Nowadays animal experiments are widely used to develop new medicines and to test other products

First of all,it is saidIt is believed that all experiments are done for welfare of humanity(this is bad phrase) . There are different types of illnesses in the world, and scientists try to treat them(them refer to what?, make it clearer) . They invent new types of drugs. However, those drugs firstly must be assayed. Certainly, in this case more preferable(where is your pronoun here) would be experimenting on animals. For example, in early days of medical science most inventions like cures have been tested on people(I suggest you to rewrite such a sentence and make it clear) . Unfortunately, it was harmful not only for one generation, but also affected several consecutive generations. Undoubtedly, it is better testing on animals rather than(I suggest you to write your grammar book as to how to use rather than) injure lots of people.

On the other hand, some experiments are too cruel and unimportant. Some people are blinded with(this is not collocate) their ambitions. In laboratories animals(this is a bad phrase, can you rewrite this?) are kept in terrible conditions instead of gratefulness for their efforts and lives. Moreover, not all experiments are necessary. For instance, testing perfumeries on animals might be very harmful or even lethal for them. Obviously, animals also are alive creatures of the mother wild. Furthermore, all cures cannot be tested on animals. Perhaps organisms of some animals are alike, but not at all. One particular drug may be harmful or has several by-effects for people, but on animals it could not be recognized. (I think your example is not straight to the point)

In conclusion, experiments on animals can be in favor only for well-being of human beings(it is not easy to follow you flow sentence) . However, overdoing on tests and useless experiments should be banned.( I think you need to add a fear, suggestion, prediction in the last sentence of your conclusion. it is useful to generalize your conclusion)

In our days most medical and other products are tested on animals. Some people dispute that it is not right and desire to prohibit this method. Although others approve these experiments and think that this is advantageous for humankind. In the following paragraphs I shall discuss both opinions with benefits and drawbacksI suggest you to make clear thesis, if you make the sentece like that you can get some trouble when you arranged the conclution, for example I strongly belive that using animal for experimenting is not right .... .

In our days
( I know you want to express that the general fact that happens in this day and age; however, I think that it will be inappropriate if you use for the beginning of your writing, commonly known as background or hook. I have discussed with native who work as an IELTS examiner and He points out that it is more likely to be a bullshit idea when student use nowadays, today, and in our days)