Environmental Sciences Chapter 2, Section 1: The Carbon Cycle The Nitrogen Cycle

Carbon Cycle - The exchange of carbon between the environment and living things All living things are “organic” – that means that they have carbon in them. Carbon is the fifth element on the periodic table. Without carbon there would be no life on earth.

A substance is considered organic if it… Grows in the ground Contains carbon Comes from the organic section of the supermarket

Like everything else in life, carbon has a cycle. The carbon cycle moves Carbon from living things, into the atmosphere and the environment and back into living things.

The carbon cycle includes Only living things Only abiotic things like the atmosphere Both living things and abiotic things like the soil and the atmosphere

Let’s start in the living things Animals (like people) breathe in air to get oxygen. When they exhale they release carbon dioxide. So we release carbon into the atmosphere every time we breathe! We also add carbon into the soil when we die and decompose.

We release carbon into the environment by… Breathing Sweating Photosynthesis

Let’s start in the living things Plants “breathe” in air to get carbon dioxide. When they “exhale” (respiration) they release oxygen. So plants release oxygen into the air by respiration, but when they die and decompose their bodies release carbon into the atmosphere and into the soil.

Plants… Need the oxygen in the air for respiration Need the carbon dioxide in the air for respiration Have nothing to do with the carbon cycle

Let’s start in the living things Photosynthesis is defined as “The process of plants making sugar; the basis of the carbon cycle. Photosynthesis uses carbon dioxide to complete photosynthesis.

Let’s review the vocabulary Something is Organic if it has carbon in it. All living things are organic. Animals breathe (respiration) and release carbon dioxide. Trees also use respiration, but they get carbon from the air and release oxygen. All living things release carbon when they die and decompose

Coal, Oil, and Natural gas are organic too! Did you know that coal, oil, and natural gas comes from once living things? These are called fossil fuels and they are made from very old plants and animals that got stuck inside the earth. Since fossil fuels were once alive they are made from carbon –they are organic

Where do coal, oil and natural gas come from? They are from the muck at the bottom of the ocean They are made of rock They were once living things like plants and small organisms

Coal, Oil, and Natural gas are organic too! Human beings use the organic fossil fuels to get energy by burning them. Burning anything is called combustion and it releases carbon into the atmosphere. We are burning so many fossil fuels for energy that we are causing global warming!

Burning fossil fuels is called.. Combustion Respiration Transpiration

Nitrogen Cycle - The movement of nitrogen between the environment and living things The crazy thing about nitrogen is that the air around us is FULL of Nitrogen – 78% of what we breathe is nitrogen – but we don’t get our nitrogen from the air! We get our nitrogen from the soil – and from plants.

Nitrogen is needed for… Plants to have strong cell walls People to keep their big brains cool All organic things to make new cells.

Nitrogen Cycle - The movement of nitrogen between the environment and living things Most of the nitrogen that we need comes to us through Nitrogen Fixation. That’s when a bacteria in the soil changes nitrogen into a compound that plants can use. We get our nitrogen when we eat plants – or when we eat other animals that have eaten plants.

Nitrogen Cycle - The movement of nitrogen between the environment and living things Nitrogen moves around in a cycle when it is “fixed” Lightning can fix nitrogen in the air. When we die and decompose we release nitrogen into the soil.

How do we get nitrogen? We breathe it in from the air 78% of the air is nitrogen We have all the nitrogen in our bodies that we will ever need We eat plants that have “fixed” nitrogen, or we eat animals that have eaten those plants