Hamilton - Honors Biology Chapter 27 Cnidarians

cnidarians

animals with radial symmetry, soft bodies, and stinging tentacles

cnidocytes

stinging cells used for defense and capturing prey

nematocysts

poison-filled capsules inside cnidocytes that shoot out to sting prey

polyp

sessile stage in cnidarians (e.g., sea anemones)

medusa

motile, ball-shaped stage (e.g., jellyfish)

gastrovascular cavity

central cavity for digestion and circulation of nutrients

gastroderm

inner tissue layer where digestion happens

mesoglea

jelly-like layer between the gastroderm and epidermis

epidermis

outer tissue layer of the body wall

extracellular digestion

food is broken down with enzymes outside of cells

nerve net

simple nervous system made of connected nerve cells

statocysts

balance-sensing organs that detect gravty

ocelli

simple eyespots that detect light

hydrostatic skeleton

water pressure within the body used for movement

asexual reproduction (cndarians)

polyp buds to form new individuals or a medusa

sexual reproduction (cnidarians)

external fertilization in water; gametes released by male/female medusas