He says animals like sponges are even more ancient, but they lack the bilateral symmetry that characterizes most animals today.

他表示，海绵等动物更古老，但它们缺少现今大多数动物的两侧对称特性。

The entire compound was laid out on a geometric grid, incorporating meticulously planned bilateral symmetry.

整个大院被布置在一个几何网格上，包含精心规划的双边对称。

So how did the ancient ancestors of starfish go from having bilateral symmetry to having radial symmetry?

那么海星的远古祖先是如何从左右对称变成径向对称的呢？

All modern echinoderms start their lives as swimming larvae with bilateral symmetry and then settle on a substrate to transform.

所有现代棘皮动物都以双侧对称的游泳幼虫开始它们的生活，然后定居在基质上进行转化。

It’s an interesting hypothetical - but it’s also representative of a pretty fundamental concept in the evolution of animal body plans: Bilateral symmetry.

这是一个有趣的假设 - 但它也代表了动物身体计划进化中的一个非常基本的概念：双边对称性。

It had right-left bilateral symmetry like us, where the left half mirrors the right half, and its mouth faced upwards at one end of its body.

它和我们一样左右对称，左半边是右半边的镜像，嘴巴在身体的一端朝上。

" Why" questions are tough to answer in paleontology, but it might be that, basically, an animal with bilateral symmetry is equipped to move in one direction, often leading with its head.

“为什么” 的问题在古生物学中很难回答，但从根本上说， 一种双侧对称的动物可能具备向一个方向移动的能力，通常是用头引导。