2.1.3 Life on Earth

Life on Earth
2.1.3

By Caitlin Ford

Objectives

- explain the conditions that allowed life to develop on Earth

- describe how Earth's atmosphere protects life on Earth

The Early Earth

Formed 4.5 billion years ago, began as a molten ball of rock and metal, was bombarded by asteroids, gas rose from the magma to form the first atmosphere

Earth cooled over time, more gases formed about the surface, continued to be bombarded by comets and asteroids

A Mars-sized object crashed into Earth and the moon was created

Earth's Position

Goldilocks zone - the habitable zone around a star; this is a region where the temperature is just right for liquid water to exist on the surface of a planet

No too hot/not too cold = Goldilocks!

Depends on the star...

Presence of Liquid Water

Earth formed out of a giant cloud of gas and dust called a nebula, as this cooled and condensed, water vapor was present during Earth's formation

Later, volcanoes erupted water vapor into the atmosphere

Comets and asteroids pummeled Earth, bringing more water to Earth

Thermal Conduction of Water

Hydrothermal vents - on the ocean floor, superheated water seeps through cracks on the ocean floor from the mantle and picks up minerals

The hot water and minerals from the vents could have initiated chemical reactions that led to the formation of the building blocks of life

Earth's Atmosphere

Crucial to life on Earth!

Acts like a blanket - traps heat and filters out some of the dangerous rays of the Sun

Gases flow between atmosphere and surface; without plants creating oxygen, animals would not survive

Ozone Layer - protects living things from UV radiation by absorbing and scattering it

Hotspot

Which of these planets is in this star's habitable zone?

Multiple Choice

What type of radiation is blocked by the ozone layer?

• infrared radiation

• x-rays

• beta rays

• ultraviolet radiation

Great Job!

Today, you learned:

- the conditions that allowed life to develop on Earth

- how Earth's atmosphere protects life on Earth