Question

analysis and interpretations

1. explain why the homologous structures in part i are evidence of evolutionary relationships.
2. explain the evolutionary relationship between the fin of a fish and the flipper of a whale.
3. list one other structure (not from table 1) that you think is vestigial and explain why.
4. re - define the three different types of evidence for evolution that you have studied in this activity in your own words.

homologous structures -
analogous structures -
vestigial organs -
part iv. embryology
embryology is the study of embryos, which are offspring that are in the process of development.

Explanation:

1. Homologous structures have a common evolutionary origin. Even if their functions differ (e.g., a human arm for grasping, a bat wing for flying), their similar bone - structure (like humerus, radius, ulna etc.) indicates that the organisms sharing these structures evolved from a common ancestor. Over time, natural selection modified these structures for different functions in different environments.
2. The fin of a fish and the flipper of a whale are analogous structures. Fish are aquatic vertebrates that evolved fins independently for swimming. Whales are mammals that evolved from land - dwelling ancestors. Their flippers are modified limbs (homologous to human arms, for example) that have been shaped by natural selection for swimming. So, they have different evolutionary origins (fish fins from fish - specific ancestral structures, whale flippers from mammalian limb - like ancestors) but similar function (swimming).
3. An example of a vestigial structure is the appendix in humans. In our herbivorous ancestors, the appendix was likely larger and played a role in digesting cellulose - rich plant material. As human diet changed over time (less reliance on tough plant fibers), the appendix has lost most of its digestive function. It is now a small, pouch - like structure that may have some immune - related functions but is greatly reduced in its original digestive role compared to what it was in our ancestors.

4.

• Homologous Structures: Body parts in different organisms that have a similar underlying anatomical structure (same bones, similar embryonic development) due to a common ancestor, even if their functions vary.
• Analogous Structures: Structures in different organisms that have a similar function (e.g., flying in bats and insects) but different anatomical origins (bat wings are modified forelimbs with bones, insect wings are outgrowths of the exoskeleton).
• Vestigial Organs: Organs that have lost most or all of their original function in the course of evolution. They are remnants of structures that were functional in ancestral species.

Answer:

1. Homologous structures show common ancestry as they have similar anatomical bases from a shared ancestor, with functions modified by natural selection.
2. The fin of a fish and whale flipper are analogous; different evolutionary origins (fish fin - fish - specific, whale flipper - mammalian limb - like) but same function (swimming).
3. Appendix in humans: Reduced from ancestral digestive (cellulose - digesting) function as diet changed.

4.

• Homologous Structures: Similar - structured body parts (due to common ancestor) with variable functions.
• Analogous Structures: Same - functioned structures with different anatomical origins.
• Vestigial Organs: Function - lost remnants of ancestral functional structures.