Question

a) Explain about the animals with jointed legs that you have studied. (3.5 Marks)
b) Write a short note on Phylum Platyhelminthes with examples. (3.5 Marks)

Answer 1

a)

• Arthropoda is the largest phylum of the animal kingdom. They are bilaterally symmetrical, triploblastic and coelomate animals. (0.5 Marks)
• The body is divisible into head, thorax and abdomen. Each thorasic segment bears paired jointed legs. (0.5 Marks)
• Exoskeleton is made of chitin and is shed periodically as the animal grows. The casting off and regrowing of exoskeleton is called moulting. (0.5 Marks)
• Body cavity is filled with haemolymph (blood). The blood does not flow in blood vessels and circulates throughout the body (open circulatory system). (0.5 Marks)
• Respiration is through body surface, gills or tracheae (air tubes). (0.5 Marks)
• Excretion occurs by malphigian tubules or green glands. Sexes are separate. (0.5 Marks)
• Example: Prawn, Crab, Cockroach, Millipede, Centipedes, Spider, Scorpion. (0.5 Marks)

b)

• Phylum Platyhelminthes (flat worms) are bilaterally symmetrical, triploblastic, acoelomate (without body cavity) animals. (1 Mark)
• Most of them are parasitic in nature. Suckers and hooks help the animal to attach itself to the body of the host. (1 Mark)
• Excretion occurs by specialized cells called flame cells. These worms are hermaphrodites having both male and female reproductive organs in a single individual. (1 Mark)

• Example: Liverfluke, Tapeworm. (0.5 Marks)