Zoology - Week 4

Sagittal plane

vertical plane

Asymmetrical Organisms

organisms body cannot be cut into two equal halves through any plane

Example for Asymmetrical Organisms

Some poriferans - Scypha and Euspongia

Reason for Asymmetry

Irregular growth of body

Radially symmetrical organisms

organisms that can be divided into similar halves through multiple planes, typically around a central axis
they have top and bottom surfaces and no left and right sides

Examples for radial symmetry

Leucosolenia, coelenterates, ctenophores and adult echinoderms

Biradial symmetry

organisms can be cut into two equal halves by 2 vertical planes only

examples of biradial symmetry

sea anemones

Bilateral symmetry

body can be divided into 2 halves by a single plane passing through the centre
organs are paired and occur on both sides of the body

examples for bilateral symmetry

Platyhelminthes, Aschelminths, annelida,arthropoda, larval echinodermata ,hemichordata and chordata