Tag: basis of classification in animals

Cleidoic eggs have a protective shell, and are laid out of water. The shell is porous to air, and may be flexible or calcareous (hard). The eggs contain all the food the embryo needs to develop into a hatchling. The significance of the cleidoic egg is that it enables reproduction out of, and often away from, water. It is a characteristic of birds and reptiles. Hence, option D is correct.

The notochord is the defining structure forming in all chordate embryos. In humans beings, the notochord is formed in the third week and eventually replaced by the vertebral column. 

Schizocoelom develops as a split in the mesoderm, e.g.-Arthropods, Annelids, and Molluscs. Enterocoelom is derived from the wall of embryonic gut, e.g.-Echinoderms, and Chordates. Haemocoel is the blood-filled cavity of arthropods. Pseudocoelom is also known as a false cavity.

Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. These are long, slender, tapered at both the ends. The body is covered with a thick cuticle secreted by a cellular or syncytial epidermis. The life cycle of Ascaris involves only one host. The man is a definitive host for worm and is present in the gastrointestinal tract and fecal matter. Hence, option A is the correct answer. 

Important class of waterborne diseases are caused by metazoan parasites. Typical examples include certain Nematode, that is to say "roundworms". As an example of waterborne Nematode infections, one important waterborne nematodal disease is Dracunculiasis. It is acquired by swallowing water. Therefore, the correct answer is option A.

Platyhelminthes or flatworms are dorsoventrally flattened and bilaterally symmetrical worms. They are endoparasites and have parasitic adaptations like hooks and suckers.