Chapter 5 is the second observational practicum: the ontogenesis. The development of new individual animals is absolutely essential and fundamental for every animal species. It is, therefore, important that students have the opportunity to observe this development in an in-class practicum. During this practicum, adolescents can observe the animalís development, from the first cell division of a fertilized egg until the cycle of growth is complete and results in a mature organism.
The development of the snail is presented as a good and informative example. However, the embryogenesis within the snail egg is difficult to observe. For this reason, it is suggested that the students follow the embryological development of a vertebrate animal as a general model; in the case of this study, the example is an unhatched chick.
The growth of young snails is easy to observe because the process of development into adulthood takes place at a steady rate without major physical changes. With arthropods, like fireflies, the process is more complicated because of the stages of larval growth and the dramatic metamorphosis that takes places as the animal becomes an adult.


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Chapter 6