Question

Macroevolution refers to evolutionary changes that a occur in multicellular organisms. b produce new species and groups of species. c occur over long periods of time. d cause changes in allele frequencies. e occur in large mammals.

Short answer

The correct answer is (b): Macroevolution refers to evolutionary changes that produce new species and groups of species.

Step-by-step solution

Elimination based on Concept Understanding

Start by eliminating incorrect options. From understanding of the topic, it's clear that (a) is incorrect because macroevolution isn't restricted to multicellular organisms, (d) refers to microevolution not macroevolution. Finally, (e) is incorrect since macroevolution isn't limited to large mammals.

Approaching the Correct Answer

Now, you are left with options (b) and (c). Both seem reasonable but remember that these changes should not just occur over time (c) but specifically lead to the formation of new species (b). Thus, (b) is the correct answer with respect to the meaning of macroevolution.

Confirming the Correct Answer

Confirm that option (b) 'produce new species and groups of species' is the correct definition for 'macroevolution'.

Key concepts

Evolutionary Changes

When we talk about evolutionary changes, we refer to the alterations that occur in the genetic makeup of a population over time. In the context of macroevolution, these changes are significant enough that they can eventually lead to the emergence of new species.

Unlike microevolution, which involves small-scale adjustments like changes in allele frequencies within a population, macroevolution encapsulates these small changes and builds upon them over extensive periods. It encompasses major morphological changes, the development of novel traits, and significant adaptive shifts. These changes are often driven by factors like mutations, genetic drift, natural selection, and gene flow, but they occur at a scale that affects the taxonomy beyond the species level.

For example, the evolution of feathers wasn't just a small change; it was a part of a series of evolutionary leaps that eventually distinguished birds from their dinosaur ancestors.

New Species Formation

New species formation, or speciation, is the pivotal moment in macroevolution where enough evolutionary changes accumulate, resulting in a population diverging to the point where it can no longer interbreed with its ancestral population.

Speciation can occur through several mechanisms:

• Allopatric speciation: Geographic isolation creates a physical barrier, leading to independent evolution.
• Sympatric speciation: Species diverge without physical barriers, often through disruptive selection or polyploidy.
• Peripatric speciation: Similar to allopatric, but involving small founding populations that become isolated at the edges of the larger ancestral population's range.
• Parapatric speciation: Neighboring populations evolve into distinct species while maintaining contact along a common border.

Each of these mechanisms reflects the dynamic nature of evolution and the intricate processes that foster biodiversity.

Long-term Evolutionary Processes

Long-term evolutionary processes are the drawn-out sequences of events that contribute to macroevolution. Over thousands or even millions of years, these processes fundamentally alter life forms, leading to the vast diversity of life we see today.

Among these processes, certain pivotal events stand out. Mass extinctions, for instance, have historically closed some evolutionary doors while opening others, enabling surviving species to radiate and fill new ecological niches. Adaptation and coevolution also play essential roles as species not only adjust to their environments but also to the presence of other living organisms with which they interact.

Understanding long-term evolutionary processes requires a historical perspective. Geological activity, climate change, and continental drift, for example, have fashioned the theater where the drama of evolution occurs, providing context to the grand narrative of life on our planet.