Why does sodium ion have a positive charge but a chloride ion have a negative charge

Which of the following occurs most often in a population when genetic variation and overproduction are present? some organisms have a lower reproductive success than others. some organisms have a higher reproductive success than others. some organisms have no reproductive success. some organisms do not have genetic variation.

Will someone me with this.. specialized cells which perform a particular function form: tissues organs or organism

How does an angiosperm prevent self pollination