问题 问答题 简答题

举例列举鱼类呼吸器官的种类。

答案

参考答案:

(1)鳃

多数鱼类的鳃除具有呼吸功能外,还具有排泄含氮废物及渗透压调节功能。一般而言,具有辅助呼吸器官的鱼类,其鳃的作用往往有不同程度的退化。

(2)皮肤

象鲤、鲫、鲶、鳗鲡等,它们的皮肤呼吸容量大约占总呼吸量的17~32%,皮肤的呼吸机能在于表皮之下分布着许多微血管,而且皮肤薄,鳞片退化,表皮是由单层鳞状上皮细胞构成,通透性强,以便与外界进行充分的气体交换。

(3)鳃上器官

鳃上器官是鳃弓及其附近的特殊结构,是一种气呼吸器官。攀鲈、尖头鱼的鳃上器官是第一鳃弓的上鳃骨及咽鳃骨扩大特化为迷路的构造,形成“皱褶”的迷路囊,外观呈花朵状或木耳状,也是气呼吸器官的一种。

(4)口腔咽粘膜

鲤科鱼类口腔黏膜布满了微血管,能够进行气体交换。当水中缺氧时,会出现浮头现象,鱼类就靠近水面,以口伸出水面吞咽空气,通过口咽黏膜摄取氧气,以弥补鳃呼吸的不足。

(5)肠道

泥鳅、条鳅和花鳅等就具有肠呼吸的机能,它们的肠道的前半段具有消化机能,肠的后段经常没有食物贮留,肠壁很薄,上皮细胞下面分布着丰富的微血管,且具有粘液细胞,能分泌粘液以包裹消化残渣,使粪便很快地通过具有呼吸机能的部分,不致损伤肠道。

(6)气鳔(肺)

多鳍鱼类和肺鱼以及弓鳍鱼、雀鳝的鳔变态为“肺”,作为一种辅助呼吸器官。

完形填空
If your family is like many in the United States, unloading the week’s groceries includes hauling a case or two of bottled water into your home. On your way to a soccer game or activity, it’s easy to grab a cold one right out of the fridge, right?
But all those plastic bottles use a lot of fossil fuels and pollute the environment. In fact, Americans buy more bottled water than any other nation in the world, adding 29 billion water bottles a year to the problem. In order to make all these bottles, manufacturers use 17 million barrels of crude oil. That’s enough oil to keep a million cars going for twelve months.
Imagine a water bottle filled a quarter of the way up with oil. That’s about how much oil was needed to produce the bottle.
So why don’t more people drink water straight from the kitchen faucet? Some people drink bottled water because they think it is better for them than water out of the tap, but that’s not true. In the United States, local governments make sure water from the faucet is safe. There is also growing concern that chemicals in the bottles themselves may leach into the water.
People love the convenience of bottled water. But maybe if they realized the problems it causes, they would try drinking from a glass at home or carrying water in a refillable steel container instead of plastic.
Plastic bottle recycling can help—instead of going out with the trash, plastic bottles can be turned into items like carpeting or cozy fleece clothing.
Unfortunately, for every six water bottles we use, only one makes it to the recycling bin. The rest are sent to landfills. Or, even worse, they end up as trash on the land and in rivers, lakes, and the ocean. Plastic bottles take many hundreds of years to disintegrate.
Water is good for you, so keep drinking it. But think about how often you use water bottles, and see if you can make a change.
Betty McLaughlin, who runs an organization called the Container Recycling Institute, says we should try using fewer bottles: “If you take one to school in your lunch, don’t throw it away—bring it home and refill it from the tap for the next day. Keep track of how many times you refill a bottle before you recycle it.”
And yes, you can make a difference. Remember this: Recycling one plastic bottle can save enough energy to power a 60-watt light bulb for six hours.
Title
Drinking Water: Bottled or From the Tap?
小题1:      situation
Americans consume the 小题2:     bottled water in the world.
小题3:       for people’s preference for bottled water
Bottled water is of higher小题4:      .
It’s more 小题5:         for people to drink bottled water.
Problems with bottled water
The 小题6:       of plastic bottles use lots of fossil fuels.
Water bottles we use cause serious 小题7:       .
小题8:     the passage offers
Use bottles 小题9:       of glass or steel.
Use a refillable plastic bottle as many times as 小题10:     before recycling.
 
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