Download Notes for Sponges and Cnidarians:

Notes for Sponges and Cnidarians:
Sponges- Key Points
• Sponges belong to the sub-kingdom Parazoa and phylum Porifera.
• Porifera means tiny pores.
• Most sponges are asymmetrical.
• Sponges have only two germ layers: endoderm and ectroderm. They do
not have a mesoderm.
• Sponges reproduce asexually by a process called budding. Sponges also
form gemmules that withstand harsh conditions and will grow into a new
sponge with conditions are more tolerable.
• Most sponges are hermaphrodites: they produce both eggs and sperm.
• The most common sponges are made of a protein called sponging that
hold tissues together.
• There are about 10 000 species of sponges, most living in salt water.
You will also need to know the parts of the sponge as outlined in the
worksheet – Sponges, A Coloring Worksheet
Cnidarians
-
Cnidarians belong to the sub-phylum Metazoa.
Examples include jellyfish, coral, anemones and hydra.
All Cnidarians are marine animals.
Cnidarians have only two germ layers: endoderm and ectoderm.
They do not have a mesoderm.
- Cnidaria means “stinging cells”
- Cnidarians exist in one of two body forms: Polyps are vase shaped,
sessile animals that attach to a surface with their mouths facing up;
Medusa is free swimming and a bit like an upside-down polyp.
- Cnidarians are not hermaphrodites. Females produce eggs and males
produce sperm. After fertilization, the zygote develops into a blastula
and then into a larva called a planula. The planula eventually attaches
itself to the bottom where it grows into a polyp. The polyp reproduces
asexually by forming medusae. When the medusae produces eggs and
sperm, the cycle is complete.