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The development of frog is divided into two phases: 1. Pre-natal or Embryonic development ·   It is the development that takes place inside the egg or inside the womb of the mother up to the gastrula stage from the zygote. 2. Post-natal or Organogenesis ·   In this period, development from the birth of an organism to death is studied or the formation of organs from three germinal layers. a. Breeding: ·  Breeding takes place during the rainy season, in water. ·  Male frog croaks (mating call) by staying at shallow water region at night time to attract females.  ·   Many female frogs attract towards a male frog and male frog mounts over a female frog. ·  This Sexual embracing condition is called  amplexus or pseudocopulation . ·   Then the females lay the eggs in water and the male also releases the sperms. b. Ovulation: ·  It is a process of release of secondary oocytes from the ovary to the body cavity. c. Spawning: ·  When the...

·  Embryology or Developmental Biology refers to the series of changes from a zygote to a complete adult. Some Important Terminology to Remember ·  Blastogenesis : It is a process of developing an individual from an asexual reproductive body. ·  Embryogenesis: The development of the new individual from fertilized egg or zygote. ·  Paedogamy: It is the sexual reproduction of animals in larval conditions. ·  Oviparous: They are egg Laying animals. ·   Their embryonic development occurs outside the body.  Examples: insects, fish, amphibians, reptiles, birds etc. ·  Ovoviviparous: Animals lay eggs inside their body and its development also takes place inside the maternal body but is not supplied by maternal nourishment.  Example: Protherian mammals. ·  Viviparous: Animal which gives direct birth to the young ones so developing embryo derives nutrients from the maternal body.  Example: Eutherian mammals. ·  Teratolo...

Spermatogenesis ·  Spermatogenesis is the process of formation of haploid, microscopic and functional male gametes, spermatozoa from spermatogonia present in testes. ·  It occurs in the seminiferous tubules of the testis and consists of the following phases. (i) Multiplication phase: ·  It includes rapid mitosis of primordial germ cells present in the germinal epithelium of seminiferous tubules. ·  As a result, a large number of diploid and round sperm mother cells, called spermatogonia, are formed. (ii) Growth phase: ·  Each spermatogonium increases in size (about twice) due to the accumulation of nutritive materials in the cytoplasm and the replication of DNA and forming a diploid primary spermatocyte. ·  This phase is of much shorter duration than in oogenesis. (iii) Maturation phase: ·  Each primary spermatocyte by meiosis, I and II, produces four spermatids. ·  Spermatids separate out in spermiogenesis. iv) Spermiogenesis...