The Water Cycle

Water

• The total amount of water on earth doesn’t change.

• Water in Earth’s oceans does not remain there indefinitely. Water is constantly recycled through the water cycle.

Energy for the Water Cycle• The sun provides energy for the

water cycle.

Evaporation

• Water is lost from the soil and from all surface water (lakes, streams, ponds, oceans) through evaporation or transpiration.1. Evaporation – occurs when the sun’s energy

heats the water, changing it from its liquid state into its gaseous state (known as water vapor)

2. Transpiration – loss of water vapor from the leaves of plants through the stomata (openings in leaves)

TRANSPIRATION

EVAPORATION

Condensation• Condensation – process

of water vapor changing from water vapor into its liquid form – As warm humid air rises, it

loses energy and cools.– As the air cools, the water

vapor collects on small particles (such as dust or volcanic ash) in the atmosphere and forms clouds.

Precipitation• When the droplets become too

heavy to remain in the atmosphere they begin to fall. – Precipitation – all moisture falling

from the atmosphere• The temperature of the air determines the

form of precipitation:1. Rain2. Sleet3. Snow4. Hail

Where Does The Precipitation Fall? 1. Ocean or Other Bodies of Water

– Most precipitation falls here since most of the earth’s surface is covered by water.

2. Land– May flow over the surface as runoff,

which flows into rivers or streams– May enter the soil

and enter the plants roots

Infiltration

• Infiltration – process of precipitation entering the ground– The water can move or percolate

through the soil and rocks until it reaches a layer of impermeable rock or clay.

– This layer of water is called groundwater.

– This layer of permeable (porous) rock where the water is stored is called an aquifer.

Aquifer

Aquifer – the layer of rock where the water is stored.

Groundwater – the layer of water

The Carbon Cycle

Why is Carbon important?

All living things are made of carbon!!!• Calcium carbonate (CaCO3) makes up

animal skeletons • Carbon Dioxide gas which makes

photosynthesis and respiration work together

1. In the atmosphere, carbon is attached to some oxygen in a gas called carbon dioxide.

2. Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant.

3. Animals consume plants. The carbon becomes part of the animal.

4. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years.

5. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon

dioxide.

Carbon Does Not Stay Still – It Is On the Move!

+ → +sunlight

Using light energy, plants combine carbon dioxide (CO2) from the atmosphere and water (H20) to form sugar and oxygen in the process of

photosynthesis.(CO2) (H2O) (C6H12O6

)(O2)

PHOTOSYNTHESIS

What is Sugar (Glucose) Used For?

1. Source of energy2. Building block for

other compounds such as proteins, oils, and starches.

RESPIRATION

• In respiration, the compounds containing carbon (the organic compounds) are broken down, and carbon dioxide is released.

Plants, animals, and microorganisms all carry out respiration!

IS THE CARBON-OXYGEN CYCLE BALANCED?

• The Carbon-Oxygen cycle is out of balance.

• There is more carbon dioxide being released into the atmosphere than is being removed.

COMBUSTION• Most of the carbon dioxide

is produced during the process of burning called combustion.

• When compounds containing carbon (wood, coal, or oil) are burned, the carbon is chemically combined with oxygen, and carbon dioxide is released.

• The use of carbon dioxide by plants during photosynthesis is a much slower process.

• As a result of the imbalance between these two processes, the level of carbon dioxide in the atmosphere is increasing.

• “Even if human emissions of CO2 magically dropped to zero, the gas already in the air would linger for many centuries, trapping heat. Global temperatures would continue to creep upward until the ocean depths reached equilibrium with the heated air, until biological systems finished adapting to the new conditions, and until Arctic icecaps melted back to their own equilibrium”

• When organisms die, decomposers break down the carbon compounds in their bodies, and carbon dioxide is returned to the atmosphere.

• During decomposition (decay), other chemicals are also returned to the soil or released into the air. One of these chemicals is nitrogen.

Decomposers

The Nitrogen Cycle

NITROGEN

• Plants and animals need nitrogen to make amino acids (proteins)

• The atmosphere is about 78% nitrogen gas, but plants and animals cannot use nitrogen directly from the air.

How Do Plants Get Nitrogen?• Special bacteria, in the

soil and water, must change or “fix” nitrogen gas (N2) into nitrogen fertilizers (NO3

-) or ammonium ions (NH4

+) that plants can use.

• These bacteria are called nitrogen-fixers. N=N → 2NH3

Nitrogen Fixers

• Legumes - members of a large family of plants that include peas, beans, alfafa, and clover.

• Convert nitrogen gas to ammonia

Most nitrogen-fixing bacteria live in little houses, or nodules, on the roots of plants called legumes.

Nitrogen Fixers• Mutualistic Relationship

– The plants provide food and cover for the bacteria, and the bacteria convert nitrogen gas into fertilizer for the plant.

How Do Animals Get Nitrogen?• Animals get nitrogen from plants or from

other plant-eating animals, in the form of protein.

Animals must eat protein to

get our nitrogen

requirements! We can’t

breathe in nitrogen.

Nitrogen is recycled by special bacteria (legumes) that break down the nitrogen compounds (proteins) in dead plants and animals, and in animal wastes.

How is Nitrogen Recycled?

If plants do not use the nitrogen compounds as fertilizer, special forms of bacteria may recycle it. These bacteria convert the unused fertilizer into nitrogen gas and release it into the atmosphere.

All natural ecosystems depend

uponbacteria to keep the

nitrogen cycle going!

Lightning and the Nitrogen Cycle• Lightning plays a small

role in the nitrogen cycle.

• The high temperature and pressure from lightning combines nitrogen and oxygen (nitrogen oxides) in the atmosphere.– The “fixed” nitrogen,

(which is dissolved in the rain making nitrates) enters the soil

Combustion: Another source of Nitrogen• The burning of

fossil fuels is another source of nitrogen. – Combustion

causes nitrogen and oxygen to combine creating nitrogen oxides (NOx). These lead to acid rain and smog

The Phosphorus Cycle

Where is Phosphorus found?• Phosphorus is important to living

organisms because it makes up DNA and RNA.• Found in enamel of teeth

(calcium phosphate)• It is not very common in the

biosphere. • Phosphorus exists as inorganic

phosphorus (does NOT contain carbon).

• Phosphorus stays on land in rock, soil, and ocean sediments never entering the atmosphere.

• Rocks and sediments wear down releasing phosphates

• On land this phosphate washes into rivers dissolving and eventually makes its way to oceans where marine animals use it

• When plants absorb phosphate they bind it making it organic instead of inorganic organic phosphate can move through the food web from producers to consumers

Nutrient Limitation

• If a nutrient is in short supply, it will limit an organism's growth.

• When an ecosystem is limited by a single nutrient that is scarce or cycles very slowly, this substance is called a limiting nutrient.

• Farmers are aware of this so they apply fertilizers that contain nitrogen, phosphorus, and potassium.