What are the main characteristics of phylum arthropoda; what are the classes with examples.
I will also love to know what makes the arthropods unique
CHARACTERISTICS OF PHYLUM ARTHROPODA
- The arthropods comprise the largest phylum in the animal kingdom, surpassing in number of species all the other phyla combined.
- They may be said to be the dominant animals on the earth at the present time, if numbers of different species and numbers of individuals are accepted as criteria of dominance.
- To the phylum belong the lobsters, crabs, water fleas,’ barnacles, millipedes, centipedes, scorpions, spiders, mites, and insects.
- The most important characteristic common to all of these is the possession of jointed appendages.
- They are bilaterally symmetrical;
- consist of a linear series of segments, on all or some of which is a pair of appendages;
- are covered with a chitinous exoskeleton which is flexible at intervals to provide movable joints;
- possess a nervous system of the annelid type;
- have a coelom which is small in the adult, the body cavity being a haemocoel filled with blood and are free from cilia.
CLASSES OF ARTHROPODS
A brief classification of the phylum is presented below. Subclasses and smaller divisions are given under each class.
- CLASS I. CRUSTACEA. e.g. Lobster, crab, barnacle, sow bug,
- CLASS II. ONYCHOPHORA. e.g. Peripatus.
- CLASS III. CHILOPODA. e.g. Centipede.
- CLASS IV. DIPLOPODA. e.g. Millipede.
- CLASS V. INSECTA. e.g. Grasshopper, honeybee.
- CLASS VI. ARACHNOIDEA. e.g. Spider, scorpion, mite.
- CLASS VII. PAUROPODA. e.g. Pauropus.
- CLASS VIII. SYMPHYLA. e.g. Scutigerella
- The arthropods are a very unique group of animals because of their cosmopolitan nature/high reproductive rate
- They are triploblastic in nature
- They are coelomates, although the coelom is enormously reduced.
- Metameric segmentation is present
- Bilaterally semetrical
- Presence of three body divisions: head, thorax and abdomen
- Possession of exoskeleton of chitin and sometimes calcareous matter
- May be rigid, stiff or flexible
- Each segments typically bears a pairs of jointed appendages
- Jointed walking legs are used for locomotion, feeding or sensory purposes.
- Their main body cavity is haemocoel
- Sexual reproduction and internal fertilization are present
- Parthenogenesis is present in some members
- They are widely distributed
- Wings may be present in some members
- Largest group of animals