Overview
This lecture covers the seven key characteristics that define living organisms, using the acronym MRS GREN, and distinguishes them from non-living things.
Characteristics of Living Things (MRS GREN)
- All living organisms share seven features: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition (MRS GREN).
- Non-living things may show some features, but only living things possess all seven.
Movement
- Movement refers to the ability of organisms to move their entire body or parts (plants may move leaves towards light).
Respiration
- Respiration is a set of chemical reactions in cells breaking down nutrients to release energy for metabolism.
- Metabolism includes all chemical processes that keep an organism alive.
Sensitivity (and Control)
- Sensitivity is the ability to detect and respond to changes in the internal or external environment (e.g., temperature).
- This feature helps organisms control their internal conditions (homeostasis).
Growth
- Growth is a permanent increase in size and dry mass (excluding water content).
Reproduction
- Reproduction is the process of making more organisms of the same kind.
Excretion
- Excretion removes metabolic waste products (e.g., urea, carbon dioxide) and excess substances (e.g., extra water or mineral ions).
Nutrition
- Nutrition involves taking in materials for energy, growth, and development (eating/drinking for animals; absorption for bacteria/fungi).
Distinguishing Features
- All living things are made up of one or more cells.
- Viruses are not considered living organisms because they do not fulfill all seven characteristics.
Key Terms & Definitions
- Organism — Any living thing that possesses all seven characteristics of life.
- Metabolism — The sum of all chemical reactions in an organism.
- Homeostasis — Maintaining a stable internal environment by responding to external changes.
- Excretion — Removal of metabolic waste and excess substances from the body.
Action Items / Next Steps
- Review the seven characteristics and ensure you understand each one.
- Prepare for questions comparing living and non-living things.
- Watch the next video on the structure of cells.