We are all part of a large ecosystem in which humans as well as each and every living organisms are considered to be entities of it. If any member of a ecosystem fail to function( one major reason of which is extinction) the whole system become imbalanced. So, it is out utmost, duty to keep the ecosystem balanced at all cost to save the environment we live in.
Nature has it's own unique way of balancing itself. If we consider the food chain, all the member's are dependent on other animals in way or other. If any one of them goes missing from the food chain the whole system breaks down. For example, Lets consider, in a forest, because of wild fire plants on which deer feeds on goes extinct. It leads to the decimation of deer because of food shortage and furthermore tigers or lions also faces food shortage and may also lead to their reduction of their number and this goes beyond weakening whole skeleton of the system. Therefore, it is vital to always keep the number of these animals in a definite range. With technological progression and burgeoning human needs we are the main reasons behind the extinction of most animals directly or indirectly to meet our requirements. Doing so, we are also destroying the food chain creating a huge natural imbalance. So, to keep the nature in a manageable shape we should protect animals from extinction at any cost.
Animals are great sources to make scientific advancement. For example, consider birds as the main factor behind the development modern Aero planes. From the study of the techniques used by the birds the fly up on the sky made it possible to today's manufacture of modern Aero planes. Like this, many other factors behind the many technological, social, economic development often there are rigorous studies made on animals based on their activities, thinking or way of life. So, extinction of any animals will hinder the progress of our life as well.
Furthermore, animals act as great economic factor too. People travel from places to visit and sight different rare animals only found in it endemics which facilitates tourism, culture and economy of a region. For, example polar bear of the great Antarctica can be mentioned. Many people from all over the world travel to Antarctica just to get sight of the polar bear which is unfortunately on the verge of it's extinction because of global warming. If these polar bears go extinct, the trend of visiting Antarctica for polar bear sight will also be stopped resulting in great economy loss.
In conclusion, it is undeniable that, animals are great natural resources and many animals are going extinct these days due to undeliberate actions of us, human beings. If these animals are not protected from it's extinction we will be the most sufferers at the end. So, it is our utmost duty to protect these animals at any cost.