Earth: The Fragile Miracle Conditions for Life

The Goldilocks Zone Earth’s life-sustaining conditions are possible because of its position in the solar system It is not too hot and not too cold – if the Earth was any closer or further away from the Sun, the planet could not support life

Other Life Sustaining Conditions Earth’s rotation on its axis and orbit around the Sun helps distribute heat evenly around the planet Earth’s magnetic field protects the planet from deadly radiation and particles Earth’s gravitational field holds the atmosphere in place preventing oxygen, nitrogen, and carbon dioxide from escaping into space

Four Conditions for Life Stable Temperature Range The Importance of Water The Importance of Gases The Role of the Atmosphere

Stable Temperature Range A stable temperature range (-50 to about +50 degrees Celsius) allows life to thrive – the average temperature has been between 10-20 degrees Celsius for 3.5 billion years The greenhouse effect allows for heat in the atmosphere (carbon and water vapor) to be re-radiated back to Earth Without proper water and carbon, the earth would be -73 degrees C.

The Greenhouse Effect Plants play a significant role in creating a stable temperature through releasing water vapor and oxygen by the processes of photosynthesis and transpiration Dark areas of vegetation absorb heat from the sun’s rays and limit the albedo effect – heat being reflected back into space

Photosynthesis

The Importance of Water First water likely came from volcanic activity – water collected on the cooling surface and as vapour in the atmosphere creating the water cycle Biologists believe earth first began in the oceans – blue-green algae Oceans cover 2/3 of the Earth – absorbs heat and distributes it around the world and controls our weather patterns and climates Helps distributes nutrients to plants and other organisms No living this consists of less than 50% water Water is the metabolizing agent that allows plants and animals to dissolve minerals and nutrients to create energy

The Importance of Gases 78% nitrogen, 21% oxygen, carbon dioxide 0.03% - quite different than other planets in the solar system The plants have removed most of the carbon dioxide that originally existed and produced lots of oxygen Without life on earth, carbon dioxide would increase The production of carbohydrates, fats, and proteins require oxygen, carbon, and nitrogen atoms from the atmosphere, and hydrogen from water

The Role of the Atmosphere Layer of gases about 80-100 kms thick – very thin compared to size of Earth Helps maintain a consistent temperature Shields earth from collisions with cosmic particles (meteors) Oxygen levels at 21 allow for life, if they drop, animal life would not be possible, if it exceeds 25% most plants would be consumed by fire Oxygen is produced by plants and consumed by animals and the burning of plants and fossil fuels

The Four Spheres Lithosphere – earth’s crust (soil, rocks, and minerals) Hydrosphere – earth’s water Atmosphere – the gases in the air Biosphere – all living things (plants, bacteria, animals)

Biosphere Encompasses all living organisms including humans Divided into separate but interdependent units called ecosystems – well defined habitats hosting systems of interacting organisms Nutrient Cycle - Continuation of life depends on the constant recycling of chemical ingredients called nutrients (Example: plants and animals die and decompose)

Biosphere – The Carbon Cycle The movement of carbon from the atmosphere into plants, animals, and the soil and then back again Plants take carbon dioxide from the atmosphere to produce food through photosynthesis and release oxygen – animals breath oxygen and eat plants Dead animals and plants decay and return carbon to cycle Over production of carbon dioxide from factories and burning rainforests causes climate change

Biosphere – Nitrogen Cycle Most powerful element in the Earth’s atmosphere Microscopic bacteria live on the roots of certain plants known as legumes and converts nitrogen to ammonia and nitrates which the plant absorbs and converts to protein – food production

Biosphere – Oxygen Cycle Oxygen produced by the respiration of plants – 90% of oxygen used is replaced by algae in oceans Oxygen created by photosynthesis

Biosphere – Water Cycle Water must be recycled through the atmosphere and back to the Earth’s surface Most from evaporation – some from transpiration; water drawn by plants and released through their leaves Groundwater dissolves nutrients in the soil