Cnidaria

cnidarians:

Overview L33

Hydra w.m. L35 Figs 5.6 & 5.7; T105 Fig 6.4(a); T114 Fig 6.13; R53 – tentacle, hypostome, mouth, base (=foot or pedal disc)

Hydra l.s & c.s. L 34 Fig 5.6; R53-54 – epidermis, mesoglea, gastrodermis, coelenteron (=gastrovascular cavity)

Hydra adult with bud L34 Fig 5.7; R53

Hydra male L36 Fig 5.9; T114 Fig 5.; R54 – testes

Hydra female L36 Fig 5.10; R54 – ovaries

nematocysts T103 Fig 6.1; R54

Obelia polyps L36 Fig 5.14; T115 Fig 6.13(a); R55 – feeding polyp, reproductive polyp

Obelia medusae L37 Figs 5.15, 5.12 and 5.13; R55 – gonad, mouth, manubrium, tentacles

Aurelia planula L39 Fig 5.22(a); T109 Fig 6.9

Aurelia strobila L39 Fig 5.22(c); T109 Fig 6.9; R55

Live Hydra:

observe behavior in petri dish under dissection scope

when adding brine shrimp, keep in mind that Hydra are freshwater organisms

Please answer the following questions in your lab notebook

What is the selective advantage of radial symmetry and a nerve net for sessile/slow-moving animals like jellies?

Cnidarans are diploblastic. What do we mean by diploblastic?

What is alternation of generations in cnidarians? What are its advantages?

Match the cnidarian class with the organism or characteristic:

_____ Aurelia	a. Class Hydrozoa
_____ Obelia	b. Class Scyphozoa
_____ sponge	c. Class Anthozoa
_____ jelly	d. None of the above
_____ both polyp and medusa forms
_____ polyp form only
_____ medusa form predominates

Which class(s) of cnidarians may be either colonial or solitary? Which class(s) is (are) entirely marine?

Which class of cnidarians is probably most closely related to the ancestor of the phylum?

What are the types of coral reefs?