Brain evolution occurred over billions of years. It to develop from a simple neural network in comb jellies etc.
Developmental Biology
How does a Tadpole change into a Frog?
Metamorphosis of the tadpole larva into an adult frog is one of the most striking transformations in all of biology. It transforms a fish-like water breathing, herbivorous tadpole into a tetrapod, amphibious, air-breathing, carnivorous frog.
Sexual Reproduction – An Important Innovation of the Early Protists.
Like the development of the flagellum for movement, sexual reproduction in protists involving meiosis, syngamy and zygote formation appears to have been a major evolutionary innovation by the primitive protists. This innovation has made a profound effect on more complex organisms.
How do cells in Embryo get their Roles to Play?
Cell Specification is a process of distributing roles among different cells of an embryo. This process starts when cells are capable of differentiating autonomously in a neutral environment. Among, three basic modes of cell specification, most of the organisms prefer an amalgam of the two or three modes.