Posts Tagged ‘adaptations’

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See nictitating membranes in action!

March 24, 2016

There’s a great nature event happening right now. Biologists have set up video cameras to watch a growing bald eagle family in the US National Arboretum in Washington DC, and anyone with an internet connection can watch them at any time.

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You can visit the DC EagleCam, 24 hours a day, at  http://dceaglecam.eagles.org

Even though this is the east coast, bald eagles also winter in the desert, usually in the high country. But the relevant  feature right now is that sometimes you can get a glimpse of the eagle’s nictitating membranes at work.

Here’s how. It’s best to watch in the day time. Click on one of the two cameras so you can more easily see the adult eagle’s eye, and enlarge the image, by clicking the bracket-box at the lower right corner of the video.

You will most often just see the eagle blinking–but every so often, you get to see the “third eyelid” swipe part way or all the way across the eye, starting from the corner nearest the beak. Wow!

And if you get so busy watching the adults and chicks and their activities you forget the third eyelid, that’s OK too!

…..Image taken April 6 2016 from dceaglecam.eagles.org © 2016 American Eagle Foundation, EAGLES.ORG

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Who’s standing tall and alone?

December 19, 2015

A striking sight in the Sonoran desert is a lone saguaro cactus.P1150608.jpeg

Saguaros (Carnegiea gigantea) provide food and shelter to a surprising number of creatures. This includes humans, who harvest their fruit, and use their skeletons for fences and construction.

These cacti have an amazing variety of adaptations to the desert.

First, check out the color of the stems, a pale green, indicating they contain chlorophyll. Since saguaros do not really have leaves, the stems have to do the work of photosynthesizing and producing food. The pale color keeps the plants from absorbing too much hot sunlight and getting burned.

If you look closely, you will see lines of defensive thorns on vertical accordion ridges. The whole plant can expand to hold more water after a good rain, then accordion back in as it uses the water

What you can’t see is the root structure. Instead of sending down a big tap root, like many plants, they send out numerous very long horizontal roots near the surface, to better gather any moisture nearby.

That’s why they’re lonesome looking—they need to grow far apart. And that’s why, in the old days before we realized it was unethical, (now it’s also illegal) people would dig them up in the desert, transplant them, and they would die, because the majority of  the root structure was left behind.