Cycles of Matter

Cycles of Matter: Why?

• Because we have a fixed amount of STUFF Because we have a fixed amount of STUFF (matter) on this planet, and no new stuff is (matter) on this planet, and no new stuff is being added from the universebeing added from the universe

• It must be cycled around and around.It must be cycled around and around.

Nitrogen Cycle – Why do we need nitrogen?

• In proteins (the building blocks of cells)• In DNA• No nitrogen?• No proteins• No cells• No life

Nitrogen Cycle

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

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

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:1.Nitrogen fixing bacteria2.Lightning3.factories

Nitrogen fixation - bacteria1.1. Nitrogen, NNitrogen, N22, diffuses into soil from the air, diffuses into soil from the air

2.2. Special species of bacteria in the ground fix Special species of bacteria in the ground fix the nitrogen into ammonia (NHthe nitrogen into ammonia (NH33) and other ) and other nitrogen compounds plants can usenitrogen compounds plants can use

• Two types of nitrogen-fixing bacteriaTwo types of nitrogen-fixing bacteria1.1. free living bacteriafree living bacteria2.2. Bacteria that live in nodules of certain plants’ Bacteria that live in nodules of certain plants’

roots in a ______________ relationshiproots in a ______________ relationship• Symbiotic mutualismSymbiotic mutualism

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

Nitrogen Fixation - lightning

1. Only a very small % of N gets fixed this way2. The high energy from lightning breaks some

nitrogen molecules apart, allowing them to bond with oxygen in the air. This makes nitrates (NO3

-)3. (N2 + 3O2 2NO3

-)

4. rain carries these new compounds down to the soil where they can be taken up by plant roots.

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

Nitrogen Cycle - Usage

• Once the nitrogen is fixed in one of the three ways, it can be used by plants

Nitrogen Cycle - Usage

• Finally, heterotrophs get the nitrogen by eating the plants or other animals that ate the plants.

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 denitrificationdenitrification.

Nitrogen Cycle

• Nitrogen cycle web site• nitrogen cycle animation

Carbon (C) and Oxygen (O) cycles

• Plants do photosynthesisphotosynthesis• What do plants use for this?• Water (HWater (H22O) and Carbon Dioxide (COO) and Carbon Dioxide (CO22))

• What do plants produce using photosynthesis?

• Glucose, a sugar (C6H12O6) and oxygen (O2), a waste product for plants

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!

Carbon (C) and Oxygen (O) cycles

• And cellular respiration produces what And cellular respiration produces what photosynthesis needs: carbon dioxide and photosynthesis needs: carbon dioxide and water.water.

• So the carbon and oxygen cycle around So the carbon and oxygen cycle around through cellular respiration and through cellular respiration and photosynthesisphotosynthesis

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

• Fossil fuels come in the form of gasoline, oil, & Fossil fuels come in the form of gasoline, oil, & coal.coal.

• When we burn these fuels, this releases the When we burn these fuels, this releases the carbon dioxide back into the air, just like carbon dioxide back into the air, just like breathing out does from cellular respiration. breathing out does from cellular respiration.

• The process of powering a car with fossil fuels is The process of powering a car with fossil fuels is the same as powering our bodies with fuel from the same as powering our bodies with fuel from plants – both produce carbon dioxide.plants – both produce carbon dioxide.

• All the energy originally came from…All the energy originally came from…• the sun .the sun .