血液流经肾小球毛细血管时发生了气体交换，由动脉血变成静脉血．______．
动脉血是氧气与血红蛋白结合后，含氧气较多，含二氧化碳较少，颜色鲜红的血液；静脉血是氧气与血红蛋白分离，含氧气较少，颜色暗红的血液．动脉血、静脉血的区别主要是含氧量的高低以及颜色是鲜红还是暗红．血液由入球小动脉流入肾小球，经肾小球滤过后的血液，由出球小动脉流出，仍然是动脉血．
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| In the deserts of North Africa and Saudi Arabia lives the smallest of all foxes with the largest of ears. This animal is the fennec fox. Fennec foxes have ears that are 5 to 6 inches long. That's big for an animal that weighs less than four pounds. Their ears help shed (去除) body heat. And, as you may have guessed, they also provide great hearing. It's also interesting to think about the hair of fennec foxes. Why would a fox that lives in the desert need a thick, fur coat? Actually, the desert isn't always warm. During the nighttime, a desert can be terribly cold! A fennec fox's fur keeps them warm during those desert nights. They also have long bushy tails that they use as a blanket. And the hair on their feet protects them from the hot sand in the daytime. Fennec foxes live in small communities of dens (兽穴).They spend most of the day sleeping in their dens, out of the hot sun. Then, when night comes, they come out in search of food. In addition to their great hearing, fennecs also use their great sense of smell and big eyes to track down dinner. Like other foxes, fennecs are omnivores. This means they eat both meat and plants. They like eating birds, eggs, insects, snails, fruit and leaves best. Fennec fox mothers have one to five babies at a time. The lifespan of a fennec fox is 10 to 12 years. The cream coloration of fennec foxes help them blend into their desert habitat. Still, they have to watch out for predators (捕食性动物). These include caracals ( a type of wild cat ) , jackals, eagle owls, hyenas and humans. Humans catch them for their fur and to sell as pets. | |
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