How does a human end up with an extra chromosome?

How is a scientific hypothesis best evaluated?

When using a hammer, a person makes use only of the bones and muscles in his/her arm

Tropism describes a virus’s affinity for specific tissues: A) True B) False

During which stage of meiosis do homologous chromosome pairs line up in the middle of the cell?

Ecological relationship

Why does air at 75% relative humidity and 30°C make your skin feel stickier than air at 75% relative humidity at 10°C? A. Warm air rises while cold air falls. B. The warmer air contains less water vapor per unit of volume. C.

When the two solutions are mixed, a clear solution with white powder at the bottom results., What has caused this change?

What receptor type is exemplified opening a channel to get sodium into the cell

What is the total amount of tissue of all organisms in a food chain called?

If an entire stack of rock layers has been folded, which of these would have occurred most recently?