题型:阅读理解 题类:常考题 难易度:普通
河北省枣强中学2017-2018学年高一下学期英语期末考试试卷
Birds' feathers are some of the most strikingly variable animal characteristics that can be observed by the eyes. The patterns that we see in birds' feathers are made up of combinations of scales, bars, and spots.
We already know why birds have colored feathers. Generally, the color of feathers may protect a bird from being noticed by the enemy in the environment, or it can make a bird more appealing to potential mates by helping them to stand out. These aspects are well known. A greater mystery has been how the patterns are created.
Dr. Ismael Galván and his team studied the color of feathers to see what types of colors were present in birds' complex feather patterns. The study shows they mainly consist of two types of colors: melanin(黑色素), which produce a range of black, grey, brown, and orange color, and carotenoids(类胡萝卜色素), which are used to create brighter colors.
Birds cannot produce carotenoids on their own. For feathers with bright colors, birds must consume food items that contain these paints, and the carotenoids circulate through the blood and to the feather. Melanin, on the other hand, is produced by special cells in the birds' bodies.
The team found that about 32% if the species studied have complex color patterns, with the vast majority of these complex patterns produced by melanin rather than carotenoids. If the birds were artists, they would use carotenoids as a broad brush to produce color patches, with melanin as a detail paint brush to produce more complex designs.
But a few birds are exceptions to this rule: Three bird families do have complex patterns without melanin.
Fitting in fitness
Do you find excuses not to exercise? {#blank#}1{#/blank#} Here are a few ways to get you going.
Do what you love.
The easiest way to fall into the habit of doing exercise is to choose an activity you enjoy — one that doesn't feel like exercise, even though it is. {#blank#}2{#/blank#} If you play to your strengths, you'll find fitness activities you can enjoy for years.
Choose your hour.
Studies have shown that people who work out in the morning are most likely to stick with a routine. By doing exercise before the day starts, they can avoid the last-minute scheduling conflicts. But if you' re not a morning person, choose whatever time works best for you. {#blank#}3{#/blank#}
Call it by another name.
{#blank#}4{#/blank#} If it's something you have to do anyway — like washing the car or planting some bushes in the yard — you'll achieve two goals at once.
Partner up.
Exercise is more fun when you do it with others. {#blank#}5{#/blank#} On days when your motivation is low, you' re more likely to stick with the programme to avoid disappointing your exercise partners. You can also train with an expert. A personal trainer will help you set goals, design a personalized fitness programme, and vary your routine to keep it challenging.
A. Ask yourself: what am I good at? B. Make fitness part of your social routine. C. For example, you can join a running, walking, hiking, biking or tennis club. D. If you're in top form from noon to 1 pm, aim for a lunchtime workout. E. Would you rather do anything else — even sort your socks or clean the fridge? F. If a damp T-shirt is not your idea of a good time, try gentler forms of exercise. G. Substitute some challenging household activity for the standard exercise routine. |
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