CHARACTERISTICS OF LIVING ORGANISMS
(HSB GRADE 10)
Introduction
All living entities display a set of fundamental biological processes that collectively define life. In
CSEC Human and Social Biology (HSB), these functions are remembered using the standard
mnemonic GRIMNER (Growth, Respiration, Irritability/Sensitivity, Movement, Nutrition, Excretion,
Reproduction) or MRS GREN.
To understand living organisms, a clear distinction must be made between living, non-living, and
dead matter:
● Living Matter: Exhibits all seven characteristics simultaneously, driven by continuous
metabolic activity (the sum of all chemical reactions in cells) and organized into one or
more cells containing active genetic material.
● Non-Living Matter: Inanimate structures (such as rocks or water) that have never
possessed metabolic capability, cellular organization, or biological processes.
● Dead Matter: Materials derived from once-living organisms where metabolic processes,
respiration, and cellular activity have permanently ceased (e.g., fallen timber or leaf litter).
Detailed Breakdown of the 7 Characteristics
1. Movement
Definition: An action by an organism or part of an organism causing a change of position or place.
● Animals vs. Plants:
○ Animals: Display active locomotion (the movement of the whole body from one
location to another), driven by organized muscular contractions working against
skeletal structures. Locomotion enables organisms to source food, escape
predators, and locate mates.
○ Plants: Fixed in place (sessile) and do not undergo locomotion. Instead, they exhibit
directional growth movements known as tropisms, controlled by plant hormones
, (auxins). Examples include phototropism (stem orientation toward light) and
geotropism (root growth downward into the soil).
● Cellular Level: At the microscopic level, all living cells exhibit movement. This includes
cytoplasmic streaming (cyclosis)—the coordinated flow of cytosol—and the active
transportation of organelles and vesicles along intracellular cytoskeletal tracks.
2. Respiration
Definition: The biochemical process occurring within cells by which nutrient molecules (primarily
glucose) are broken down to release chemical energy in the form of adenosine triphosphate
(ATP).
● Aerobic Respiration:
○ Requires oxygen to completely breakdown glucose, generating a high yield of
energy.
○ Chemical Equation:
$$\text{C}6\text{H}{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 +
6\text{H}_2\text{O} + 38\text{ ATP}$$
○ Primarily takes place within the mitochondria of eukaryotic cells and is the default
pathway for human tissue metabolism.
● Anaerobic Respiration:
○ Occurs in the absence of oxygen, resulting in incomplete glucose breakdown and a
lower energy yield (2 ATP).
○ Human Muscle Cells (Lactic Acid Fermentation): During strenuous physical
exertion, oxygen supply may fall below demand, converting glucose to lactic acid:
$$\text{Glucose} \rightarrow \text{Lactic Acid} + 2\text{ ATP}$$
○ Yeast Cells (Alcoholic Fermentation): Used in food production and biotechnology:
$$\text{Glucose} \rightarrow \text{Ethanol} + \text{Carbon Dioxide} + 2\text{
ATP}$$
● Critical CSEC Distinction: Do not confuse respiration with breathing (gaseous exchange).
Breathing is the physical mechanism of moving air in and out of the lungs, whereas
respiration is the biochemical cell-level breakdown of nutrients to yield ATP.
3. Sensitivity (Irritability)
Definition: The ability of an organism to detect or sense changes in its internal or external
environment (stimuli) and execute appropriate physiological or behavioral responses.
(HSB GRADE 10)
Introduction
All living entities display a set of fundamental biological processes that collectively define life. In
CSEC Human and Social Biology (HSB), these functions are remembered using the standard
mnemonic GRIMNER (Growth, Respiration, Irritability/Sensitivity, Movement, Nutrition, Excretion,
Reproduction) or MRS GREN.
To understand living organisms, a clear distinction must be made between living, non-living, and
dead matter:
● Living Matter: Exhibits all seven characteristics simultaneously, driven by continuous
metabolic activity (the sum of all chemical reactions in cells) and organized into one or
more cells containing active genetic material.
● Non-Living Matter: Inanimate structures (such as rocks or water) that have never
possessed metabolic capability, cellular organization, or biological processes.
● Dead Matter: Materials derived from once-living organisms where metabolic processes,
respiration, and cellular activity have permanently ceased (e.g., fallen timber or leaf litter).
Detailed Breakdown of the 7 Characteristics
1. Movement
Definition: An action by an organism or part of an organism causing a change of position or place.
● Animals vs. Plants:
○ Animals: Display active locomotion (the movement of the whole body from one
location to another), driven by organized muscular contractions working against
skeletal structures. Locomotion enables organisms to source food, escape
predators, and locate mates.
○ Plants: Fixed in place (sessile) and do not undergo locomotion. Instead, they exhibit
directional growth movements known as tropisms, controlled by plant hormones
, (auxins). Examples include phototropism (stem orientation toward light) and
geotropism (root growth downward into the soil).
● Cellular Level: At the microscopic level, all living cells exhibit movement. This includes
cytoplasmic streaming (cyclosis)—the coordinated flow of cytosol—and the active
transportation of organelles and vesicles along intracellular cytoskeletal tracks.
2. Respiration
Definition: The biochemical process occurring within cells by which nutrient molecules (primarily
glucose) are broken down to release chemical energy in the form of adenosine triphosphate
(ATP).
● Aerobic Respiration:
○ Requires oxygen to completely breakdown glucose, generating a high yield of
energy.
○ Chemical Equation:
$$\text{C}6\text{H}{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 +
6\text{H}_2\text{O} + 38\text{ ATP}$$
○ Primarily takes place within the mitochondria of eukaryotic cells and is the default
pathway for human tissue metabolism.
● Anaerobic Respiration:
○ Occurs in the absence of oxygen, resulting in incomplete glucose breakdown and a
lower energy yield (2 ATP).
○ Human Muscle Cells (Lactic Acid Fermentation): During strenuous physical
exertion, oxygen supply may fall below demand, converting glucose to lactic acid:
$$\text{Glucose} \rightarrow \text{Lactic Acid} + 2\text{ ATP}$$
○ Yeast Cells (Alcoholic Fermentation): Used in food production and biotechnology:
$$\text{Glucose} \rightarrow \text{Ethanol} + \text{Carbon Dioxide} + 2\text{
ATP}$$
● Critical CSEC Distinction: Do not confuse respiration with breathing (gaseous exchange).
Breathing is the physical mechanism of moving air in and out of the lungs, whereas
respiration is the biochemical cell-level breakdown of nutrients to yield ATP.
3. Sensitivity (Irritability)
Definition: The ability of an organism to detect or sense changes in its internal or external
environment (stimuli) and execute appropriate physiological or behavioral responses.
