Cycles of NatureCycles of Nature•Matter, as well as energy, moves through an ecosystem and is constantly recycled.

•Nitrogen, water, oxygen and carbon are cycled globally because they are found in their gaseous form most of the time.

•Phosphorus is cycled locally because it remains almost entirely in the soil.

Biogeochemical CyclesBiogeochemical Cycles

• The movement of particular The movement of particular chemicals through the biological and chemicals through the biological and geological, or living and non-living, geological, or living and non-living, parts of an ecosystemparts of an ecosystem

• May involve a change in state as May involve a change in state as they move through their cyclesthey move through their cycles

Cycles in the Ecosystem

One-way flowof energy from Sun

Cycling ofElements

Fig. 4-8 p.60

CarbonPhosphorus

NitrogenWaterOxygen

Oxygen CycleOxygen Cycle• Oxygen is released from plants as a waste Oxygen is released from plants as a waste

produce of photosynthesis.produce of photosynthesis.

• Humans and other organisms, including plants, Humans and other organisms, including plants, take in this oxygen and release it as carbon take in this oxygen and release it as carbon dioxide through cellular respiration.dioxide through cellular respiration.

• Oxygen is also indirectly transferred through an Oxygen is also indirectly transferred through an ecosystem by the cycling of other nutrients, ecosystem by the cycling of other nutrients, including carbon, nitrogen, and phosphorus.including carbon, nitrogen, and phosphorus.

Oxygen CycleOxygen Cycle

Water CycleWater Cycle• Water from lakes, rivers, oceans undergoes Water from lakes, rivers, oceans undergoes

EVAPORATION.EVAPORATION.• Water vapor CONDENSES on dust in the air to Water vapor CONDENSES on dust in the air to

form clouds.form clouds.• Water forms small drops that get bigger and Water forms small drops that get bigger and

heavier and PRECIPITATION occurs.heavier and PRECIPITATION occurs.• INFILTRATION occurs. INFILTRATION occurs. • Runoff occurs as some water enters the streams, Runoff occurs as some water enters the streams,

rivers and eventually the ocean.rivers and eventually the ocean.• Plants pull water from the ground and then lose Plants pull water from the ground and then lose

water through their TRANSPIRATION.water through their TRANSPIRATION.• Animals also put water vapor and water back into Animals also put water vapor and water back into

the cycle by exhaling and urinating.the cycle by exhaling and urinating.• Only about 1% of the Earth’s water is available to Only about 1% of the Earth’s water is available to

us. The rest is either frozen or salty.us. The rest is either frozen or salty.

The Water CycleThe Water CycleHydrologic (Water) CycleHydrologic (Water) Cycle

Fig. 4-28 p. 76

Carbon CycleCarbon Cycle• Carbon is the element of life and forms the basis for Carbon is the element of life and forms the basis for

carbohydrates, proteins and fats.carbohydrates, proteins and fats.

• Autotrophs (producers) use carbon dioxide from the Autotrophs (producers) use carbon dioxide from the atmosphere during photosynthesis to form glucose.atmosphere during photosynthesis to form glucose.

• Heterotrophs (consumers) consume producers and Heterotrophs (consumers) consume producers and take in these carbon containing molecules.take in these carbon containing molecules.

• Both heterotrophs and autotrophs carry out cellular Both heterotrophs and autotrophs carry out cellular respiration to release COrespiration to release CO2 2 into the atmosphere.into the atmosphere.

• When organisms die and decay, they return carbon to When organisms die and decay, they return carbon to the soil. Microorganisms break down these molecules the soil. Microorganisms break down these molecules to release carbon dioxide into the atmosphere.to release carbon dioxide into the atmosphere.

The Carbon CycleThe Carbon Cycle

Nitrogen CycleNitrogen Cycle• Lightning and some nitrogen-fixing bacteria Lightning and some nitrogen-fixing bacteria

convert atmospheric nitrogen into nitrates. convert atmospheric nitrogen into nitrates. (Plants can’t use nitrogen in the atmosphere)(Plants can’t use nitrogen in the atmosphere)

• Nitrates enter the ground and plants take them Nitrates enter the ground and plants take them up and use them to produce proteins.up and use them to produce proteins.

• Herbivores eat plants and convert plant proteins Herbivores eat plants and convert plant proteins into animal proteins.into animal proteins.

• Urine is formed and contains excess nitrogen in Urine is formed and contains excess nitrogen in the form of ammonia which is released to the the form of ammonia which is released to the water or soilwater or soil

• Organisms die and release nitrogen containing Organisms die and release nitrogen containing molecules to the soil.molecules to the soil.

• Plants reuse the nitrogen containing molecules Plants reuse the nitrogen containing molecules and bacteria break them down and release and bacteria break them down and release nitrogen back to the atmospherenitrogen back to the atmosphere..

The Nitrogen CycleThe Nitrogen CycleThe Nitrogen CycleThe Nitrogen Cycle

Fig. 4-31 p. 80

Phosphorus CyclePhosphorus Cycle• Phosphorus is needed for ATP, DNA, teeth and Phosphorus is needed for ATP, DNA, teeth and

bones.bones.• Cycles in two ways, moving between the living and Cycles in two ways, moving between the living and

non-living parts of the environment.non-living parts of the environment.• Phosphates are the most common form of Phosphates are the most common form of

phosphorus found in the environment.phosphorus found in the environment.• Short-Term Cycling Short-Term Cycling a. Plants get phosphorus from the soila. Plants get phosphorus from the soil b. Animals get phosphorus from plants.b. Animals get phosphorus from plants. c. Animals die/decompose and return phosphorus c. Animals die/decompose and return phosphorus

to the soil.to the soil.• Long- Term CyclingLong- Term Cycling a. Phosphates washed into the sea from runoff are a. Phosphates washed into the sea from runoff are

incorporated into rock formation as insoluble incorporated into rock formation as insoluble compounds.compounds.

b. Rocks containing phosphorus are exposed as b. Rocks containing phosphorus are exposed as they erode and weather and phosphorus again they erode and weather and phosphorus again becomes part of the system.becomes part of the system.

The Phosphorus CycleThe Phosphorus Cycle

Human Impact on Nature’s Human Impact on Nature’s CyclesCycles• Burning of fossil fuels and wood is raising

the levels of carbon dioxide and contributing to global warming.

• Large amounts of inorganic nitrogen compounds are washed into rivers and streams from farming, sewage treatment and golf courses, causing heavy growth of algae and eutrophication.

• Phosphates from runoff pollute the lakes and streams causing heavy growth of algae.

• Destruction of forests causes a decrease in transpiration, altering weather patterns on Earth.

What are we doing to What are we doing to ensure that these Cycles ensure that these Cycles continue?continue?• We need to understand the delicate We need to understand the delicate

interactions (relationships) between interactions (relationships) between organisms and their environments organisms and their environments

to address the environmental to address the environmental problems we have created.problems we have created.

CONSERVATION!CONSERVATION!