Answer:
Neurulation of organogenesis is the last stage of human development. The gastrula stage forms three germ layers called ectoderm, mesoderm, and endoderm
Excretory as in excretes things..... anus, bladder, etcetera release waste products.
In cells, the vacuole disposes of waste.
Sweat glands secrete, well, sweat, which can also release toxins from the body.
That's about all I can think of at the moment...
In the experiment, the independent variable is the drug amount. Experiment group is given certain amount of drug, control group is not given the drug. The dependent variable is the body fat. I think you means the control is the living environment including food and water.
Factors such as gender of offspring or gender of parents can determine what the offspring gets. I think I'm not exactly sure.