The writing materials,the envelopes and the stamps are all made of paper and this led to a great waste as the papers have to be disposed after use. This is not the case with electronic mails. Electronic mails do not need paper at all and it has drastically reduce the amount of papers that is used in writing letters.
I hope this helps :)
Crystallization
This is a technique commonly done by chemists to purify compounds. During crystallization, an impure,solid compound is dissolved with a hot solvent. In the container the impurities and the needed compound move freely. When the solution cools down, the solvent can cannot hold all the solutes. Each solute will form a crystal. Therefore each crystal is made of only one molecule. Once it cools down if will be placed in a cold bath to complete the crystallization.
Answer;
-Allele frequency change
In single-gene traits, natural selection can lead to allele frequency change.
Explanation;
-Allele frequencies can change over time within a single population, and frequently differ between populations. This change is due to four different processes: mutation, selection (natural and artificial), gene flow and genetic drift.
-Random forces lead to genetic drift. Sometimes, there can be random fluctuations in the numbers of alleles in a population. These changes in relative allele frequency, called genetic drift, can either increase or decrease by chance over time.
All eukaryotic cells have membrane covered compartment called organelles. They include the nucleus, the Golgi, mitochondria, endoplasmic reticulum and many others. So the answer is- organelles. ;)
