What Makes Something Alive
- All living organisms share a set of functions that define life.
- Cells are the smallest units capable of carrying out these functions independently.
Viruses, although containing genetic material, do not meet these criteria and are therefore non-living.
The Characteristics of Living Things
- Living organisms can be distinguished from non-living matter by a universal set of functions of life:
- Metabolism: Chemical reactions that convert energy and build molecules (e.g., respiration, photosynthesis).
- Reproduction: The ability to produce offspring and pass on genetic information.
- Homeostasis: Maintaining a stable internal environment despite external changes.
- Growth: Increasing in size or cell number.
- Response to Stimuli: Detecting and reacting to changes in the environment.
- Excretion: Removing waste products from metabolism.
- Nutrition: Acquiring energy and materials, either by producing food (autotrophs) or consuming others (heterotrophs).
- Non-living things, like rocks or water, may change over time but do not perform these functions internally.
- Use MR H GREN to quickly recall the seven functions in structured or list-based questions:
- Metabolism
- Reproduction
- Homeostasis
- Growth
- Response
- Excretion
- Nutrition
Cells: The Smallest Units of Life
Definition
Self-sustaining life
The ability of a system to maintain and regulate its internal order and functions (metabolism, energy use, repair, reproduction) independently, without requiring assembly from external agents.
- Key properties of cells:
- Metabolic regulation: Cells use energy (ATP) to maintain internal order. Without energy, they lose structure and die.
