The aspect of his experimental process which is most important for obtaining reliable results is repeating his data collection many times.
Epithelial, muscle, connective, nerve and blood.
LOCAL ENVIRONMENT ISSUE:
People dump a lot of trash in the sea, and the sea creatures living there goes through a lot of trouble to live with all the muck getting in them. Of course, don't write it like that in your assignment - you'll get told off for the straight forwardness.
Is an organism in its earliest stage of development. In humans, this is the stuff and defined as the developing organism from the fourth day after fertilization to end of the week. After that unborn baby is usually referred to as the fetus.