1. Sponges and Cnidarians 7 th Grade Biology

2. Sponges Sponges are the simplest form of multi- cellular animals. A sponge is a bottom- dwelling creature which attaches itself to something solid in a place where it can find enough food to grow. The scientific name for sponges is "Porifera," which translates into "pore-bearing."

3. Pores or Ostia A sponge exists by pumping water through its body. A sponge is covered with tiny pores which lead internally to a system of canals and eventually out to one or more larger holes. These canals exist to move water through the sponge's body. The sponge feeds on bacteria found in the filtered water.

4. Reproduction Most sponges are both male and female. During mating, one sponge plays the male role while the other plays the female role, even though both are capable of playing either role. A sponge may play a female role one time and a male role the next time.

5. Reproduction Sperm is released by the "male" sponge and enters the "female" sponge. After internal fertilization, larvae are released. After floating around for a few days, they settle down and start growing.

6. Reproduction After fertilization, a larva develops. A larva is an immature form of an animal that looks very different from the adult.

7. Two Types of Sponges Encrusting sponges are similar to moss because they tend to cover the surfaces of rocks. Free-standing sponges have lots of inner volume compared with their surface area. Sometimes, they grow into strange shapes and gigantic sizes.

9. Tube Sponge

10. Basket Sponge

11. Barrel Sponge

12. Free Standing Sponges Because of their strange and large shapes, free standing sponges are best known to people. The barrel sponge, a tropical sponge, can grow large enough to fit a person inside of it. Tube sponges are well known for very varied coloration.

13. Collar Cells Lining these canals are special collar cells. The collar cells force water through the sponge which brings oxygen and nutrients, while removing carbon dioxide and waste. The collar cells are how sponges feed. The water brings with it bacteria and other organisms which the cells capture and filter out. Larger sponges can filter as much as 1,000 liters of water per day.

15. Tube Sponges

16. Cnidarians Jellyfishes, corals, and sea anemones are types of cnidarians. Invertebrates with stinging cells, and they take food into a central body cavity. Cnidarians use stinging cells to capture food and defend themselves.

18. Body Structure There are two body types- vase-shaped polyp, and the bowl shaped medusa. The vase-shaped body plan is called a polyp. A polyp’s mouth opens at the top and its tentacles spread out from around the mouth. Most polyps are adapted for a life attached to an underwater surface. The sea anemone is an example of a polyp.

20. Body types The bowl-shaped body is called a medusa. The medusa is adapted for a swimming life. The medusa has a mouth that opens downward with trailing tentacles. Some go through both a polyp stage and a medusa stage sometime during their life. A jellyfish is an example of a medusa.

23. Obtaining Food Both polyps and medusas obtain food in the same way. Cnidarians use stinging cells to catch their prey. They have a stinging cell. It contains a threadlike structure, which has many sharp spines. When the stinging cell touches the prey, the threadlike structure shoots out of the cell and into the prey. Some stinging cells even release venom into the prey. When the prey is stunned, the cnidarian uses its tentacles to put the prey into its mouth. The prey passes into a hollow body cavity, where it is digested. Undigested food is spit back out of the mouth.

24. Movement

25. Reproduction