Evolution of money. (integrated essay) Please check it up

[Scientist_A]

In the listening passage the professor mentions that before the using of coins and money as a mean of exchange people used barter. They were changing what they grew with their neighbors. Of course it was not convenient for them because there was not a common measurement. In the reading passage it is demonstrated that people began to use coins as a means of exchange and purchase a long time ago. They did it because they needed something that has a fixed value to make their purchase. Coins were made of metals especially gold and silver. They preferred metals because they were portable, long-lasted and easy to identify. But there were some disadvantages of using coins. They could be manipulated by people. They could change the material of coins without any noticeable change of shape and size of them.
Because of some disadvantages of coins people began to use paper money in the form of bank notes, and then they used plastic cards. This was the next step of evolution of money. From that time banks began to issue a paper receipt to their customers and they began to exchange coins and precious metals with them. It was also a safety way of keeping precious metals. In the listening lecture the professor underlines that it was the first time The Diamond Company issued plastic cards for their customers in 1951. But they were in a limited quantity only they were for 200 customers. And these cards could be used only in 27 restaurants. But, after some time banks began to issue debit cards which was very practical. Customers could spend their money directly and safely from their bank account with these cards.

TOEFL listening discussions: How does Dr Beech characterize the assistantship?

[Sddk]

Dear buddy firstly i have to express that i not a native speaker. İ read your assay and i certanly understood what you try to explain but you have to obey some rule for write a appropriate essay for example you must suggest a thesis statemen for the reader. There are some rule like this if you search and use them in your assey you can reach a good level on english language

[Luschen]

Hi Sddk, I would agree with you if this was an essay, but I think it is a integrated writing exercise where the writer tries to summarize and compare a written article and a spoken lecture.

[Luschen]

Hi, very good writing. I got confused with the "from that time" sentence - could you rephrase it. If you are interested in this topic and want a short listening exercise, the following short radio broadcast is very interesting:

http://www.npr.org/blogs/money/2011/02/15/131430755/a-chemist-explains-why-gold-beat-out-lithium-osmium-einsteinium

[Scientist_A]

Thank both you.
Luschen I am from the begining of using paper money there. may be I did not use the relevant way to explain my view.

Thank again for your correction.