Mollusca (Mollusks) Definition Molluscs (also know as mollusks) are soft-bodied, bilaterally symmetrical, segmented, coelomate animals; usually shelled having a mantle, ventral foot, anterior head, and a dorsal visceral mass. Phylum Mollusca (Mollusks) Characteristics They are essentially aquatic mostly marine, few … Read more
Protozoa Definition Protozoa may be defined as “microscopic acellular animalcules existing singly or in colonies, without tissue and organs, having one or more nuclei”. Some of the characteristics are: There are about 50,000 known species of Phylum Protozoa. Protozoans exhibit … Read more
Nematoda Definition Nematodes (Gr., nema thread+ eidos, form) are commonly referred to as non-segmented roundworm, threadworm or pinworm, as distinct from flatworm and higher segmented annelids. Image Source: Wikipedia Phylum Nematoda Characteristics They are widely distributed, aquatic or terrestrial, parasitic … Read more
Ctenophora Definition Ctenophores are free-swimming, transparent, jelly-like, soft-bodied, marine animals having biradial symmetry, comb-like ciliary plates for locomotion, the lasso cells but nematocytes are wanting. They are also known as sea walnuts or comb jellies. Phylum Ctenophora Characteristics They are … Read more
What are Aschelminthes? Aschelminthes are pseudocoelomate, bilaterally symmetrical, triploblastic, unsegmented, vermiform, organ- system grade of construction with complete digestive tubes. Phylum Aschelminthes characteristics They are mostly aquatic, free-living or parasitic. They are bilaterally symmetrical, unsegmented worms. The body is slender, … Read more
Porifera Definition The Porifera may be defined as an asymmetrical or radially symmetrical multicellular organism with a cellular grade of an organization without well- definite tissues and organs; exclusively aquatic; mostly marine, sedentary, solitary or conical animals with body perforated … Read more
Arthropoda (Arthropods) Definition Arthropods are bilaterally symmetrical, triploblastic, metamerically segmented animals with coelom which is reduced and modified. Their body is covered externally in a chitinous exoskeleton which molts periodically and their appendages are joined. Phylum Arthropoda Characteristics They are … Read more
Platyhelminthes (flatworms) definition Platyhelminthes are triploblastic, bilaterally symmetrical, dorsoventrally flattened, acoelomate flatworms with organ grade of construction without a definite anus, circulatory, skeletal or respiratory system but with Protonephridial excretory system and mesenchyme filling the space between the various organ … Read more
Echinodermata (Echinoderms) Definition Echinoderms are enterocoelous coelomates with pentamerous radial symmetry, without distinct head or brain having a calcareous endoskeleton of separate plates or pieces and a peculiar water vascular system of coelomic origin with podia or tube-feet projecting out … Read more
Coelenterata (Cnidaria) Definition The Coelenterata may be defined as diploblastic metazoa with tissue grade of construction having nematocyst and a single gastrovascular cavity or the coelenteron. Phylum Coelenterata (Cnidaria) Characteristics They are aquatic, mostly marine except few freshwater forms like … Read more
Hemichordata Definition Hemichordata (Gr., hemi, half; chorde, cord) means they are ‘half’ of ‘part’ chordates, a fact that is disputed. They are usually vermiform, solitary, or colonial enterocoelous coelomate animals with an intra-epidermal nervous system and a pre-oral with or … Read more
Annelida definition Annelids are defined as triploblastic, bilaterally symmetrical, metamerically segmented, a coelomate worm with a thin flexible cuticle around the body. Figure: Diagram of Phylum Annelida. Source: Wikipedia Phylum Annelida Characteristics They are mostly aquatic; marine or freshwater some … Read more