Most migratory birds gather in one area and then migrate in large groups rather than individually. This behaviour is a result of evolution. Which of the following is the best scientific explanation for the evolution of this behaviour in most migratory birds? *

Background: Bird migration is a seasonal large-scale movement of birds to and from their breeding grounds. Every year volunteers count migrating birds at specific locations. Scientists capture some of the birds and tag their legs with a combination of coloured rings and flags. The scientists use sightings of tagged birds together with volunteers' counts to determine the migratory routes of birds.

As a meteoroid approaches Earth and its atmosphere, it speeds up. Why does this happen? *

Background: Rocks in space that enter Earth's atmosphere are called meteoroids. Meteoroids heat up, and glow as they fall through Earth's atmosphere. Most meteoroids burn up before they hit Earth's surface. When a meteoroid hits Earth it can make a hole called a crater.

What is the effect of a planet's atmosphere on the number of craters on a planet's surface? *

The thicker a planet's atmosphere is, the _(a)_ craters its surface will have because _(b)_ meteoroids will burn up in the atmosphere.

Researchers have noticed that the water that is being returned to the ocean contains a large quantity of nutrients. Adding which of the following to the farm will reduce this problem? *


Which procedure would make fish farming more sustainable? *