1. Five human activities are listed below. 1. Raising cattle
2. Driving a gasoline powered car
3. Using a natural gas fireplace
4. Walking
5. Swimming in a lake
Which of the above activities could contribute to the greenhouse effect?
A) 1 and 2 only
B) 1, 2 and 3
C) 2 and 3 only
D) 4 and 5 only

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?

In sheep, the allele for belly fur (a) is dominant to the allele for no belly fur (a). a mother with the genotype aa and a father with the genotype aa produce an offspring.

Glands that the body deal with stress and respond to emergencies.