Name: Foetus Development
Uploaded: 2019-07-19
Duration: 9 min 51 s
Description: A baby goes through several stages of development, beginning as a fertilised egg. The egg develops into a blastocyst, an embryo, and then a foetus.

Question

Give distinguished characters of phylum Annelida and give five examples of this phylum.

Accepted Answer

Salient features of Annelids
• Annelids are mostly aquatic and few are terrestrial forms.
• The body is elongated, cylindrical or flattened. It is divided into various segments.
• True metameric segmentation is present. The number of segments is fixed with no gain or loss of segments in their life.

• Body is triploblastic and bilaterally symmetrical.
• The body cavity is a true coelom (schizocoelomate or eucoelomate), as it is lined by mesodermal epithelium
• They have tube within a tube body plan.
• Most of them are free living and some are ectoparasites.

• Blood is red in colour due to haemoglobin which dissolves in plasma.
• The heart is neurogenic.
• Alimentary canal is complete.
• Gaseous exchange occurs by general body surface as the special respiratory organs are absent.

• Ectodermally derived nephridia are the organs of excretion.
• They may be ammonotelic or ureotelic
• A closed type of circulatory system in which the blood flows within the blood vessels is found. It appeared for the first time in animal kingdom.

• Development may be direct (without larva) or indirect.
• Fertilization may be internal or external.
• These are monoecious or hermaphrodite.

The examples of this phylum:Nereis, Earthworm, Aphrodite, Hirudinaria, Arenicola.

Give distinguished characters of phylum Annelida and give five examples of this phylum.

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