Question

The geologic record suggests that when supercontinents break up, a pulse of rapid evolution, with many new species appearing and many existing species becoming extinct, takes place. Why might this be? (Hint: Consider how the environment, both global and local, might change as a result of breakup, and keep in mind the widely held idea that competition for resources drives evolution.) \((\mathrm{A})\)

Short answer

When supercontinents break up, significant environmental changes, such as climate changes, habitat alterations, population isolation, and shifts in ocean currents and sea levels, occur. These changes can lead to increased competition for resources, survival of the fittest, and the creation of new niches. As a result, rapid evolution and species extinction take place, with species that can adapt and compete for resources thriving, while those unable to adapt face extinction.

Step-by-step solution

Understanding the concept of supercontinents

Supercontinents are large landmasses composed of multiple continents that have collided and joined together. Over geologic time, the Earth's tectonic plates have moved and collided, leading to the formation and subsequent breakup of these supercontinents.

Exploring environmental changes due to supercontinent breakup

When a supercontinent breaks up, several significant environmental changes occur. These changes include: 1. Climate changes - As continents drift apart, their climate may change due to shifts in ocean currents, atmospheric circulation, and the position of the continent on Earth's surface. Ice sheets may form or melt, and temperature and precipitation patterns may change. 2. Change in habitat - As continents separate, ecosystems may be divided, resulting in different habitats with varying resources, temperature, and landscape structures. 3. Isolation of populations - Populations previously part of a single landmass may become isolated from each other and evolve separately, leading to the formation of new species. 4. Changes in ocean currents and sea levels - The breakup of supercontinents can lead to changes in ocean currents and sea levels, influencing the distribution of resources and habitats.

Explaining rapid evolution and extinction

The environmental changes that occur when supercontinents break up can contribute to rapid evolution and species extinctions: 1. Competition for resources - As habitats change and populations become isolated, species may face new competition for resources. Adaptations that help species survive and reproduce more efficiently in the new environment will be favored by natural selection. 2. Survival of the fittest - Some species may not be able to adapt quickly enough to the changing environment and may face extinction. Other species that can adapt and compete for resources may flourish and evolve. 3. Creation of new niches - The environmental changes may create new niches (specialized roles within an ecosystem) for species to exploit, leading to rapid evolution as species adapt to fill these new niches.

Drawing conclusions

When supercontinents break up, the resulting environmental changes and species isolation create conditions that can lead to rapid evolution and species extinction. The competition for resources in changing habitats can drive the evolution of new species while also causing the extinction of species that cannot adapt to these changes.

Key concepts

Rapid Evolution

Rapid evolution refers to the fast-paced changes in species over relatively short periods. This often happens when new environmental pressures or opportunities appear suddenly. When a supercontinent breaks, the separation of landmasses creates isolated regions for species to inhabit.

• As populations become isolated, genetic differences accumulate over generations.
• Natural selection acts upon these differences, promoting advantageous traits in different environments.
• This can quickly lead to the emergence of new species, as organisms adapt to fill different ecological roles.

Isolation plays a crucial role here. With barriers like oceans emerging between populations, gene flow (exchange of genetic material) is reduced, allowing unique adaptations to flourish.

Species Extinction

Species extinction is a natural part of evolutionary history, but it can be intensified during supercontinent breakups. As environments shift, not all species can adapt fast enough. Facing new challenges, many species may struggle and eventually disappear.

• Many species rely on specific conditions or resources that might vanish due to environmental upheaval.
• Species that once dominated might become less competitive in newly formed habitats.
• Adaptation requires time, often more time than a species has to adjust to rapid changes.

The extinction of some species often clears the way for others to thrive, creating a dynamic balance in the ecosystem. This cycle of extinction and adaptation fuels long-term biodiversity.

Environmental Changes

Environmental changes are significant when supercontinents break apart. As continents drift, they experience different climates, leading to diverse habitats.
Changes in climate can alter ecosystems dramatically, affecting plant and animal life. When continents were joined, certain climates, like warm shores, could stretch for vast distances. When they divide, these may become spread out, resulting in:

• Variance in temperature and rainfall.
• Altered ocean currents that affect coastal climates and resources.
• New landscapes and habitats forming, like mountains and valleys, that stimulate different adaptive strategies.

These changes can drastically alter the living conditions for countless species, prompting both extinction and evolution.

Tectonic Plates

Tectonic plates are massive slabs of Earth's crust that slowly move over the molten layer beneath. Their movement is the fundamental force behind the creation and breakup of supercontinents.
Geologically, tectonic activity shapes the planet's physical features, causing continents to collide, merge, and then drift apart over millions of years:

• When plates move, they create mountain ranges, ocean basins, and other geographic features that influence climate and habitat distribution.
• This movement causes continents to drift, rearranging ecosystems and isolating species.
• The constant shift encourages biodiversity as it allows varied evolutionary paths.

Understanding tectonic plates is crucial to comprehend how they set the stage for dramatic developments in Earth's species and environments.