5.2 The simplest invertebrates

Porifera

Porifera or sponges are aquatic animals and most of them are marine. They are attached to sand or rocks.

Cnidaria

Are aquatic animals and most of them are marine. For example, jellyfish,coral, sea anemones and hydra are cnidarian

Worms

The term worm includes animals with a soft, elongated body, without skeleton. The most important ones are platheyelminthes, nematodes and annelids.

ACTIVITIES:

1. Which of the following statements are true (T) and which are false (F)? 

1.  In oviparous animals, the egg develops inside the mother’s body. 
2.  Porifera live freely, floating on sea water. 
3.  Corals are porifera with the shape of a polyp and a skeleton. 
4.  Budding is a kind of sexual reproduction. 
5.  Cnidaria reproduce sexually and develop from eggs.
6.  In viviparous animals, the embryo develops inside the mother’s body. 
7.  Medusae are porifera without pores. 
8.  Swimming medusa have an umbrella shape. 
9.  Asexual reproduction happens through internal fertilization. 
10.  Porifera can reproduce sexually or asexually. 

2. Classify the next picture in platheyelmintes, nematodes or annelids:

  1

2

   3