Recycling Materials

• All materials in the living world need to be recycled so that they can be used again for future organisms
• What does the carbon cycle describe?

  How carbon is recycled in nature
• The carbon cycle relies on decomposers to return carbon to the atmosphere as carbon dioxide , through respiration
• What does the water cycle describe?

  How fresh water circulates between living organisms , rivers and the sea
• Describe the 2 stages of the carbon cycle

  Carbon dioxide from the atmosphere (0.04% of it in the air) enters the carbon cycle through photosynthesis - which uses light energy and is carried out by plants . Carbon dioxide returns to the atmosphere through aerobic respiration
• Describe the role of plants in the carbon cycle carbon cycle?

  Plants take in carbon dioxide from the atmosphere for photosynthesis - the carbon is used to make carbohydrates , fats and proteins which make up the cells of plants - plants then respire so some of the carbon is released back into the atmosphere as carbon dioxide
• Describe the role of animals in the carbon cycle?

  Plants that take in carbon (from photosynthesis) are eaten by animals - these animals are eaten by other animals - so the carbon in the plants, becomes part of the carbohydrates , fats and proteins in the cells of animals - the animals respire and some of the carbon is released back into the atmosphere as carbon dioxide - carbon is also present in the waste and dead remains of animals - these are broken down by decomposers - they then respire and release carbon dioxide back into the atmosphere
• Decomposers are important as they cycle materials through an ecosystem
• Decomposers release mineral ions to the soil
• What happens if decomposers cannot function effectively?

  The carbon in dead remains can slowly be converted into fossil fuels
• Over millions of years , a large amount of carbon has been trapped underground as fossil fuels
• Describe the role of combustion in the carbon cycle?

  Over the last 200 years, humans have been burning fossil fuels (e.g. coal and oil) - combusting fossil fuels releases a large amount of carbon dioxide back into the atmosphere
• The majority of water on Earth is found in the oceans - this is salt water
• Describe the Water cycle?

  Energy from the sun causes water to evaporate from the surface of the sea - the water vapour travels into the air and cools down. When it cools, the water vapour condenses to form clouds - The clouds contain water which falls to the ground as precipitation (e.g. rain and snow) - some of it evaporates back into the atmosphere as water vapour - some of it passes through rocks and forms aquifers - most of the water forms rivers, and the water in these drains back into the sea
• All forms of precipitation contain fresh water (do not contain salt)
• How do living organisms play a part in the water cycle?

  Plants take up water in their roots and move this water up the xylem and passes out of the stomata as water vapour (This process is transpiration) - Animals take in water from drinking and food , and release water in their urine , faeces and when they exhale