Friday, September 20, 2013

Cell PPT 9th Class

Roll no.- Z
Academic Session: 201_-201_

We would like to acknowledge the efforts of our Biology teacher Ms. Aaaaaaa Bbbbb who helped us understand the topic and helped us by motivating. Time to time she made sure that we were going on correct path.


Basic structural and functional unit of life.
Often called Building block of life.
Discovered by Robert Hooke in 1665.
Named from the Latin word “Cellula”.
Can be differentiated by structure, number, size, shape, etc.

Discovery of Cell
Discovered by Robert Hooke.
He saw that cork resembled the structure of honeycomb.
In 1665, he discovered cell with the help of self designed microscope.
He called these boxes cell. Cell is a Latin word for a “little room”.
His discovery was important as it indicated for the first time that living organisms consisted of a smaller structures or units.

Cell Theory
In 1838, Jacob Matthias Schleiden, a German botanist, first proposed the idea that all plants consist of cell.
In 1839, Theodor Schwann, a German zoologist, asserted that all animals and plants are made up of cell.
This joint finding forms the basis of cell theory.
The cell theory was refined further in 1855, when another German Biologist, R. Virchow presented the idea that all cells arise from pre-existing cells(‘Omnis cellulae e cellulae’).

Cell theory II     
Thus cell theory comprise the following postulates :
All organisms are composed of cell and cell secretion.
All metabolic reactions take place in cells. Thus, cells are structural and functional unit of life.
All cells arise from pre-existing cells. No cell can originate spontaneously but comes into being only by division of already existing cells.
Every organism starts its life as a single cell. Viruses are an exception to cell theory.

Instruments for Studying Cells

Cells are too small to be seen with naked eyes.
Cells are studied with the help of microscopes.
Microscopes are high resolution instruments that are used for observing fine details of very fine objects.
Two common types of microscope are light microscope and electron microscope.

Cells in living organisms
All living organism on earth can be divided into 2 types :
Non-cellular organisms which do not contain any cell in their body organization, e.g., viruses. Viruses lack any membrane and hence do not show characteristics of life until they enter a living body.
Cellular organisms which contain either one or many cells in their bodies, eg., bacteria, plants and animals.

Eukaryotes and Prokaryotes.

Cellular organisms can be divided into following two main types :

These organisms have primitive and incomplete cells.
Prokaryotes have all 3 basic structures of a typical cell but lack nuclear membrane around their genetic substances (DNA).
Undefined nuclear region in the cytoplasm is called nucleoid, i.e., there is no nuclear membrane.
Cell organelles like ER are absent except Ribosome.
They include archaebacteria, bacteria and cyanobacteria.

These have advanced and complete cells.
These cells contain membrane bound nuclei and other cell organelles and are called eukaryotes.
They are found in unicellular and multicellular plants and animals and contain plasma membrane, nucleus, DNA and cytoplasm with ribosomes and cellular organelles such as mitochondria.

Difference Prokaryotes and Eukaryotes
Prokaryotic Cells
Size of the cell is small.
Nucleus is absent.
Contains single chromosome.
Nucleolus is absent.
Membrane bound cell organelles are absent.

Eukaryotic Cells
Size of the cell is large.
Nucleus is present.
Contains more than one chromosome.
Nucleus is present.
Membrane bound cell organelles are present.
Division of Labour
Same organism like humans can have cell of different type, e.g., sperm, WBC, Bone cells, muscle cells, nerve cells, fat cells, etc.
This is due to the fact that there is a division of labour in multicellular organism.
This means that different parts of human body perform different functions.
This is only possible if some cells or tissues are specialized to any specific function.

Cell Shape
The basic shape of eukaryote is spherical but is determined by specific function of the cell.
Shape of cell is variable (Amoeba, WBC) or fixed (most plants and animals, Euglena, Paramecium).
Some cell shapes are :

Cell Size
The size of different cells ranges between broad limits.
Only a few cells are visible with naked eyes while most cells are visible by microscope only.
The size of cell varies from very small cells of bacteria (0.2 to 5µm) to very large eggs of the ostrich (18 cm).
The prokaryotes usually range from 1 to 10µm.
The eukaryotes usually range from 10 to 100µm.
Amoeba proteus is biggest (60 µm) among the unicellular organisms.

Cell Volume
The volume of a cell is approx. constant for a particular cell type and is independent of the size of the organism.
For example, kidney or liver cells are about the same size in the bull, horse and mouse.
The difference in the total mass of the organ or organism depends on the number, not on the volume of the cells.
Thus, the cells of elephants may always not be larger than the cells of tiny organism.

Cell Number

The no. of cells in most multicellular organism is indefinite.
The no. of cells in an organism may be genetically fixed. This phenomenon is called eutely. It is seen is Ascaris, a type of roundworm.
No. of cells in large size animals like elephant may be countless.
No. of cells in humans are estimated to be around 100 trillion.

Plant Cell
They are Eukaryotes.
Differ from other cells because of some different features.
There wall is made up of cellulose.

Animal Cell
They are Eukaryotes.
They are the most common cell found.

Structure of Cell
Though their shape size and activities vary, all cells have following three major functional regions.
The cell membrane or plasma membrane and cell wall.
The nucleus.
The cytoplasm

Plasma Membrane
The plasma membrane (cell membrane) is made of two layers of phospholipids.
The membrane has many proteins embedded in it.
The plasma membrane regulates what enters and leaves the cell.
It is called semi-permeable membrane.
Many molecules cross the cell membrane by diffusion and osmosis.

Plasma Membrane II
Plasma membrane contains 75% phospholipids.
It also contains proteins, cholesterol and polysaccharides.
In 1972, Singer and Nicholson suggested a model, called fluid mosaic model, for explaining ultrastructure of the plasma membrane.
The fluid mosaic model of the membrane has been described as ‘a number of protein icebergs floating in the sea of lipids”.

Cell Wall
Cell walls made of cellulose are only found around plant cells.
Cell walls are made of specialized sugars called cellulose.
Cellulose provides a protected framework for a plant cell to survive
Cell walls also help a plant keep its shape

The nucleus is a major centrally located spherical cellular component.
It is bounded by 2 nuclear membranes, both forming a nuclear envelop.
It has a ground substance named nucleoplasm.
2 Type of nuclear structures-the nucleolus and the chromatin network are embedded in nucleus.
Nucleus may be 1 or more and it is not bound by any membrane.

Nucleolus and Chromatin Material
Nucleus is 1 or more and is not bound by any membrane.
It is rich in protein and RNA and is the site of ribosome formation.
It is known as factory of ribosomes.

Chromatin material is a thin, thread like intertwined mass of chromosomes material.
It is composed of genetic substance DNA and proteins.
It is condensed into 2 or more thick ribbon-like chromosomes during division of cells.

Cell Organelles
They are backbone of cells.
Various life processes are performed by them.
They may be single or double membrane bounded, or membrane may be absent.
They are essential for functioning of cell.
They may contain DNA in them.
eg. Mitochondria, Chloroplast, Lysosomes, etc.

Endoplasmic Reticulum
The endoplasmic reticulum (ER) is repsonible for the production of the protein and lipid components of most of the cell's organelles.
This internal space is called the ER lumen. The ER is additionally responsible for moving proteins and other carbohydrates to the Golgi apparatus, to the plasma membrane, to the lysosomes, or wherever else needed.
There are two types of ER - rough, which is coated with ribosomes, and smooth, which isn't.
Rough ER is the site of protein synthesis. The smooth ER is where the vesicles carrying newly synthesized proteins (from the rough ER) are budded off.

They are dense, spherical and grannular particles which occur freely in the matrix.
They may remain attached to RER.
The 2 main constituents of ribosomes are RNA and proteins.
They are not bounded by a membrane.
They are both found in eukaryotes and prokaryotes.

Golgi Apparatus
It consists of fluid filled vacuoles and flattened cisternae.
It is single membrane bound cell organelle.
It is absent on bacteria, blue green algae, mature sperms and RBC of mammals.
Golgi apparatus originates ER, which in turn originates the former.
It stores, processes and packages various cellular secretions.

They are tiny spherical sac-like structures evenly distributed in the cytoplasm and contain powerful enzymes.
It is single membrane bounded cell organelle.
They are capable of breaking down all the organic matter.
They remove worn out and poorly working cellular organelles by digesting them to make way for their new replacement.
They are also called demolition squads, scavengers, etc.

Significance of Lysosomes
In WBC : Cells of WBC digest foreign proteins, bacteria and viruses.
In Autophagy : During starvation, the lysosomes digest stored food contents such as proteins, fats and glycogen of the cytoplasm and supply the necessary amount of energy to cell.
In metamorphosis : During the transformation of a tadpole into frog, the embryonic tissues such as gills and tails are digested by the lysosomes and utilized by other body cells.

It is known as power house of the cell.
ATP synthesis take place here.
It is double membrane bounded cell organelle.
It has their own genome.
It is absent in bacteria and the red blood cell of mammals.
It contains cristae, F1 particles and matrix.
It can make their own protein, so they are regarded as semiautonomous organelles.

Plastid occur in most plant cells and are absent in animal cells.
They have their own genome.
They are self replication organelles.
Plastids are of 3 types :

Chloroplasts are present in green algae and higher plants.
They have the green pigment called chlorophyll that are involved in photosynthesis of food. So, chloroplasts are called “kitchen of the cells”.
Chloroplast is a double membrane bounded cell organelle.
Chloroplasts trap solar energy and utilize it to manufacture food for plant.

Vacuoles are fluid filled or solid filled and membrane bounded spaces. They are a kind of storage sacs.
In plant cells, the vacuoles are large, distinct and permanent. In mature plant cells the vacuole occupies almost the entire (90%) volume of the cell.
The vacuole is bounded by a membrane, called tonoplast.
Vacuole help to maintain the osmotic pressure in a cell. They store toxic metabolic by-product or end products of plant cells.

Impact of monsoon on Indian Society PPT - Class 9

Impact of monsoon on Indian Society.
By- Xxxxxxxx Yyyyyy
IX-Z Roll No. 1
AAAA Public School

Web Sites

Bibliography 2
9th Class Geography NCERT
NTSE Study Package
Chasing The Monsoon by Alexander Frater -

Monsoon plays an essential role in economy of a country.
In the countries like India, where agriculture is the greatest source of economy, monsoon season plays a pivotal role.
In India, directly or indirectly, 70% of employment is dependent on agricultural sector.
This is one the major reason for dependence on monsoon season for the economic growth of India.

Monsoon in India
In India, the monsoon hits the southern shore in the month of June and lasts till September.
If the monsoon is good, the economy of the India gets a boost which sequentially helps in maintaining the GDP growth chart.
But, a little delay in monsoon may prove to be disaster for the Indian government as it becomes difficult to maintain the GDP growth.

Monsoon in India (2012)
Usually southwest monsoon hits the southern states i.e Kerala in the mid of June month. But, this year, the country is experiencing the delay in the monsoon.
The monsoon touched India in the first week of July.
The monsoon is getting slower and scanty rainfall can be experienced this year in major part of the country.

Reason for less rainfall in India in 2012
The less rainfall in the country may create drought like situation. In India, the winter 2011 was longer and colder.
Similarly, the summer was usually less hotter than usual. The reason for all this seasonal variation is the El Nino effect of the Pacific ocean which lasted for about four months.

Impact of good monsoon in India
Increased output of grains and oil seeds
Better irrigation
Reduction in inflation

Increased output of grains and oil seeds
A good rainfall tends to increase the productivity of rice, sugarcane, millet, oil seeds and cotton. This encourages the government to ease the edges on the export of wheat and rice.

Better irrigation
A good rainfall increases the ground water level and replenishes the reservoirs. This helps in good irrigation system and better hydroelectricity power output.
Better Irrigation facilities is a major reason for increased agriculture in US.

Reduction in inflation
The good monsoon in the country also increases the production of vegetables and fruits. This reduces the price and thus calms down the inflation.

Impact of less rainfall in India
Price of agricultural products rises
Shortage of power supply
Shortage of water supply

Price of agricultural products rises
Since there is deficit in the rainfall this year, the production of crops, vegetables and fruits is highly affected.
Due to shortage of rainfall, sowing of groundnut, paddy fields, soya beans, and kharif crops in the different states have been affected.

Shortage of power supply
Rise in temperature has resulted in shortage of power supply in many states of India. The power cut is also one of the main reasons for shortage of products. And this finally results in the hike in the price of agricultural products.

Shortage of water supply
In states like Maharashtra, where the water supply of whole year is dependent on the monsoon rainfall, people experience the shortage of water supply. In Mumbai, the rainwater is collected in the huge tanks which is processed and supplied across the city around the year.

Less rainfall will result in less production. This will create drought like situation. Though India is self-sufficient for production of agricultural needs, but, if such situation occurs, then, India will be pushed into global market. This will result in inflation.

Extreme Flooding
Occasionally, particularly heavy rains lead to large-scale or even catastrophic floods.
In 2005, more than 1,000 people were killed in floods and landslides. In 2008, more than a million people were left homeless, and 250,000 homes destroyed after the Kosi river in Nepal burst its banks.
Flood waters rushed down the eastern flank of the Himalayas and flooded a significant portion of the state of Bihar.

Extreme flooding due to monsoon.
How to cope up with bad monsoon rainfall
Install rainwater harvesting units in your building.
Save water and do not misuse the water.
Dig the ponds and well to store rain water.
Plant as many as trees in you nearby locality. Encourage others to plant the trees.

Indian economy is highly dependent on the agricultural sector
If the condition remains same, then agricultural sector is going to experience very bad situation which will directly affect the Indian economy.
Therefore, Indian government must initiate some actions to improvise the infrastructure of agricultural sector in order to make the Indian economy independent of monsoon rains.