IB Biology Sub-topic A1.1 Definitions

The hypothesis that Earth's water was delivered by water-rich asteroids that collided with the Earth during the early stages of its formation

A liquid absorbing heat to turn into a gas. Evaporation can occur randomly from a liquid's surface. Synonym for boiling and vaporization. 

Large planets composed mostly of gases such as hydrogen and helium, found in the outer parts of the Solar System (e.g., Jupiter, Saturn, Uranus, Neptune)

The region around a star where conditions are just right for liquid water to exist on a planet's surface, potentially allowing for life

A rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, from which planets are formed

A young star still in the process of forming, gathering mass from its parent molecular cloud.

Streams of charged particles released from the upper atmosphere of the Sun, which can influence planetary atmospheres and magnetic fields