Question

Examination of the skeleton of whales shows bones similar to the human pelvic girdle. In whales, these bones would be considered: a. vestigial structures c. analogous structures b. anachronisms d. heterologous structures

Short answer

Option (a) vestigial structures.

Step-by-step solution

- Understanding the Concept

First, understand the key concepts. Vestigial structures are remnants of organs or structures that had a function in an earlier ancestor but are now reduced or nonexistent in current organisms. Analogous structures have similar functions but different evolutionary origins. Anachronisms are anything out of time or place, and heterologous structures refer to different parts of the body.

- Analyzing Whales' Pelvic Bones

Consider the pelvic girdle in whales. These bones are remnants of hind legs, which have little to no function in modern whales. This matches the definition of vestigial structures.

- Comparing to Other Structures

Review the other options. Analogous structures do not apply as whale pelvic bones are not functional like human pelvis. Anachronisms and heterologous structures are also not applicable in this biological context.

- Concluding the Correct Option

Based on the analysis, the pelvic bones in whales are best described as vestigial structures. Therefore, option (a) is correct.

Key concepts

whale pelvic girdle

Whales have a pelvic girdle, much like humans. However, theirs is greatly reduced and does not serve the same purpose. In ancient ancestors of whales, these bones were part of the hind limbs, helping them walk on land. We can still see these pelvic bones in modern whales, but they are small and not connected to any functional limbs. The whale pelvic girdle serves as a fascinating clue into their evolutionary past.

vestigial structures

Vestigial structures are body parts that have lost their original function over time. They are remnants from ancestors who used these parts actively. In whales, the pelvic girdle is one such vestigial structure.

Here are a few more examples to help you understand vestigial structures better:

• The human appendix, which is a tiny organ left over from our plant-eating ancestors.
• The wings of flightless birds like ostriches.
• The hind limb bones in snakes.

These examples show how evolution leaves behind traces of our past in our anatomy.

evolutionary biology

Evolutionary biology studies how living organisms evolve and adapt over time. It looks at how species change their form, function, and behavior through generations.

For whales, evolutionary biology explains their transition from land-dwelling creatures to the marine giants we see today. This field helps us understand the development of vestigial structures, like the whale pelvic girdle.

Important concepts in evolutionary biology include:

• Natural selection - how species evolve by adapting to their environments.
• Common ancestry - how different species share a common ancestral origin.
• Genetic mutation - how changes in DNA lead to new traits and abilities.

By studying evolutionary biology, we can trace the history and biological changes of organisms like whales.

comparative anatomy

Comparative anatomy involves comparing the body structures of different species. It helps us identify similarities and differences in anatomy that reveal their evolutionary connections. By studying the pelvic girdles of whales and other mammals, we can see how these structures have changed over time.

Key aspects of comparative anatomy include:

• Homologous structures - body parts that share a common ancestry but may serve different functions (like the limbs of humans and the fins of whales).
• Analogous structures - body parts that serve similar functions but evolved independently (like the wings of bats and insects).
• Vestigial structures - reduced or nonfunctional remnants from ancestors, providing insights into evolutionary history.

Understanding comparative anatomy enriches our knowledge of how species evolve and adapt in different environments.