Porifera and cnidaria

Phylum Porifera (sponges)

Appearance Symmetry: Asymmetric (usually) 2 layers of independente cells (not real tissue***): a) pinacocytes: cell plates on the exterior that contract b) choanocytes: flagellated cells on the inside, also called collar cells Spicules: thin tiny fibres made of glasslike silica or CaCO3 that forms the delicate skeleton on the sponges. Some have a protein called spongin. (softer)

Structure pinacocytes Choanocyte (outside) (inside) osculum amibocytes Gastric cavity pore pores spicule flagellum

Circulation Water and nutrients entre through pores Water and wastes exit through the osculum (giant hole) oscule Gastric cavity pore

Movement Sessile: adults always attached to a surface Ciliated larva swim to find a new place to settle

***Digestion INTRACELLULAR*** choanocyte amibocytes Feeding Filtration Choanocytes beat their flagella to create a flow of water that brings suspended food particles to the interieur of the sponge The particles are transported to the amoebocytes, the site of digestion The amoebocytes wander and deliver the digested nutrients to the other parts of the sponge ***Digestion INTRACELLULAR***

Respiration The Nervous System Oxygen is obtained and carbon dioxide released through diffusion between the cells and water Each cell is in contact with water The Nervous System none

Defense Sponges produce numerous chemical compounds (toxic) that gives them a bad tast and can stop other organisms from growing on or near them (competition)

Reproduction Asexual: through budding Sexual: hermaphrodites (each individual produces male and female gametes but they never self-fertilize) The sperm are released into the water where they fertilize the eggs in another sponge The zygote develops into a cilliated larva that swims away (or carried by water currents) before it settles down and grows into a new sponge Regeneratoin: seperated sponge cells can regroup together to form a new sponge

Ecological and Economical Importance Filtre water Important source of noutrition for snails, sea stars and fish Homes for little invertebrates Used by artists Chemicals used for anitbiotics

Phylum Cnidaria (jellies, sea anemones & corals)

Appearance Radial Symmetry 2 layers of cell tissues: 2 formes: a) ectoderme: the outer layers of cells (epidermis) b) endoderme: lines the gastrovascular cavity (gastrodermis) Mesoglea lies between the 2 layers 2 formes: a) polyp: sessile, tubular, tentacles surround opening b) medusa: free-swimming, bell shaped with tentacles

Structure Gastric cavity mouth tentacle Gastric cavity mouth tentacle a) polyp b) medusa

Circulation Water, nutrients and waste all enter or leave through the mouth ** (not very sanitary) Cnidarians have a ‘mouth/anus’ This is why you don’t stick your finger in the middle of a sea anemone.

Movement Epidermis cells contract which allows them to expand or shrink Do not possess true muscle cells Polyp: contract and dialate the body and tentacles (body waves) Medusa: contracts the ‘bell’ forcing water out of the shell – moves via jet propulsion

Feeding Nematocysts: stinging organelles located on the cnidarians surface, a tiny capsule containing a filament covered with tiny spines that and injects poison that can cause paralysis Nematocysts found on tentacles, capture prey and bring in towards the mouth Food is digested by enzymes secreated in the gastrovascular cavity ***digestion EXTRACELLULAR***

The Nematocysts Cnidocil Filament Nematocyst Barb Cnidocyte URL: http://en.wikipedia.org/wiki/Nematocyst; Searched 09/12/06

Respiration The Nervous System Oxygen is acquired and carbon dioxide release through diffusion between the cells and water Every cell touches water The Nervous System Very primitive nerve net

Defense Uses nematocyst as a means of defense Corals have an exoskeleton made of calcium carbonate

Reproduction Typically, cnidarians have a sexual phase (medusa) and an asexual phase (polyp) Asexual: through budding and regeneration Sexual: medusa males or females release gametes into the water ***(external fertilization)***

Ecological and Economical Importance Food and shelter for other organisms Coral reefs protect the coast from the effects of waves Coral reefs have economic value as tourist attractions Very vulnerable to pollutants

Photos