It is a matter of great pleasure to present this book Zoology Paper-I (ZOL-101) for the students of F.Y. B.Sc. (Semester I ) Zoology written accordance with syllabus of Dr.Babasaheb Ambedkar Marathwada University, Aurangabad. You are aware that diversity in animal kingdom does not exists in their shape, and size but also in their species, number and habitat. Starting from the indefinitely deep oceans to snow covered mountain peaks and from the poles of the earth to the equator, the animals inhabit all the places. To study this large groups of animals which are grouped basically in invertebrates and vertebrates a vast number of books, research papers were published worldwide. Marathwada region is still economically backward and majority of students are residing in rural areas where teaching learning in virtual class and availability of reference books in libraries is a major setback in “overall development” of the student. It is very hard for a educational institute from rural areas to purchase reference books as per the number of students. To minimize the problem I decided to publish / written the book according to syllabus so that a student can afford the price and study the subject. The present venture is an attempt to put the available information together in the form of a critical review. As this subject is very vast large number of books have been consulted so the author claims no originality of work. For this, I am deeply grateful to the authors and publishers. The subject matter has been presented in an easy, lucid language and in an systematic manner. After every chapter various types of questions have been added as per the requirement. I feel that this book will fullfil the requirements of the students.