PROBLEM 4 Hoiv Do the More Cojiiplex Animals 



Reproduce? 



Fig. 368 What distinguishing secondary sexual characteristics do you see in these 

 deer? (Canadian travel bureau) 



Male and female. Just as in the more 

 complex animals there are special organs 

 of digestion and circulation, so there are 

 special organs of reproduction. The male 

 reproductive organs, called sperjnaries or 

 testes (singular, testis), produce the male 

 gametes or sperms; the female organs, 

 called ovaries, produce the female gam- 

 etes or ova (eggs). In a few kinds of in- 

 vertebrates, earthworms for example, 

 both male and female organs are in the 

 same individual. But in most animals the 

 orfi^ans are in seoarate individuals. 



In some kinds of animals it is difficult 

 to distingruish males from females with- 

 out cutting the animals open to examine 

 the reproductive organs. Other animals 

 develop secondary sex characteristics 

 which distinguish the two sexes. For ex- 

 ample, in some species of birds the feath- 

 ers of the male are much more brightly 

 colored. The striking differences be- 

 tween males and females in some wild 

 bird species make an interesting study. 

 See Exercise i. Frequently the males are 

 larger and more powerful than females. 



