that lizard talks

Evolution Series: A Series of Sirenians

Sirenians, or sea cows, are very unique animals. Related to elephants and hyraxes but originating in the Americas, they are the only fully herbivore aquatic mammals and live in both freshwater and salwater habitats.

*The animals represented here are not to scale and don’t represent a direct line of descent, but rather plausible models for how this amazing transition happened.*

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Science Fact Friday: Bird lungs! Just like every other part of a bird, they’re weird.

This gif shows the path of a single breath, but the circuit holds 2 breaths at a time. So when the bird inhales, the just-inhaled breath goes through Inhalation 1 while the previous breath goes through Inhalation 2. Rinse, repeat. Thus, the lungs are constantly receiving oxygen - in mammals, our oxygen content dips slightly between inhalations because there’s no fresh air coming in. We also don’t empty 100% of our lung volume so some air is “stale” even during an inhalation.

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Transcript below the break.