Regions with high concentrations of species, especially species that are endangered or threatened, are referred to as .

Babies with very low or very high weight are less likely to survive .

Scientists discover two populations of mice on either side of a major river. the two populations have almost identical genes but the mice from one side cannot breed with mice from the other. this is most likely because

Easy 6th grade work! 100 points! i need fast! compare the parts of a cell and the cell as a whole to another common nonliving system (i.e., a car, a city, describe the parts of a cell and their primary function.