EARTH IN SPACE “The Fragile Miracle”

The Four Conditions for Life There are several unique conditions that make Earth the only planet capable of sustaining life. The other planets cannot sustain life because of the temperature, levels of radiation, toxic gases or the lack of water and gases necessary to support life

The Four Conditions for Life On Earth there are four conditions that make it possible for complex and simple life forms to survive.

The Four Conditions for Life There is a constant and relatively mild temperature. There is an abundance of water. There is a sufficient quantity of the gases, such as oxygen, nitrogen, and carbon dioxide, which are necessary to sustain life. There is an atmosphere of sufficient thickness to protect living things from the sun’s ultraviolet radiation.

1. Temperature Temperature on Earth ranges from -50ºC to 50ºC. The average temperature on Earth is in the narrow range of 10ºC to 20ºC. The greenhouse effect help keep the Earth at a stable temperature

Water Water covers 2/3 of the world's surface Water absorbs heat from the sun and helps distribute it around the Earth (ocean currents regulating weather patterns) Water circulates through the soil and distributes nutrients to plants (which are the source of all food on Earth) All living organisms are at least 50% water - water transports vitamins and minerals throughout the body.

Gases Oxygen, carbon and nitrogen are what make up carbohydrates, proteins and fats, the basic foods all organisms use

Atmosphere The atmosphere is 80-100 km thick (very thin when compared to the size of the Earth) Helps maintain a stable temperature on Earth Shields Earth from particles such as meteors Oxygen makes up ozone, which protects humans from skin cancer and plant life from other damage

The Earth as a System A system is defined as a set of parts that work together In an open system, parts can either be added to or lost from the system. In a closed system, all the parts exist in precise amounts, and nothing can be lost or added. The Earth is a closed system. All essential nutrients exist in fixed quantities and must be continually recycled. Example: the water cycle.