The concept of the cell is one of the most important foundations of biology because it explains how living organisms are structured and how life functions at the most basic level. Every plant, animal, and microorganism is made up of cells, which perform all the essential activities needed for survival. Understanding the cell in biology involves knowing its meaning, how it was discovered, and the ideas behind the cell theory that guide modern biological studies.
Table Of Contents
- Meaning of a cell
- Classification of living organisms based on the number of cells
- History of the cell
- The cell theory.
- Revision question.
Cell As Living Unit Of An Organism
Meaning of a cell in Biology
The cell is defined as a structural and functional unit of a living organism. In other words, the cell is the simplest, the smallest and basic unit of life. All living things (plants and animals) are made of cells.
The cell is regarded as the basic unit of all living things because it can carry out all life activities such as feeding, reproduction, excretion, growth, adaptation, respiration, definite lifespan, sensitivity and movement. All these activities possessed by a cell are Characteristics of living things.
Classification of living organisms based on the number of cells
Living organisms are classified into two major groups based on the number of cells. These groups are:
1. Unicellular or accelular organisms: These are organisms which consists of only one cell.
Examples of unicellular organisms are:
- Amoeba
- Chlamydomonas
- Euglena
- Paramecium
2. Multicellular organism: These are organisms which consists of two or more cells. In other words, these organisms have many cells.
Examples of multicellular organisms are:
- Volvox
- Hydra
- Spirogyra
- Flowering plants
- Fish
- Bird
- Man.
History of the Discovery of the Cell
The discovery of the cell dates back to the seventeenth century when scientific curiosity and the invention of the microscope opened new paths in biological research. In 1665, Robert Hooke observed thin slices of cork under a simple microscope and noticed small box-like compartments, which he named “cells” because they resembled the small rooms occupied by monks. Although the cork cells were dead, Hooke’s observation marked the first recorded description of cells.
Later, Antonie van Leeuwenhoek improved microscope lenses and became the first scientist to observe living cells, which he described as “animalcules.” His discoveries included bacteria, protozoa, and sperm cells. Over time, other scientists such as Matthias Schleiden and Theodor Schwann expanded the understanding of cells by studying plant and animal tissues, leading to the development of a unifying concept known as cell theory.
Many scientist contributed to the history of the cell. Among the scientists are:
- Robert Hooke, An English scientist could be seen as the father of cells. He was the first human being to discover honey-comb structure of the cell in 1665. In his book, micrographia, he described his observations of a magnified thin slice of a cork of an oak tree. He established that the cork is made up of thin component or rooms. He then named the component cells.
- Felix Dujarding, A French biologist in 1835 discovered that the cell was made up of living substance. He however name the Living substance protoplasm.
- Matthias Schleiden, A German botanist in 1838 revealed that the bodies of plants are made up of cells which were described as units of life.
- Theodore Schwann, Another German zoologist in 1839 also discovered that the body of all animals are composed of cells. The discoveries of Schleiden and Schwann led to the postulation of the cell theory in 1839.
- Rudolph Von Virchow, A German biologist in 1855 concluded in his research that all cells come from previous existing cells.
The Cell Theory
Cell theory is a fundamental principle in biology that explains the nature of cells and their role in living organisms. The theory was developed in the nineteenth century based on extensive microscopic observations and scientific research.
The main statements of cell theory include the idea that all living organisms are made up of one or more cells, the cell is the basic unit of structure and function in living things, and all cells arise from pre-existing cells through cell division. These statements emphasize that life does not arise spontaneously and that every new cell originates from another living cell.
The cell theory states that:
- The cell is the structural and functional unit of life.
- All living organisms are made up of cells.
- All cells come from previously existing cells.
- There is no life apart from the life of cells.
- All living things are either single cell (unicellular) or group of cells (multicellular).
Importance of Cell Theory in Biology
Cell theory is important because it provides a scientific explanation for growth, reproduction, and development in living organisms. It helps biologists understand how diseases occur when cells malfunction and forms the basis for fields such as genetics, microbiology, and medicine. Without cell theory, the study of life processes at the microscopic level would lack a clear scientific foundation.
Read Also
- Types of Respiration, Meaning And Importance
- Reproductive systems in mammals and their functions
- Reproductive systems in plants and mechanisms
Revision Questions on Meaning of a Cell in Biology
- What is the meaning of a cell?
- Explain the forms in which living cells exist and give an example in each case.
- Briefly describe the history of the cell.
- (a) Explain briefly the cell theory (b) Name two scientist who contributed to the development of the set theory.
Frequently Asked Questions On Cell in Biology
1. What is a cell?
A cell is the smallest structural and functional unit of life capable of carrying out all life processes.
2. Who discovered the cell and when?
The cell was discovered by Robert Hooke in 1665.
3. What did Antonie van Leeuwenhoek contribute to cell discovery?
He was the first to observe living cells using improved microscopes.
4. State one principle of cell theory.
All living organisms are made up of one or more cells.
5. Why is cell theory important in biology?
It explains the structure, growth, and functioning of living organisms.