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Being attacked by a predator can be scary, but tiger moths have a very distinguished way to survive predatory bats. Meanwhile, scientists have presented findings on the importance of microbial ecosystems beneath the soil.

Hosted by: Hank Green

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Sources:
https://www.frontiersin.org/articles/10.3389/fevo.2019.00480/full
https://www.eurekalert.org/emb_releases/2019-12/f-lmt121119.php
Special thanks to Dr. Nicolas J. Dowdy

https://www.eurekalert.org/emb_releases/2019-12/uow-haa121119.php
https://courses.lumenlearning.com/boundless-microbiology/chapter/chemolithotrophy/
https://www.pnas.org/content/early/2019/12/11/1909970117

Image Sources:
https://www.istockphoto.com/photo/colorful-granular-poison-dart-frog-gm527799477-53846156
https://www.istockphoto.com/photo/flying-greater-horseshoe-bat-in-forest-gm1185632698-334208470
https://www.videoblocks.com/video/close-up-of-young-plant-growing-from-soil-background-low-angle-view-hiw506dfgjese0pf0
https://www.istockphoto.com/photo/soil-layers-four-cross-section-soil-layers-3d-illustration-dark-background-gm869719354-145141103
https://www.istockphoto.com/photo/bedrock-stacked-in-black-and-white-gm501361792-81288899
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Go to Brilliant.org/SciShow to learn more about gifting a Brilliant Premium subscription this month. [♪ INTRO ]. Being attacked by a predator can be scary, but a new study in the journal Frontiers in.

Ecology and Evolution helps us understand how some animals can keep cool under even that most extreme pressure. Even weirder, it turns out we can gain insight into how an animal would behave, even if we can't watch it doing the thing. Some animals are… yucky.

They contain chemicals that make them toxic, nasty-tasting, or otherwise unpleasant to be around, which is a great defense against predators. It's so reliable that many of these animals are aposematic, meaning they have bright colors or other signals that warn predators to keep away. They don't hide, they advertise.

Aposematic animals tend to be relatively sluggish in their day-to-day movements. After all, there's no need to rush if most predators won't mess with you. But being under direct attack from a predator is a different story.

This study aimed to find out if animals with chemical defenses are able to remain relaxed under predatory pressure. To do so, the researchers tracked the behavior of 5 different species of tiger moths. These moths have a remarkable ability to detect the echolocation of predatory bats.

If a moth hears a bat coming, it can take evasive maneuvers by spiraling or diving out of the way. But this comes with a cost: quick, panicky flight can make it easier to get yourself lost, get stuck on a spider web, or draw the attention of other predators, not to mention just uses their energy. So if a moth has another line of defense — say, chemical grossness — it may be best for them to stay relaxed when attacked.

To observe the moths' behavior, the researchers released a bunch of moths in an outdoor arena where bats were known to hunt. Over three years, they observed more than 300 bat-moth interactions. Each time a moth was caught, the researchers observed whether the bat ate them or spat them back out.

This data let them grade the moths on a spectrum of palatability, or tastiness. The researchers also observed whether the moths tried to avoid the bats, or whether they just kept flying pretty normally under attack. That let them rank the moths according to nonchalance.

They found that the less palatable species were also cooler under pressure. It seems those chemical defenses allow the moths to save energy on evasive maneuvers. This is pretty exciting because it means we might be able to predict animals' behavior from chemical traits.

Researchers could study a bug in a lab, or even a museum specimen, and based on its chemical makeup, predict how it would act to avoid predators. This is not only much easier than observing bugs under attack, but it could be done for rare or even extinct species. And it's not just tiger moths that do this.

Similar bat-avoiding behavior is seen in many species of beetles, mantises, lacewings, and other moths and butterflies. These findings could open up a whole new way to study aerial predator-prey interactions. And while those researchers were exploring ecological dynamics in the air, another group of scientists have presented findings on the importance of microbial ecosystems beneath the soil.

Soil is obviously super important for life. It not only provides a home for lots of living things, but also contains the nutrients necessary for plants and other organisms to thrive. A new study in the journal PNAS sheds new light on the ways bacteria are responsible for creating that life-giving soil.

Soil is more than mere dirt. It's a mixture of minerals, water, air, and organic matter, both alive and dead. Beneath all that life-rich soil is a subsoil made of crumbly rocks, and beneath that is tough bedrock.

Soil contains minerals that life needs — things like phosphorus and potassium. Those are generally thought to come from down in the bedrock. But plant roots and wind erosion can only break down rocks near the surface, and bedrock can be several meters down.

So these scientists set out to explore how microbes deep underground might contribute to the breakdown of bedrock. To do so, they drilled a bunch of core samples from the soil and bedrock at the Luquillo. Critical Zone Observatory in Puerto Rico.

They ground up samples of the bedrock, added soil bacteria to some of the samples, and then let all of the samples sit in the lab for 864 days. After this extensive waiting period, they observed that the rocks had experienced some chemical breakdown, but only if the bacteria were present. What's more, the bacteria had increased in abundance.

Despite being in a dark room with no organic food sources, they were thriving. The bacteria in question are chemolithotrophs, meaning they get their energy through chemical reactions with inorganic materials in their environment. Basically, they can feed on rocks.

Genetic analysis of these soil bacteria found that they produce special proteins on their cell surface that allow them to swipe electrons from the iron in certain minerals, using those electrons to power their own metabolism. In the process, they accelerate the chemical weathering of the rock, breaking it down and releasing all those wonderful nutrients that become part of the soil. There are still some open questions.

For example, we don't how quickly this bacterial weathering occurs in nature, or how this microbial action varies at different levels of soil. But one thing is clear: these bacteria are a major player in the breakdown of rocks, meaning we have them to thank for the abundance of minerals in soil that help give life to the organisms on the surface. It takes a long time to degrade bedrock into soil, but the time for holiday shopping is almost up.

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