Question

Through _________, a body part of an ancestor is modified differently in different lines of descent. a. homologous structures b. convergent evolution c. analogous structures d. divergent evolution

Short answer

d. divergent evolution

Step-by-step solution

Define Key Terms

First, we need to understand what each term means. 'Homologous structures' are structures in different species with a common ancestor but have different functions. 'Convergent evolution' is when unrelated species evolve similar traits. 'Analogous structures' are structures in different species that serve similar functions but do not share a common ancestor. 'Divergent evolution' is when two species with a common ancestor evolve different traits.

Identify the Concept

The task asks about modification of a body part in different lines of descent. This implies that the modifications arise from a common ancestor but evolve into different forms.

Match Term with Concept

Divergent evolution fits the description because it describes how related species evolve different traits from a common ancestor, resulting in body parts being modified in different ways.

Key concepts

Homologous Structures

In the fascinating world of biology, homologous structures provide a clear window into understanding how different species can share a common ancestor. Though these structures may appear differently and serve various functions in each species, their underlying similarity points to a shared evolutionary past.
Understanding homologous structures can be made easier by exploring a few classic examples:

• The forelimbs of humans, whales, and birds: Though used for lifting, swimming, and flying respectively, a close examination shows a similar set of bones organized in the same general pattern.
• Leaf spines in cacti and tendrils in peas: Both evolved from leaves but have adapted to minimizing water loss and climbing, respectively.

These examples illustrate how, over time, species can adapt homogenous bones or body structures to fit different environments. This shows how slight changes in genes can lead to vast diversifications across lineages.

Analogous Structures

While homologous structures highlight a shared ancestry, analogous structures showcase how different evolutionary paths can lead to similar solutions. When different species evolve structures that serve similar functions but lack a common evolutionary origin, these are known as analogous structures.
Here are some examples to wrap your mind around the concept:

• The wings of birds and insects: Though both serve the purpose of flight, bird wings are supported by bones, whereas insect wings are membrane-like.
• Bat wings and butterfly wings: Again, both provide the ability to fly, yet they evolved independently, with different structures and origins.

The development of analogous structures is often a result of adapting to similar environmental challenges, where the most efficient shape or feature is naturally selected for, despite the organisms having different ancestries.

Convergent Evolution

Convergent evolution is like nature’s echo of innovation, where unrelated organisms independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. It's a powerful example of nature's knack for finding optimal solutions to similar problems across varying contexts.
Consider these fascinating examples:

• Cacti and certain species of Euphorbia plants: Both have evolved thick, fleshy structures to store water, a necessary adaptation for survival in arid environments, despite their distant relation.
• Dolphins and sharks: Though mammals and fish respectively, both have sleek, streamlined bodies and fins that allow them to navigate efficiently in water.

This concept reveals that distant organisms can develop similar adaptations, demonstrating how similar environmental pressures can lead to the evolution of similar physical features or behaviors in organisms that do not share a close common ancestor.