Answer:
the branch of mechanics concerned with the motion of objects without reference to the forces which cause the motion.
I think convergent boundary
Answer:
Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).
Hope this helped :)
The answer you are looking for is chitin.
According to a page that I found with info on the subject,
"All arthropods have bodies divided into segments and covered with a hard EXOSKELETON. This tough casing is made of a protein called chitin, which is also found in human fingernails."
https://www.factmonster.com/dk/encyclopedia/nature/arthropods
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