Coordinated Science B1 Characteristics of Living Organisms
Institutional Context and Academic Overview
These study notes belong to the Coordinated Science course, specifically module B1, which covers the characteristics of living organisms. This academic material is coordinated through SISC, located at #367, Polaris Street, Borey Peng Huoth Boeung Snor, National Road No. 1, Phnom Penh, Cambodia (0654). The primary learning objective is to provide a comprehensive description of the seven fundamental characteristics common to all living entities, as defined by regulation B1.1.1.
The Mnemonic MRS GREN and the Definition of Life
All living organisms display seven specific characteristics that distinguish them from non-living matter. These characteristics can be remembered using the mnemonic MRS GREN, which represents Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition. Every living thing, regardless of its size or complexity, must demonstrate all seven of these biological processes at some stage in its life cycle to be classified as a living organism. Under the B1.1.1 syllabus, each characteristic is defined by specific physical or chemical parameters.
Physiological Processes: Movement and Respiration
Movement is defined as an action performed by an organism, or a part of an organism, that causes a change of position or place. This can refer to the locomotion of an entire animal from one point to another or the subtle shifting of a plant's leaves or roots.
Respiration involves the chemical reactions occurring within cells that break down nutrient molecules to release energy. This energy is essential for metabolism, which represents the sum total of all chemical reactions taking place within the cells of an organism, including those that sustain life and allow the organism to perform work.
Interaction and Development: Sensitivity and Growth
Sensitivity is the ability of an organism to detect and respond to changes in the internal or external environment. This involves sensing stimuli, which are specific changes in the surroundings or within the body, and initiating appropriate responses to maintain survival or homeostatic balance.
Growth is characterized by a permanent increase in size and dry mass. This process occurs through two primary mechanisms: an increase in the number of cells within the organism, an increase in the individual size of those cells, or a combination of both. Because growth is defined by dry mass, it excludes temporary increases in size due to water intake.Maintenance and Continuation: Reproduction and Excretion
Reproduction encompasses the various biological processes that result in the creation of more organisms of the same kind. This ensures the survival of the species over generations.
Excretion is the process of removing substances from the organism that are no longer needed or are harmful. This includes the removal of waste products of metabolism, such as those generated by chemical reactions like respiration. Excretion also involves the clearance of toxic materials and any substances that are present in quantities that exceed the biological requirements of the organism.
Nutritional Requirements across Kingdoms
Nutrition is the process of taking in materials required for energy, growth, and development. The requirements for nutrition differ significantly between plants and animals. Plants are autotrophic in nature and requires light, carbon dioxide, water, and ions to synthesize their own nutrients. Animals are heterotrophic and require the intake of organic compounds and ions; they also generally require a consistent supply of water to facilitate their biological processes.
Practical Identification and Evaluative Resources
A critical part of studying these characteristics is the ability to identify and differentiate between living and non-living things based on the presence of MRS GREN. This is explored through observational exercises and visual data analysis. Specific case studies and demonstrations of these characteristics can be found in supplementary educational videos at the following locations:
https://www.youtube.com/watch?v=MipF2kPnwH4
https://www.youtube.com/watch?v=nDW27n5qtN8
Assessment of this knowledge is typically conducted through the completion of dedicated worksheets, and students are expected to master these definitions as provided without the use of a textbook during the initial evaluation phase.