Flowers make people happy. Some new studies by Rutgers University scientists support the idea strongly, and the experts go on to guess that flowers have flourished(繁荣) on the earth, with their beauty evolving(进化) in recent several thousand years, partly because humans love them.

In the first test, 122 men and women were given either a flower, a pen, or nothing. Those who got flowers smiled more and talked more.

In the second test, bouquets(花束) were sent by flower sellers to 113 men and women. All 113 got flowers and a notebook, but some got them earlier and received a second bouquet when the others got theirs. By now you can guess the result. The more flowers, the more smiles.

From there, it’s a bit of a jump to the idea that flowers grow better because we love them.

Geneticist(遗传学家) Terry McGuire suggests that nature’s prettier flowers continued to live and develop well because people didn’t destroy them when they cleared for agriculture(农业). Instead, they grew them and have been doing so for over 5,000 years. “Because they make us happy, we take care of them. In that sense they’re like dogs. They are the pets of the plant world.” McGuire says.

Here is one way that might have worked:

Many kinds of flowers that are now planted used to grow only when people arrived there, McGuire explains. “As humans moved into a new place to clear land for agriculture, these flowers would have been weeds.” “These prettier flowers might have been kept because of beauty. The seeds(种子) would have been kept and replanted. Over time, the best of these flowers might have been chosen and the seeds more carefully kept.”

Whether you enjoy taking a daily walk or working out hard in the gym, you may wonder which exercise burns the most calories(卡路里). Let’s find out!

Running

Running is one of the best calorie burners out there. An average person can burn anywhere from 500 to 1,000 in one hour of running. Speed, pace and endurance (耐力) all influence this number. But running uses every muscle group (肌肉群) in the body, allowing you to burn more calories.

Swimming

In just 30 minutes of swimming, an average person can burn 200 to 300 calories. Swimming also improves cardiovascular health (心血管健康), builds endurance and increases strength—all great reasons to jump into the water.

Cycling

There’s nothing like a nice evening bike ride when the weather’s nice, and it’s actually a great workout for you as well. A long steady bike ride can burn up to 500 to 700 calories in an hour.

Boxing

Not only is boxing a great way to reduce stress, but it also helps improve balance and endurance. Boxing helps you get a good calorie burn, too, with the average person burning up 500 to 800 calories in an hour.

Pigs do it. Mice do it. Dogs also do it. Kangaroos? No, not so much. Why do some animals shake(抖动)? The short answer is because they are wet. But there's actually more to it than that—a lot more.

In an article, Andrew Dickerson and others took a look at this strange problem. The scientists wrote down the shaking of 33 animals, of them are five kinds of dogs.

It shows that mammals(哺乳动物) can keep stronger by doing their cute little shakes. If they do not shake, animals would have to use up to 20% of their daily energy simply for staying dry. And nearly all furry(皮毛的) mammals shake to help themselves keep dry.

Those animals that are similar to kangaroos shake only part of their body. They usually live in dry places where keeping dry isn't very hard. But not all animals shake in the same way. Also some shake less often than others. Smaller animals seem to shake more quickly. 30 shakes per second for a mouse, while bears, tigers and big dogs only about four.

In an interesting finding, Dickerson and his team have shown that these animals do the job as well as possible. In each example, the animals shake off about 70% of water in a few seconds. This should all be great to people. It takes us not seconds but minutes to dry our hair.