Share Answer Sexual dimorphism is the difference in the form of individuals of different sexes but of same species. Sexes in Ascaris are separate and sexual dimorphism is well defined. Males are smaller than females. They possess a recurved tail with pre and post anal papillae, a cloaca, and a pair of spicules or penial setae. In Anopheles, the ends of maxillary palps in males are club-shaped while in females they are not.

Share Answer Pharyngeal nephridiaand septal nephridiaare enteronephric as they discharge excretory matter into the gut. Discharge of waste matter via gut is an adaptation to conserve water by its reabsorption in the gut. Integumentary nephridra are exonephric, as they discharge waste matter to the exterior.

Share Answer Hydra, has tissue level of organization, its body is multicellular and the cells occur in 2 distinct layers or tissues of specialized cells. Sponges have cellular level of organization. Liver fluke and Ascaris have organ- system level of organization.

Share Answer Cleavage in mammals is holoblastic unequal. Mammals have microlecithal eggs so they have holoblastic cleavage in which the segmentation lines pass through the entire egg, dividing it completely. As the eggs are microlecithal so one would expect that first cleavage will produce two equal blastomeres. But, this is not the case. The two blastomeres produced are unequal which divide further to form 4 unequal blastomeres and this process continues to form a ball of cells called morula. Superficial cleavage occurs in insects and discoidal cleavage occurs in birds.

Share Answer In Hydra indigestible residues are egested through mouth, for there is no anus. Egestion occurs by a sudden squirt due to muscular contraction of body, so that the debris is thrown at a distance. Hydra has neither blood and blood vessels, nor organs of excretion. <br />Due to thinness of body wall and circulation of water in gastrovascular cavity, most cells of body remain freely exposed to the surrounding water. Therefore, excretion of waste nitrogenous matter (chiefly ammonia) occurs directly by diffusion through cell membranes in the outside world.

Share Answer Snakes are limbless reptiles with elongated cylindrical body, covered with overlapping scales differentiated into shields and plates and have post anal tail which is long.

Share Answer In molluscs, blood often has a copper- containing, blue respiratory pigment called haemocyanin. In insects, the blood called haemolymph is colourless. In echinodermates, blood is colourless as it has no respiratory pigment. In annelids, the blood is red with haemoglobin dissolved in plasma.

Share Answer The function of contractile vacuole is osmoregulatory. Water in freshwater protozoa enters the organism by endosmosis and during feeding. If the organism does not possess a mechanism to get rid of this excess water, it will swell to the point of rupture and dissolution. The mechanism which is assumed to effect water regulation is the contractile vacuole. The vacuole periodically increases in volume (diastole) to get filled with water and contracts (systole) to discharge its water content to the surrounding environment.

Share Answer Chordates are the animals that have notochord, a skeletal rod present at some stage in life cycle. In lower vertebrates, notochord persists throughout life while in higher vertebrates it is replaced by vertebral column in adults. Nonchordates never develop notochord, not even in embryonic stage.

Share Answer Dimorphic nucleus means two types of nuclei are present in P. caudatum -large macronucleus and small micronucleus. The macronucleus is roughly kidney- shaped and with inconspicuous nuclear membrane. Macronucleus is the somatic or vegetative nucleus and controls the day-to-day metabolic activities of the cell. <br />The micronucleus is lodged in a depression on the surface ofthe macronucleus. It is usually spherical, with a nuclear membrane and with diploid number of chromosomes. It controls the reproductive activities of the organism. Amoeba, Trypanosoma and Plasmodium have only one nucleus.