Re: have a problem in academic IELTS writing
Remember that you have to have a space after your punctuation mark and that the pronoun "I" is always capitalized. It is very hard for me to look past these types of mistakes to the content of what you write.
No, you do not simply link related words. You have to have a plan.
It is important to properly test drugs before they are used widely to make sure they don't cause harm.
-- Give an example.
Scientists use animals to make sure things are safe for humans. (I'm pretty sure they have never tested drugs on robots!) This is good for the humans, but bad for the animals.
When animal testing is necessary, humans have a responsibilty to be humane - to ensure the test is needed, that it will lead to useful results, and that the experiments will cause as little pain and suffering as possible.
You have to come up with your three main ideas first (mine are just suggestions), and then figure out how to build your story.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.