Question

name: _______________________ class: ___________________
you have now studied three different types of anatomical structures:

• homologous structures show individual variations on a common anatomical theme. these are seen in organisms that are closely related.

1. give an example of a homologous structure from this activity:

• analogous structures have very different anatomies but similar functions. these are seen in organisms that are not necessarily closely related, but live in similar environments and have similar adaptations.

1. give an example of an analogous structure from this activity:

• vestigial structures are anatomical remnants that were important in the organism’s ancestors, but are no longer used in the same way.

1. give an example of a vestigial structure from this activity:
2. below are some vestigial structures found in humans. for each, hypothesize what its function may have been.

structure	possible function?
appendix
muscles for moving the ear
body hair
little toe
tailbone

1. how are vestigial structures an example of evidence of evolution?

Explanation:

1. Homologous structures share a common anatomical origin; a standard activity example is the forelimbs of humans, bats, and whales.
2. Analogous structures have similar functions but different origins; a standard activity example is the wings of insects and birds.
3. Vestigial structures are unused ancestral remnants; a standard activity example is the hip bones in snakes.
4. For human vestigial structures:

• Wisdom teeth: Our ancestors had larger jaws, and these teeth helped chew tough, raw plant material.
• Appendix: Likely aided in digesting fibrous plant matter and may have played a role in the immune system for early humans.
• Muscles for moving the ear: Allowed ancestors to rotate ears to localize sounds from predators or prey.
• Body hair: Provided insulation for hairier ancestors and may have helped with sensing small insects on the skin.
• Little toe: Aided in balance and stability when our ancestors climbed trees or walked on uneven terrain.
• Tailbone: Supported a tail in our primate ancestors, which was used for balance and grasping.

1. Vestigial structures show that organisms have inherited traits from ancestors that are no longer needed, indicating that species change over time (evolve) as their environments and lifestyles shift.

Answer:

1. Example: Forelimbs of humans, bats, and whales
2. Example: Wings of insects and birds
3. Example: Hip bones in snakes

4.

Structure	Possible function?
Appendix	Digesting fibrous plants, immune support
Muscles for moving the ear	Localizing sounds from threats/prey
Body hair	Insulation, detecting small insects
Little toe	Balance for climbing, uneven terrain travel
Tailbone	Supporting a tail for balance/grasping

1. They demonstrate that species inherit traits from ancestral forms, and as environments/lifestyles changed, these structures lost their original purpose, showing evolutionary change over time.