Introducing 

Prezi AI.

Your new presentation assistant.

Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.

Loading…
Transcript

Conditions for Life on Earth - Lesson 1: How Did The Conditions for Life Come About?

http://tiny.cc/bhnq8y

Earth...

1

List as many features that you can think of that are responsible for life being able to start on Earth...

We think life requires...

2

  • Liquid water.

  • Carbon.

  • Protection from UV radiation.

  • Energy.

#1

For water to exist as a liquid, it requires certain temperatures and atmospheric pressures.

Molecules larger than H and He only exist in area of the universe where stars have passed through at least one life-cycle, producing elements through fusion that are essential for the complex carbon chemistry of life to occur.

UV radiation from stars can break the complex molecules required for life. The atmosphere of a planet can prevent this (e.g. dense clouds, or an ozone layer), as can deep enough oceans, or an underground environment.

Energy is required to drive the chemical reactions that allow for life processes. The Sun is a great source of energy.

Note that atmospheric Oxygen is not a requirement...

#2

The early Earth had very little atmospheric oxygen - most of it was bonded to Hydrogen (in water) or Carbon (in Carbon Dioxide)

3

So, Why Earth?

#1: Position.

The Earth formed at a distance of 150,000,000 Km from the Sun. At this distance the amount of energy we receive from the sun is enough to melt ice into a liquid, but not enough to boil water into steam. The region where this is possible is called the "habitable zone".

#1

Habitable zones exist for planets around other stars, depending on the temperature of the star.

#2: Rotation

The Earth rotates once on its axis every 24 hours. This is a few hours slower than in the Earths early history, but still fast enough to prevent one side of the Earth being constantly heated by the sun, and the other being permanently dark and cold (Mercury, Venus). No rotation would cause extreme day/night conditions not suited to life.

A rapidly rotating planet also produces a magnetic field in its core - this is useful in preventing ionizing radiations from reaching the surface.

#2

#3: The Mass of the Earth

The Earth is large enough for its gravitational field to hold on to enough of the right gases that allow for an atmosphere capable of producing life.

Too small a planet: gravity not strong enough to hold on to water, such as Mars.

Too large a planet: gravity too strong, thick atmosphere of hydrogen and helium forms... e.g. Gas giant planets.

#3

Summary:

  • The Solar System fromed from the remains of a star with enough of the larger elements required for life in it.

  • The Earth formed the right distance from the Sun for liquid water to form.

  • The Earths atmosphere and oceans protected early complex chemistry from UV radiation.

  • The rotation of the Earth prevents extreme conditions, and produces a magnetic field that protects us from ionizing radiation from the sun.

  • The Earth was just the right size to hold on to the right chemical mixture of elements.

4

The combination of these conditions allowed for chemcial processes of increasing complexity to occur, eventuially giving rise to simple single celled organisms (ABIOGENESIS)

How Do We Know All This?

5

Our ideas about the origins of life rely on 3 main branches of investigation:

1) Studying the geology of the early earth, which looks at what the conditions were like on Earth when life arose.

2) The study of ancient fossil evidence for life on the early Earth.

3) Biochemical experiments that look to recreate the conditions present on the early Earth.

6

Your Task...

Take an information sheet, and give it a skim read.

Under a suitable heading, use bullet points to summarise its key ideas.

Consider using 5W+H as a framework...

Learn more about creating dynamic, engaging presentations with Prezi