Chapter 26-3 Cnidarians Notes
 _______________ invertebrates
 9,000 species
 Include__________________, corals, sea anemones and
________________.
 Found ______________________, but mainly in warmer oceans
Characteristics of Cnidarians
 _________________ Symmetry
 ___________ layers (the ectoderm and the endoderm) with one body
opening
 ____________________ becomes a protective outer layer of cells
 The ______________________ is internal and is adapted mainly to aid in
digestion
Cnidarians Body Forms
 ________________ body forms that occur at _______________
________of their life cycle
 _______________- Tube shaped body and a mouth surrounded by
_________________
 ________________________ in hydras (spends most of its life in this
form)
 Corals and sea anemones only have this stage
 ______________________- body shaped like an umbrella with tentacles
hanging down
 Dominant in jellyfish
Body Systems
 Have simple _________________ _________________ and other tissues
 Nerve net – conducts ______________ _____________ from all parts of
the body
 There is no ______________
 Both cell layers have cells that can contract like muscles
 ________________ digestive system
Digestion in Cnidarians
 __________________ that capture or poison their ___________ with
nematocysts
 __________________- capsule that contains a coiled, thread like tube that
may contain a toxin
 Digestion involves _____________ and cells adapted for this purpose
 ____________________ takes place in the gastrovascular cavity
 Undigested materials are__________________ back out the mouth
Reproduction in Cnidarians
 __________________ reproduction usually occurs in the ____________
___________ (unless there is none)
 Asexual may occur in ________________ the polyp or medusa stage
 Technically no _________________ of generations like in plants because
both stages are ___________________
Common Reproductive Cycle in Cnidarians
 __________ medusae release sperm
 ____________ medusae release eggs
 Fertilization occurs
 The ________________ develops into an _____________ and then into a
________________
 The ___________ _____________ larva settles down and develops into a
polyp
 The ______________ reproduces ______________to form male and female
_________________
Respiration
 Oxygen ______________ cells directly
 Because of its body plan, no cell is ever far from water
 Oxygen dissolved in the water _______________ directly into the cells
 ____________ ___________ and other _____________ diffuse directly out
and into the water
Diversity of Cnidarians
 Most of the ____________ species belong to one of 3 classes
 Hydrozoans
 _____________________
 Anthozoans
Most Hydrozoans Form Colonies
 Class _____________ has 2 groups – 1. _____________ (hydra) and 2.
Siphonophores (Portuguese Man-O-War)
 Most hydroids are ______________ polyp colonies formed by
_____________
 Siphonophores are ________________or ____________________colonies
of medusae
 Each individual in__________________________ colonies has a different
function, but they all function together for the survival of all
Scyphozoans are the Jellyfish
 Jellyfish
 Medusa stage is ___________________
 Can be found _____________________ in the oceans and as deep as
________ meters
 The ______________________ cavity has _______ internal divisions
 Range in size from ___________________________ to more than a
____________
Anthozoans Build Coral Reefs
 Found in ____________________, temperate and _______________ seas
 ________________________ that exhibit only the _______________ form
 Have _____________ divisions in their ________________________ cavity
 Corals live in ________________
 _______ ______________ live as individual ______________
Coral Reefs
 Corals secrete a ________________ ______________‘skeleton’ that
remains after it ___________ forming reefs
 Reefs grow _________ ___________
 Coral reefs are very ______________ towards the changes in temperature
and water level
Corals
 Most of Coral _____________ mutual ________________ with
photosynthetic ______________ which offer the corals
________________and _______________ and use the carbon dioxide and
wastes from the corals
 These protists are ________________ responsible for the bright
___________ of coral _____________
 If these protists leave the corals, the _____________ die
Origins of Cnidarians and Sponges
 Sponges represent the ______________ animal phylum dating from ______
million years ago
 Thought to have ______________ directly from ________________
_______________similar to the collar cells of today
 _________________ first appear about 630 ___________________years
ago.
 We have ____________ evidence for cnidarians as they are _________
bodied and do not _______________ well
 Believed that cnidarians evolved from _________________