- Living organisms respond to the stimuli
- Living organisms interact with their environment, which includes members of the same and other species.
- Living organisms have a metabolism: they take in food which they then convert as energy to perform their daily or day to day activities.
- Living organisms reproduce: they give birth to others of the same species, in order to continue their ancestral living. This is not true of all individual organisms. In eusocial organisms, some castes cannot reproduce. But, since the sterile workers are all the produce of a single queen, they are one collective.
Many things that appear to be one organism are in fact several living together. An example is lichen. Lichen is a symbiosis between a blue-green algae and fungi. Organisms that live together may not reproduce together, but their life processes bound up together. They help each other to live.
five examples of life processes[change | change source]
- Physiological process, those processes specifically pertinent to the functioning of integrated living units: cells, tissues, organs, limbs, and organisms.
- Response to stimulus: (in terms of movement impulses, secretion, enzyme production, gene expression, etc). In animals, this is mainly the function of the nervous system.
- Other processes: cell growth, cellular differentiation, fermentation, fertilisation, germination, tropism, hybridisation, metamorphosis, morphogenesis, photosynthesis, transpiration.
Modern ideas[change | change source]
Cells and macro-molecules[change | change source]
All life processes on Earth use the chemistry of carbon compounds. In particular, all life uses long-chain molecules such as proteins and nucleic acid. With water, which is essential, the long molecules are wrapped inside membranes to form cells. This is true of all known life.
Systems theory[change | change source]
Living organisms are open systems. The main idea is that the processes serve to keep them alive by homeostasis. They are always changing, but always staying within certain limits as long as they live. 
They do this by exchanging materials and information with their environment. They undergo metabolism, maintain homeostasis, possess a capacity to grow, respond to stimuli and reproduce. All of this preserves the individual and its race or species.
Related pages[change | change source]
References[change | change source]
- Cannon W.B. 1932. The wisdom of the body. London.
- Reiner J.M. 1960. The organism as an adaptive control system. Prentice-Hall, Englewood Cliffs, New Jersy.