WHAT IS A CELL –
Unicellular organisms are capable of
(i) independent existence and
(ii) performing the essential functions of life. Anything less than a complete
structure of a cell does not ensure independent living. Hence, cell is the
fundamental structural and functional unit of all living organisms.
Anton Von Leeuwenhoek first saw and described a live cell. Robert
Brown later discovered the nucleus. The invention of the microscope and
its improvement leading to the electron microscope revealed all the
structural details of the cell.
In 1838, Matthias Schleiden, a German botanist, examined a large numberof plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant. At about the same time, Theodore Schwann (1839), a British Zoologist, studied different types of animal cells
and reported that cells had a thin outer layer which is today known as the
‘plasma membrane’. He also concluded, based on his studies on plant
tissues, that the presence of cell wall is a unique character of the plant
cells. On the basis of this, Schwann proposed the hypothesis that the bodies
of animals and plants are composed of cells and products of cells.
Schleiden and Schwann together formulated the cell theory.
This theory however, did not explain as to how new cells were formed. Rudolf Virchow (1855) first explained that cells divided and new cells are formed from
pre-existing cells (Omnis cellula-e cellula). He modified the hypothesis of
Schleiden and Schwann to give the cell theory a final shape. Cell theory
as understood today is:
(i) all living organisms are composed of cells and products of cells.
(ii) all cells arise from pre-existing cells.
AN OVERVIEW OF CELL-
You have earlier observed cells in an onion peel and/or human cheek
cells under the microscope. Let us recollect their structure. The onion cell which is a typical plant cell, has a distinct cell wall as its outer boundary and just within it is the cell membrane. The cells of the human cheek
have an outer membrane as the delimiting structure of the cell. Inside each cell is a dense membrane bound structure called nucleus.
This nucleus contains the chromosomes which in turn contain the genetic material, DNA. Cells that have membrane bound nuclei are called eukaryotic whereas cells that lack a membrane bound nucleus are prokaryotic. In both prokaryotic and eukaryotic cells, a semi-fluid matrix
called cytoplasm occupies the volume of the cell. The cytoplasm is the main arena of cellular activities in both the plant and animal cells.
Various chemical reactions occur in it to keep the cell in the ‘living state’. Besides the nucleus, the eukaryotic cells have other membrane bound distinct structures called organelles like the endoplasmic reticulum (ER),
the golgi complex, lysosomes, mitochondria, microbodies and vacuoles. The prokaryotic cells lack such membrane bound organelles. Ribosomes are non-membrane bound organelles found in all cells –
both eukaryotic as well as prokaryotic.
Within the cell, ribosomes are found not only in the cytoplasm but also within the two organelles –
chloroplasts (in plants) and mitochondria and on rough ER. Animal cells contain another non-membrane bound organelle called centrosome which helps in cell division.
Cells differ greatly in size, shape and activities. For example, Mycoplasmas, the smallest cells, are only 0.3 μm in length while bacteria could be 3 to 5 μm. The largest isolated single cell is the egg of an ostrich.
Among multicellular organisms, human red blood cells are about 7.0 μm in diameter. Nerve cells are some of the longest cells. Cells also vary greatly in their shape. They may be disc-like, polygonal, columnar, cuboid,
thread like, or even irregular. The shape of the cell may vary with the
function they perform.
The prokaryotic cells are represented by bacteria, blue-green algae,
mycoplasma and PPLO (Pleuro Pneumonia Like Organisms). They are
generally smaller and multiply more rapidly than the eukaryotic cells . They may vary greatly in shape and size. The four basic
shapes of bacteria are bacillus (rod like), coccus (spherical), vibrio (comma
shaped) and spirillum (spiral).
The organisation of the prokaryotic cell is fundamentally similar even
though prokaryotes exhibit a wide variety of shapes and functions. All
prokaryotes have a cell wall surrounding the
cell membrane except in mycoplasma. The fluidmatrix filling the cell is the cytoplasm. There is
no well-defined nucleus. The genetic material is basically naked, not enveloped by a nuclear
membrane. In addition to the genomic DNA (the single chromosome/circular DNA), many
bacteria have small circular DNA outside the genomic DNA. These smaller DNA are called
plasmids. The plasmid DNA confers certain unique phenotypic characters to such bacteria.
One such character is resistance to antibiotics.
In higher classes you will learn that this plasmid DNA is used to monitor bacterial transformation with foreign DNA. Nuclear membrane is found
in eukaryotes. No organelles, like the ones in eukaryotes, are found in prokaryotic cells except for ribosomes. Prokaryotes have something
unique in the form of inclusions.
A specialised differentiated form of cell membrane called mesosome is the characteristic
of prokaryotes. They are essentially infoldings of cell membrane
The eukaryotes include all the protists, plants, animals and fungi. In neukaryotic cells there is an extensive compartmentalisation of cytoplasm through the presence of membrane bound organelles.
Eukaryotic cells possess an organised nucleus with a nuclear envelope. In addition,
eukaryotic cells have a variety of complex locomotory and cytoskeletal structures. Their genetic material is organised into chromosomes.
All eukaryotic cells are not identical. Plant and animal cells are different as the former possess cell walls, plastids and a large central vacuole which are absent in animal cells. On the other hand, animal cells have centrioles which are absent in almost all plant cells Let us now look at individual cell organelles to understand their structure and functions
The detailed structure of the membrane was studied only after the advent
of the electron microscope in the 1950s. Meanwhile, chemical studies onthe cell membrane, especially in human red blood cells (RBCs), enabledthe scientists to deduce the possible structure of plasma membrane.
These studies showed that the cell membrane is mainly composed of lipids and proteins. The major lipids are phospholipids that are arranged in a bilayer. Also, the lipids are arranged within the membrane with the polar head towards the outer sides and the hydrophobic tails towards the inner part.This ensures that the nonpolar tail of saturated hydrocarbons is protected from the aqueous environment In addition to phospholipids membrane also contains cholesterol.
The lipid component of the membrane mainly consists of phosphoglycerides. Later, biochemical investigation clearly revealed that the cell membranes also possess protein and carbohydrate. The ratio of protein and lipid varies considerably in different cell types. In human beings, the membrane of the erythrocyte has approximately 52 per cent protein and 40 per cent lipids.
Depending on the ease of extraction, membrane proteins can be classified as integral and peripheral. Peripheral proteins lie on the surface of membrane while the integral proteins are partially or totally buried in the membrane.
An improved model of the structure of cell membrane was proposed by Singer and Nicolson (1972) widely accepted as fluid mosaic model According to this, the quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer. This ability to move
within the membrane is measured as its fluidity.
The fluid nature of the membrane is also important from the point of view of functions like cell growth, formation of intercellular junctions, secretion, endocytosis, cell division etc.
One of the most important functions of the plasma membrane is the transport of the molecules across it. The membrane is selectively permeable to some molecules present on either side of it.
Many molecules can move briefly across the membrane without any requirement of energy and this is called the passive transport. Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient, i.e., from higher concentration to the lower.
Water may also move across this membrane from higher to lower concentration. Movement of water by diffusion is called osmosis. As the polar molecules cannot pass through the nonpolar lipid bilayer, they require a carrier protein of the membrane to facilitate their transport across the membrane.
A few ion sor molecules are transported across the membrane against their concentration gradient, i.e., from lower to the higher concentration. Such a transport is an energy dependent process, in which ATP is utilised and is called active transport, e.g., Na+/K+ Pump.
As you may recall, a non-living rigid structure called the cell wall forms an outer covering for the plasma membrane of fungi and plants. Cell wall not only gives shape to the cell and protects the cell from mechanical damage and infection, it also helps in cell-to-cell interaction and provides barrier to undesirable macromolecules. Algae have cell wall, made of cellulose,
galactans, mannans and minerals like calcium carbonate, while in other plants it consists of cellulose, hemicellulose, pectins and proteins. The cell wall of a young plant cell, the primary wall is capable of growth, which gradually diminishes as the cell matures and the secondary wall is formed on the inner (towards membrane) side of the cell.
The middle lamella is a layer mainly of calcium pectate which holds or glues the different neighbouring cells together. The cell wall and middle lamellae may be traversed by plasmodesmata which connect the cytoplasm of neighbouring cells.
Nucleus as a cell organelle was first described by Robert Brown as early as 1831. Later the material of the nucleus stained by the basic dyes was given the name chromatin by Flemming.
The interphase nucleus (nucleus of a cell when it is not dividing) has highly
extended and elaborate nucleoprotein fibres called chromatin, nuclear matrix
and one or more spherical bodies called nucleoli (sing.: nucleolus) (Figure 8.11).
Electron microscopy has revealed that the nuclear envelope, which consists of two
parallel membranes with a space between (10 to 50 nm) called the perinuclear
space, forms a barrier between the materials present inside the nucleus and
that of the cytoplasm.
The outer membrane usually remains continuous
with the endoplasmic reticulum and also bears ribosomes on it. At a number of
places the nuclear envelope is interrupted by minute pores, which are formed by the fusion of its two membranes. These nuclear pores are the passages through which movement of RNA and protein molecules takes place in both directions between the nucleus and the cytoplasm. Normally,
there is only one nucleus per cell, variations in the number of nuclei are also frequently observed. Can you recollect names of organisms that have more than one nucleus per cell? Some mature cells even lack nucleus, e.g., erythrocytes of many mammals and sieve tube cells of vascular plants. Would you consider these cells as ‘living’? The nuclear matrix or the nucleoplasm contains nucleolus and chromatin.
The nucleoli are spherical structures present in the nucleoplasm. The content of nucleolus is continuous with the rest of the nucleoplasm as it is not a membrane bound structure. It is a site for active ribosomal RNA synthesis. Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis.
You may recall that the interphase nucleus has a loose and indistinct network of nucleoprotein fibres called chromatin. But during different stages of cell division, cells
show structured chromosomes in place of the nucleus.
Chromatin contains DNA and some basic proteins called histones, some non-histone proteins and also RNA. A single human cell has approximately two metre long thread of DNA distributed among its forty six (twenty three pairs) chromosomes. You will study the details of DNA packaging in the form of a chromosome in class XII. Every chromosome (visible only in dividing cells) essentially has a primary constriction or the centromere
on the sides of which disc shaped structures called kinetochores are present (Figure 8.12). Centromere holds two chromatids of a chromosome. Based on the position
of the centromere,
the chromosomes can be classified into four types . The metacentric chromosome has middle centromere forming two equal arms of the chromosome. The sub-metacentric chromosome has centromere slightly away from the middle of the chromosome resulting into one shorter arm and one longer arm.
In case of acrocentric chromosome the centromere is situated close to its end forming one
extremely short and one very long arm, whereas the telocentric chromosome has a terminal centromere
Mitochondria (sing.: mitochondrion), unless specifically stained, are not
easily visible under the microscope. The number of mitochondria per cell is variable depending on the physiological activity of the cells. In terms of shape and size also, considerable degree of variability is observed.
Typically it is sausage-shaped or cylindrical having a diameter of 0.2-1.0μm (average
0.5μm) and length 1.0-4.1μm. Each mitochondrion is a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments,
i.e., the outer compartment and the inner compartment. The inner compartment is filled with a dense homogeneous substance called the matrix. The outer membrane forms the continuous limiting boundary of the organelle. The inner membrane forms a number of infoldings called the cristae (sing.: crista) towards the matrix . The cristae increase the surface area. The two membranes have their own specific enzymes associated with the mitochondrial function.
Mitochondria are the sites of aerobic respiration. They produce cellular energy in the form of ATP, hence they are called ‘power houses’ of the cell. The matrix also possesses single circular DNA molecule, a few RNA molecules, ribosomes (70S) and the components required for the synthesis of proteins. The mitochondria divide by fission.
The system in which information can be sent and receive
from one place to other is called communication system.
Now a days three types of communication system are used:
(1)Electrical (2)Electronic (3)Optical
In every system of communication there are three important parts : (i)Transmission (ii)Communication Channel (iii)Receiver
(i)Transmitter : The main function of a transmitter is to collect signal produced by source and to transmit it in suitable form to channel for sanding it to receiver. if the out put of a source is sound and so signal (sound signal).
Then it is converted into electrical signal by microphone (Transducer) before sending it. This is called information (message) signal. So conversion of main signal into message signal is main part of the process of transmitter.
(ii)Communication Channel : Communication Channel is a physical medium which connect transmitter and receiver i.e. It provides a path between transmitter and receiver by which signal is communicated .
Communication channel is also called medium link between transmitter and receiver. The form of channel depends upon type of communication system. This can be a form of wire or cable between transmitter and receiver or can be wireless system.
When the signal to be transmitted propagates along the communication channel due to imperfection it is distorted and in the communication signal noise also get’s superpose so signal in distorted form is available.
(iii)Receiver : The main part of a receiver is to detect the signal and to rebuilt the received message and to convert it into main signal to be detected in orignal form.
So that the message can be send to receiving person. So main function of receiver is to receive the output of channel and to convert it into desirable signal i.e. to rebuilt it into main form.
Explanation : When a person wants to tell something to another person sitting near to him then he speaks something to tell him about something. The person who is speaking is the source of information and is a transmitter and sound waves are propagating in air medium (channel).
The sound waves are the signal which is communicated by our medium to other person who listens all signals. So Ears of the person who receives the sound are receiver. This is simplest form of communication system.
If the distance between source (Transmitter) and receiver is very large then signal gets weak before reaching to receiver i.e. to the listener. In this case the sound waves are converted into electrical signal and with the help of wires are communicated to long distance .
The part by sound waves are converted into electrical signal is called microphone (Transducer) converts electrical to sound signal. When it is not possible to have contact between transmitter and receiver with the help of wire or cables in that case main signal first is converted into electrical signal and with the help of antenna is sent in the space.
The free space acts as communication channel and the signal is received by the antenna of receiver at a large distance. The received signal with the help of transducer and amplifier is converted into main signal.
Modes of communications :(a) Point to point communication : in this mode there is one transmitter and one receiver. In this the message sent by a person by a transmitting media or by communication is given to receiver. Example: Telephone system.(b) Broadcast : In this there only one transmitter and there many receiver by so many receivers. In this one transmitter.
broadcasts the information or message and it is received by so many receivers. Example : Radio and Television.
Basic Of Science –
Basic Science Principally Refers to the Scientific Disciplines Of Physics. Chemistry. Biology And Mathematics as well as to their Subtopics .the Principal idea Behind Something Being the label as Basic Science is that Study Of Basic Science Leads to a Better Understanding Of Natural things
In electricity generation, a generator is a device that converts motive power (mechanical energy) into electrical power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines and even hand cranks. The first electromagnetic generator, the Faraday disk, was invented in 1831 by British scientist Michael Faraday. Generators provide nearly all of the power for electric power grids.
बिजली उत्पादन में, एक जनरेटर एक उपकरण है जो एक बाहरी सर्किट में उपयोग के लिए मकसद शक्ति (यांत्रिक ऊर्जा) को विद्युत शक्ति में परिवर्तित करता है। यांत्रिक ऊर्जा के स्रोतों में भाप टरबाइन, गैस टर्बाइन, पानी टर्बाइन, आंतरिक दहन इंजन और यहां तक कि हाथ क्रैंक शामिल हैं।
विद्युत जनित्र (एलेक्ट्रिक जनरेटर) एक ऐसी युक्ति है जो यांत्रिक उर्जा को विद्युत उर्जा में बदलने के काम आती है
इसके लिये यह प्रायः माईकल फैराडे के विद्युतचुम्बकीय प्रेरण (electromagnetic induction) के सिद्धान्त का प्रयोग करती है।
विद्युत मोटर इसके विपरीत विद्युत उर्जा को यांत्रिक उर्जा में बदलने का कार्य करती है।
विद्युत मोटर एवं विद्युत जनित्र में बौत कुछ समान होता है
और कई बार एक ही मशीन बिना किसी परिवर्तन के दोनो की तरह कार्य कर सकती है।
Pre-adulthood (from Latin adolescere, signifying ‘to grow up’) is a transitional phase of physical and mental improvement that by and large happens amid the period from adolescence to legitimate adulthood (time of dominant part). Youthfulness is normally connected with the adolescent years, yet its physical, mental or social articulations may start prior and end later. For instance, pubescence presently commonly starts amid preadolescence, especially in females. Physical development (especially in guys) and subjective improvement can stretch out into the mid twenties. Along these lines, age gives just a harsh marker of puberty, and researchers have thought that it was hard to concur upon an exact meaning of youthfulness.
A careful comprehension of youthfulness in the public eye relies upon data from different points of view, including brain science, science, history, human science, instruction, and human studies. Inside these viewpoints, pre-adulthood is seen as a transitional period among adolescence and adulthood, whose social reason for existing is the planning of youngsters for grown-up jobs. It is a time of numerous advances including instruction, preparing, business, and joblessness, just as advances starting with one living situation then onto the next
किशोरावस्था मनुष्य के जीवन का बसंतकाल माना गया है। यह काल बारह से उन्नीस वर्ष तक रहता है, परंतु किसी किसी व्यक्ति में यह बाईस वर्ष तक चला जाता है। यह काल भी सभी प्रकार की मानसिक शक्तियों के विकास का समय है। भावों के विकास के साथ साथ बालक की कल्पना का विकास होता है। उसमें सभी प्रकार के सौंदर्य की रुचि उत्पन्न होती है और बालक इसी समय नए नए और ऊँचे ऊँचे आदर्शों को अपनाता है। बालक भविष्य में जो कुछ होता है, उसकी पूरी रूपरेखा उसकी किशोरावस्था में बन जाती है। जिस बालक ने धन कमाने का स्वप्न देखा, वह अपने जीवन में धन कमाने में लगता है। इसी प्रकार जिस बालक के मन में कविता और कला के प्रति लगन हो जाती है, वह इन्हीं में महानता प्राप्त करने की चेष्टा करता और इनमें सफलता प्राप्त करना ही वह जीवन की सफलता मानता है। जो बालक किशोरावस्था में समाज सुधारक और नेतागिरी के स्वप्न देखते हैं, वे आगे चलकर इन बातों में आगे बढ़ते है।
पश्चिम में, कई मनोवैज्ञानिकों द्वारा किशोरावस्था का विशेष अध्ययन किया गया है। किशोर अवस्था का काम विकास की अवस्था है। यौन इच्छा के कारण, बच्चा अपने आप में नवीकरण का अनुभव करता है। वह सौंदर्य के उपासक और महानता के पुजारी हैं। उसी से उन्हें शौर्य कार्य करने की प्रेरणा मिलती है। किशोर अवस्था शारीरिक परिपक्वता का चरण है। इस स्तर पर, बच्चे की हड्डियों को मजबूती से स्थापित किया जाता है; भूख अच्छी लगती है। 13 साल से बच्चे से कामुकता की अनुभूति शुरू होती है। इसका कारण उसके शरीर में स्थित ग्रंथियों का स्राव है। इसलिए कई किशोर लड़के अनायास ही कई तरह की कामुक गतिविधियाँ करने लगते हैं। जब बड़े लोगों को पहली बार यह पता चलता है, तो वे चौंक जाते हैं।
आधुनिक मनोविश्लेषण विज्ञान ने माता-पिता के अनजाने डर को सुलझा दिया है, बच्चे के बचपन को प्राकृतिक बताया है। ये प्रेरणाएं बच्चे के शारीरिक विकास का परिणाम हैं। किशोरावस्था का स्वार्थ कभी-कभी वयस्कता तक बना रहता है। किशोरावस्था के विकास के दौरान, किशोरी को अपने लिंग के बच्चे से विशेष प्रेम होता है। जब यह मजबूत हो जाता है, तो समलैंगिक गतिविधियाँ भी होने लगती हैं। बच्चे की समलैंगिक गतिविधियाँ सामाजिक भावनाओं के प्रतिकूल हैं, इसलिए वह आत्म-साक्षात्कार का अनुभव करता है। इसलिए, वह समाज के सामने निडर नहीं है। समलैंगिक प्रेम के दमन के कारण, मानसिक ग्रंथि मनुष्यों में व्यामोह नामक पागलपन पैदा करती है। इस पागलपन में, आदमी खुद को बहुत महान व्यक्ति समझने लगता है और दूसरी तरफ अपने ही साथियों को दुश्मन के रूप में देखता है।
ऐसी ग्रंथियाँ हिटलर और उसके सहयोगियों में थीं, जिसके कारण वे अन्य राष्ट्रों की प्रगति को नहीं देख सकते थे। इसके परिणामस्वरूप द्वितीय विश्व युद्ध हुआ। किशोरावस्था का बच्चा उपर्युक्त मन-अवस्थाओं को पार करता है, उसमें विषमलैंगिक प्रेम का विकास करता है और फिर जब एक परिपक्व अवस्था आती है, तो एक सीधा व्यक्ति अपना प्रेम केंद्र बनाता है, जिसके साथ वह अपना जीवन जीता है। कामेच्छा के विकास के साथ-साथ इंसान का भी विकास होता है। किशोर बच्चों का भोगराग बहुत तीव्र होता है। वह अपने प्यार या श्रद्धा की खातिर सब कुछ कुर्बान करने को तैयार है। इस अवधि के दौरान किशोर बच्चों को कला और कविता में रखना फायदेमंद है। ये कार्य बच्चे को सामाजिक रूप से उपयोगी बनाते हैं। किशोर बच्चा हमेशा के लिए असाधारण काम करना चाहता है। वह दूसरों का ध्यान आकर्षित करना चाहता है।
जब तक वह इस काम में सफल होता है, वह अपने जीवन को सार्थक मानता है और जब वह इसमें असफल होता है, तो वह अपने जीवन को नीरस और निरर्थक समझने लगता है। किशोर बच्चों की डींग मारने की प्रवृत्ति भी बहुत अधिक है। वह हमेशा एक नया प्रयोग करना चाहता है। वह इसके लिए दूर-दूर जाने में रुचि रखते हैं। किशोर बच्चे का बौद्धिक विकास पर्याप्त है। उसकी विचार शक्ति अच्छी है। इसके कारण पर्याप्त बौद्धिक कार्य देना आवश्यक है। किशोर बच्चे में अभिनय, भाषण और लेखन में गहरी रुचि है। इसलिए कुशल शिक्षक इन माध्यमों से बच्चे का बौद्धिक विकास करते हैं। किशोर बच्चे की सामाजिक भावना मजबूत होती है। वह समाज में ही प्रतिष्ठित रहना चाहता है। वह अपने माता-पिता के सम्मान की भी उम्मीद करता है।
10, 12 वर्ष के बच्चों के साथ व्यवहार करने से, द्वेष की मानसिक ग्रंथियां उत्पन्न होती हैं जो इसकी ताकत को कमजोर करती हैं और कई मानसिक रोगों का कारण बनती हैं। बच्चे का जीवन दो नियमों के अनुसार विकसित होता है, सहज परिपक्वता का नियम और दूसरा सीखने का नियम। बच्चे के समुचित विकास के लिए, हमें उसे जल्द ही कुछ भी नहीं सिखाना चाहिए। सीखना तभी अच्छा है जब यह सहज रूप से हो। जब बच्चा अपनी सारी मानसिक वृत्ति तुरन्त पार कर लेता है, तब वह एक स्वस्थ और सक्षम नागरिक बन जाता है। कोई भी व्यक्ति बुद्धिमान नहीं है या परोपकारी नहीं है। उसकी बुद्धि अनुभव की वृद्धि के साथ विकसित होती है और परोपकार, दया और बहादुरी के गुण धीरे-धीरे आते हैं। उसकी इच्छाओं का विकास क्रमिक है। सबसे पहले, उसकी निम्न रैंक की इच्छाएं जागृत होती हैं और जब उनकी पूर्ति में संतुष्टि होती है, तो उच्च इच्छाओं की अभिव्यक्ति होती है। यह मानसिक परिपक्वता के नियम के अनुसार है। ऐसे व्यक्ति के चरित्र में स्थायी गुण का विकास और ऐसे व्यक्ति अपने कार्यों के माध्यम से समाज में स्थायी लाभ लाते हैं।
99 Facts About Human Body
The human body is the structure of an individual. It is made out of various kinds of cells that together make tissues and in this way organ frameworks. They guarantee homeostasis and the practicality of the human body.
It involves a head, neck, trunk (which incorporates the thorax and belly), arms and hands, legs and feet.
- 1.The only part of the body that has no blood supply is the cornea of the eye. It receives oxygen directly from the air.
- The human brain has a memory capacity which is the equivalent of more than four terabytes on a hard drive.
- A newborn child can breathe and swallow at the same time for up to seven months.
- Your skull is made up of 29 different bones.
- Nerve impulses sent from the brain move at a speed of 274 km/h.
- A single human brain generates more electrical impulses in a day than all the telephones of the world combined.
- The average human body contains enough sulfur to kill all the fleas on the average dog, enough carbon to make 900 pencils, enough potassium to fire a toy cannon, enough fat to make seven bars of soap and enough water to fill a 50-liter barrel.
- The human heart pumps 182 million liters of blood during the average lifetime.
- 50,000 cells in your body died and were replaced by new ones while you were reading this sentence.
- The human embryo acquires fingerprints within three months of conception.
- Women’s hearts beat faster than men’s.
- A man named Charles Osborne hiccupped for a total of 68 years.
- Right-handed people live, on average, nine years longer than left-handed people.
- About two-thirds of people tilt their heads to the right when kissing.
- The average person forgets 90% of their dreams.
- The total length of all the blood vessels in the human body is about 100,000 km.
- On average, a person’s respiration rate is one third higher in spring than in autumn.
- By the end of a person’s life, they can recall, on average, around 150 trillion pieces of information.
- We lose 80% of our body heat from the head.
- When you blush, your stomach also turns red.
- A feeling of thirst occurs when water loss is equal to 1% of your body weight. The loss of more than 5% can cause fainting, and more than 10% causes death from dehydration.
- At least 700 enzymes are active in the human body.
- Human beings are the only living things which sleep on their backs.
- The average four-year-old child asks 450 questions a day.
- Not only human beings but also koalas have unique fingerprints.
- Only 1% of the bacteria can result in the human body becoming ill.
- Everyone alive on Earth could comfortably be placed into a cube with sides 1000 meters long.
- The scientific name for the belly button is the umbilicus.
- Teeth are the only part of the human body that cannot heal themselves.
- On average, a person needs seven minutes to fall asleep.
- Right-handed people chew most of their food on the right side of their mouth, whereas left-handed people do so on the left.
- Only 7% of people are left-handed.
- The fragrance of apples and bananas can help a person to lose weight.
- If allowed to grow for their whole lifetime, the length of someone’s hair would be about 725 kilometers.
- Out of all the people who can move their ears, only one-third of them are able to move just one ear.
- During their lifetime, a person will on average accidentally swallow eight small spiders.
- The total weight of the bacteria in the human body is 2 kg.
- 99% of the calcium contained in the human body is in one’s teeth.
- Human lips are hundreds of times more sensitive than the tips of a person’s fingers.
- A kiss increases a person’s pulse to 100 beats per minute or more.
- The total strength of the masticatory muscles on one side of your jaw is equal to 195 kilograms.
- A person passes on 278 different types of bacteria to another person when they kiss them. Fortunately, 95% of them are not harmful.
- Parthenophobia is a fear of virgins.
- If you collected all the iron contained in the human body, you would get just a small cog, big enough only for use in your watch.
- There are more than 100 different viruses that cause a cold.
- If someone kisses another person for a certain amount of time, this is much more effective in terms of hygiene than using chewing gum, as it normalizes the level of acidity in your oral cavities.
- You can lose 150 calories per hour if you hit your head against the wall.
- Human beings are the only animals that can draw straight lines.
- Human skin is completely replaced by about 1,000 times during a person’s lifetime.
- A person who smokes a pack of cigarettes a day is doing the equivalent of drinking half a cup of tar a year.
- Women blink about two times less often than men.
- The structure of the human body contains only four minerals: apatite, aragonite, calcite, and cristobalite.
- A passionate kiss causes the same chemical reactions in the brain that skydiving and firing a gun do.
- Men are officially classified as dwarves if their height is below 1.3 m, whereas for women the measure is 1.2 m.
- Fingernails grow about four times faster than your toenails.
- People with blue eyes are more sensitive to pain than others.
- Nerve impulses in the human body move at about 90 m/s.
- 100,000 chemical reactions occur in the human brain every second.
- Everyone has dimples on their lower back, but in some people, they are more pronounced than on others. They appear where the pelvis joins with the sacrum, so their appearance makes sense.
- If one identical twin lacks a certain tooth, the other twin will not have that tooth either.
- The surface area of the human lungs is approximately equal to the area of a tennis court.
- During a person’s lifetime, they spend about 2 weeks kissing.
- The facial hair of a blonde-haired man grows faster than that of a man with dark hair.
- Leukocytes in the human body live for two to four days and erythrocytes for three to four months.
- The strongest muscle in the human body is the tongue.
- The human heart is approximately equal in size to that of a person’s fist. An adult’s heart weighs 220-260 grams.
- At birth, there are 14 billion cells in the human brain. This number does not increase throughout a person’s lifetime. After 25 years, the number of cells falls by 100,000 every day. About 70 cells die in the minute it takes you to read a page in a book. After 40 years, the decline of the brain accelerates sharply, and after 50 years of neurons (that is, nerve cells) shrink and the brain gets smaller.
- At birth, a child’s body is made up of around 300 bones. But an adult has just 206.
- During a person’s lifetime, the small intestine is about 2.5 meters. After they die, the muscles in the walls of their intestine relax, and it’s length increases to 6 meters.
- Your right lung can take in more air than your left.
- An adult person performs around 23,000 inhalations and exhalations a day.
- The smallest cells in a man’s body are sperm cells.
- There are about 40,000 bacteria in the human mouth.
- Each of us has around 2,000 taste buds.
- The human eye can distinguish 10 million different colors.
- The chemical compound in the body which causes feelings of ecstasy (phenylethylamine) is also contained in chocolate.
- The human heart pumps blood at such pressure that it would be able to raise blood up to the fourth floor of a building.
- A person burns more calories when they are asleep than when they watch TV.
- Children grow faster in the spring.
- Every year more than 2 million left-handed people die because of mistakes they make when using machines designed for right-handed people.
- It turns out that one man in every three hundred is capable of satisfying themselves orally.
- A person uses 17 muscles when they smile, and 43 when they frown.
- By the age of 60, most people lose half of their taste buds.
- The rate at which a person’s hair grows doubles during an airplane flight.
- One percent of people can see infra-red light and 1% can see ultraviolet radiation.
- If you were locked in a completely sealed room, you would not die due to a lack of air, but from carbon dioxide poisoning.
- Statistically, only one person out of two billion reaches the age of 116 years old.
- On average, a person says 4,800 words in 24 hours.
- The retinas inside the eye cover about 650 square mm and contain 137 million light-sensitive cells: 130 million are for black and white vision and 7 million are for helping you see in color.
- Our eyes remain the same size as they were at birth, but our nose and ears never stop growing.
- In the morning, a person is about 8 millimeters taller than in the evening.
- The muscles which help your eyes to focus complete around 100,000 movements a day. In order to make your leg muscles do the same amount of movements, you would need to walk 80 kilometers.
- A cough amounts to an explosive charge of air which moves at speeds up to 60 miles per hour.
- According to German researchers, the risk of having a heart attack is higher on Monday than on any other day of the week.
- Bones are about 5 times stronger than steel.
- It is impossible to sneeze with your eyes open.
- Ingrown toenails are hereditary.
- A person would die quicker from a total lack of sleep than from hunger. Death would occur after ten days without sleep, whereas from hunger it would take several weeks.
- The average life expectancy is 2,475,576,000 seconds. During this time we pronounce, on average, around 123,205,750 words and have sex 4,239 times.
The Solar System is the gravitationally bound planetary arrangement of the Sun and the items that circle it
The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud.
सूर्य अथवा सूरज सौर मंडल के केन्द्र में स्थित एक G श्रेणी का मुख्य-अनुक्रम तारा है जिसके इर्द-गिर्द पृथ्वी और सौरमंडल के अन्य अवयव घूमते हैं। सूर्य हमारे सौर मंडल का सबसे बड़ा पिंड है, जिसमें हमारे पूरे सौर मंडल का ९९.८६% द्रव्यमान निहित है और उसका व्यास लगभग १३ लाख ९० हज़ार किलोमीटर है, जो पृथ्वी से लगभग १०९ गुना अधिक है।ऊर्जा का यह शक्तिशाली भंडार मुख्य रूप से हाइड्रोजन और हीलियम गैसों का एक विशाल गोला है। परमाणु विलय की प्रक्रिया द्वारा सूर्य अपने केंद्र में ऊर्जा पैदा करता है। सूर्य से निकली ऊर्जा का छोटा सा भाग ही पृथ्वी पर पहुँचता है जिसमें से १५ प्रतिशत अंतरिक्ष में परावर्तित हो जाता है, ३० प्रतिशत पानी को भाप बनाने में काम आता है और बहुत सी ऊर्जा पेड़-पौधे समुद्र सोख लेते हैं।
बुध सौर मंडल का सूर्य से सबसे निकट स्थित और आकार में सबसे छोटा ग्रह है। यम(प्लूटो) को पहले सबसे छोटा ग्रह माना जाता था पर अब इसका वर्गीकरण बौना ग्रह के रूप में किया जाता है। यह सूर्य की एक परिक्रमा करने में ८८ दिन लगाता है। यह लोहे और जस्ते का बना हुआ हैं। यह अपने परिक्रमा पथ पर २९ मील प्रति क्षण की गति से चक्कार लगाता हैं। बुध सूर्य के सबसे पास का ग्रह है और द्रव्यमान से आंठवे क्रमांक पर है। बुध व्यास से गैनिमीड और टाईटन चण्द्रमाओ से छोटा है लेकिन द्रव्यमान में दूगना है।
शुक्र Venus –
शुक्रसूर्य से दूसरा ग्रह है और छठंवा सबसे बड़ा ग्रह है। इसका परिक्रमा पथ 108¸200¸000 किलोमीटर लम्बा है। इसका व्यास 12¸103•6 किलोमीटर है। ।शुक्र सौर मंडल का सबसे गरम ग्रह है। शुक्र का आकार और बनाबट लगभग पृथ्वी के बराबर है। इसलिए शुक्र को पृथ्वी की बहन कहा जाता है। ग्रहपथ :0.72 AU या 108,200,000 किमी (सूर्य से)। शुक्र शुक्र की ग्रहपथ लगभग पूर्ण वृत्त है। व्यास : 12,103.6 किमी द्रव्यमान : 4.869e24 किग्रा