LESSON 1
FORMS IN WHICH CELLS EXIST
History of cell
In 1665, Robert Hooke, a British scientist examined thin slice of cork tissue under
the compound microscope and found that the cork consisted of many neatly
arranged little chamber or cavities. Since each chamber was enclosed by walls
similar to cell of honey combs, he named the chamber cells.
Felix Dujardin
In 1835, Dujardin, a French biologist, examined thin slice of living plants under
much improved microscope and discovered that cells have content. He named the
content sarcode, later named protoplasm by Purkinje in 1839 and von Mohl in 1846.
In 1839,Mathias Schleiden was a German botanist discovered that all plants
are made up of cells.
Theodor Schwann
In 1839, Theodor, a German zoologist examined bits of animals under a
microscope and observed that animals were composed by cells.
In 1839, Schleiden and Theodor Schwann jointly stated what is now known as the
cell theory, namely that all living things are made up of cells. After the statement
of the cell theory, in 1846, Hugo Von- Mohl fisrt applied the term protoplasm to the
living substances in the cell, the name by which it is still known till today. In 1858
Rudolf Virchow stated that cells come from pre- existing cells.
The cell Theories
1. All living things are made up of a cell or cells
2.The cell is the structural and functional unit of all living things
3.New cells arise from pre-existing cells by cell division
4.There is no life apart from the life of cell
5.All living things are either single cell or a group of unicellular or multicellular
CELL AS A LIVING UNIT OF AN ORGANISM
A cell is defined as the basic structural and functional unit of a living organism. In
other word, the cell is the simplest, smallest and basic unit of life because it can
carryout all life activities
Forms in which living things exist
Cell of different organisms exist in different forms. Some are
, single and free living, others may be colonial, filamentous or part of a living
organisms.
1. Cell as independent or single or free living organisms are capable of living
freely on their own. Such organism even though it has only one cell is able
to carry out life processes such as Movement, Reproductions, Sensitivity,
Excretion, Growth. e.t.c. Example of such organisms are Amoeba,
Paramecium, Euglena, Chlamydomonas.
Chlamydomonas
The Chlamydomonas is oval or spherical in shape and is bounded by cell wall
consistin g of hemi-cellulose. At the anterior end, the wall projects and thickens into
a colourless papilla. Two flagella which arise from the anterior end are used for
movement. Close to the base of the flagella are two contractile vacuoles which are
used for osmoregulation.
Within the cytoplasm is the nucleus and a cup shaped chloroplast which contains
chlorophyll which the organism use for photosynthesis. A pyrenoid responsible for
the storage of starch occur within the chloroplast. An eye spot is embedded on one
side of the cell close to the anterior end. The eye spot responds to light stimulus.
Chlamydomonas is an organism that shares both the characteristics of plants and
animals. The animal characteristics include flagella for locomotion, eye spot
responds to light source, contractile vacuole for osmoregulation. The presence of
chloroplast containing chlorophyll for photosynthesis and storage of excess
carbohydrate as starch are plant characteristic for chlamydomonas
FORMS IN WHICH CELLS EXIST
History of cell
In 1665, Robert Hooke, a British scientist examined thin slice of cork tissue under
the compound microscope and found that the cork consisted of many neatly
arranged little chamber or cavities. Since each chamber was enclosed by walls
similar to cell of honey combs, he named the chamber cells.
Felix Dujardin
In 1835, Dujardin, a French biologist, examined thin slice of living plants under
much improved microscope and discovered that cells have content. He named the
content sarcode, later named protoplasm by Purkinje in 1839 and von Mohl in 1846.
In 1839,Mathias Schleiden was a German botanist discovered that all plants
are made up of cells.
Theodor Schwann
In 1839, Theodor, a German zoologist examined bits of animals under a
microscope and observed that animals were composed by cells.
In 1839, Schleiden and Theodor Schwann jointly stated what is now known as the
cell theory, namely that all living things are made up of cells. After the statement
of the cell theory, in 1846, Hugo Von- Mohl fisrt applied the term protoplasm to the
living substances in the cell, the name by which it is still known till today. In 1858
Rudolf Virchow stated that cells come from pre- existing cells.
The cell Theories
1. All living things are made up of a cell or cells
2.The cell is the structural and functional unit of all living things
3.New cells arise from pre-existing cells by cell division
4.There is no life apart from the life of cell
5.All living things are either single cell or a group of unicellular or multicellular
CELL AS A LIVING UNIT OF AN ORGANISM
A cell is defined as the basic structural and functional unit of a living organism. In
other word, the cell is the simplest, smallest and basic unit of life because it can
carryout all life activities
Forms in which living things exist
Cell of different organisms exist in different forms. Some are
, single and free living, others may be colonial, filamentous or part of a living
organisms.
1. Cell as independent or single or free living organisms are capable of living
freely on their own. Such organism even though it has only one cell is able
to carry out life processes such as Movement, Reproductions, Sensitivity,
Excretion, Growth. e.t.c. Example of such organisms are Amoeba,
Paramecium, Euglena, Chlamydomonas.
Chlamydomonas
The Chlamydomonas is oval or spherical in shape and is bounded by cell wall
consistin g of hemi-cellulose. At the anterior end, the wall projects and thickens into
a colourless papilla. Two flagella which arise from the anterior end are used for
movement. Close to the base of the flagella are two contractile vacuoles which are
used for osmoregulation.
Within the cytoplasm is the nucleus and a cup shaped chloroplast which contains
chlorophyll which the organism use for photosynthesis. A pyrenoid responsible for
the storage of starch occur within the chloroplast. An eye spot is embedded on one
side of the cell close to the anterior end. The eye spot responds to light stimulus.
Chlamydomonas is an organism that shares both the characteristics of plants and
animals. The animal characteristics include flagella for locomotion, eye spot
responds to light source, contractile vacuole for osmoregulation. The presence of
chloroplast containing chlorophyll for photosynthesis and storage of excess
carbohydrate as starch are plant characteristic for chlamydomonas
