Poriferans

Phylum Porifera Phylum Porifera – “pore-bearers” Sponges Tiny openings, pores, all over the body Cambrian Period – 540 m.y.a.; oldest and simplest animals Adults are sessile – attached to a single spot Heterotrophic, multicellular, no cell walls, few specialized cells No mouth or gut, no tissues, no organ systems Evolutionary dead end

Form and Function of Sponges Movement of water through sponge provides for feeding, respiration, circulation, and excretion Body plan –Asymmetrical “water pump” – body forms wall around central cavity, where water is continuously pumped –Choanocytes (aka Collar Cells) – create currents with flagella –Most have an osculum – large exit hole at top of sponge

Form and Function of Sponges (continued) Simple skeletons –Spicules – sponge “bones” made of calcium carbonate (CaCO 3 ) or silica (SiO 2 ) – these are in hard sponges –Archaeocytes – make spicules –Softer sponges have skeletons made of spongin – these are used as natural bath sponges

Sponge Anatomy Water flow Choanocyte Spicule Pore cell Pore Epidermal cell Archaeocyte Osculum Central cavity Pores

Feeding in Sponges Filter feeders – sift microscopic food particles from water Digestion is intracellular Food particles engulfed by choanocytes lining body cavity by endocytosis Food may be digested or passed on to archaeocytes Archaeocytes digest food and wander around to other cells delivering nutrients

Respiration, Circulation, and Excretion in Sponges Rely on movement of water through bodies to provide simple mechanism for respiration, circulation, and excretion Diffusion is important for sponges

Response in Sponges No nervous system, but can produce toxins

Reproduction in Sponges Sexually or asexually Sexual – most sponges have eggs and sperm in one sponge –Eggs held in body wall –Sperm released into water –Eggs and sperm produced at different times within sponge –Sperm absorbed by archaeocytes and carried to eggs

Reproduction in Sponges (continued) Asexual –Gemmules – collections of archaeocytes surrounded by spicules that can survive freezing and heat –Conditions favorable, gemmule grows into new sponge –Budding – part of sponge breaks off, settles, grows into new sponge

Ecology of Sponges Form sponge “habitats” for worms, shrimps, snails, and starfish Symbionts with bacteria, blue-green bacteria, or plant-like protists Natural bath sponges Provide toxins that fight bacteria, viruses, leukemia, and herpes

Examples of Sponges

Cnidarians

Phylum Cnidaria – cnidocytes – stinging cells Jellyfish, sea anemone, coral Soft-bodied, carnivorous animals with stinging tentacles arranged around their mouth Simplest animals to have body symmetry and specialized tissues Within each cnidocyte is a nematocyst (poison- filled stinging structure used for food capture and protection)

Form and Function of Cnidarians Only a few cells thick and simple body systems Body plan Radial symmetry with 2 possible body forms: –Polyp – sessile and flower-like –Medusa – motile and bell-shaped Three layers of cells –Gastroderm – inner lining of gastrovascular cavity - digestion –Mesoglea – middle layer – can be a thin or thick layer –Epidermis – outer layer

Body Forms of Cnidarians Epidermis Mesoglea Gastroderm Mesoglea Gastrovascular cavity Mouth/anus Tentacles Mouth/anus Gastrovascular cavity Polyp Medusa

Feeding in Cnidarians Nematocysts – located on tentacles; tiny spring-loaded harpoons Food pushed into mouth by tentacles Food digested and absorbed by diffusion

Respiration, Circulation, and Excretion in Cnidarians Respiration and wastes eliminated by diffusion through body wall No organized internal transport network or excretory system

Response in Cnidarians No organized central nervous system (CNS) Simple nerve nets – loosely organized network of nerve cells allowing detection of stimuli Statocysts – sensory cells for balance Ocelli – eyespots detect light

Movement in Cnidarians Hydrostatic skeleton – layer of longitudinal muscles, together with the water in the gastrovascular cavity, allow movement Epidermal cells act as muscles

Reproduction in Cnidarians Sexual and asexual Asexual – polyps reproduce by budding Sexual – external fertilization in the water Polyp MedusaZygote Larvae Asexual Reproduction Sexual Reproduction

Groups of Cnidarians Includes hydras and their relatives, jellyfishes, sea anemones, and corals

Class Hydrozoa – Hydras and Other Relatives Long polyp stage Short medusa stage Hydra – fresh-water – no medusa Portuguese Man-O-War – floating colony contains specialized polyps; one polyp is enlarged and full of air to keep the animal afloat, the other polyps are for feeding and reproduction

Examples of Hydrozoans Portuguese Man-O-War Colonial Hydrozoan Green Hydra

Class Scyphozoa – Jellyfish Same life-cycle as hydrozoans Medusa – long-lived Lion’s Mane Reproduce sexually Some very toxic and even deadly

Examples of Scyphozoans

Class Anthozoa – Sea Anemones and Corals Only polyp life stage Colonial Sexual and asexual reproduction Corals – reef builders and symbionts with photosynthetic algae Skeleton of calcium carbonate (CaCO 3 ) Colony grows slowly and lives for thousands of years

Examples of Anthozoans

Ecology of Corals Great Barrier Reef – 2,000km long, 80 km wide Sea anemone and clown fish – mutualism Coral – habitat for many animals –Protect land from wave action –Building blocks –Jewelry –Anti-cancer drugs –In danger due to human activity