Lesson Activity on Sponges, Cnidarians, Flatworms and Roundworms

1. Lesson Activity on Sponges, Cnidarians, Flatworms and Roundworms 1 Sponges 2 Cnidarians 3 Flatworms 4 Roundworms

2. 1 Sponges – phylum Porifera • Asymmetrical • Invertebrates • No tissues, organs or organ systems • Over 5000 species in a variety of sizes, shapes and colors

3. Sponges Are Pore-Bearers • Porifera = pore bearer • Almost all live in shallow areas of the ocean • Mainly sessile • Sessile - it is permanently attached to a surface for all of its adult life • Get food by filter feeding (filter small particles of food from the water as it passes by or through some part of the organism)

4. Cell Organization in Sponges • Sponges have different types of cells that perform different functions • Sponge embryos do not develop endoderm or mesoderm, so their cells are not organized into tissues • Endodrem and Mesoderm: The germ layers in the process by which the embryo is formed and develops

5. Why Are Sponges Important? • Can be separated into individual types of cells but if left alone (over time) the cells will reorganize back into a sponge • Believed to have evolved from colonial, flagellated protists • Demonstrate the major evolutionary step between unicellular life to a division of labor among groups of organized cells

6. Reproduction in Sponges • Reproduce both sexually and asexually • Asexually through fragmentation or external buds • Buds may break off and float away to become new animals or they may remain attached and form a colony

7. Sexual Reproduction in Sponges • All are hermaphrodites • Hermaphrodites can produce both eggs and sperm AT different times • It increases the likelihood of fertilization in sessile animals • Cannot self-fertilize • Can use either internal or external fertilization

8. Internal Fertilization • Internal fertilization – sperm is brought into the body and fertilization takes place inside the organism • Eggs remain inside the sponge • Collar cells collect sperm and transfer it to the amoebocytes

9. External Fertilization • External fertilization – sperm and eggs are released into the water and fertilization occurs out in the water • Some sponges in temperate zones produce gemmules which are like seeds and lie dormant over the winter and grow into new sponges in the spring

10. 2.Cnidarians (the C is silent)

11. What are Cnidarians? • Marine invertebrates • 9,000 species • Include jellyfish, corals, sea anemones and hydras • Found worldwide, but mainly in warmer oceans

12. Characteristics of Cnidarians • Radial Symmetry • 2 cell layers (the ectoderm and the endoderm) with one body opening • Ectoderm becomes a protective outer layer of cells • The endoderm is internal and is adapted mainly to aid in digestion

13. Cnidarians Body Forms • 2 basic body forms that occur at different stages of their life cycle • Polyp - Tube shaped body and a mouth surrounded by tentacles • Dominant in hydras (spends most of its life in this form) • Corals and sea anemones only have this stage • Medusa- body shaped like an umbrella with tentacles hanging down • Dominant in jellyfish

14. Body Systems • Have simple nervous systems and other tissues • Nerve net – conducts nerve impulses from all parts of the body • There is no brain • Both cell layers have cells that can contract like muscles • Simple digestive system

15. Digestion in Cnidarians • Predators that capture or poison their prey with nematocysts • Nematocyst- capsule that contains a coiled, thread like tube that may contain a toxin • Digestion involves enzymes and cells adapted for this purpose • Digestion takes place in the gastrovascular cavity • Undigested materials are ejected back out the mouth

16. Reproduction in Cnidarians • Sexual reproduction usually occurs in the medusa stage (unless there is none) • Asexual may occur in either the polyp or medusa stage • Technically not alternation of generations like in plants because both stages are diploid

17. Common Reproductive Cycle in Cnidarians • Male medusae release sperm • Female medusae release eggs • Fertilization occurs • The zygotes develops into an embryo and then into a larva • The free swimming larva settles down and develops into a polyp • The polyp reproduces asexually to form male and female medusae

18. Respiration • Oxygen enters cells directly • Because of its body plan, no cell is ever far from water • Oxygen dissolved in the water diffused directly into the cells • Carbon dioxide and other wastes diffuse directly out and into the water

19. Diversity of Cnidarians • Most of the 9000 species belong to one of 3 classes • Hydrozoans • Scyphozoans • Anthozoans

20. Most Hydrozoans Form Colonies • Class Hydrozoa has 2 groups – 1. hydroids (hydra) and 2. Siphonophores (Portuguese Man-O-War) • Most hydroids are branching polyp colonies formed by budding • Siphonophores are floating or swimming colonies of medusae • Each individual in Siphonophores colonies has a different function, but they all function together for the survival of all

21. Scyphozoans are the Jellyfish • Jellyfish • Medusa stage is dominant • Can be found everywhere in the oceans and as deep as1000 meters • The gastrovascular cavity has 4 internal divisions • Range in size from microscopic to more than a meter

22. Anthozoans Build Coral Reefs • Found in tropical, temperate and arctic seas • Cnidarians that exhibit only the polyp form • Have many divisions in their gastrovascular cavity • Corals live in colonies • Sea Anemones live as individual animals

23. Coral Reefs • Corals secrete a calcium carbonate ‘skeleton’ that remains after it dies forming reefs • Reefs grow very slowly • Coral reefs are very sensitive towards the changes in temperature and water level

24. Corals • Most of Coral form mutual relationships with photosynthetic protists which offer the corals oxygen and food and use the carbon dioxide and wastes from the corals • These protists are primarily responsible for the bright colors of coral reefs • If these protists leave the corals, the corals die

25. Origins of Cnidarians and Sponges • Sponges represent the oldest animal phylum dating from 700 million years ago • Thought to have evolved directly from flagellated protists similar to the collar cells of today • Cnidarians first appear about 630 million years ago. • We have little evidence for cnidarians as they are soft bodied and do not fossilize well • Believed that cnidarians evolved from protists

26. 3. Flatworms – phylum Plathelminthes

27. What Is a Flatworm? • Acoelomates - thin solid bodies • Bilateral symmetry • Approx. 14,500 species • Live in salt and freshwater • Planarians (Class Turbellaria) • Tapeworms (Class Cestoda) • Flukes(Class Trematoda)

28. Feeding and Digestion in Planarians • Feed on dead or slow moving organisms • Pharynx – tube-like muscular organ that a planarian extends from its mouth to feed • Enzymes begin digesting the food outside the animal’s body • Food is digested by individual cells • Cells lining the digestive tract obtain food by phagocytosis

29. Nervous Control in Planarians • Some have a nerve net, other have the beginnings of a central nervous system (CNS) • CNS in planarians • 2 eyespots • 2 nerve cords that run the length of the body • Brain-like structure called a ganglion which sends messages to/from the eyespots and along the nerve cords

31. Reproduction in Planarians • Most are hermaphrodites • During sexual reproduction individual flatworms exchange sperm • Fertilization is internal • Zygotes (fertilized eggs) are released into the water to hatch

32. Planarians Can Also Reproduce Asexually • If it is damaged it can regenerate (grow back) new body parts • Missing body parts are replaced through mitosis • If cut in half the head end will grow a new tail and the tail end will grow a new head

33. Feeding and Digestion in Parasitic Flatworms • Parasites are adapted to living inside a host and obtaining nutrients from their host • Have mouthparts with hooks to hold the worm inside its host • Did not evolve complex nervous or muscular systems because they didn’t need them

34. Tapeworms (Class Cestoda) Parasitic • Made up of a head (scolex) and repeating sections (proglottids) • The proglottids are detachable and each contains nerves, muscles, flame cells, as well as male and female reproductive organs • Each proglottid can have up to100,000 eggs • A tapeworm can have as many as 2,000 proglottids

35. Flukes(Class Trematoda) • Flukes are parasitic flatworms that embed themselves in the internal organs of vertebrates • Feeds on cells, blood and other fluid of the host • Blood flukes can cause schistosomiasis

36. 4. Roundworms phylum Nematoda

37. What is a Roundworm? • Varied habitat - live in soil, saltwater and freshwater environments • Most are parasitic • Smaller than tapeworms with a thick outer covering that keeps them from being digested • Tapered at both ends

38. Muscular and Digestive Systems of Roundworms • Have a pseudocoelom 2 body openings (mouth and anus) • Simplest animals with a tubelike digestive system Have pairs of lengthwise muscles • Lack circular muscles • Move in a thrashing motion

39. Diversity of Roundworms • Free-living species have well developed eyespots/sensory organs • Some species are parasitic to plants and fungi • Can form symbiotic relationships with bacteria • 50 species are human parasites (including hookworm and pinworm)

40. Roundworms infect humans by several methods • Can go through the host’s: • Digestive tract (Ascarsis) • Through the skin (Hookworms) • Through undercooked food (pigs infected with Trichinella)

41. Roundworm parasites of other organisms • Nematodes infect pine trees, cereal crops and food plants • Attracted to plant roots • 1200 species cause disease in plants • Soil nematodes invade roots for food