The higher the temperature, the more energy the particles have and the faster they will move and diffuse.  As we move slower we wind up getting hotter or cooler?
cooler

The smaller a population is, the more allele frequencies may drift.  A family that is very small, compared to one that is enormous, will have allele differences that are smaller or greater?
smaller

In erosion, a slower moving stream will only carry smaller particles.  A slow stream is capable of moving boulders or sand?
sand

The larger the animal, the heavier the exoskeleton, making movement more difficult.  Ease of mobility increase or decrease when the animal is decreased in size?

increase