NEET Biology Notes Structural Organisation in Animals Earthworm
- It inhibits the upper layer of moist soil, can be traced by their faecal deposits called worm castings.Morphology
- Cylindrical, divided into similar segments (metameres). First body segment, peristomiun contain the mouth. Segments 14-16 in mature worm covered by a prominent dark band of glandular tissue, clitellum. Four pairs of spermathecal aperture on ventro-lateral sides of intersegmental grooves i.e. 5-9 segments. A pair of male genital pore and a single female genital pores is present on ventro-lateral side of 14th and 18th segment respectively.
Anatomy of Earthworm
- Alimentary canal straight. Calciferous glands, present in stomach, neutralise the humic acid present in humus. Typhlosole present between 26-35 segment.
- Circulatory system closed type. No specialised breathing devices.
- Respiratory exchange through moist body surface.
- Excretory organ nephridia (3 types, septal integumentary and pharyngeal).
- Nervous system represented by ganglia.
- Sensory system no eyes but light and touch sensitive organs. Special chemoreceptors (taste receptors) react to chemical stimuli.
- Reproduction — Sexual
- Development — Direct.