1) Explain the three kinds of the mammals based upon how their young grows. Beginning with the fertilization, explain the main stages of the animal development. Provide a brief, simplified explaination of each stage.

2) Describe functions of the sensory neurons, interneurons, and the motor neurons.

a) Explain briefly the functions of sensory neurons, inter-neurons, and motor neurons in nervous system.

b) In the context of science of ecology and concept of niche specialization, explain in brief the competitive exclusion principle and resource portioning.