Meaning of Biology and Characteristics of Living Organisms

Meaning of Biology

Biology is the scientific study of life. It focuses on living organisms—plants, animals, and microorganisms—because living organisms possess life and are made of cells.

Because biology is a science, any definition that does not acknowledge its scientific nature is incomplete.
Most students encounter biology in secondary school because it forms the foundation for many science courses.

Etymology (Origin of the Word Biology)

The term Biology is derived from two Greek words:

• Bios — meaning life
• Logos — meaning study

Therefore, Biology = the study of life.

Biologists study anything that has life, and anything that has life must be made up of cells.

FIELDS OF BIOLOGY

Biology is a broad subject with many specialized branches. Examples include:

• Zoology – study of animals
• Botany – study of plants
• Fisheries – study of fish
• Anthropology – study of humans
• Evolutionary Biology – study of the origin and changes in organisms over time
• Ethology – study of animal behavior
• Entomology – study of insects

All these fields study organisms that possess life and are made of cells.

WHY AN ORGANISM IS CONSIDERED LIVING

What qualifies something as a living organism?

1. Presence of Cells

Cells are the basic structural and functional units of life.
Key words to note:

• Basic
• Structural
• Functional

Cells give organisms structure and enable them to carry out life processes. Anything that has cells is living; anything without cells is non-living.

From your secondary school biology, the major points of cell theory include:

1. All living things are made up of cells.

It is the presence of cells that makes organisms living.

2. All cells arise from pre-existing cells.

Cells do not appear out of nowhere; they form by cell division.

3. Cell division

This is the process through which cells reproduce and give rise to new cells, ensuring the continuity of life.

Types of Cells

Depending on classification:

• Prokaryotic cells – simple cells without a true nucleus (e.g., bacteria).
• Eukaryotic cells – cells with a true nucleus (plants, animals, fungi).
• Somatic cells – body cells.
• Gametic cells – reproductive/sex cells (sperm and egg).

PROPERTIES (CHARACTERISTICS) OF LIVING ORGANISMS

Living things possess certain features that distinguish them from non-living things.
If an object lacks these features, it is not a living organism.

1. Cellular Organisation

Life begins at the cellular level.
Hierarchy of structural organization:
Cell → Tissue → Organ → Organ System → Organism

2. Orderliness / Organisation

Living organisms are highly organized and complex.
Their parts are arranged in a coordinated and hierarchical manner.

3. Sensitivity / Response to Stimuli

Living organisms detect and respond to changes in their environment.
They respond to:

• Touch
• Heat
• Cold
• Gravity
• Light

Unlike non-living things (e.g., chairs, books), living organisms can sense and react to their surroundings.

4. Other Classical Characteristics (MR NIGER D or MR NADCEL)

From secondary school, these include:

• Movement
• Respiration
• Nutrition
• Irritability (Sensitivity)
• Growth
• Excretion
• Reproduction
• Death (or sometimes Digestion if using MR NADCEL)

Biologists expand these characteristics with additional cellular and molecular properties.