The layer chromosphere is #2000# km thick.

The radius of the sun is #0.7 * 10^6# km.

To calculate this you have to just do same as we do in calculation of our exam's marks percentage.

Just imagine,

Your exam is of total marks of #0.7 * 10^6#(not possible but you have #color(white)0000000000000000000000000000000#to just imagine this )
out of this you got #2000# marks.

To calculate the percentage you have to do something like this:

#=2000/(0.7 * 10^6) * 100#


Just do same calculation for this question,
Total radius of sun is #0.7 * 10^6# km.
out of this #2000# km is chromosphere.

#=2000/(0.7 * 10^6) * 100#



I have added image for your help by which you can know where is chromosphere of the sun.


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Sister chromatids separate:--

  1. During anaphase of mitosis.
  2. During anaphase II of meiosis.

the duplicated chromosomes (with two sister chromatids attached at centromere) are lined up at the equatorial region of dividing cell and then microtubules attach at the centromeres to pull the chromatids apart toward opposite poles.

Here is a real time image of anaphase occuring in a plant cell




Minamata Disease, Taiwan and Japan rice, Love Canal, etc.


I use only one reference for this assay (LaGrega et al., 1994).

Mercury salts, which were used to form felt in the Dutch hat industry, caused neurulogic disorder renowned as being "mad as a hatter." Organic forms of mercury (e.g. methyl mercury) have proven to be more pernicious, having caused hundreds of cases of paralysis and sensory loss at Minamata Bay area in Japan. Inorganic mercury discharged from a chemical plant became methylated in sediments and then bioaccumulated in shellfish. Due to the fact that shellfish are the principal protein source of the local people, this situation was an epidemic waiting to happen. In the late 1960s, this poisoning (itai itai disease) heightened global awareness of industrial pollution.

Two cases of accidental contamination of rice cooking oil in Japan and Taiwan in the late 1960s and mid-1970s exposed thousands of Asians to hşgh concentrations of PCBs (poly chlorinated biphenlys). Miscarriages and birth defects increased within the exposed populations. Although later it would be shown that these prenatal health problems resulted not from PCBs themselves but from polychlorinated dibenzofurans (PCDFs) that formed when heating the contaminated rice cooking oil, the riveting environmental journalism made the World population vividly aware of the adverse human effects of "PCB" exposure.

Nearly the same time in the United States, the contamination of Michigan cattle feed by polybrominated biphenyls (PBBs) not only caused widespread human exposures via milk and other dairy products, but also followed more complex pathways to reach humans.

Afflicted cattle were rendered and then used to prepare chicken feed; thousands of human consumers were exposed to PBBs through eggs and egg products. One incident involved 24 thousand crates of PBB-contaminated shorthcakes which were confiscated in Alabama. PBBs were found in some Michigan mothers' breast milk.

Love Canal is the symbol of environmental contamination by hazardous wate. Not useful as a canal, this canal was sealed off at the ends and used in the 1940s and 1950s by Hooker Chemical Company and others as a hazardous waste disposal site. Later, this site was sold to the Niagara Falls, New York, School Districts. The School District built an elementary school on the site despite the fact that a warning was made against any excavation and underground construction.

Later the developed area caused sickness in children and some residents. You can get details: https://www.geneseo.edu/history/love_canal_history


LaGrega, M. D., Buckingham, P. L., and Evans, J. C. (1994). Hazardous Waste Management. McGraw Hill, Inc. New York, NY. USA.



#1/3# lies in the range #(1/4,2/5)#, #11/12# lies in the range #(13/15,1)#, but #4/7# does not lie in any of the given range.


If #a/b < c/d# then #(color(blue)ma+color(red)nc)/(color(blue)mb+color(red)nd)# lies between #(a/b,c/d)#, if #color(blue)m>0# and #color(red)n>0#

Observe that #1/3=3/9=(color(blue)1xx1+color(red)1xx2)/(color(blue)1xx4+color(red)1xx5)#

Hence #1/3# lies in the range #(1/4,2/5)#

Similarly as #13/15<1# i.e. #13/15<9/9#, #(color(blue)1xx13+color(red)1xx9)/(color(blue)1xx15+color(red)1xx9)=(13+9)/(15+9)=22/24=11/12#

Hence #11/12# lies in the range #(13/15,1)#.

Although above is an interesting way for such problems, the easiest is to convert every number to decimal form.

Hence numbers are #4/7=0.57#, #1/3=0.33# and #11/12=0.916#

and ranges are #(0,0.25)#, #(0.866,1)# and #(0.25,0.40)#

and as is seen #1/3# lies in the range #(1/4,2/5)#, #11/12# lies in the range #(13/15,1)#, but #4/7# does not lie in any of the given range.

Additional Information #-# If in #(color(blue)ma+color(red)nc)/(color(blue)mb+color(red)nd)#, one of the #m# or #n# is negative, #(color(blue)ma+color(red)nc)/(color(blue)mb+color(red)nd)# gives out a number which is outside the range.

Observe that #(color(blue)((-9))xx0+color(red)4xx1)/(color(blue)((-9))xx1+color(red)4xx4)=(color(blue)3xx13+color(red)((-3))xx1)/(color(blue)3xx15+color(red)((-3))xx1)=(color(blue)((-2))xx1+color(red)3xx2)/(color(blue)((-2))xx4+color(red)3xx5)=4/7#



#A = 238 " "units^2#


Area of a regular polygon #= 1/2 xx perimeter xx apothem#

#A = (Pa)/2#

Perimeter #= "number of sides" xx "side length"#

#P = ns = 8s#

#A = (8s*8.5)/2 = 34s#

Since we know that the octagon is regular and we know the apothem (height from a side to the center of the polygon, we can calculate the side length):

Each angle of the central angle: #(360^@)/8 = 45^@#

and each side of the polygon forms an isoceles triangle when joined to center. Further, a perpendicular from center to the side of the polygon divides the side in two equal parts and also cuts this angle at the center (#45^@#) in half i.e. #22.5^@#.

Using trigonometry, we can find half the side length (#x#):

#tan 22.5^@ = x/a = x/8.5#

#x = 8.5*tan 22.5^@ ~~ 3.52#

side length: #s = 2x ~~ 7#

#A = 34 * s ~~ 34 * 7 ~~238 " units"^2 #

enter image source here



The sentence is an example of the stylistic sentence pattern called polysyndeton where a conjunction (such as and) is repeated in quick succession for dramatic effect.


The repeated use of and in this sentence could be avoided by just listing the servers and networks affected. In this case the author wanted to enhance the negative effect of the devastation due to the virus, so the reader would experience a greater impact from reading it.

There is more information here:



Self pollination is pollination of flowers of a plant with itself. Cross pollination is pollination between two plants of same species.


Self pollination
Transfer of pollen grain from the anther to stigma of same flower is called self pollination.


Cross pollination
Transfer of pollen from the anther of a flower to the stigma of a flower on a different plant of the same species is called cross pollination.

Chances of variations is more in cross pollination than in self pollination.



Thymidine is a nucleoSIDE.

Thymidine monophosphate is a nucleoTIDE. It is also called thymidylic acid. It is a component of DNA.


Here is thymidine

It consists of a nitrogenous base (pyrimidine) and a 5-carbon sugar (deoxyribose). Together, they make up a nucleoSIDE .



Here is thymidine monophosphate

It consists of a nitrogenous base (pyrimidine), 5 carbon sugar (deoxyribose), and a phosphate group (monophosphate/1 phosphate). Together, they make up a nucleoTIDE .



Tetrads are pairs of homologous chromosomes, seen in pachytene of meiosis prophase I. Homologous chromosomes do not retain the pairing otherwise.


Although both are very similar, the difference between the two is the pairing.

Homologous chromosomes are basically two similar chromosomes inherited from father and mother. They are homologous because they have the same genes, though not same alleles.

During meiosis, the homologous chromosomes pair up during first prophase. When they do so, the homologous pair becomes known as a bivalent.

Each chromosome of a bivalent undergo further coiling and sister chromatids could be distinctly seen under microscope. So each bivalent appears as 'tetrad' i.e. consisting of four chromatids.

Homologous chromosomes exchange parts in a process called crossing as the first prophase stage of meiosis continues. For this, homologous pairing and appearance of bivalent is important. Crossing over can take place when bivalent is in tetrad stage.


Hope this helps :)





Primarily to store large amounts of #"Ca"^(+2)# ions for muscle contraction.


It is a specialized type of endoplasmic reticulum in muscles cell which primarily functions to store large amounts of #Ca^(+2)# ions for muscle contraction.

When an action potential occurs, the signal reaches the SR and causes the release of the large stores of #"Ca"^(+2)# ions. These calcium ions will initiate the start of contraction of muscle cells. When contraction is no longer needed, the SR will actively pump #"Ca"^(+2)# back into the SR lumen for future use.



A unicellular organism's growth is limited, and it divides pretty soon.


The answer lies in the structure of bacteria.
Most bacteria are unicellular,sessile (fixed to a place, unable to move) organisms.

  1. The cell is bound by a membrane and a cell wall. The cell singlehandedly does all the work of living. A living membrane is rather fragile and beyond a size it would not be able to 'grow' without bursting at the seams. The physical limitations of surface area:volume ratio do not permit growth to larger dimensions.

  2. There are in bacteria no mechanical support systems: no rigid apparatus within or on the outside of the cell that would allow growth to exceed microscopic dimensions.

  3. Most significantly bacterial species have evolved such that they can colonize an immense variety of substratum and use the various substrata to survive. A small size helps in this.

  4. Bacteria are genetically equipped so as to make the best use of their small size. The bacterial cell can take in only a limited amount of nutrition, and divides at a faster rate when nutrient supply is abundant. So individual cells do not grow in size, rather the population grows in number.

(Bacteria however often get together to form * mats * and overcome the limitations of being single celled and microscopic.)

For a more advanced explanation