Hello!

Which books to read entirely depends upon the syllabus of subjects ,As you have not mentioned the particular syllabus , I would  speculate about the syllabus and hence I recommend these specific books accordingly.

Invertebrates: R.L. Kotpal or P.S Verma

Vertebrates: R.L Kotpal (You can get P.S Verma if Kotpal is not available)

Ethology(Animal behaviour): V.K Aggarwal(S.chand)

Ecology: PD Sharma

Evolution: Vir Bala Rastogi

College Botany by S.Chand

Animal behaviour: V.K Aggarwal

physiology: principles of anatomy and physiology by tortora

Genetics:concept of genetics by klug and Cummings

molecular biology and cell biology: cell and molecular biology by karp

biochemistry:lehninger

biotechnology:text book of biotechnology by dr. R. C. Dubey

comparative anatomy: kardong

embryolgy:A.k berry

economic zoology:jaiswal

immunology: kuby

microbiology: Prescott

The pdfs of most of above enlisted books are also available.

Hope this helps you!