These animals are bilaterally symmetrical, triploblastic and have a coelom. In addition, they show a new feature of body design, namely a notochord, at least at some stages during their lives. The notochord is a long rod-like support structure (chord=string) that runs along the back of the animal separating the nervous tissue from the gut. …
In Greek, echinos means hedgehog (spiny mammal), and derma means skin. Thus, these are spiny skinned organisms. These are exclusively free-living marine animals. They are triploblastic and have a coelomic cavity.They also have a peculiar water-driven tube system that they use for moving around. They have hard calcium carbonate structures thatthey use as a skeleton. …
In the animals of this group, there is bilateral symmetry. The coelomic cavity is reduced.There is little segmentation. They have an open circulatory system and kidney-like organs for excretion. There is a foot that is used for moving around. Examples are snails and mussels
This is probably the largest group of animals. These animals are bilaterally symmetrical and segmented. There is an open circulatorysystem, and so the blood does not flow in well defined blood vessels. The coelomic cavity is blood-filled. They have jointed legs (the word‘arthropod’ means ‘jointed legs’). Some familiar examples are prawns, butterflies, houseflies, spiders, scorpions …
Annelid animals are also bilaterally symmetrical and triploblastic, but in addition they have a true body cavity. This allows true organs to be packaged in the body structure. There is, thus, extensive organ differentiation.This differentiation occurs in a segmental fashion, with the segments lined up one after the other from head to tail. These animals …
The nematode body is also bilaterally symmetrical and triploblastic. However, the body is cylindrical rather than flattened. There are tissues, but no real organs, although a sort of body cavity or a pseudocoelom, is present. These are very familiar as parasitic worms causing diseases, suchas the worms causing elephantiasis (filarial worms) or the worms in …
The body of animals in this group is far more complexly designed than in the two other groups we have considered so far. The body is bilaterally symmetrical, meaning that the left and the right halves of the body have the same design. There are three layers of cells from which differentiated tissues can be …
These are animals living in water. They show more body design differentiation. There is a cavity in the body. The body is made of two layers of cells: one makes up cells on the outside of the body, and the other makes the inner lining of the body. Some of these species live in colonies …
The word Porifera means organisms with holes. These are non-motile animals attached to some solid support. There are holes or ‘pores’, all over the body. These lead to a canal system that helps in circulating water throughout the body to bring in food and oxygen. These animals are covered with a hard outside layer or …
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