Tag Archives: biology

Cicadas can avoid predators by emerging in prime numbered intervals

Cicadas emerge from the underground only periodically. Depending on the species, that period will be 7, 13, or 17 years, which are all prime numbers. Why does this make sense?

Suppose there are some predators (like birds, and the Cicada Killer Wasp) that attack cicadas, and that the cicadas emerge every 12 years. Then the predators that come out every two years will attack them, and so will the predators that come out every 3 years, 4 years and 6 years. But according Mario Markus, “if the cicadas mutate to 13-year cycles, they will survive.

The other advantage is that cicada species with different intervals will rarely compete with each other for food.

Via Reddit.

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We’re 98.6 degrees for a reason

Why is the human body 98.6 degrees Fahrenheit? Some scientists have an idea:

Albert Einstein College of Medicine researchers previously showed that every one degree Celsius rise in body temperature wards off about 6 percent more fungal species. So tens of thousands of fungi can infect reptiles and amphibians, but we can only be invaded by a few hundred fungi.

In the new work, the researchers created a mathematical model that weighed the fungal protection benefits versus the metabolic cost of high body temperature. And the optimal temperature was 98.1, quite close to what evolution figured out. The research was published in the open-access journal mBio. [Aviv Bergman and Arturo Casadevall, “Mammalian Endothermy Optimally Restricts Fungi and Metabolic Costs”]

Via 80 Beats.

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