Question 8: Differentiate between:
a. Open and closed circulatory system
b. Oviparity and viviparity
c. Direct and indirect development
d. Aceolomate and pseudocoelomate
e. Notochord and nerve cord
f. Polyp and medusa
Answer:
a. Open circulatory system: Blood is directly circulated in the cells and tissues without any network of vessels. Example: Mollusca, Arthropoda.
Closed circulatory system: Blood is circulated through a proper network of vessels (arteries, veins and capillaries). Example: Annelida and Chordata.
b. Oviparous: Oviparous are the animals that lay eggs. Oviparous animals or organisms look after their eggs after laying them.
Example: Birds, Reptilia.
Viviparous: are those animals that gives birth to the live young ones. They show parental care after their birth.
Example: Mammals.
c. Direct development: In this development larval stage is not present. An embryo develops into a mature individual without involving larval stage. Example: Human beings.
Indirect development: In this development sexually immature larval stage is present. Example: Butterflies.
d. Acoelomate: The animals in which the body cavity is absent. Example: Poriferans, Ctenophores.
Pseudocoelomate: The animals in which the body cavity is not lined by mesoderm layer and mesoderm is present in scattered pouches in between ectoderm and endoderm. Example: Aschelminthes.
e. Notochord: It is mesodermally derived rod- like structure formed on the dorsal side during embryonic development.
Nerve cord: Nerve cord is a strand of nervous system.
f. Polyp: Poly is sessile and cylindrical form. Example: Hydra, Adamsia.
Medusa: Medusa is free swimming and an umbrella shaped structure. Example: jelly fish.
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