For each phylum it is important to know:
- General features.
- The classification of one member species.
As you go through each phylum, try to relate the structures with the functions.
For example: Platyhelminths - these are flatworms. They are thin, but have a large surface area. This means that they can obtain oxygen and food by diffusion from the external environment. Therefore they need no lungs, no gills, no specialised gut, and no circulatory system.
Also, many are parasitic, most of these being endoparasites. So, the reason they have a thick cuticle is to be protected against being digested by the host's enzymes. The conditions inside the host remain fairly constant so they only need a simple nervous and sensory system.
A table showing the features of some of the most commonly examined Phyla are shown in the next Learn-it.
You will be expected to remember a number of the details from these tables, not necessarily all of them. Check with your teacher how much you need to learn for your exam.
Phylum Chordata has well-known classes. You will need to know examples for each class:
Fish with cartilaginous skeletons
No gill cover
No swim bladder
Fish with bony skeleton
Swim bladder present
Lungs in adult
Dry skin with horny scales
Eggs with leathery shell
Forelimbs modified to form wings
Hair over body surface
Sweat and subaceous glands
Pinna (external ear)