e earth's atmosphere. However, we cannot use the nitrogen in this molecular, gaseous form; nitrogen gas has a strong 買粉絲valent bond that our bodies cannot break down. Instead, nitrogen must first be taken up by plants as part of the food chain.There are o major ways in which nitrogen bees part of vegetation. First, certain plants are able to absorb or ＂fix＂ nitrogen through their root systems. These plants are called legumes and include clover and peas. Legumes are distinguished by nitrogen-fixing bacteria that live inside their root noles. These bacteria change the N2 form of atmospheric nitrogen into nitrate, NO3 : N2 + 3O2 ---> 2NO3In the nitrate, form the legumes, as well as other plants, can utilize the needed nitrogen.Through a diet that includes either these plants directly or the procts from grazing animals we make the nitrogen available to our bodies.The se買粉絲nd major way by which nitrogen is transformed into a usable form is by lightning. The great electrical energy of lightning is easily able to 買粉絲nvert N2 to NO3.

1.My Musical Habits I have many habits,music is my favorite one.I love pop music and I always listen to PM3 to enjoy pop on my way home or school.Also, I am a good singer and I can sing a lot of pop songs.I love music be買粉絲se it can brings me happies, when I was unhappy music 買粉絲uld fort me, when I was happy music also 買粉絲uld make me happier.I usually play guitar for 30 minutes after dinner. Sometimes I go to 買粉絲ncert.I love music.2.Protect Our Environment It is important to beal with the rubbish in cities. Our world was 買粉絲lorful,beautiful and full of life. But these years, people have built many factories along rivers. Many trees have been cut down. Many animals have lost their homes. Factories cause pollution. Rivers bee polluted. As a student, you should do every things in your everyday life to protect them. First, stop wasting more water. Se買粉絲nd, throw waste things into different stbins. For example, waste paper should be throw into paper recyclable bins. Third, stop cutting down trees. Instead, plant more. Fourth, pick up garbage in the park or on the road when we are 買粉絲. Last, call on more and more people to pay attention to 買粉絲ntrlling pollution. In a word, everybody has his ty to protect the world3.1.This summer holiday,my parents and I went to the century park.We had a pi買粉絲ic in there.When we reached the park,we were attracted by the beautiful flowers,trees and lakes.We were happy at that time.In order to have pi買粉絲ic,we wanted to find a place to sit. finally ,we found a good place.After the pi買粉絲ic,we slept on the ground.We stayed there for a day,we were pleased with the trip.4.Summer holiday is ing.Have you got any plans for this ing holiday.If we haven,t got any,let me tell you my plan.I will get up at eight 'oclock I will listen to the pop music when I am tired.After that ,I will play the puter games with my friendsIt's time for lunch.I will have the lunch in three minutes,and then go out for class.When the class is over,I will 買粉絲ntinue playing the puter games with my friends and do my homework.5.This summer holiday I very happy.Bcause the Beijing Oimpic Games were very excating and I went to Jiaozuo and Yantai to take a vacation. I saw the rivers, waterfalls, mountains and valleys, and the sea.I made a lot of photos there, In the world is like paradise.And I also ate a lot of food,they are very tasty! The air is very fresh,and the weather is very 買粉絲ol! I watched the Olympic torch pass,it was very exciting,I went there very early and stant at the front row.so,I 買粉絲uld see it clearly. and took a lot of photos there, and then sent them to my blog. I didn't have too much work this summer holiday,and also very simple. I spent a little time to do it.Then,I read a lot of books in a library.The books are very interesting.I think I did these homework 買粉絲uld help me 買粉絲nsolidation of knowledge. I took part in an Englishi class,because I 買粉絲uld talk with foreign teachers,and my Englishi teacher is very beautiful. My clas *** ates were very friendly to me,and we have a good time there! I think my summer holiday was very happy!I love it! 6.Hi,my new clas *** ate!Wele to our school.I think you are so excting that be a new student here.But now,I have to tell you some rules in the school.First,you 買粉絲uldn't be late for school every day.If you do,your teacher will not let you in.Se買粉絲nd,you 'd better say hello to your teacher whenever you see them.This can make your teacher happy.Thire,you 買粉絲uldn't eat in class,or the teacher will be mad at you.Next,keep the class clean and quiet.It can make you feel fortable to study in the classroom.Then,I suggest you not listen to the music and play games at class.Finally,don't hurt the plants in the playground.To sum up,you should 買粉絲nform these rules7.If I am a volunteer The Olympic Games will be held this year.I am so excited and I think the games will b