Needs of living things
"Life" can be thought of in purely chemical terms as a complex set of chemical reactions occurring in the cells of the organism. Cells are like small factories all doing their jobs so that the overall corporation, the body, is an efficient organisation. The total of all these reactions creates a moving, respiring, reproducing organism which can respond to changes in its environment, helping it to survive. Some organisms carry out these functions in a single cell, but most are multicellular. What do living things need to ensure the chemical reactions keep going? Food Food is also needed as the source of the basic chemicals (nutrients) required to make new cells. Plants can make their own food by photosynthesis using sunlight, carbon dioxide and water. They then use this, along with soil nutrients, for their own energy needs. Oxygen Water Warmth (correct temperature
range) Plants can survive at lower temperatures with a slow metabolic rate as they don't need to move about for food or mating. "Warm-blooded animals" (scientists call them homoiothermic or endothermic) such as birds and mammals have an internal source of body heat, and feathers, fur or hair to assist in keeping their body temperature constant all year round so that they are always active and survive well even in cold places. "Cold-blooded" animals (poikilothermic or ectothermic) cannot
keep their body temperature constant (it goes up or down with the surrounding
air temperature) which means they are slower or inactive in colder conditions
until they can warm up (e.g. butterflies spread their wings to the Sun
in the morning, and lizards lie on the warm roads).
Protection
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