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Ch 2 Review. The Water Cycle. The water cycle is the movement of water between the oceans, atmosphere, land, and living things. Stages of the Water Cycle. Evaporation – The change of a substance from a liquid to a gas, where the water is cycled back into the atmosphere.

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the water cycle
The Water Cycle
  • The water cycle is the movement of water between the oceans, atmosphere, land, and living things.
stages of the water cycle
Stages of the Water Cycle
  • Evaporation – The change of a substance from a liquid to a gas, where the water is cycled back into the atmosphere.
  • Condensation- The change of state from a gas to a liquid due to the cooling of water vapor.
  • Precipitation- Any form of water that falls to the Earth’s surface from the clouds. It is water that moves from the atmosphere to the land and oceans- includes rain, snow, sleet and hail
  • Ground Water (collection)- The precipitation that seeps into the ground, where it is stored in spaces between or within porous rocks and underground caverns.
the water cycle1
The Water Cycle

E (Evaporation) – The change of a substance from a liquid to a gas

B (Condensation)- The change of state from a gas to a liquid

D (Groundwater) - Water that seeps into the ground & slowly flows back into soil, streams, rivers, & oceans

A (Transpiration) - The process of plants releasing large amounts of water vapor

F (Runoff) - The precipitation that falls on land that flows into streams, rivers, oceans, and lakes

C (Precipitation) - Any form of water that falls to the Earth’s Surface from the clouds

G (Water Cycle) - The movement of water between the oceans, atmosphere, land, and living things

the water cycle2
The Water Cycle
  • ____________________ 4. ____________________

2. ____________________ 5. ____________________

3. ____________________ 6. ____________________








The Water Cycle

  • 1.) Name the several different types of precipitation:


  • 2.) Explain the significance of the water cycle:

__ _ _____ _____________ _

  • 3.) Where does the energy that powers the water cycle come from?

Rain, snow, sleet, & hail

The water cycle is how the Earth’s water recycles itself. Without water, there would be no life on Earth. All organisms are composed mostly of water and eventually, all the water taken in by organisms is returned to the environment.

  • A. plants C. electrical outlets
  • B. animals D. sun

The Water Cycle

  • *BONUS: Why are the oceans salty?
  • As runoff water flows into the lakes, streams, and rivers, it picks up small quantities of minerals from rocks and soil.
  • This salty water then flows into the oceans, making the ocean salty too!
  • When the ocean water evaporates, the salt does not evaporate and remains in the ocean.
the carbon cycle
The Carbon Cycle
  • The carbon cycle is the exchange of CARBON between the environment and living things (it moves from the environment into living things and back into the environment).

The Carbon Cycle

Decomposition – The breakdown of dead materials into carbon dioxide and water

Combustion - The process of burning fossil fuel or wood

  • Decomposition and Combustion
  • Photosynthesis and Respiration
  • Organic Molecules and Inorganic Molecules

** Both have organic matter that releases carbon dioxide

into the atmosphere.

Photosynthesis– The process by which plants use carbon dioxide from the air to make sugars

Respiration - sugar molecules are broken down to release energy  carbon dioxide & water

Organic – molecules that contain carbon

Inorganic - molecules that do not contain carbon


The Carbon Cycle

  • Then sketch a diagram
stages of the carbon cycle
Stages of the Carbon Cycle
  • Photosynthesis – The basis of the carbon cycle, in which plants use carbon dioxide from the air to make sugars.
  • Respiration – The process by which sugar molecules are broken down to release energy. Carbon dioxide and water are released as byproducts.
  • Decomposition – The breakdown of substances into simpler molecular substances. It The breakdown of dead materials into carbon dioxide and water
  • Combustion – The process of burning a substance, such as wood or fossil fuels. Releases CO2

The Nitrogen Cycle


  • 1. The Earth’s atmosphere is made up of ______ percent of nitrogen.
  • 2. When organisms die, _________________ breaks down the remains which helps release nitrogen into the soil for plants to use.
  • 3. ________________ in the soil are able to change nitrogen gas into forms that plants can use.
  • Short Answers
  • 4. Why is nitrogen essential to life? __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________



Because it allows for the exchange of nitrogen between the environment and living things. During the cycle, nitrogen is changed into a form that organisms can use. Nitrogen is needed to build proteins and DNA for new cells.

the nitrogen cycle
The Nitrogen Cycle
  • The nitrogen cycle is the movement of NITROGEN from the environment to living things and back again because organisms need nitrogen to build proteins and DNA for new cells.

The Nitrogen Cycle

5. Describe, in detail, the importance of nitrogen fixation in the nitrogen cycle. ____________________________________________________________________________________________

  • 6. How do animals contribute to the nitrogen cycle? ________________________________________________________________________________________________________________________________________________________________________________________

It is when bacteria in the soil are able to change nitrogen gas into forms that plants can use.

Animals eat nitrogen contained in plants, which helps them make protein and new cells. When an animal dies, decomposition releases nitrogen back into the

soil that can be used again.


The Nitrogen Cycle

Match the organism to its role in the nitrogen cycle.

____ Nitrogen fixation A. Herbivores and Omnivores

____ Decomposition B. Bacteria

____ Receives nitrogen by eating plants C. Plant roots

____ Takes up nitrogen from soil D. Decomposers





*BONUS: Do the three cycles you learned about (water, carbon, and nitrogen cycles) affect each other in any way? Explain.


Each cycle is connected in many ways. Some forms of nitrogen & carbon are carried through the environment by water. Many nutrients pass from soil to plans and animals and back. Living organisms play a part in each of the cycles.


Earth’s atmosphere.

  • Nitrogen is found in the form of gas in the:
  • Since most organisms cannot use the nitrogen gas, it is changed into usable forms by
    • This is called
  • Organisms get the nitrogen they require by eating
  • When an organism dies the nitrogen is returned to land by

Bacteria, lightning.

nitrogen fixation.

plants or eating organisms that eat plants.

decomposers breaking down remains.



Stages of primary succession

  • Stages of secondary succession in order
  • Bare rock where nothing lives is exposed
  • Acids from pioneer species creates small particles from rocks that start to form soil
  • Enough soil forms for mosses to grow which replaces pioneer species and other tiny organisms begin to live there
  • over time, mosses are replaced by ferns, which are then replaced by grasses and wildflower; enough soil also allows shrubs and small trees to grow
  • The soil is deep enough to support a forest

A natural disaster causes a major disturbance and destroys a community leaving only some weeds left to grow

Either the wind blows seeds or insects carry seeds allowing new weeds to appear

Small trees (such as conifers may start to grow among the weeds and continue to grow to form a forest

As older trees dies, they are replaced by different trees if the climate can support them

  • Natural, gradual changes in the types of species that live in an area; can be primary or secondary
  • The gradual replacement of one plant community by another through natural processes over time
primary succession
Primary Succession

1. Begins in a place without any soil

    • Sides of volcanoes
    • Landslides
    • Flooding

2. Starts with the arrival of living things such as lichens that do not need soil to survive



  • 1.) Compare and contrast primary and secondary succession.
  • ______________________________________________________
  • ______________________________________________________
  • ______________________________________________________
  • ______________________________________________________
  • ______________________________________________________
  • ______________________________________________________
  • 2.) Describe what a pioneer species is. Why is it important to the ecosystem? ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Primary succession is when a small community of living things starts to live in an area that had no plants or animals. Starts with bare rock -> organisms living and dying on rock-> rock turning to soil. Secondary succession is the regrowth of the original plant community in an existing area that was destroyed by a natural disaster.

Pioneer species are the first organisms to grow in an area undergoing ecological succession. Pioneer species are important because they allow for the development of an ecosystem. For example, lichens are pioneer species and they help break down the rocks during primary succession that eventually leads to soil.


primary succession1
Primary Succession

Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces

When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

primary succession2
Primary Succession

3. Simple plants like mosses and ferns can grow in the new soil

primary succession3
Primary Succession
  • The simple plants die, adding more organic material

4. The soil layer thickens, and grasses, ferns, wildflowers, and other plants begin to take over

primary succession4
Primary Succession

These plants die, and they add more nutrients to the soil

  • Shrubs and tress can survive now

primary succession5
Primary Succession
  • Insects, small birds, and mammals have begun to move in
  • What was once bare rock now supports a variety of life

secondary succession
Secondary Succession

5. After hundreds or thousands of years, conifers start to grow into a forest.

secondary succession1
Secondary Succession
  • Begins in a place that already has soil and was once the home of living organisms
  • Occurs faster and has different pioneer species than primary succession
  • Example: after forest fires, in abandoned fields
secondary succession2
Secondary Succession
  • A disturbance leaves a field abandoned. Weeds, crab grass grow.
  • Year 2 - Horseweed grows.
  • Year 5-15 – small conifers start and may form forest after 100 years.
  • Conifers replaced by hardwoods if climate supports it.
climax community
Climax Community
  • A stable group of plants and animals that is the end result of the successionprocess
  • Does not always mean big trees
    • Grasses in prairies
    • Cacti in deserts