Ovipary – is the development of embryo inside the egg but outside the body of female. The phenomenon occurs in egg laying animals.
Vivipary – is the fertilization and development of embryo occurring inside the body of female. Placenta is present. Young ones are directly given birth. E.g. Metatherian and Eutherian mammals.
Ovovivipary – female allows the development of embryo inside the body but do not provide any other extra nourishment as the placenta is absent. E.g. shark, rattle snake, marsupials etc.
Sex(Some Terms):

  1. Monoecious or bisexual or hermaphrodite – one organism consists of both sexes in it. E.g. flatworms, annelids
  2. Dioecious or unisexual – Each organism either male or female sex. E.g. Roundworms, arthropords etc.
  3. Sexual dimorphism – male and female animals can be distinguished morphologically (externally). E.g. lion &lioness, man & women etc.
  4. Protoandry – Male reproductive organs mature before female organs
  5. Protogyany – Female reproductive organs mature earlier than male ones.


  1. Direct:
    In this, there is no larval stage and newly born young resembles the adult.
  2. Indirect:
    Young ones quite differ from adult ones and called nymphs or larvae. They lead independent life and undergo metamorphosis to become an adult.

Sinuses – cavity filled with blood
Book lung – is a primitive, leaf like & flatted type of lung found in class arachnida of phylum arthropoda. E.g. in spider, scorpion etc.
Malphagian Extretin in mosquito, coaxial glands (attached to leg and body in arthropods).