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CHARACTERISTICS OF LIFE:
Cells
- Living things are made of cells while non-living things aren't, cells carry out activities necessary for the organism to stay alive.
- All organisms need energy to stay alive. They need materials to make protoplasm in the cells.
- Nutrition = the process by which organisms take in food and convert it into new protoplasm.
- Organisms gain energy and materials needed from food. Plants photosynthesize while animals feed on other organisms.
- Non-living things don't require nutrition. (Unable to to convert substances into part of them)
- Living organisms gain energy through respiration. Respiration = Oxidation of food substances to release energy for call activities.
- Organic food substances such as carbohydrates and fats are used to store energy. This energy is set free when these substances are broken down through respiration into carbon dioxide and water.
Excretion
- Glucose broken down(in respiration) ---> chemical reaction takes place
- Numerous chemical reactions occur in the cells of a living organisms.
- These chemical reactions are called biochemical reactions, metabolism is the sum of all biochemical reactions that take place within the cell.
- Some biochemical reactions produce waste substances that are useless or harmful to the organism, and must be removed, this process is excretion.
- Substances which are to be removed are excretory products.
- Living organisms are open systems continually receiving and disposing both energy and materials.
- Cells require a constant chemical and physical environment in order to carry out their functions. The maintenance of a constant internal environment = homeostasis.
- Growth is a permanent increase in the mass and volume of an organism when absorbed food is converted into protoplasm. Some of the new matter formed is used to repair worn-out parts of the cells while the rest is added to the original living matter and this increases its size.
- Growth may make an organism more complex or even change its form.
- The body of an organism can change and become larger in size and can also become more complex.
- A non-living thing does not grow.
- The movement of organisms is independent of external forces.
- Most animals are able to move from one place to another and such movement is termed locomotion.
- Animals such as corals and sponges do not have the power of locomotion and most plants are unable to carry out locomotion.
- In reproduction, some characteristics are passed on from parents to their offspring.
- Organisms are mortal, they die of disease, old age, in accidents or being eaten by other organisms.
- Reproduction is necessary for a species to survive.
- Animals and plants are sensitive to changes in their environment, they often react to changes in ways which are beneficial to themselves.
- A change in the environment or an external influence causes the organisms to react in a predictable way. Such a change/external influence is called stimulus (plural: stimuli).
- The reaction to a stimulus is known as a response, this response to stimuli is termed sensitivity/irritability.
- Living organisms are able to adjust and adapt to changes in their environment. Non-living things do not show adaptive responses.
- An adaptation is any characteristic of an organism that improves its chances of surviving in its environment. It improves chances of survival, support reproduction and the rearing of an offspring.
Machines do not reproduce and they do not grow. All characteristics of life must be considered when distinguishing between a living organism from non-living matter.
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