Published in 1859, Charles Darwin’s On the Origin of Species made a number of brave claims about the nature of evolution—including the suggestion that an animal species with greater diversity in its line will produce more subspecies too. This assumption is not as obvious as you might think at first. And it was finally found to be true for birds only a couple of years ago. Now, researchers from the University of Cambridge in the UK have shown that Darwin was right on this point for mammals (哺乳动物), too.

Apart from being an important contribution to our understanding of evolution in general, the findings could also be useful in ongoing conservation efforts—helping experts to figure out which species need to be protected in order to ensure their survival.

“My research investigating the relationship between species and the variety of subspecies proves that subspecies play a vital role in long term evolutionary dynamics and in future evolution of species,” says biological anthropologist Laura van Holstein. There are three subspecies of northern giraffe, for example, and 45 subspecies of the red fox—the highest in the animal kingdom. 36 different species of wild cats have been found and most of these are further divided into subspecies. Human beings, on the other hand, don’t have any subspecies.

To test Darwin’s assumption, van Holstein looked at a huge database of animal classifications, analysing the collected knowledge we have about mammal species and subspecies to look for patterns. The data showed that habitat (land versus sea, for example) plays an important role in subspecies’ form and increase. The findings show that those living in the sea, or spending a lot of time in the air are less affected by physical boundaries like mountains.

The discoveries on subspecies habitat are particularly significant when it comes to conservation, because the habitats of so many animals are under threat from climate change and human activity, and these findings indicate that our actions are really having an effect on the process of evolution.

People who are good at growing plants know that it's possible to plant what seems to be a lifeless stick and produce a tree or other kinds of plants. The stick is really what is called a hardwood cutting. From these cuttings, trees, vines(藤蔓) except pine trees can grow. They are called hardwood because the pieces are woody rather than leafy.

Gardeners can expect close to 100 percent success with plants such as grape, gooseberry, privet, spiraea and honeysuckle. However, this method does not work with apple, maple or oak trees, for example. Because they lack leaves, hardwood cuttings are less perishable(易腐烂的) than softwood cuttings.

If you want to develop a green thumb-or get really good at growing plants-start your effort with hardwood cuttings of willow. Willow trees often spread from branches that take root on top of the ground through the winter. Most other plants demand a little more attention.

Autumn is a good time to start hardwood cuttings. First, choose some shoots(新枝) that grew during the most recent growing season-the youngest shoots. Cut the shoots to a length of about 15 centimeters. Make sure you remember which end was up - the end that is farther from the root. Experts do this by cutting the bottoms off directly and the tops at an angle so they avoid mistakes during planting. Then, place the bottom of each cutting into some well-drained(排水良好的) soil.

If you have to plant in the spring, the cuttings need to be kept cool and wet through the winter. The traditional method is to place the cuttings together and bury them upside down in the soil. This lets the bottoms of the cuttings be first to feel the warming effects of spring sun on the ground. Put the cuttings in a closed plastic bag, put a wet paper towel around the bag, and then put the whole thing in another plastic bag.

I used to think ants knew what they were doing. The ones marching across my kitchen counter looked so confident; I just figured they had a plan, knew where they were going and what needed to be done. How else could ants organize highways, build elaborate nests, launch impressive attacks, and do all the other things ants do?

Turns out I was wrong. Ants aren’t clever little engineers, architects, or soldiers after all --- at least not as individuals. When it comes to deciding what to do next, most ants don’t have a clue. “If you watch an ant try to accomplish something, you’ll be impressed by how awkward it is,” says Deborah M. Gordon, a biologist at Stanford University.

“Ants aren’t smart,” Gordon says. “Ant colonies are.” A colony can solve problems unthinkable for individual ants, such as finding the shortest path to the best food source, assigning workers to different tasks, or defending a territory from neighbors. As individuals, ants might be tiny dummies, but as colonies they respond quickly and effectively to their environment. They do it with something called collective intelligence.

Where this intelligence comes from raises an essential question in nature: How do the simple actions of individual ants add up to the complex behavior of a group? How do hundreds of honey-bees make a critical decision about their hive (蜂巢)if many of them disagree? The collective abilities of such animals --- one of which grasps the big picture, but each of which contributes to the group’s success --- seem miraculous even to the biologists who know them best. Yet during the past few decades, researchers have come up with fascinating insights.