Unit 3 The Cycles on our Planet

What is a cycle?  In your notebooks, take 2 minutes to try to come up with your own definition of what a cycle is.  Work with your lab/table partners to come up with a complete and scientific definition of a cycle.  Let’s share out!

Definitions of Cycle  Biological Definition :  A repeating series of events or processes in plants and/or animals  Physical/Chemical Definition:  A continuous change or chain of changes in the state of a system that leads to a return of the system to its original state.

Understanding Earth’s Cycles

Earth’s Cycles Types of Cycles  Carbon Cycle  Water Cycle  Nitrogen Cycle  Phosphorus Cycle Areas of Cycling on Earth  Atmosphere – Air  Biosphere – Living things  Geosphere – Land  Hydrosphere – Water  Cryosphere – Ice and Glaciers We will be focusing only on these cycles and locations during this unit.

The Carbon Cycle  The Carbon Cycle:  The process by which carbon is cycled between the atmosphere(air), geosphere (land), hydrosphere(water) and biosphere(living things).  Why does Carbon matter?  Carbon is a building block of proteins, fats and carbohydrates  This is our FOOD!  CO 2 (Carbon Dioxide) is a greenhouse gas  Too little and our planet gets cold  Too much and our planet gets hot

The Carbon Cycle Variations  Short-Term Cycle  This is a daily cycle  Involves the following spheres  Atmosphere  Biosphere  Hydrosphere  Long-Term Cycle  This is a drawn-out or protracted cycle (taking hundreds and millions of years)  Involves the following spheres  Atmosphere  Biosphere  Geosphere  Hydrosphere

The Short-Term Cycle  The pathway of this cycle is:  Atmosphere  Biosphere  Atmosphere  The Hydrosphere (mostly the oceans) acts like a Carbon Dioxide “Warehouse”  CO 2 can be “Stored” and “Released” as needed when there are temporary imbalances.  When these imbalances go too long we get other problems but we will talk about that later.

How can Carbon move from the Atmosphere to the Biosphere? Plants!  Without Plants and photosynthesis we would not be able to access the Carbon in the atmosphere.  Photosynthesis  Conversion of Carbon Dioxide (CO 2 ) into sugars and carbohydrates.  Carbon Dioxide + Water + Sunlight  Sugar + Oxygen

How does Carbon move back to the Atmosphere from the Biosphere? Cellular Respiration!  This is done by both animals and plants  It breaks down the sugar created in photosynthesis to give living things energy! (sun energy to chemical energy )  Cellular Respiration  The conversion of sugar into usable energy Sugar + Oxygen  Carbon Dioxide + Water + Energy

The Carbon Cycle – Recap The combination of photosynthesis and cellular respiration allows Carbon to move continuously from the Atmosphere to the Biosphere and then back to the Atmosphere.  Changes in one sphere can lead to changes in another spheres. For example If we loose a large number of plants, less carbon dioxide will be removed from the atmosphere and converted to sugar, animals will continue to release carbon dioxide as a waste product and it will build up in the atmosphere. Based on what you learned about Carbon Dioxide in previous units, what impact could that have on the environment?