CHAPTER - 5
THE FUNDAMENTAL UNIT OF LIFE
Introduction
• Cell is the structural and functional unit of life. It is the basic unit of life.
• It was discovered by Robert Hooke in 1665 in a cork slice with the help of a primitive
microscope.
• Leeuwenhoek (1674), discovered the free living cells in pond water with the improved
microscope.
• Robert Brown discovered the nucleus in the cell in 1831.
• Purkinje coined the term ‘protoplasm’ for the fluid substance of the cell in 1839.
The cell theory
• The theory that all plants and animals are composed of cells and the cell is the basic unit of
life, was presented by two biologists, Schleiden and Schwann.
• The cell theory was further expanded by Virchow by suggesting that all cells arise from
pre-existing cells.
Types of organisms
• On the basis of no. of cells, organisms are of two types:
(i) Unicellular Organism
(ii) Multicellular Organism
(i) Unicellular Organism:
These organisms are single celled which perform all the functions. Example: Amoeba,
paramecium, bacteria.
(ii) Multicellular Organism:
Many cells are grouped together to perform different functions in the body and also form various
body parts. Example: fungi, plants, animals.
• The shape and size of cells are different according to the kind of function they perform. There
is division of labour in cells.
• Each cell has a certain kind of cell organelles to perform different types of function like
mitochondria for respiration.
Types of cells
• There are two types of cells:
, (i) Prokaryotes
(ii) Eukaryotes
Prokaryotes Eukaryotes
● Cells of organisms lacks nuclear ● Cells of organism have nuclear
membrane. membrane.
● Nucleolus is absent. ● Nucleolus is present.
● Single chromosomes. ● Single or multi chromosomes.
● Reproduction is always asexual. ● Reproduction is both sexual and
asexual.
● Always unicellular. ● Often multicellular.
● Membrane bound cell organelles are ● Membrane bound organelles are
absent. present like mitochondria.
● Centriole is absent ● Centriole is present only in animals
cell.
● Cell division is by binary fission. ● Cell division is by mitosis or meiosis.
● Example: Bacteria, Blue green algae, ● Example: Fungi, Plant cell, Animal cell
etc. etc.
Difference between Animal cell and Plant cell
THE FUNDAMENTAL UNIT OF LIFE
Introduction
• Cell is the structural and functional unit of life. It is the basic unit of life.
• It was discovered by Robert Hooke in 1665 in a cork slice with the help of a primitive
microscope.
• Leeuwenhoek (1674), discovered the free living cells in pond water with the improved
microscope.
• Robert Brown discovered the nucleus in the cell in 1831.
• Purkinje coined the term ‘protoplasm’ for the fluid substance of the cell in 1839.
The cell theory
• The theory that all plants and animals are composed of cells and the cell is the basic unit of
life, was presented by two biologists, Schleiden and Schwann.
• The cell theory was further expanded by Virchow by suggesting that all cells arise from
pre-existing cells.
Types of organisms
• On the basis of no. of cells, organisms are of two types:
(i) Unicellular Organism
(ii) Multicellular Organism
(i) Unicellular Organism:
These organisms are single celled which perform all the functions. Example: Amoeba,
paramecium, bacteria.
(ii) Multicellular Organism:
Many cells are grouped together to perform different functions in the body and also form various
body parts. Example: fungi, plants, animals.
• The shape and size of cells are different according to the kind of function they perform. There
is division of labour in cells.
• Each cell has a certain kind of cell organelles to perform different types of function like
mitochondria for respiration.
Types of cells
• There are two types of cells:
, (i) Prokaryotes
(ii) Eukaryotes
Prokaryotes Eukaryotes
● Cells of organisms lacks nuclear ● Cells of organism have nuclear
membrane. membrane.
● Nucleolus is absent. ● Nucleolus is present.
● Single chromosomes. ● Single or multi chromosomes.
● Reproduction is always asexual. ● Reproduction is both sexual and
asexual.
● Always unicellular. ● Often multicellular.
● Membrane bound cell organelles are ● Membrane bound organelles are
absent. present like mitochondria.
● Centriole is absent ● Centriole is present only in animals
cell.
● Cell division is by binary fission. ● Cell division is by mitosis or meiosis.
● Example: Bacteria, Blue green algae, ● Example: Fungi, Plant cell, Animal cell
etc. etc.
Difference between Animal cell and Plant cell
