Question

1. How do sponges reproduce?

2. How do sponges feed?

3. What is the basic body plan of the cnidarians?

4. What are the two stages of the Cnidarian life cycle?

5. Which stage of Cnidarian is sexual and which is asexual?

Answer 1

1. Sponges belong to Phylum Porifera. They reproduce either sexually or asexually. In a sexual reproduction, male releases sperm into the water and they enter female sponge. They fuse and fertilization occurs. Larvae are released in water, they get to bottom and develop as new sponge. In asexual reproduction sponges reproduce by budding. Small buds develop and detach and starts to form new sponges.

2. Feeding in sponges occur as filter feeding. These are attached to sub-stratum, they cant move and collect food. Sponges are made of tiny holes all over their body. Water passes through them, it brings along gases, food and everything thts needed. And throws waste material out of the body. The pores that bring water inside are incurrent pores and that take out are excurrent pores. These all are lined with collar cells, whose whip like movement brings water in and out of body, along with small food particles for the sponge.

3. Cnidarians belong to Phylum Cnidaria, found in freshwater as well as marine environments. Cnidarians are made up of a more complex plan than sponges. Their distinguishing feature is presence of cnidocytes which help them in capturing prey. Cnidarians are made of two cell layers and a jelly like layer in between those two. They have an oral and aboral end. And are radially symmetrical.

4. Two stages of cnidarian life cycle includes wo different types of body forms : polyps and medusae. Polyp is attached stage and free swimming stage is medusae. For eg, larva of a jelly fish becomes polyp in earlier life cycle and later becomes medusae and float. Medusae is reproductive stage.

5. Polyp stage is asexual stage and medusae stage is sexual stage.