have nerves and

muscle tissue (hint for locomotion), jellylike and often umbrella shaped. Radial symmetry

• Polyp- tubelike, sessile,(another hint for locomotion) often attached to a rock or some other substance. Radial symmetry

• Many cnidarians exist only as medusas, while others exist only as polyps. Others alternate between the two.

Cnidocytes – what makes cnidarians sting! Example of

body coverings• Cnidocytes are stinging

cells located on the tentacles of the gastrovascular cavity of cnidarians.

• Nematocyst – Harpoons inside the cnidocytes used for defense and to spear prey. Some have deadly toxins, while others contain chemicals that stun.

The Three Classes of Cnidarians and examples of

each• Hydrozoans – most primitive, polyp and

medusa stages, freshwater and marine, many individuals (medusa and polyps) live together in a colony example: Portuguese man-of-war,

• Scyphozoans – true jellyfish, active predators, both medusa and polyp stages, box jellies

• Anthozoans – exist only as polyps, examples sea anemones and corals

Marine Hydrozoa

• Much more complicated. Colonies incorporate both medusa and polyps together

• Example: Physalia, Portugese Man of War

• Gas filled polyp helps it float, other medusa and polyps help it reproduce and eat.

• A single colony can contain 1,000 individual medusas and polyps.

Fertilization and Reproduction in Hydrozoans

• Asexually by budding– Buds turn into polyps– Polyps turn into medusaFertilization:Medusa male and female release sperm

and eggs– Produce zygotes that develop into free

swimming, ciliated larvae called planulae.– Planulae eventually settle on ocean

bottom and develop into new polyps.

Hydrozoans

• Body coverings: Polyps form calcium carbonate skeletons

2nd Class of Cnidarians- Scyphozoans

• True jellyfish(example)

• Active predators, ensnare and sting prey with tentacles (body coverings)

• Live as both polyps and medusas (skeletal structure)

2nd Class of Cnidarians- Scyphozoans

• Body symmetry: Radial

2nd Class of Cnidarians- Scyphozoans

• Locomotion: Free swimming medusa, sessile polyp stage

2nd Class of Scyphozoans Reproduction and Fertilization

• Most medusas reproduce sexually• Some have polyp stage reproduce

asexually• Medusa release sperm and eggs into

water, fertilized zygote forms polyp eventually medusa

3rd Class of Cnidarians: anthozoans

• Largest class of cnidarians• Exist only as polyps (skeletal

structure)• Thick stalklike body topped by

tentacles (skeletal structure) tentacles (body covering)

• Examples: Sea anemones, corals (skeletal structure of corals: hard outer covering of calcium carbonate)

Fertilization and Reproduction of anthozoans

• Fertilization: sperm and eggs released into ocean, where fertilization occurs

• Reproduction: asexually form buds, also reproduce sexually by the above method of releasing sperm and eggs into ocean

Examples of Anthozoans: Sea Anemones

Examples of anthozoans: Corals

Radially symmetric

Final simple invertebrates: Flatworms and Roundworms

• Flatworm examples: marine, tapeworms, flukes

• Skeletal structure: acoelomate, flat ribbonlike,

• Body symmetry: bilaterally symmetric meaning they have left and right halves that mirror each other

Flatworms

• Some flatworms reproduce asexually by tearing in two, each half regenerates

• Some reproduce sexually: hermaphrodites that fertilize each other’s eggs.

• Fertilization occurs when sperm and egg form zygote. Zygotes released in clusters in a protective capsule

Examples of Flatworms: Marine Flatworms Locomotion:

ribbonlike, undulating

Examples of Flatworms: Tapeworms

Examples of Roundworms: vinegar eels, parasitic roundworms, pinworms, hookworms, heartworms (in

dogs), and ascaris (intestinal roundworm).  Humans can contract parasitic worms by eating under cooked beef or

pork

Roundworms

• Skeletal structure: pseudocoelom have one way gut

• Fertilization: Internal in the female• Reproduction: Reproduction is

usually sexual. Males are usually smaller than females (often much smaller) and often have a characteristically bent tail

Roundworms cause elephantitis

Roundworms (picture is of a hookworm)

• Body coverings of both flatworms and roundworms: flexible thick outer covering and cuticle (tegument)

Roundworm Locomotion

• Locomotion: wriggling or thrashing, muscles on one side contracting, while the other side expands

If you have not completed all the blanks on the spreadsheet,

find the answers in your textbook for homework, pages

617-636We are now going to watch a

video on Sponges, you will take a quiz as you are watching the video- pass this in at the end of

the period.