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Evolution Gets Colorful August 24, 2009

Posted by Mrs Weird Scientist in Brain Power, Environment, Evolution, Tough Stuff.
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Summer is still going strong but soon it will be fall – a time when we can enjoy the pretty autumn leaves. Or as I always like to do, throw leaves at my wee dog and race through the massive piles of foliage.

Unless you’ve traveled a bit and have a sharp eye for detail, you might not have noticed that autumn leaves are usually red in America but yellow in Europe. Seems strange, doesn’t it? If you’re wondering why, then you’re not the only one. Two professors thought about these differences too and they came up with a cool theory.

Prof. Simcha Lev-Yadun of the Department of Science Education at the University of Haifa-Oranim in Israel and Prof. Jarmo Holopainen of the University of Kuopio in Finland had their work published in New Phytologist.

Stepping Back In Time

Red leaves in America serve as a warning flag to ward off insects. But in Europe, none of these evolutionary 'tricks' are needed, which means leaves are yellow.

To find out more, we have to step back 35 million years to sort out the mystery. Up until that time, huge areas of the globe were rich in evergreen forests. Then, a bunch of ice ages and dry spells came into the picture. Lots of the tree species evolved to become deciduous – meaning they lose their leaves depending on the season. Some trees even started to produce red leaves to keep the pesky insects away. But, something else came into play and you might be surprised to learn just what it was!

Look To The Mountains

It’s true. We have to check out the orientation of the mountains to get the scoop on why the leaves evolved to be red in America but yellow in Europe. In North America, north-to-south mountain chains created a protected area, enabling the plants and animals to migrate south or north. Joining them were the insects. So, the leaves in America remained red to continue warding off these annoying bugs.

But in Europe, the mountains are oriented from east-to-west, leaving no protected areas as the ice and other environmental conditions came to visit. Loads of the tree species just couldn’t survive the extreme cold. When they died, so did those insects that needed the trees for their survival. By the time the ice ages were over, those trees that had managed to survive didn’t have to deal with the now-extinct insects. So, no need for red leaves to keep them away!

Curious Minds Want To Know

I asked Simcha Lev-Yadun how he ended up studying leaves. While my background is in the life sciences (medicine and nutrition), I always wonder how people end up in the many different, neat areas of science. He explained:

I wanted to be a biologist and archaeologist since I was ten years old. For me, science is a lifestyle, not a job. At the age of 57…I look backwards and see that I made the right decision.

He also shared his plans to meet up in Scandinavia with his colleague Jarmo Holopainen, where they hope to find out even more about why plants have such cool and different colors.

My Wishful Thinking

While my dog Tiko probably doesn’t care much about leaf color when he dashes through the crisp autumn leaves, I like to understand what makes one leaf a bright yellow and another a brilliant red. Now, if only leaves could somehow evolve to become fluorescent pink, my favorite color. Somehow though, I just don’t see it happening!

Secrets Of Climbing June 1, 2008

Posted by Mrs Weird Scientist in Animals, Environment, Evolution, Think About It.
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Treetops

Ever had a favorite tree in your yard that you liked to climb once in a while? You probably scurried up the tree and maybe hung out for a bit before carefully making your way down to your abode on the ground. We all know that some creatures like to live up in the trees but what makes the trees such a cool place to inhabit? Scientists may have found some clues as to why early primates liked to make their home in the forest canopy. It’s all about size!

Apes and monkeys – ancestors of humans – might have ended up in the trees because of their small size. Researchers have been curious for a while now about why early primates happily lived up in the trees. Why so curious? It’s because they thought that climbing used up more energy than walking. When it comes to walking, for example, smaller animals use up more energy in comparison with larger animals. Generally, we would expect the animals to live in a way that conserves energy. So, it has been somewhat of a confusing question as to why primates would make a transition to the trees if it meant that their energy efficiency was compromised.

Using A Treadmill To Investigate

Mongoose Lemur

You’re probably reading the word ‘treadmill,’ and wondering to yourself what I’m talking about! Well, treadmills can be useful for many things – not just for us humans to use as exercise equipment. In this case, researchers from Duke University in North Carolina observed primates as they walked and climbed on a special treadmill that was designed for the study. The results were surprising!

The researchers found that there was no difference in how much energy was consumed for small primates whether they walked or climbed the treadmill. This means that climbing didn’t have a higher energy consumption. In this way, the small primates could make good use of the treetop environment without compromising their energy. These early primates would have been approximately the size of a very big rat. The results were published in the journal Science and the information gives us some clues about how the ancestors of these primates ended up in the trees approximately 65 million years ago.

Yummy Food

You might be wondering what was so great about the trees? Well for early primates, moving into this new environment provided them with an abundance of tasty insects and fruits. On top of that, evolutionary changes then occurred, which means that the primates developed characteristics to help them better adapt to this new environment. For these mammals, the changes included the development of nails instead of claws. Jandy Hanna, a Duke graduate student at the time of the study, created the treadmill apparatus and measured primate activity and energy consumption. She explained:

We assumed it would be more energetically expensive for all of them to climb than to walk, so this finding was unexpected. What we have shown is that they could have made this shift into a rich environment with insects and fruits without increased energetic cost.

Ultimately, the small size of the primates meant that they could make the transition into the trees to enjoy the goodies up there. From the perspective of energy consumption, heavier animals had less incentive to climb than walk, so it was the smaller primates who had the competitive edge. Still, even if it does take more energy for humans to climb – that sure never stopped me when I was a kid and I liked climbing the tree to my playhouse.

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