COMMON DESCENT

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Far to the north and far to the south, conditions on Earth get weird. Cold climates and periods of perpetual night or day create some of the most unique habitats on the planet, and yet life has thrived there throughout Earth history and continues to do so today. This episode, we discuss the diversity, history, and adaptations of Polar Life.

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Polar Regions

The northernmost and southernmost regions of Earth’s surface experience a set of unique and unusual conditions. They’re much colder than the rest of the planet, they experience long periods of day in the summer and long periods of night in the winter, and in our modern world, they’re partially covered in ice at all times.

There are multiple ways to define the borders of the Arctic or Antarctic regions. If you’re going by sunlight, the polar region is the area that receives permanent daylight during the summer. If you use average temperature, the border can be wiggly as it passes through different climate regions affected by weather patterns and ocean currents. If you go with the kind of life found there, the border can be blurry as the warmer-climate forests and oceans gradually transition into cooler grasslands and cold seas.

But the polar regions haven’t always looked like they do today. As continents have shifted through time, the amount of land and ocean near the poles has varied. And polar climate has changed over time as ocean currents have moved, the Earth’s tilt toward the sun has wobbled, and global climate patterns have fluctuated. In fact, although the poles have frozen multiple times, they’ve been largely ice-free for most of Earth history.

High Latitude Life

The polar regions aren’t nearly as rich with life as most other parts of the planet. Cold climate and long dark winters really put a strain on plants and animals, and some – like most trees, reptiles, and amphibians – don’t survive there at all. But the poles are far from lifeless. In the Arctic, there are diverse ecosystems of plants and animals, even large mammals like caribou, musk oxen, and polar bears. In the Antarctic, some species do manage to live on land, including penguins, migratory birds, and occasional plants, while the Antarctic Ocean is surprisingly rich with cold-adapted marine life.

Polar animals often have physical adaptations for staying warm, including insulating fur, blubber, or feathers. Many have highly efficient respiratory and circulatory systems that keep warm air and blood near the internal organs as much as possible. Some plants and animals even have cellular or molecular adaptations that allow them to survive freezing body temperatures, including ice algae, wood frogs, and Arctic ground squirrels. Many plants adjust their growth patterns to conserve resources in harsh climates. And many polar animals just leave when it gets cold – seabirds, caribou, whales, and more embark on regular migrations to warmer climates.

The fossil record provides evidence of a variety of polar ecosystems through time. In warmer periods of the past, both poles were home to a diversity of plants, including those that made up the polar forests of the Cretaceous Period. Dinosaurs are also known from the Arctic and Antarctic, and some researchers have suggested some of these dinosaurs might have migrated like modern Arctic animals, though there is evidence that at least some polar dinosaurs lived there all year. During the Pleistocene, the Arctic was home to mammoth steppe biomes, which were by some measures as diverse as modern African savannas.

Learn More

World Ocean Review has lots of information about the history, geography, and life of the polar regions.

The strange lives of polar dinosaurs

Abbott 2008. History, evolution and future of arctic and alpine flora (technical)

What Arctic Fossils Reveal About Our Future Climate

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If you enjoyed this topic and want more like it, check out these related episodes:

• Episode 11 – Antarctica
• Episode 124 – Snowball Earth
• Episode 113 – Paleoclimate
• Episode 108 – Penguins

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