Question

speech competition on 'Ozone Layer is
important for our survival.'

Answer 1

Hey cool, it is easy. First greet all the who are gathered there.
Then, start speaking this. 
Ozone layer is important for survival because ozone layer protects us from the harmful ultraviolet rays of the sun. Hence, it is important for our survival. The ozone gets depleted by the excessive carbon-dioxide and other green house gases emissions.
Then, u can say a story of a man who even uses motor bikes to go to a nearby shop, and pollutes the environment; and then you can say the statics of greenhouse gases emissions, and conclude by saying that,
Ozone layer is important for our survival. But, due to the excessive pollution, the ozone layer is getting depleted, which may lead to global warming. So, it is our duty to protect our defender. 
Then say, Thank you for giving me this opportunity to speak. 
Hope this will help you Baneshibishan.

Answer 2

Good morning/good evening to one and all presented here.Respected chief guests. Management Community of ______ and teachers.And hello to all my dear colleagues.
Today I am here, in front of you to give a speech and topic of my speech is 'Ozone Layer is important for our survival.'

What is ozone layer→ozone layer is a layer of OZONE high above the earth's surface that helps to protect the earth from harmful RADIATION from the sun.It is also known as OZONE SHIELD and located in the stratosphere layer of the atmosphere of earth 
Why Ozone is important for us→Ozone Layer is important as it prevents the Ultraviolet (UV) Rays to come towards the earth by absorbing them.