1 - The visible differences between male and ........... that appear during the life are called ........... ............
2. During the breeding period, the male and female have attitudes and perform actions which together constitute the reproductive ................. This latter is translated by a change of .............. in fish, ............... in frog, and ............. in rooster.
3 - The partners, approach often leads to a .............. This approach is realized by means of visual, olfactory or ................ communication.
4. Certain .............. animals do not mate, yet their reproduction is ensured. Their eggs are released into the ................ and covered by .............. and .................. occurs which results in the formation of eggs.