Tree of Life The tree of life according to Ernst Haeckel, 1891

How does Porifera fit in? Porifera Other animals unknown common ancestor eukaryote multicellular heterotrophic Blastula stage cellular level of organization choanocytes 3 body types

How does Cnidaria fit in? Porifera Other animals unknown common ancestor eukaryote multicellular heterotrophic Blastula stage cellular level of organization choanocytes 3 body types Cnidaria

Phylum Cnidaria

Level of Organization Tissue cells are organized into tissues and work together to accomplish physiological functions

Tissue Layers Diploblastic = 2 germ layers endoderm  gastrodermis ectoderm  epidermis mesoglea gelatinous matrix between the 2 layers epidermis mesoglea gastrodermis gastrovascular cavity

General Body Plan sac-like body (only 1 opening) Food and waste go in/out the same opening  no anus! water within GVC acts as a hydrostatic skeleton Gastrovascular cavity mouth oral surface aboral surface epidermis gastrodermis mesoglea

General Body Forms 2 different body forms are usually present in the life cycle: polyp & medusa ** one animal may pass through both forms during its life **

General Life Cycle

Radial Symmetry - body parts are arranged concentrically around an oral-aboral axis oral aboral

Nematocysts specialized stinging organelles found within cnidocytes (cells) cnidocytes are located in epidermis A cnidocyte with a nematocyst within it

Nematocysts nematocysts are like “mini-harpoons” cnidocil senses movement & acts like a “trigger” can inject poison, coil around prey, or be adhesive functions: - prey capture; defense UndischargedDischarged cnidocil cnidocyte nematocyst

Colony formation colony formation is common (colonial animals) occurs via asexual reproduction (e.g. fission) individual polyps are connected to one another by the GVC individual polyp

Physiology Feeding –nematocysts within cnidocytes –tentacles Digestion –extracellular (in GVC) –intracellular (by gastrodermal cells) –incomplete system (no anus) Gas exchange & Excretion –these systems are absent

Physiology Nervous System –nerve net (no central nervous system= no brain) –sense organs –statocysts (equilibrium organs) –ocelli (photosensitive organs) Skeletal System –water in GVC acts as a hydrostatic skeleton

Physiology Reproduction Asexual –budding –longitudinal fission –pedal laceration (e.g. sea anemones)

Physiology Reproduction Sexual –usually dioecious (separate sexes  e.g. humans) –monoecious (both male + female gonads in 1 individual) –results in Planula larva

Phylum Cnidaria Class Hydrozoa Class Scyphozoa Class Anthozoa

Class Hydrozoa medusa & polyp body forms Fire coral

Class Hydrozoa medusa & polyp body forms most are colonial  colonies are formed of individual zooids a single zooid

Class Hydrozoa many of these colonies show polymorphism  this is where there are several different types of polyps/zooid and each type is specialized for a different function e.g. gastrozooids = feeding polyps e.g. dactylzooids = defense polyps  all the zooids within a colony are genetically identical  these different zooids work together in the colony

Class Hydrozoa gastrozooid gonozooid - a sessile colony showing polymorphism entire colony

Class Hydrozoa gastrozooid dactylzooid - a Portugese Man-o-war is a floating hydrozoan colony showing polymorphism entire colony pneumatophore

Class Hydrozoa- life cycle sexual reproduction asexual reproduction

Class Hydrozoa asexual reproduction Hydra is an example of a solitary, freshwater hydrozoan sexual reproduction gonads bud

Class Scyphozoa “true” jellyfish medusa & polyp body forms thick mesoglea

Class Scyphozoa- life cycle egg sperm larva scyphistoma strobila ephyraAdult medusa

Class Anthozoa polyp body form ONLY all marine

Class Anthozoa some are colonial  colonies are formed of individual zooids some are solitary

Class Anthozoa Sea anemones

Class Anthozoa Soft Corals Sea pen Sea pansy

Class Anthozoa Stony Corals

Class Anthozoa- life cycle egg sperm larva Sexual reproduction

Class Anthozoa- life cycle asexual reproduction fission pedal laceration fission

How does Cnidaria fit in? Porifera unknown common ancestor eukaryote multicellular heterotrophic Blastula stage cellular level of organization choanocytes 3 body types Cnidaria tissue level of organization diploblastic 3 classes:Hydrozoa, Scyphozoa, Anthozoa 2 body types: polyp, medusa

Symbiosis Mutualism – Corals contain endosymbiotic algae called zooxanthellae the zooxanthellae photosynthesize and provide food for the coral while the coral provides a safe home zooxanthellae

Symbiosis Mutualism – Many species of anemone fish (clown fish) live within anemones and are immune to their stinging nematocysts the fish may lure in other fish for the anemone to capture and eat, while the anemone provides protection and a home

Coral Reefs What are they? stony corals lay down a calcium carbonate skeleton these skeletons are laid down on top of one another and over thousands of years, form large calcium carbonate structures these large structures, along with the plants and animals that inhabit them, are known as coral reefs Where do they form? in optimal conditions for their zooxanthellae  shallow, warm, nutrient-poor waters

Importance of Coral Reefs one of the most productive ecosystems although the water is nutrient-poor “hot spots” for biodiversity

Threats to Coral Reefs over-enrichment of nutrients from sewage and agricultural run-off overfishing of herbivorous fish global warming (leads to coral bleaching where corals expel their zooxanthellae)