Saturday 9 March 2019
Thursday 28 February 2019
Chapter 1 Cell (class 8 NCERT science)
Cell was discovered by Robert hooke in 1665.
He observed slices of cork under a simple magnifying device. cork is a part of the bark of tree.
He took thin slices of cork and observe them under a microscope he noticed partitioned boxes or compartment in the cork slice.
Amoeba is a single cell that has no definite shape like other organisms , it keeps on changing its shape it is due to formation of pseudopodia which facilities movement and help in capturing food.
Pseudopodia means false feet.
For example -
WBC in human blood is a type of single cell which change its shape but amoeba is also a single cell but it is a full fledged organism capable of independent existence.
Membrane provides shape to the cell of plants and animals.
Cell wall is found in the plants which are made up of cellulose it gives shape and rigidity to these cells bacteria also have cell wall.
The smallest cell is 0.1 to 0.5 micrometre in bacteria.
The largest cell measuring 170 mm into 130 mm is the egg of an ostrich.
Cell membrane -
The basic component of cell or cell membrane, cytoplasm and nucleus the cytoplasm and nucleus are enclosed within the cell membrane also called plasma membrane. the membrane separates cell from one another and also the cell from the surrounding medium.
the plasma membrane is a porous and allows the movement of substance or materials both inward and outward.
Cytoplasm
it is the jelly like substance present between the cell membrane and nucleus various other components are organelles of cells are present in the cytoplasm these organelles are mitochondria Golgi bodies ribosomes lysosomes centrosome ribosome etc.
Nucleus
Nucleus is an important component of the cell it is also called brain of cell.
it is generally spherical and located in the centre of the cell it can be stained and seen easily with the help of microscope.
nucleus is separated from the cytoplasm by a membrane called nuclear membrane.
this membrane is also porus and allows the movement of materials between the cytoplasm and inside of nucleus.
with the microscope of higher magnification we can see a small spherical body in the nucleus it is called nucleolus.
in addition, nucleus contains thread like structure called chromosomes they carry genes and help in inheritance or transfer of character from parents to the offsprings.
The chromosome can be seen only when the cell divides.
The entire content of a cell is known as protoplasm it was discovered by purkinje.
It includes cytoplasm and nucleus protoplasm is called the living substance of cell.
Large vacuole is found in plants and smaller vacuoles is found in animal cells.
Coloured body is called plastids are found in the plant cells only green plastic container chlorophyll are called chloroplast.
He observed slices of cork under a simple magnifying device. cork is a part of the bark of tree.
He took thin slices of cork and observe them under a microscope he noticed partitioned boxes or compartment in the cork slice.
Amoeba is a single cell that has no definite shape like other organisms , it keeps on changing its shape it is due to formation of pseudopodia which facilities movement and help in capturing food.
Pseudopodia means false feet.
For example -
WBC in human blood is a type of single cell which change its shape but amoeba is also a single cell but it is a full fledged organism capable of independent existence.
Membrane provides shape to the cell of plants and animals.
Cell wall is found in the plants which are made up of cellulose it gives shape and rigidity to these cells bacteria also have cell wall.
The smallest cell is 0.1 to 0.5 micrometre in bacteria.
The largest cell measuring 170 mm into 130 mm is the egg of an ostrich.
Cell membrane -
The basic component of cell or cell membrane, cytoplasm and nucleus the cytoplasm and nucleus are enclosed within the cell membrane also called plasma membrane. the membrane separates cell from one another and also the cell from the surrounding medium.
the plasma membrane is a porous and allows the movement of substance or materials both inward and outward.
Cytoplasm
it is the jelly like substance present between the cell membrane and nucleus various other components are organelles of cells are present in the cytoplasm these organelles are mitochondria Golgi bodies ribosomes lysosomes centrosome ribosome etc.
Nucleus
Nucleus is an important component of the cell it is also called brain of cell.
it is generally spherical and located in the centre of the cell it can be stained and seen easily with the help of microscope.
nucleus is separated from the cytoplasm by a membrane called nuclear membrane.
this membrane is also porus and allows the movement of materials between the cytoplasm and inside of nucleus.
with the microscope of higher magnification we can see a small spherical body in the nucleus it is called nucleolus.
in addition, nucleus contains thread like structure called chromosomes they carry genes and help in inheritance or transfer of character from parents to the offsprings.
The chromosome can be seen only when the cell divides.
The entire content of a cell is known as protoplasm it was discovered by purkinje.
It includes cytoplasm and nucleus protoplasm is called the living substance of cell.
Large vacuole is found in plants and smaller vacuoles is found in animal cells.
Coloured body is called plastids are found in the plant cells only green plastic container chlorophyll are called chloroplast.
Friday 22 February 2019
Monday 4 February 2019
Sunday 3 February 2019
Should it be allowed to carry a Video Camera to everywhere or it should be banned for few places?
Answer -
Should it be allowed to carry a Video Camera to everywhere
- 21th Century brought Digital revolution in the whole world, it revolutionized every sphere.
- Although in the initial stage there were not much awareness about , what is internet even very few peoples knew the use of Computers.
- As time proceeds the awareness spread and a common man get knowledge of Computers and its benefits.
- Our Former PM Rajiv Gandhi did great job to bring technology in India , later on the use of technology becomes necessity for better and quick job, as Computers do.
- Our first Super Computer was made and named PARAM, and the world recognize our capabilities in the field of technologies. ( we have also developed indigenous Cryogenic engine, super computer etc.)
Should it be allowed to carry a Video Camera to everywhere
- No doubt technology gives us what we even can not Imagine in our life but every things has its pros and cons nothing is absolute in the world.
- Now a days every smart phone has a Camera its good , every body is busy in taking shot but they don't know which scene or incident should not be captured.
- If you have little knowledge of internet , can easily make an account on YOUTUBE and upload a video.
- Some times people capture scenes or make videos which can ruin somebodies life.
- People goes to holy places (Pilgrims) with their families , on the bank of river they usually bath (including Females) but they are not aware of that somebody is capturing this moment in there camera and he is going to upload this on Internet.
For an Example - People is going to KUMBH MELA at Pryag Raj and they are Capturing Photos or Videos of Naga Hermits and uploads on Internet and by this unknowingly an unethical debates goes on , on Internet.
- People easily associates themselves in such debates and comments what they want, without even having a little Knowledge about Culture.
it should be banned for few places
- In My opinion we are enjoying Fundamental Rights but remember they are not Absolute, that means we have some limitations on regard of our freedom.
- Government can ban the unethical use of anything which cause differences and disturbances in Society.
To Conclude , It should be the duty of every citizen to know what is right or ethical and what is wrong.In our Constitution we have 11 Fundamental Duties but Unfortunately very few people are aware of it. its duty of every citizen to understand the Values of Constitution and respect each other.
"Unlike a drop of water which loses its identity when it joins the ocean, man does not lose his being in the society in which he lives. Man's life is independent. He is born not for the development of the society alone, but for the development of his self."
B. R. Ambedkar
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