Question

Name the term used for:

(i) Left and right halves of the body having the same design

(ii) Animals where tissues develop from three germinal layers.

Answer 1

(i) Bilateral Symmetry

1. The balanced arrangement of body parts or structures around a central axis is referred to as symmetry in biology. – i.e., the size, form, and relative location on one side of a dividing line are mirrored on the opposite side.
2. In bilateral symmetry, only one plane (called the sagittal plane) will divide an organism into roughly mirror-image halves (concerning external appearance only).
3. Thus the body can be divided into identical left and right halves in only one plane.

(ii) Triploblastic

Those organisms in which the developing embryo has three germinal layers, i.e., ectoderm, endoderm, and mesoderm, are called triploblastic organisms.