Brain in all organisms can be simply defined as a mass of nerve tissue that integrates sensory information and directs motor responses and in higher organisms, it is also the center of learning. The evolution of the brain occurred over a time scale of 3.5 billion years. It transformed from simple nerve conduction through ion channels in single-celled bacteria into a complex human brain made up of billions of cells. Continue reading Evolution of Brain – Where did our brains come from?
A freshly hatched tadpole larva has a limbless body divide into an ovoid head, a short trunk, and a slender tail. At this stage, there is no mouth and as a result, it cannot take anything from outside. Most of the nutrition is provided by the yolk material. The exchange of gases takes place in three pairs of highly vascular and feathery external gills. Continue reading How does a Tadpole change into a Frog?
The Kingdom Protista includes diverse kinds of predominantly water-dwelling unicellular eukaryotic microorganism. Protists, like Monerans, have an immense reproductive potential. In an optimal environment, they may reproduce several times a day. This is mainly by asexual reproduction, using the process of mitosis. However, they also reproduce sexually. Continue reading Sexual Reproduction – An Important Innovation of the Early Protists.
The cells of an embryo get their roles when they are capable of differentiating autonomously in a neutral environment such as a petri dish or test tube. (the environment is neutral with respect to the development pathway.) This process of giving different roles to embryonic cells is called Cell Specification. Continue reading How do cells in Embryo get their Roles to Play?