What do plants and animals need to grow?

Almost all plants and animals need air, water, light, and nutrition to grow. Green plants use a complicated chemical process, called photosynthesis, to create energy for survival and growth. Since plants create their own energy, they are the first link in the food chain. Animals need to drink water and eat plants or other animals to get energy. Therefore, they are present at the next step in the food chain. There are some animals, like camels, that can survive for days without drinking water. Since they live in deserts with very little water, they have adapted to the special conditions of their habitat.

How do plants get food?

Unlike animals, plants produce their own food and except for a few carnivorous plants, do not eat other organisms. Green plants use water, nutrients, and a green matter in their leaves called 'chlorophyll' to produce their food. Normally water and nutrients are absorbed from the ground through their roots. Some plants, however, have developed other methods for obtaining water and nutrients. Many plants make funnel-shaped 'containers' with their leaves to catch water. Carnivorous plants use their digestive juices to convert the insects, made in their folding or sticky traps, into nutrients.

What happens when we keep plants in the dark?

In the absence of light, plants shed their leaves and die, leaving only their roots and stems. Plants grow slowly at night and in winters. Most animals are also dependent on light, although some have adapted to their dark habitats. For example, the moles living below the ground are almost blind because they do not need their eyes underground. We humans also need sunlight to help produce vitamin D in our skin, which in turn is needed for building bones. We will also lose time if it is pitch dark around us for very long.

What is photosynthesis?

The chloroplast inside the green leaves of plants is the 'workshop' where photosynthesis takes place. Water is supplied to the leaves by the roots, and carbon dioxide is absorbed from the air through tiny pores on the lower side of the leaf. Both of these are broken down into the elements hydrogen, carbon, and oxygen with the help of chlorophyll and sunlight. Plants build 'glucose' (grape sugar) from these elements and oxygen is released in the atmosphere as a by-product. Photosynthesis has been the source of oxygen in the air since the origin of life on the Earth.

How do camels survive long voyages in the desert?

Camels can manage for about two weeks without drinking water because they can store up to 150 liters of water in their bodies. Fat is also stored in their humps and this store of energy can sustain them for about 30 days without food. Furthermore, unlike most other mammals, camels can change their body temperature. At night they lower their body temperature considerably so during the day the body warms slowly and they do not sweat much. Consequently, there is no loss of fluids early in the day.

What is the food chain?

In nature, there are 'producers' that build the biological mass, and 'consumers' that eat. Producers are the plants, which grow and create energy with the help of photosynthesis. They are eaten by a consumer, and that consumer is often eaten by another consumer. This chain of consumers is called the 'food chain'. A short food chain is grass-cow-man. A longer one is algae-water flea-herring-seal-polar bear: A water flea eats algae, a herring eats many water fleas, a seal eats herrings, and the polar bear eats the seal. Ultimately, a lot of algae are needed to feed a polar bear. When the polar bear dies, its meat is either eaten by other animals or it is decomposed into nutrients by bacteria. These nutrients are again used by the algae to create energy, and then the food chain gets completed.