The Earth is believed to have formed as a result of the Big Bang which created our Universe over 13 billion years ago. Earth is a closed system for matter. That means all the matter that formed Earth after that event is still here today (give or take the materials sent into space, and the arrival of meteorites).
The Earth is composed mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements. Due to mass segregation, the core region is believed to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements. 
Earth is the third planet from the sun and the densest in the solar system. Whilst being a closed system for matter, it is an open system for energy. Energy is delivered every day from the sun, and returned into space through radiation.
The biosphere is the global sum of all living systems on Earth. It is believed to have started forming over 3.5 billion years ago. The biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, geosphere, hydrosphere, and atmosphere.
Humans have evolved over millions of years as part of the biosphere. However, it was only about 12,000 years ago that we began to form communities around organised agriculture; and just 250 years since the start of the Industrial Revolution. In that small period of time, humans have rapidly spread across all corners of the planet and emerged as the dominant shaping force on the surface of the Earth.
In this learning pathway you will:
- Learn how the ecological system works, and how humans are adversely affecting it.
- Learn how the social system works.
- Learn how humans have become the dominant shaping force on the planet.
- Retrieved on 30th October 2014 from http://en.wikipedia.org/wiki/Earth