A substance that enters Earth's cycles and does harm to living things is

a. a pollutant.

b. hydrogen.

c. freshwater.

d. oxygen.

What is a quantitative observation? A. An observation that proves the hypothesis is wrong. B. An observation about the number or amount of something. C. An observation about the color, shape, size, or condition of something. D.

An abiotic factor affecting the behavior and survival of birds is the A) length of daylight. B) number of carnivores. C) presence of harmful bacteria. D) size of the insect population.

What is the main reason that species are being lost to extention?

Chemicals which serve as signals from one neural cell to another neural cell are called

How is nitrogen from the atmosphere, the aiotic part of the ecosystem, converted into the biotic part of the ecosystem n organisms

If a molecule is too large to slip through the spaces in the membrane, how will that molecule enter the cell? A. The molecule will shrink so that it can fit in the spaces. B. The molecule will move through a protein channel. C.

What symbol indicates the cardinal directions

Which will have a better chance of surviving a major change in the environment where it lives: A) A bacteria strain with only twenty minutes between generations B) A large mammal (like bears) with decades between generations Explain your choice

What are the three-letter "words"of mRNA

What are the two ways that carbon enters into the atmosphere?