Answer the following questions.
(a) What is a 'cell' ?
(b) Name the different organelles in a cell ?
(c) What are micro-organisms ?
(d) which are the different types of micro-organisms ?
(a) What is a 'cell' ?
(b) Name the different organelles in a cell ?
(c) What are micro-organisms ?
(d) which are the different types of micro-organisms ?
a. Cell is the smallest unit of life. They are the structural, functional and biological uits of life. The discovery of cells was first made by Robert Hooke. While examining a section of a cork under the microscope, he observed small compartment-like structures and named them cells. However, Hooke observed dead cells under the microscope as cork is made up of dead cells. Cells exhibit different types of properties like:
- It is the smallest living unit of life.
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It is so small that it is not visible to the naked eye.
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The shape of the cell varies in different organisms and within an organism.
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Size of cells also differs.
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All living cells exhibit certain basic characteristics like respiration, growth, metabolism, etc.
- Cells originate from a pre-existing cell. A mother cell divides to produce daughter cells. Hence, cells exhibit cell division.
b. The cells may conatin the following cell organelles depending upon wether it is a plant or animal cell:
Cell membrane, cell wall, vacuole, plastids, endoplasmic reticulum, chloroplast, golgi apparatus, ribosomes, mitochondria, nucleus, lysosomes, centrosome and inclusion bodies.
c. Living organisms which are not visible to the naked eye are known as micro-organisms. They are living organisms that can be seen only with a microscope or a magnifying glass. Microorganisms were observed for the first time by Anton von Leeuwenhoek in 1674, using a microscope of his own.
d. Microorganisms can be divided into 5 major groups like:
Bacteria- Bacteria are the most primitive and diverse unicellular organisms found in living world. They are prokaryotic in nature as their genetic material, i.e. DNA, is not enclosed within a nuclear membrane. Because of their unique biochemical pathways and properties, they are of high economic importance to the human beings.
Fungi- Fungi is a group of eukaryotic, unicellular as well as multicellular, non-photosynthetic organisms that includes mushrooms, moulds and yeasts. These organisms have a rigid cell wall made up of chitin and are found in diverse shapes and sizes.
Algae- Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis.
Protozoa- Protozoa are a group of unicellular micoorganism which are non photosynthetic in nature. Many protozoa cause disease in animals and humans.
​Viruses- Viruses are ultra microscopic and non cellular organisms. They have simple structure having genetic material coated by protein coat. They are obligate parasites and highly pathogenic.
- It is the smallest living unit of life.
-
It is so small that it is not visible to the naked eye.
-
The shape of the cell varies in different organisms and within an organism.
-
Size of cells also differs.
-
All living cells exhibit certain basic characteristics like respiration, growth, metabolism, etc.
- Cells originate from a pre-existing cell. A mother cell divides to produce daughter cells. Hence, cells exhibit cell division.
b. The cells may conatin the following cell organelles depending upon wether it is a plant or animal cell:
Cell membrane, cell wall, vacuole, plastids, endoplasmic reticulum, chloroplast, golgi apparatus, ribosomes, mitochondria, nucleus, lysosomes, centrosome and inclusion bodies.
c. Living organisms which are not visible to the naked eye are known as micro-organisms. They are living organisms that can be seen only with a microscope or a magnifying glass. Microorganisms were observed for the first time by Anton von Leeuwenhoek in 1674, using a microscope of his own.
d. Microorganisms can be divided into 5 major groups like:
Fungi- Fungi is a group of eukaryotic, unicellular as well as multicellular, non-photosynthetic organisms that includes mushrooms, moulds and yeasts. These organisms have a rigid cell wall made up of chitin and are found in diverse shapes and sizes.
Algae- Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis.
Protozoa- Protozoa are a group of unicellular micoorganism which are non photosynthetic in nature. Many protozoa cause disease in animals and humans.
​Viruses- Viruses are ultra microscopic and non cellular organisms. They have simple structure having genetic material coated by protein coat. They are obligate parasites and highly pathogenic.
