MRS GREEN.

Movement

Living things are able to move in a controlled way, usually towards food and nutrients and away from less favourable conditions, even danger. Whilst animals can often move quickly, most plant responses are much slower e.g. a plant growing towards light. However, some plants can move much faster – the Venus fly trap can close its leaves to imprison its victim in less than a second!

Respiration

Respiration is the process of releasing energy from food, and is a series of chemical reactions inside all living cells. The energy produced drives processes such as growth and movement, so is essential to all living things.

Sensitivity

This is the ability to sense and respond to the external environment. Special receptors detect stimuli like light, sound, temperature and even gravity, allowing the organism to alter its behaviour or growth.

Growth

This is where organisms increase in size. Some organisms e.g. plants, may grow continually throughout their lifetime, and most animals grow from young into adults, not only increasing in size but also developing. An adult bird looks very different from the newly hatched chick.

Reproduction

All living things live for a time, then die. Reproduction allows organisms to continue the species after death, and to colonise new habitats to extend their range. Some reproduce asexually where the offspring grows from part of the parent so is genetically identical. Most reproduce sexually with the resultant offspring being the product of two parents. Gametes produced by both parents come together resulting in fertilisation – often by very elaborate means e.g. pollen (the male gamete), which is transferred to the female parts of another flower with the help of insects like bees.

Excretion

This is the removal of waste materials produced within cells (often during respiration) that would build up to toxic levels if not eliminated. Examples include urea, and carbon dioxide. Simple single-celled organisms eliminate these materials via diffusion, but more complex organisms have organ systems dedicated to the process e.g. kidneys and bladder dedicated to removal of urea in mammals.

Environment

Control of the internal environment to be precise. Whether maintaining a constant internal temperature, maintaining a suitable oxygen concentration, water levels, even pH, these all allow cellular processes to proceed at their optimum rates.

Nutrition

Organisms need a source of food which can be respired to produce energy (respiration). Plants are unique as they can make their own food by photosynthesis. They combine carbon dioxide with water to produce simple sugars and oxygen as a by-product. They are known as autotrophs. All other organisms obtain their food by eating other plants and animals (heterotrophs), some by feeding on dead plants and animals (saprobionts) and some bacteria can even oxidise inorganic compounds.