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Section 26-2 • No Sinking or Swimming • You likely have a green, yellow, blue, or pink sponge in your kitchen sink at home. This is a synthetic (human-made) sponge, not a natural sponge. But you may have used a natural sponge in the bath or when washing the car. These sponges are usually brownish and are irregularly shaped. • 1. Natural sponges live in the water, and are attached to a single spot. Although they cannot move from place to place like many other animals, sponges are still animals. Because they are animals, what characteristics must sponges have? • 2. What characteristics does a kitchen sponge have? Which of these characteristics do you think a natural sponge has? All animals are heterotrophic multicellular eukaryotic organisms whose cells lack cell walls. A kitchen sponge is full of holes, which make a network of spaces that hold water. Students may say that natural sponges also are full of holes. Students may not be aware that a natural sponge is hollow, while a kitchen sponge is not.
Sponges & Cnidarians • 26.2.1 Explain what a sponge is • 26.2.2 Describe how sponges carry out essential functions • 26.2.3 Describe the ecology of sponges • 26.3.1 Explain what a cnidarian is • 26.3.2 Describe the 2 body plans that exist in the cnidarian life cycle • 26.3.3 Describe how cnidarians carry out essential functions • 26.3.4 Identify the 3 groups of cnidarians • 26.3.5 Describe the ecology of cnidarians
Apart of the phlyum Porifera (pore-bearers) Classified as animals b/c they are multicellular, heterotrophic, lack cell walls, & a few specialized cells Obtain food & O2, eliminate waste, & reproduce They lack mouths, stomachs, brains, & muscles Key survival: H2O which provides a simple mechanism for feeding, respiration, circulation &excretion. What is a sponge?
Forms of sponges • They lack tissues & organ and are asymmetrical; no front or back ends or sides • Forms a wall around lg. cavities, have simple skeletons • Hard sponges skeleton are made of spiny spicules (spike-shaped structure made of chalklike Ca+ Carbonate of glasslike silica). Spicules are made of archaeocytes (specialized cells that move around the walls of a sponge) http://www.phschool.com/atschool/phbio/active_art/structure_of_a_sponge/index.html
Functions in sponges • Feeding • Filter feeders that sift microscopic food particles from the H2O • Digestion is intracellular • Respiration, Circulation, & Excretion • As water moves thru the body cavity, O2 dissolved in the H2O diffuses into the surrounding cells; Simultaneously CO2 & other waste, diffuse into the water & are carried away. H2O movement carries out body functions http://www.phschool.com/atschool/phbio/active_art/structure_of_a_sponge/index.html
Functions in sponges cont’d • Reproduction • reproduce both asexually and sexually • Both male and female (meiosis) • Internal fertilization: eggs are fertilized inside the sponge’s body. • The sperm cells enter through the pores, where the sperm fertilizes the egg. The egg will eventually turn into larvae (immature stage of an organism) that will attach itself to the ocean floor and grow into an adult sponge. • The asexual form of reproduction is by budding. Budding is where a piece breaks off of the old sponge and forms a new sponge which is an exact copy of the parent and gemmules are produced. • See Fig 26-9 http://www.phschool.com/atschool/phbio/active_art/structure_of_a_sponge/index.html
Ecology of sponges • Very important to aquatic ecology b/c they provide habitats for marine animals • Form partnerships w/ photosynthetic bacteria, algae, & plantlike protist (supplies food & O2) • 1° productivity of coral reefs • Attached to the sea floor; low levels of filtered sunlight • The spicules help sponges carry out photosynthesis which allows for them to survive in a wider range of habitats
Checking your understanding • What features do sponges share with all other animals? • How do sponges use water to carry out essential functions? They are heterotrophic, have no cell walls, & contain specialized cells. The movement of H2O thru the sponge carries needed materials, such as food & O2, and carries wastes away. H2O carries sperm to eggs. http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbp&wcsuffix=8262
Bell Ringer • What’s in a Name? • Perhaps you have heard about creatures called jellyfishes on television,in school, or at an aquarium; maybe you live near the ocean and have actually seen jellyfishes. • 1. Do jellyfishes look like what their name describes? Make a simple drawing of what you think a jellyfish looks like. 2. Some scientists suggest that jellyfishes should be called “jellies.” What might this new name tell you about jellyfishes? Students should draw sac-like animals with tentacles This new name suggests that these animals have jelly-like bodies, but they are not fish.
What are Cnidarians? • Soft-bodied, carnivorous animals that have stinging (cnidocytes) tentacles arranged in circles around their mouths; used for defense. Inside the cnidocyte is a nematocyst (poision-filled structure which contains a tightly coiled dart) . Used to paralyze or kill prey
2 basic body forms • Medusa • Free-swimming or floating. They usually have umbrella-shaped bodies and tetramerous (four-part) symmetry. The mouth is usually on the concave side, and the tentacles originate on the rim of the umbrella. EX. adult jellyfish • Polyp • usually sessile. They have tubular bodies; one end is attached to the substrate, and a mouth (usually surrounded by tentacles) is found at the other end. Polyps may occur alone or in groups of individuals; in the latter case, different individuals sometimes specialize for different functions, such as reproduction, feeding or defense. • See Fig 26-12
Function of Cnidarians • radial or bi-radial symmetric • bodies have two or sometimes three layers. • A gastrovascular cavity (coelenteron) has a single exterior opening that serves as both mouth and anus. Often tentacles surround the opening. • Some cells are organized into two simple nerve nets, one epidermal and the other gastrodermal, that help coordinate muscular and sensory functions • Mucus-secreting cells cover the animal with a protective slime. A single opening serves as the entrance to the gastrovascular cavity, within which prey is digested.
Functions cont’d • Lacking an anus, any undigested material is ejected through the mouth. With most of the living cells in direct contact with the water, specialized excretory, circulatory, and respiratory are not needed. • Have nerve cells to gather their info from their environment; statocysts: help determine the direction of gravity; ocelli: eyespots made of cells that detect light • Some types move such as sea anemones by using a hydrostatic skeleton: enable movement in cnidarians made up of layers of circular & longitudinal muscles • Reproduction • Sexually –have separate male and female medusae that produce gametes that join through external fertilization to produce polyps. Asexually – budding (polyp form)
Three types of cnidarians • Anthozoa: true corals, anemones, and sea pens • Hydrozoa: the most diverse group with siphonophores, hydroids (hydra), fire corals, and many medusae • Scyphozoa: the true jellyfish.
Checking your understanding • Describe 3 characteristics that all cnidarians share. • How do the 2 body plans of cnidarians differ? • Describe the 3 groups of cnidarians & give an example from each. Soft-bodied, carnivorous, & stinging tentacles arranged in circles around the mouth A polyp has a cylindrical body w/ armlike tentacles; the mouth points upwards. A medusa has a bell-shaped body w/ the mouth pointing downward. Hydrozoans (hydras) spend most of their lives as polyps. Scyphozoans (jellyfishes) live their lives as medusas. Anthrozoans (corals) have only one polyp stage in their life cycle.
