creation of new organisms
reproduction of new cells
When cells are damaged, they usually die. Also, they don't grow, instead, they multiply to form new tissue. Therefore, answers (1) and (3) are not correct.
Answer: radiation i think
First option:
Ecosystem --> population —> community —> organism
Epithelial cells also carry out active transport.
Hope this helps.
~Jurgen
Numerous barriers can prevent sperm from reaching and fertilizing the egg, this can be that the Sperm may be defected, or lack the required number of mitochondria needed to help move the sperm. Also, if sperm had already fertilized the egg, there is a change that takes place to the membrane surrounding the egg preventing further sperm from fertilizing.
