Question

some species that appear to be very different from other species can actually have similar anatomy. for example, scientists believe that whales evolved from land mammals. one reason for this is the presence of several functionless hind - limb bones still found internally in a number of whale species.
what is the term for a reduced, often functionless anatomical structure that serves as evidence of an organisms evolutionary past?
a. vestigial structure
b. homologous structure
c. trace structure
d. absorbed structure

Explanation:

• vestigial structure：指的是在进化过程中，生物体中残留的、通常无功能的解剖结构，如题目中提到的鲸鱼体内无功能的后肢骨，符合题意。
• homologous structure：同源结构强调的是不同物种间由于共同祖先而具有相似结构和发育来源，但功能可能不同，与“reduced, often functionless”（退化、通常无功能）这一关键特征不符。
• trace structure：“trace structure”不是生物学中表示此类结构的专业术语。
• absorbed structure：“absorbed structure”也不是生物学中表示此类结构的专业术语。

Answer:

A. vestigial structure