EVOLUTION
(Sir Malik is a science teacher and today he is going to discuss EVOLUTION).
He enters the classroom and starts a conversation with students about evolution.
Sir Malik: Class today we are going to discuss evolution. Do you have any idea, what is evolution?
(the students raise their hands and say, yes sir, yes sir)
Sir Malik: Good, that means you know much more about evolution. (then Sir Malik pointed to a student to tell about evolution).
Student: Sir, evolution is the change with respect to time in life.
Sir Malik: What kind of change is it?
Student: The changes of inheritance, the changes in chromosomes, the changes in genes, and the change in the DNA of any organism.
Sir Malik: Good, anyone who wants to add something.
Student: Yes sir, evolution is some kind of modification in an individual.
Sir Malik: Nice, Does anyone to add much more?
Student: Sir, mutation plays a key role in evolution.
Sir Malik: That’s the point. Now, what is mutation?
Student: Sir, it is any change in the chromosomes or genes or in the DNA of any organism.
Sir Malik: Good, what kind of change is it?
(silence in the classroom).
Sir Malik: Students, mutation can be divided into two types I.e. harmful mutation, and beneficial mutation.
As the name shows, a harmful mutation is a mutation that causes death or any kind of harmful effect on the organism. While beneficial mutation results in the ability of the organism to survive or is beneficial for the organism.
Now, how do these two conditions relate?
Student: Sir, I think it is the process of natural selection.
Sir Malik: yes, it is.
As we are discussing evolution, I want to know first, the one keyword that is as essential for evolution as the heart of our body. In simple words, describe evolution in just one word.
(silence in the classroom, then a student raises his hand and says “Sir can I answer”. Everybody looks at this student and is curious about what kind of answer he has).
Sir Malik: Yes, please!
Student: Sir, I think it is Reproduction, because if there is no reproduction between species or different organisms, then there is no evolution.
Sir Malik: That’s a good answer.
(everybody in the classroom claps for this student).
Sir Malik: When we discussed the term evolution, we actually discussed reproduction and the changes from parents to the new generation. These changes have great importance because it decides whether the new individual can survive in the environment or not.
Student: Sir, can you please explain the term “changes”?
Sir Malik: You know the fingerprints of every human are unique and no other human in the whole world has a matching fingerprint. This is because of the uniqueness of the DNA of every human. This is an example of changes that any organism has from generation to generation but it is not evolution.
Can anybody know, why?
(Another silence because nobody knows the logic behind this question).
Sir Malik: I will answer this question but first I want to continue the types of mutation. Anybody knows what are the two types of mutation?
Students: Harmful mutation and beneficial mutation.
Sir Malik: Good, now we know that the effect of mutation may be harmful or beneficial for the organism.
Here, we have to understand one thing and that is life or nature wants to reduce the harmful effect of mutation and make it beneficial for the organism. Can anyone want to know what I mean?
(Nobody in the class understands this and so again silence in the classroom).
Sir Malik: You can understand this by the term natural selection. It is a very famous term, hope you all know about this.
Students: Yes sir, the fittest organisms can survive in nature.
Sir Malik: Good, now revise all the terms that we have discussed.
- We discussed that evolution is the process of changes in individuals from generation to generation and reproduction is a key material for the process of evolution.
- We also learned that evolution occurs with the help of mutation and mutation can be divided into two types according to their effects.
- And last we learned the behavior of nature that the body of organisms wants to stabilize the things that cause bad effects.
Am I right? (Said Sir Malik)
Students: Yes sir!
Sir Malik: Now, how does this work? How do changes occur in DNA?
You can understand this by taking some examples. We have an idea about immunity in living organisms. Let us understand evolution with the help of immunity.
- If we take bacterial cells (suppose it is E.coli bacteria) and placed them in a culture medium. Then we will observe that they divided after every 20 minutes and increased their population.
- Now if we add a material that is harmful to this bacteria (suppose this material damages the cell wall of E.coli bacteria), then as a result, the bacterial cells are going to die and hence the decrease in the numbers of bacterial cells.
- But not every time all the cells of bacteria have died and sometimes some cells are able to survive in these harsh conditions. These cells now reproduce and form new colonies of bacterial cells and all the new cells have the ability to survive in that harsh conditions.
- This is because that the changes of information in the DNA of this bacterial cell and the same DNA transferred from the old generation to the new generation. We can say the new generation mutants or can observe the evolution.
This process is very common and can be observed in different kinds of organisms like the resistance of insects against insecticides and the resistance of many bacterial cells in humans against antibiotics.
Humans can also boost their immune system and so we can say it is evolution but the most appropriate word for the process is microevolution. It is also an example of natural selection and survival of the fittest.
Do you have any questions about the above example?
Students: Sir, it means humans are evolving themselves.
Sir Malik: Evolution can only be seen if the mutations or changes occur in germ cells. In somatic cells, evolution can’t be seen because only germ cells take part in reproduction and we learn that reproduction is the key point of evolution.
Students: Then why in bacterial cells of E.coli shows evolution?
Sir Malik: E.coli is a unicellular organism and can reproduce only by asexual means (simple cell division). Thus identical copies are formed.
Students: Sir it means it is important for evolution that germ cells are affected.
Sir Malik: it may be yes or maybe no. You can understand this by taking another example.
Do you listen to Mendal’s experiment on pea plants?
Students: Yes sir, he is the father of genetics.
Sir Malik: Good, then you also know about the character of the short and tall height of the pea plant.
Students: Yes sir.
Sir Malik: Do you know why one plant has always a short height?
Students: Sir, because of factors or alleles present in the genetic material of pea plants.
Sir Malik: Can you elaborate on your answer?
Student: The pea plant has two kinds of alleles, one is called a dominant allele and the other can be said as recessive. A single gene has two pairs of alleles or any one character controlled by these two alleles (two traits).
For the short height of the pea plant, it is important that both alleles are recessive. If any single dominant allele is present in the pairing then the phenotype of the pea plant is tall height.
Sir Malik: Good, what if I say that both alleles are responsible for a pea's plant height but only the dominant allele has the information for the tall heighted plant while the recessive allele has no such information like that? Do you agree with me?
Students(after some thinking): You may be correct because a single dominant allele can result in a tall height pea plant.
Sir Malik: This is the same story of germ cells and another reason why evolution occurs.
Student: Sir, can you please explain this?
Sir Malik: Suppose two parents, one is the mother, and the other is the father. For the formation of the embryo, the fertilization of both sperm and egg is essential.
Suppose the sperm from the father’s side has some unnecessary information that may be harmful to the new generation. In this situation, how does the process of fertilization act, and the newborn individual has some disorders or not?
Students: We think there is a 50/50 percent chance.
Sir Malik: Think again and focus on the lesson we learned earlier. Good and bad mutation, natural behavior, and presence of information in Mendel’s pea plant case.
Students: Sir, you mean that newborn individuals will be healthy!
Sir Malik: Yes there is a great chance of a healthy individual but the affected allele will also be present in the newborn organism however it may not be expressed but can express itself in future generations.
I hope you understand the relationship between mutation and evolution and will understand the importance of germ cells or reproduction in the process of evolution.
Students: Yes sir!
Sir Malik: As we discussed that mutations are important for evolution and we know some mutagenic factors such as X-rays, radiation, and many chemicals that can cause mutations in organisms. The mutation introduced in the organism by a man with the help of mutagenic materials is called Induced mutation and it is first observed by Hermann Joseph Muller. He induced mutation with the help of X-rays.
But there are also some examples of natural mutations. One of the natural mutations can be seen in fruit flies with white eye color. It was first observed by Thomas Hunt Morgan in 1915 when he was observing fruit flies in his laboratory. You have to know the genetic history if you want to understand the evolution process.
In simple words, when a mutation enters into the offspring of a new generation and survives in the external environment then evolution is seen. This is the simplest rule to understand evolutionary processes.
Now students, do you clear about evolution?
Students: Yes sir, it is clear about evolution.
Sir Malik: Evolution is a theory, not a hypothesis or a law. Anyone knows why?
Student: Sir, maybe some scientists have problems with it.
Sir Malik: What kinds of problems do you mean?
Student: Some religious problems!
Sir Malik: Can you explain it?
Student: Because some religious people are not going to accept it.
Sir Malik: Once Einstein said that “Science without religion is lame, religion without science is blind.”
Many religious books like Quran and Bible are the base of such scientific research. Quran says that life begins from the water thousand of years ago when there is no scientific research available. And this is the base of evolution and life. Allah says in Quran:
“We made from water every living thing....”
(Surah 21, verse 30).
So how can you say that religion denies the scientific facts?
Student: Sir, scientists believed that life starts from a single cell but according to the religious books God created man in its original and complete form.
Sir Malik: Different organisms have different numbers of chromosomes. For example, humans have 23 pairs of chromosomes (the total number of chromosomes in humans is 46), the buffalo has 60 diploid chromosomes while the cat has 38, and the dog has 78 total chromosomes. You can observe the difference in the numbering of chromosomes between organisms. Not a single scientist in history and in the present time is able to defend or explain this difference with the help of evolution.
- One of the problems with evolutionary studies is that it fails to describe the fact that how the size or number of DNA increased or decreased.
- Why do different organisms have different numbers of chromosomes and why this numbering is not changed even in the case of mutation?
- Why, how, and from where the first living cell originates and converts into complex forms of life? Evolution fails to describe all these facts.
Students: Sir, if all these major facts are not described by evolution then why it has such importance for scientists?
Sir Malik: if we divide evolution into microevolution and macroevolution then it is easy for us to understand this.
Microevolution relates to microbes like bacteria and we noticed some kind of evolution in it. But the problem is with large size animals or plants or any other form of life because it has two characteristics, one is complexity while the other is perfection. And because of these two characters, it is difficult for us to find a conclusion.
Student: Sir, is this the answer to your question that why evolution is the theory?
Sir Malik: Good, yes it is because some factors support evolution and some deny the process of evolution.
Students: Sir is this problem can be solvable or not?
Sir Malik: Evolutionary studies have so much diversity in them that we can’t ignore them anyway because with this concept we can relate life from a simple to complex manner.
But from my point of view, scientists missing some things that can solve this problem and restricting themselves to the same thing and that is evolution. If we work on it then it is possible to find a good conclusion.
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