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Nutrients are very important for life to exist. An essential nutrient is any chemical element that is needed for a plant to be able to grow from a seed and complete its life cycle. The same is true for animals. A macronutrient is one that is required in large quantities by the plant or animal, while a micronutrient is one that only needs to be present in small amounts for a plant or an animal to function properly.
A nutrient is a substance that is used in an organism's metabolism or physiology and which must be taken in from the environment.
In plants, the macronutrients include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P) and potassium (K). The source of each of these nutrients for plants, and their function, is summarised in [link] . Examples of micronutrients in plants include iron, chlorine, copper and zinc.
| Nutrient | Source | Function |
| Carbon | Carbon dioxide in the air | Component of organic molecules such as carbohydrates, lipids and proteins |
| Hydrogen | Water from the soil | Component of organic molecules |
| Oxygen | Water from the soil | Component of organic molecules |
| Nitrogen | Nitrogen compounds in the soil | Part of plant proteins and chlorophyll. Also boosts plant growth. |
| Phosphorus | Phosphates in the soil | Needed for photosynthesis, blooming and root growth |
| Potassium | Soil | Building proteins, part of chlorophyll and reduces diseases in plants |
Animals need similar nutrients in order to survive. However since animals can't photosynthesise, they rely on plants to supply them with the nutrients they need. Think for example of the human diet. We can't make our own food and so we either need to eat vegetables, fruits and seeds (all of which are direct plant products) or the meat of other animals which would have fed on plants during their life. So most of the nutrients that animals need are obtained either directly or indirectly from plants. [link] summarises the functions of some of the macronutrients in animals.
| Nutrient | Function |
| Carbon | Component of organic compounds |
| Hydrogen | Component of organic compounds |
| Oxygen | Component of organic compounds |
| Nitrogen | Component of nucleic acids and proteins |
| Phosphorus | Component of nucleic acids and phospholipids |
| Potassium | Helps in coordination and regulating the water balance in the body |
Micronutrients also play an important function in animals. Iron for example, is found in haemoglobin, the blood pigment that is responsible for transporting oxygen to all the cells in the body.
Nutrients then, are essential for the survival of life. Importantly, obtaining nutrients starts with plants, which are able either to photosynthesise or to absorb the required nutrients from the soil. It is important therefore that plants are always able to access the nutrients that they need so that they will grow and provide food for other forms of life.
Plants are only able to absorb soil nutrients in a particular form. Nitrogen for example, is absorbed as nitrates , while phosphorus is absorbed as phosphates . The nitrogen cycle (Grade 10) describes the process that is involved in converting atmospheric nitrogen into a form that can be used by plants.
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