Question

The wing of a bird and the arm of a human are examples of ________. a. vestigial structures b. molecular structures c. homologous structures d. analogous structures

Short answer

c. homologous structures

Step-by-step solution

Understand the terms

Let's start by understanding the meaning of each of the given terms. 1. Vestigial structures: These are structures that have lost most of their original function or purpose through evolution and may become reduced or nonfunctional over time. 2. Molecular structures: These are structures at the molecular level of an organism, such as DNA or proteins. 3. Homologous structures: These are structures that originate from a common ancestor and have a similar structure, but they might be used in different ways or serve different functions in different species. 4. Analogous structures: These are structures that have similar functions but do not share a common ancestry. They evolved independently due to similar environmental pressures, resulting in convergent evolution.

Identify the correct term

Now, we need to determine which term applies to the relationship between the wing of a bird and the arm of a human. As these structures share a common ancestry and have the same basic skeletal structure (though they serve different functions), we can identify them as homologous structures. So, the correct answer is: c. homologous structures

Key concepts

Vestigial Structures

When we talk about vestigial structures, we refer to parts of an organism that once had a function in its ancestors but have since lost most or all of their original purpose.

Think of the human appendix, for instance. It's widely believed to be a remnant of a larger structure that was used by our herbivorous ancestors to digest cellulose from plants. Today, the appendix is comparatively small and, while it may have some immune functions, it is not essential for digestion as it was in the past. Another example is the tiny leg bones found in some modern whales, which are remnants from when their ancestors walked on land.

Understanding vestigial structures is crucial because they provide powerful evidence of a species' evolution over time. They are like historical markers within an organism's body, showcasing their journey through millions of years of adaptation to different environments and lifestyles.

Analogous Structures

Moving on to analogous structures, these are a bit different from vestigial structures. They don't indicate common ancestry but rather, they represent an example of similar evolutionary solutions to similar problems.

Let’s consider the wings of bats and insects, or the fins of fish and flippers of dolphins. These structures look and function in comparable ways but evolved independently in these different groups of animals. This is because each of these species faced similar environmental challenges that required a similar adaptation for survival - like the need to swim or fly.

Why Are Analogous Structures Important?

Studying these structures helps scientists understand how different species adapt to similar environments and the processes that guide evolutionary change. Moreover, they highlight the principle that function can shape form in distinct lineages that don't share a close genetic relationship.

Convergent Evolution

The concept of convergent evolution is related to analogous structures as it describes the process by which different species develop similar traits independently, usually due to similar environmental pressures or ecological niches.

For example, the streamlined body shape of sharks and dolphins is a product of convergent evolution. Although they are not closely related genetically -- one being a fish and the other a mammal -- both have evolved a similar body plan optimized for swimming efficiently through water.

Roles of Convergent Evolution in Nature

This phenomenon emphasizes the role that the environment plays in shaping the course of evolution. It also tells us that there can be multiple paths to solving the same 'problems' life faces, resulting in diversity in nature. What's fascinating is that convergent evolution brings about similar solutions across different realms of the tree of life, underlining the idea that some forms and structures are particularly suited for certain functions, regardless of ancestry.