iGCSE Biology (Combined) CAIE

Characteristics of Living Organisms

Characteristics of Living Organisms

Movement

• All organisms exhibit some form of movement, although this can vary widely. For example, animals can move their entire body, plants grow towards light, and single cells move structures within themselves.

Respiration

• Respiration is a process by which energy is released from substances, usually glucose, in all living cells.
• This energy is used to carry out various bodily functions and activities.

Sensitivity

• Organisms must be sensitive and responsive to the environment around them. Sensitivity involves detection of and responses to changes in both the internal and external environments.
• For example, an organism might respond to temperature changes, light levels, or the presence of certain chemicals.

Homeostasis

• This is the ability to control internal conditions. For example, maintaining a constant body temperature or balancing water levels in the body.
• Homeostasis helps organisms to function efficiently and survive in their specific environment.

Growth

• Organisms increase their size and complexity through cell division and cell expansion, this process is known as growth.
• In some organisms like mammals, growth is more rapid during earlier stages of life.
• Some organisms like plants continue to grow throughout their life.

Reproduction

• All organisms reproduce in order to ensure the survival of their species. This can happen asexually (single parent, offspring identical to parent) or sexually (two parents, offspring genetically different to parents).
• Reproduction may result in the growth of new organisms or cells.

Excretion

• Organisms need to get rid of waste products that result from metabolic reactions. This process is called excretion.
• If these waste products were to accumulate, they could cause harm to the organism.

Nutrition

• Lastly, all organisms require nutrition. This can be in the form of light energy (for plants), the consumption of other organisms, or the absorption of simple food molecules.
• Essential nutrients include vitamins, minerals, water, carbohydrates, proteins, and fats.

Remember, there can be some variation in the way these characteristics are exhibited but in order to be considered a living organism, all must be present in some form or another.