Study Notes
Living organisms share several key characteristics that define life, including movement, respiration, sensitivity, homeostasis, growth, reproduction, excretion, and nutrition.
- Movement — action by an organism or part of an organism causing a change of position or place. Example: Plants moving according to light (phototropism).
- Respiration — chemical reactions that break down nutrient molecules in living cells to release energy. Example: Energy release for essential functions.
- Sensitivity — ability to detect or sense changes in the environment (stimuli) and to make appropriate responses. Example: Plants responding to gravity (geotropism).
- Homeostasis — a state of balance among all the body systems needed for the body to survive and function correctly. Example: Sweating to cool down in hot weather.
- Growth — permanent increase in size and dry mass by an increase in cell number or cell size or both. Example: Animals growing larger over time.
- Reproduction — processes that make more of the same kind of organism. Example: Sexual and asexual reproduction.
- Excretion — removal from organisms of toxic materials, the waste products of metabolism, and substances in excess of requirements. Example: Animals exhaling carbon dioxide.
- Nutrition — taking in of materials for energy, growth, or development. Example: Plants absorbing nutrients from the soil.
Exam Tips
Key Definitions to Remember
- Movement: Change of position or place
- Respiration: Energy release from nutrients
- Sensitivity: Detecting environmental changes
- Homeostasis: Balance of body systems
- Growth: Increase in size and mass
- Reproduction: Making more of the same organism
- Excretion: Removal of waste products
- Nutrition: Intake of materials for energy and growth
Common Confusions
- Confusing respiration with breathing
- Mixing up excretion and egestion
Typical Exam Questions
- Which process is carried out by all organisms? Growth
- Which process occurs both in plants and animals? Excretion
- Some lizards detach their tails when threatened by a predator. Which characteristic is shown? Sensitivity
What Examiners Usually Test
- Understanding of each characteristic of living organisms
- Ability to identify examples of each characteristic
- Distinguishing between similar processes like excretion and egestion