13. water is a polar molecule because
a. it contains two hydrogen atoms for each oxygen atom.
b. it has a charge.
c. different parts of the molecule have slightly different charges.
d. it does not have a charge.

The leopard frog and the pickerel frog are two closely related species. in areas where their ranges overlap, the frogs will remain separate species if they

African penguins, which inhabit the coasts of southern africa, were classified as an endangered species in 2010. two significant threats to their survival are ecosystem damage from oil spills and overfishing by humans. overfishing depletes the food supply of african penguins. the best method to reduce the threat of overfishing would be to . the risk of oil spills could be reduced by increasing the use of , which should oil consumption. if an oil spill does occur, could be used to remove the oil so the ecosystem may more quickly recover.

Dna. we have heard that we are a product of our dna. but where is it? how do we "get" our dna? it is passed to us, from our parents, but in what form? several vocabulary words associated with inheritance are used interchangeably and sometimes, incorrectly. let's see if you can clear this up for someone just learning about inheritance and cell structure.