It is a measure of how acidic or basic a body of water is (more specifically of the concentration of hydrogen ions). You use special paper to monitor this. Many organisms cannot survive below 5.

He could not tell why or how the continents were moving.

A star that is fusing hydrogen into helium.

This is always followed by mass extinctions as many species are unable to cope with the new conditions.

This is a waterborne disease caused by a bacteria. To eliminate the bacteria you can filter and boil the water. Moving toilets away from water and washing hands and food with clean water are all good ideas to avoid this nasty disease.

It is a measure of the clarity (or conversely, murkiness) of water. The murkier the water, the less light is able to penetrate the water, and the less oxygen there will be.

Draw a picture of how convection works in the mantle.

A large star that is fusing helium into heavier elements like carbon and oxygen.

A substance has a half life of 20 minutes. After 80 minutes, you have 5g of this substance left. How much did you start with?

Red Shift, Cosmic Background Radiation and the Abundance of Hydrogen in the universe

Nutrients for plants. Can cause harmful algeal blooms when there are too many.

Why do the plates move?

Nebula, Main Sequence, Red Super Giant, Supernova, then either planetary nebula, black hole or neutron star

The time when the entire Earth was covered in ice, in many places up to 3km thick, even at the equator. After this time period, life on Earth exploded in its diversity.

These organisms do not mind warm water or low pH or pollution; this water could be very polluted if these are the only things you find.

An increase in this value could be caused by lack of shade, industrial pollution, runoff from impervious surfaced, etc. It directly impacts dissolved oxygen.

Why is the oldest oceanic crust only 180 million years old if the first oceans formed 3.9 billion years ago?

The DISTANCE light travels in one year. Approximately 5.8 trillion miles.

Its half life is 5370 years. It is often used for dating formerly living organisms. It is only useful for samples younger than 70,000 years

Model the events of the nebular hypothesis with your bodies. You have two minutes to prepare.

It is the most important measurement of water quality, measuring the amount of a certain gas in the water. It is dependent upon nearly every other factor, especially including temperature. As temperature rises, this measurement decreases.

The 5 pieces of evidence Alfred Wegener used for the Continental Drift hypothesis.

When a light source is moving away from a fixed point, the fixed point sees light that has a longer wavelength. This is one of the pieces of evidence for the Big Bang.

Put the following events in order on a small timeline: dinosaurs go extinct, snowball earth, Earth is born, Thea impact makes the Moon, humans rule the Earth, Cambrian explosion of life, first dinosaurs

These are the most sensitive macro invertebrates that require the cleanest water; it is not polluted because pollution kills these organisms.