1. Cycles of Matter

2. Cycles of Matter: Why?
Because we have a fixed amount of STUFF (matter) on this planet, and no new stuff is being added from the universe
It must be cycled around and around.

3. Nitrogen Cycle – Why do we need nitrogen?
In proteins (the building blocks of cells)
In DNA
No nitrogen?
No proteins
No cells
No life

4. Nitrogen Cycle ~79% of air is made up of nitrogen
We can’t use this form
Must be “fixed” into solid form

5. Nitrogen Cycle
The process of converting nitrogen from the gaseous form, N2, into a solid form that’s usable for our bodies is called NITROGEN FIXATION

6. Nitrogen Fixation
It takes a lot of energy to change nitrogen from its very stable form in the air, N2 to a form organisms can use.
There are 3 ways nitrogen can be fixed:
Nitrogen fixing bacteria
Lightning
factories

7. Nitrogen fixation - bacteria
Nitrogen, N2, diffuses into soil from the air
Special species of bacteria in the ground fix the nitrogen into ammonia (NH3) and other nitrogen compounds plants can use
Two types of nitrogen-fixing bacteria
free living bacteria
Bacteria that live in nodules of certain plants’ roots in a ______________ relationship
Symbiotic mutualism

8. Nitrogen fixation - bacteria
Plants that contain nitrogen-fixing bacteria in their root nodules:
Alfalfa, legumes, clover & soy
Farmers sometimes rotate these crops in just to add more nitrogen to their soil

9. Nitrogen Fixation - lightning
Only a very small % of N gets fixed this way
The high energy from lightning breaks some nitrogen molecules apart, allowing them to bond with oxygen in the air. This makes nitrates (NO3-)
(N2 + 3O2  2NO3-)
rain carries these new compounds down to the soil where they can be taken up by plant roots.

10. Nitrogen Fixation - factories
Humans have learned how to take gaseous nitrogen, N2, and fix it into compounds to make fertilizer
This takes huge amounts of energy

11. Nitrogen Cycle - Usage
Once the nitrogen is fixed in one of the three ways, it can be used by plants

12. Nitrogen Cycle - Usage
Finally, heterotrophs get the nitrogen by eating the plants or other animals that ate the plants.

13. Nitrogen Cycle – Back to Air
When organisms die, decomposers get the last of their stored energy, and return their elements back to the soil.
Some decomposing archaea break down the nitrogen compounds and release them back to their gaseous form, N2.
This process of breaking down nitrogen compounds and releasing them back as air is called denitrification.
chaea

14. Nitrogen Cycle

15. Nitrogen cycle web site
nitrogen cycle animation

16. Carbon (C) and Oxygen (O) cycles
Plants do photosynthesis
What do plants use for this?
Water (H2O) and Carbon Dioxide (CO2)
What do plants produce using photosynthesis?
Glucose, a sugar (C6H12O6) and oxygen (O2), a waste product for plants

17. Carbon (C) and Oxygen (O) cycles
All living things do cellular respiration to get…
ENERGY
What do plants and animals use for cellular respiration?
Oxygen (O2) and glucose (C6H12O6) – exactly the products of photosynthesis!

18. Carbon (C) and Oxygen (O) cycles
And cellular respiration produces what photosynthesis needs: carbon dioxide and water.
So the carbon and oxygen cycle around through cellular respiration and photosynthesis

19. Carbon (C) and Oxygen (O) cycles
When organisms die, their bodies still contain the substances they had when they were alive.
These get cycled back into the ground by …
decomposers.
When organisms die, the energy left over in their bodies is still stored in the carbohydrate compounds in their tissues.
Organisms that died long ago and were buried under layers of sediments have been pressurized for many years and converted into …
Fossil fuels

20. Fossil fuels come in the form of gasoline, oil, & coal.
When we burn these fuels, this releases the carbon dioxide back into the air, just like breathing out does from cellular respiration.
The process of powering a car with fossil fuels is the same as powering our bodies with fuel from plants – both produce carbon dioxide.
All the energy originally came from…
the sun .