Textbook: Heredity and Evolution | Science and Technology Class 10 (Maharashtra SSC Board) PDF Download

 Page 1


1
1. Which component of the cellular nucleus of living organisms  
 carries hereditary characters?
2. What do we call to the process of transfer of physical and   
 mental  characters from parents to the progeny?
3. Which are the components the DNA molecule?
Heredity and hereditary changes
 You know that heredity is the transfer of biological characters from one generation to 
another via genes. Gregor Johann Mendel is pioneer of the modern genetics. It took a long 
time to understand the conclusions of his research about heredity.  In 1901, the reasons behind 
the sudden changes were understood due to the mutational theory of Hugo de Vries. Meanwhile 
in 1902, Walter Sutton observed the paired chromosomes in the cells of grasshopper; until 
then it was not known to anyone. Research started in the direction of finding the nature of 
genetic material when it was proved that genes are carried via chromosomes. Through which 
1944, trio of scientists Oswald Avery, Mclyn McCarty and Colin McLeod proved that except 
viruses, all living organisms have DNA as genetic material.
 In 1961, the French geneticists Francois Jacob and Jack Monod proposed a model for 
process of protein synthesis with the help of DNA in bacterial cells. It helped to uncover the 
genetic codes hidden in DNA. Thereby, the technique of recombinant DNA technology 
emerged which has vast scope in the field of genetic engineering.
 The science of heredity is useful for diagnosis, treatment and prevention of hereditary 
disorders, production of hybrid varieties of animals and plants and in industrial processes in 
which microbes are used.
Transcription, Translation and Translocation
 With the help of RNA, the genes present in the form of DNA participate in the functioning 
of cell and thereby control the structure and functioning of the body. Information about protein 
synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is 
necessary for body. These proteins are synthesized by DNA through the RNA. This is called 
as ‘Central Dogma’. mRNA is produced as per the sequence of nucleotides on DNA. Only one 
of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being 
produced is always complementary to the DNA strand used for synthesis. Besides, there is 
uracil in RNA instead of thymine of DNA.  This process of RNA synthesis is called as 
‘transcription’.
Can you tell?
Can you recall?
1.  Sketch and explain the structure of DNA and various types of RNA.
2.  Explain the meaning of genetic disorders and give names of some      
  disorders.
1. Heredity and Evolution 
Ø Heredity and Hereditary Changes   Ø   Transcription, Translation & 
                      Translocation
Ø	Evolution       Ø 	Evidences of Evolution
Ø   Darwin’s Theory of Natural Selection   Ø 	Lamarckism
Ø Speciation      Ø 	Human Evolution
Page 2


1
1. Which component of the cellular nucleus of living organisms  
 carries hereditary characters?
2. What do we call to the process of transfer of physical and   
 mental  characters from parents to the progeny?
3. Which are the components the DNA molecule?
Heredity and hereditary changes
 You know that heredity is the transfer of biological characters from one generation to 
another via genes. Gregor Johann Mendel is pioneer of the modern genetics. It took a long 
time to understand the conclusions of his research about heredity.  In 1901, the reasons behind 
the sudden changes were understood due to the mutational theory of Hugo de Vries. Meanwhile 
in 1902, Walter Sutton observed the paired chromosomes in the cells of grasshopper; until 
then it was not known to anyone. Research started in the direction of finding the nature of 
genetic material when it was proved that genes are carried via chromosomes. Through which 
1944, trio of scientists Oswald Avery, Mclyn McCarty and Colin McLeod proved that except 
viruses, all living organisms have DNA as genetic material.
 In 1961, the French geneticists Francois Jacob and Jack Monod proposed a model for 
process of protein synthesis with the help of DNA in bacterial cells. It helped to uncover the 
genetic codes hidden in DNA. Thereby, the technique of recombinant DNA technology 
emerged which has vast scope in the field of genetic engineering.
 The science of heredity is useful for diagnosis, treatment and prevention of hereditary 
disorders, production of hybrid varieties of animals and plants and in industrial processes in 
which microbes are used.
Transcription, Translation and Translocation
 With the help of RNA, the genes present in the form of DNA participate in the functioning 
of cell and thereby control the structure and functioning of the body. Information about protein 
synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is 
necessary for body. These proteins are synthesized by DNA through the RNA. This is called 
as ‘Central Dogma’. mRNA is produced as per the sequence of nucleotides on DNA. Only one 
of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being 
produced is always complementary to the DNA strand used for synthesis. Besides, there is 
uracil in RNA instead of thymine of DNA.  This process of RNA synthesis is called as 
‘transcription’.
Can you tell?
Can you recall?
1.  Sketch and explain the structure of DNA and various types of RNA.
2.  Explain the meaning of genetic disorders and give names of some      
  disorders.
1. Heredity and Evolution 
Ø Heredity and Hereditary Changes   Ø   Transcription, Translation & 
                      Translocation
Ø	Evolution       Ø 	Evidences of Evolution
Ø   Darwin’s Theory of Natural Selection   Ø 	Lamarckism
Ø Speciation      Ø 	Human Evolution
2
` The mRNA formed in nucleus comes in 
cytoplasm. It brings in the coded message 
from DNA. The message contains the codes 
for amino acids. The code for each amino 
acid consists of three nucleotides. It is called 
as ‘triplet codon’. 
 Dr Har Govind Khorana, a scientist of 
Indian origin has made an important 
contribution in discovery of triplet codons 
for 20 amino acids. For this work, he has 
been awarded with the Nobel Prize in 1968, 
along with two other scientists. 
 Each mRNA is made up of thousands of 
triplet codons. As per the message on mRNA, 
amino acids are supplied by the tRNA. For 
this purpose, tRNA has ‘anticodon’ having 
complementary sequence to the codon on 
mRNA. This is called as ‘translation’. The 
amino acids brought in by tRNA are bonded 
together by peptide bonds with the help of 
rRNA. During this process, the ribosome 
keeps on moving from one end of mRNA to 
other end by the distance of one triplet codon. 
This is called as ‘translocation’. Such many 
chains come together to form complex 
proteins. These proteins control various 
functions in the body of living organisms 
and their appearance too.
 Living organisms can produce new 
individuals like themselves due to genes 
only and some of those genes are transmitted 
to the next generation without any changes. 
Due to this, some of the characters of parents 
are transmitted to their offsprings. However, 
sometimes sudden changes occur in those 
genes. Sometimes, any nucleotide of the 
gene changes its position that causes a minor 
change which is nothing but the ‘mutation’. 
1.2  Translation & Translocation
1.1  Transcription 
1.3  Mutation
RNA Polymerase
RNA Nucleotides  
Transcription 
Main Sequence 
Replacement
 Some mutations may be minor but some may be considerable. Ex. Mutation may cause 
the genetic disorders like sickle cell anaemia.   
Nucleus
Amino Acid 
Ribosome 
Codon
mRNA
tRNA
mRNA
Page 3


1
1. Which component of the cellular nucleus of living organisms  
 carries hereditary characters?
2. What do we call to the process of transfer of physical and   
 mental  characters from parents to the progeny?
3. Which are the components the DNA molecule?
Heredity and hereditary changes
 You know that heredity is the transfer of biological characters from one generation to 
another via genes. Gregor Johann Mendel is pioneer of the modern genetics. It took a long 
time to understand the conclusions of his research about heredity.  In 1901, the reasons behind 
the sudden changes were understood due to the mutational theory of Hugo de Vries. Meanwhile 
in 1902, Walter Sutton observed the paired chromosomes in the cells of grasshopper; until 
then it was not known to anyone. Research started in the direction of finding the nature of 
genetic material when it was proved that genes are carried via chromosomes. Through which 
1944, trio of scientists Oswald Avery, Mclyn McCarty and Colin McLeod proved that except 
viruses, all living organisms have DNA as genetic material.
 In 1961, the French geneticists Francois Jacob and Jack Monod proposed a model for 
process of protein synthesis with the help of DNA in bacterial cells. It helped to uncover the 
genetic codes hidden in DNA. Thereby, the technique of recombinant DNA technology 
emerged which has vast scope in the field of genetic engineering.
 The science of heredity is useful for diagnosis, treatment and prevention of hereditary 
disorders, production of hybrid varieties of animals and plants and in industrial processes in 
which microbes are used.
Transcription, Translation and Translocation
 With the help of RNA, the genes present in the form of DNA participate in the functioning 
of cell and thereby control the structure and functioning of the body. Information about protein 
synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is 
necessary for body. These proteins are synthesized by DNA through the RNA. This is called 
as ‘Central Dogma’. mRNA is produced as per the sequence of nucleotides on DNA. Only one 
of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being 
produced is always complementary to the DNA strand used for synthesis. Besides, there is 
uracil in RNA instead of thymine of DNA.  This process of RNA synthesis is called as 
‘transcription’.
Can you tell?
Can you recall?
1.  Sketch and explain the structure of DNA and various types of RNA.
2.  Explain the meaning of genetic disorders and give names of some      
  disorders.
1. Heredity and Evolution 
Ø Heredity and Hereditary Changes   Ø   Transcription, Translation & 
                      Translocation
Ø	Evolution       Ø 	Evidences of Evolution
Ø   Darwin’s Theory of Natural Selection   Ø 	Lamarckism
Ø Speciation      Ø 	Human Evolution
2
` The mRNA formed in nucleus comes in 
cytoplasm. It brings in the coded message 
from DNA. The message contains the codes 
for amino acids. The code for each amino 
acid consists of three nucleotides. It is called 
as ‘triplet codon’. 
 Dr Har Govind Khorana, a scientist of 
Indian origin has made an important 
contribution in discovery of triplet codons 
for 20 amino acids. For this work, he has 
been awarded with the Nobel Prize in 1968, 
along with two other scientists. 
 Each mRNA is made up of thousands of 
triplet codons. As per the message on mRNA, 
amino acids are supplied by the tRNA. For 
this purpose, tRNA has ‘anticodon’ having 
complementary sequence to the codon on 
mRNA. This is called as ‘translation’. The 
amino acids brought in by tRNA are bonded 
together by peptide bonds with the help of 
rRNA. During this process, the ribosome 
keeps on moving from one end of mRNA to 
other end by the distance of one triplet codon. 
This is called as ‘translocation’. Such many 
chains come together to form complex 
proteins. These proteins control various 
functions in the body of living organisms 
and their appearance too.
 Living organisms can produce new 
individuals like themselves due to genes 
only and some of those genes are transmitted 
to the next generation without any changes. 
Due to this, some of the characters of parents 
are transmitted to their offsprings. However, 
sometimes sudden changes occur in those 
genes. Sometimes, any nucleotide of the 
gene changes its position that causes a minor 
change which is nothing but the ‘mutation’. 
1.2  Translation & Translocation
1.1  Transcription 
1.3  Mutation
RNA Polymerase
RNA Nucleotides  
Transcription 
Main Sequence 
Replacement
 Some mutations may be minor but some may be considerable. Ex. Mutation may cause 
the genetic disorders like sickle cell anaemia.   
Nucleus
Amino Acid 
Ribosome 
Codon
mRNA
tRNA
mRNA
3
1. What is the function of the appendix of our digestive system?
2. Are our wisdom teeth really useful for chewing the food?
3. Why did the huge animals like dinosaur become extinct?
4. Why are many species of animals and birds getting extinct?
 3.5 billion years ago, life had been non 
existent on the Earth. At the beginning, there 
may have been only simple elements in the 
ocean on the Earth and simple type of organic 
and inorganic compounds may have been 
formed from those. Complex compounds like 
proteins and nucleic acids may have formed 
over the long period from those simple 
compounds. First primitive type of cells may 
have been formed from the mixture of different 
types of organic and inorganic compounds. 
Number of those cells may have increased at 
the cost of surrounding chemicals. There may 
had been some differences among those cells 
and according to the principle of natural 
selection, some may have shown good growth 
and some may have perished which could not 
adjust with the surrounding.
 At present, crores of species of plants and 
animals with huge diversity regarding shape 
and complexity are present on the Earth. 
Animal diversity ranges from the unicellular 
Amoeba and Paramecium to man and giant 
whale. The plant diversity consists of various 
species ranging from unicellular Chlorella to 
the huge banyan tree. The life exists on Earth 
everywhere from equator to both the poles. 
Organisms are present at all the places like 
air, water, land, rock, etc. Humans have 
shown curiosity about origin of life and 
reasons for such a great diversity in life 
present on the Earth since ancient period. 
Different theories about origin and evolution 
of life have been proposed till today of which 
theory of 'Gradual development of living 
organisms is accepted.
A peek into History
Many philosophers and religious scholars 
have written their views about formation of 
life. There seems to be a thorough discussion 
over the formation of Universe, in various 
cultures like Indian, Chinese, Roman, 
Greek, etc. Various cultures have noted 
different type of information about planets, 
stars, the ‘panchmahabhuta’, living 
organisms, etc. in the form of poetry, stories 
and religious / sacred books.
Evolution  
 Evolution is the gradual change occurring in living organisms over a long duration.  This is 
a very slow-going process through which development of organisms is achieved. All the stages 
in changes occurred in various components ranging from stars and planets in space to the 
biosphere present on the Earth should be included in the study of evolution. Formation of new 
species due to changes in specific characters of several generations of living organisms as a 
response to natural selection, is called as evolution.
Internet is my friend
 Collect the information from internet 
about Big-Bang theory related with the 
formation of stars and planets and present it 
in your class.
Can you recall?
Theory of Evolution:
According to this theory, first living material 
(protoplasm) has been formed in ocean. In 
due course of time, unicellular organism was 
formed. Gradually, changes occurred in the 
unicellular organisms from which larger and 
more complex organisms were formed. All 
those changes were slow and gradual. Duration 
of all these changes is at most 300 crore years. 
Changes and development in living organisms 
had been all round and multi-dimensional 
and this led to evolution of different types 
of organisms. Hence, this overall process is 
called as evolution which is organizational. 
Progressive development of plants and animals 
from the ancestors having different structural 
and functional organization is called evolution.
Page 4


1
1. Which component of the cellular nucleus of living organisms  
 carries hereditary characters?
2. What do we call to the process of transfer of physical and   
 mental  characters from parents to the progeny?
3. Which are the components the DNA molecule?
Heredity and hereditary changes
 You know that heredity is the transfer of biological characters from one generation to 
another via genes. Gregor Johann Mendel is pioneer of the modern genetics. It took a long 
time to understand the conclusions of his research about heredity.  In 1901, the reasons behind 
the sudden changes were understood due to the mutational theory of Hugo de Vries. Meanwhile 
in 1902, Walter Sutton observed the paired chromosomes in the cells of grasshopper; until 
then it was not known to anyone. Research started in the direction of finding the nature of 
genetic material when it was proved that genes are carried via chromosomes. Through which 
1944, trio of scientists Oswald Avery, Mclyn McCarty and Colin McLeod proved that except 
viruses, all living organisms have DNA as genetic material.
 In 1961, the French geneticists Francois Jacob and Jack Monod proposed a model for 
process of protein synthesis with the help of DNA in bacterial cells. It helped to uncover the 
genetic codes hidden in DNA. Thereby, the technique of recombinant DNA technology 
emerged which has vast scope in the field of genetic engineering.
 The science of heredity is useful for diagnosis, treatment and prevention of hereditary 
disorders, production of hybrid varieties of animals and plants and in industrial processes in 
which microbes are used.
Transcription, Translation and Translocation
 With the help of RNA, the genes present in the form of DNA participate in the functioning 
of cell and thereby control the structure and functioning of the body. Information about protein 
synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is 
necessary for body. These proteins are synthesized by DNA through the RNA. This is called 
as ‘Central Dogma’. mRNA is produced as per the sequence of nucleotides on DNA. Only one 
of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being 
produced is always complementary to the DNA strand used for synthesis. Besides, there is 
uracil in RNA instead of thymine of DNA.  This process of RNA synthesis is called as 
‘transcription’.
Can you tell?
Can you recall?
1.  Sketch and explain the structure of DNA and various types of RNA.
2.  Explain the meaning of genetic disorders and give names of some      
  disorders.
1. Heredity and Evolution 
Ø Heredity and Hereditary Changes   Ø   Transcription, Translation & 
                      Translocation
Ø	Evolution       Ø 	Evidences of Evolution
Ø   Darwin’s Theory of Natural Selection   Ø 	Lamarckism
Ø Speciation      Ø 	Human Evolution
2
` The mRNA formed in nucleus comes in 
cytoplasm. It brings in the coded message 
from DNA. The message contains the codes 
for amino acids. The code for each amino 
acid consists of three nucleotides. It is called 
as ‘triplet codon’. 
 Dr Har Govind Khorana, a scientist of 
Indian origin has made an important 
contribution in discovery of triplet codons 
for 20 amino acids. For this work, he has 
been awarded with the Nobel Prize in 1968, 
along with two other scientists. 
 Each mRNA is made up of thousands of 
triplet codons. As per the message on mRNA, 
amino acids are supplied by the tRNA. For 
this purpose, tRNA has ‘anticodon’ having 
complementary sequence to the codon on 
mRNA. This is called as ‘translation’. The 
amino acids brought in by tRNA are bonded 
together by peptide bonds with the help of 
rRNA. During this process, the ribosome 
keeps on moving from one end of mRNA to 
other end by the distance of one triplet codon. 
This is called as ‘translocation’. Such many 
chains come together to form complex 
proteins. These proteins control various 
functions in the body of living organisms 
and their appearance too.
 Living organisms can produce new 
individuals like themselves due to genes 
only and some of those genes are transmitted 
to the next generation without any changes. 
Due to this, some of the characters of parents 
are transmitted to their offsprings. However, 
sometimes sudden changes occur in those 
genes. Sometimes, any nucleotide of the 
gene changes its position that causes a minor 
change which is nothing but the ‘mutation’. 
1.2  Translation & Translocation
1.1  Transcription 
1.3  Mutation
RNA Polymerase
RNA Nucleotides  
Transcription 
Main Sequence 
Replacement
 Some mutations may be minor but some may be considerable. Ex. Mutation may cause 
the genetic disorders like sickle cell anaemia.   
Nucleus
Amino Acid 
Ribosome 
Codon
mRNA
tRNA
mRNA
3
1. What is the function of the appendix of our digestive system?
2. Are our wisdom teeth really useful for chewing the food?
3. Why did the huge animals like dinosaur become extinct?
4. Why are many species of animals and birds getting extinct?
 3.5 billion years ago, life had been non 
existent on the Earth. At the beginning, there 
may have been only simple elements in the 
ocean on the Earth and simple type of organic 
and inorganic compounds may have been 
formed from those. Complex compounds like 
proteins and nucleic acids may have formed 
over the long period from those simple 
compounds. First primitive type of cells may 
have been formed from the mixture of different 
types of organic and inorganic compounds. 
Number of those cells may have increased at 
the cost of surrounding chemicals. There may 
had been some differences among those cells 
and according to the principle of natural 
selection, some may have shown good growth 
and some may have perished which could not 
adjust with the surrounding.
 At present, crores of species of plants and 
animals with huge diversity regarding shape 
and complexity are present on the Earth. 
Animal diversity ranges from the unicellular 
Amoeba and Paramecium to man and giant 
whale. The plant diversity consists of various 
species ranging from unicellular Chlorella to 
the huge banyan tree. The life exists on Earth 
everywhere from equator to both the poles. 
Organisms are present at all the places like 
air, water, land, rock, etc. Humans have 
shown curiosity about origin of life and 
reasons for such a great diversity in life 
present on the Earth since ancient period. 
Different theories about origin and evolution 
of life have been proposed till today of which 
theory of 'Gradual development of living 
organisms is accepted.
A peek into History
Many philosophers and religious scholars 
have written their views about formation of 
life. There seems to be a thorough discussion 
over the formation of Universe, in various 
cultures like Indian, Chinese, Roman, 
Greek, etc. Various cultures have noted 
different type of information about planets, 
stars, the ‘panchmahabhuta’, living 
organisms, etc. in the form of poetry, stories 
and religious / sacred books.
Evolution  
 Evolution is the gradual change occurring in living organisms over a long duration.  This is 
a very slow-going process through which development of organisms is achieved. All the stages 
in changes occurred in various components ranging from stars and planets in space to the 
biosphere present on the Earth should be included in the study of evolution. Formation of new 
species due to changes in specific characters of several generations of living organisms as a 
response to natural selection, is called as evolution.
Internet is my friend
 Collect the information from internet 
about Big-Bang theory related with the 
formation of stars and planets and present it 
in your class.
Can you recall?
Theory of Evolution:
According to this theory, first living material 
(protoplasm) has been formed in ocean. In 
due course of time, unicellular organism was 
formed. Gradually, changes occurred in the 
unicellular organisms from which larger and 
more complex organisms were formed. All 
those changes were slow and gradual. Duration 
of all these changes is at most 300 crore years. 
Changes and development in living organisms 
had been all round and multi-dimensional 
and this led to evolution of different types 
of organisms. Hence, this overall process is 
called as evolution which is organizational. 
Progressive development of plants and animals 
from the ancestors having different structural 
and functional organization is called evolution.
4
Observe the following images and note the similarities between given 
 animal images and plant images.
1.4  Morphological evidences
2. Anatomical Evidences
 If you carefully observe the 
pictures, there doesn’t seem any 
superficial similarity between human 
hand, foreleg of ox, flipper of whale 
and patagium of bat. Similarly, use of 
each of those structures is different in 
respective animals. However, there is 
similarity in structure of bones and 
joints in organs of each of those 
animals. This similarity indicates that 
those animals may have common 
ancestor.
1.5  Structure of bones
Human        foreleg         Patagium          Flipper
  hand            of ox             of Bat          of Whale           
1. Which are the different organs in body of organisms?
2.  Is each of the organs useful to organism?
Use of ICT  :  
      Collect the information of geological dating and Present it classroom.  
Evidences of evolution 
 Collective thinking upon all above mentioned theories implies that evolution 
is everlasting process of changes. However, it needs proof to prove it. Following are 
various proofs available in support of the theories mentioned above.
1. Morphological Evidences 
Try this
 Various similarities like 
structure of mouth, position of 
eyes, structure of nostrils and 
ear pinnae and thickly 
distributed hairs on body are 
seen in animals whereas 
similarities in characters like 
leaf shape, leaf venation, leaf 
petiole, etc. occur in case of 
plants. This indicates that there 
are some similarities in those 
groups and hence it proves that 
their origin must be same and 
must have common ancestors
Can you tell?
Page 5


1
1. Which component of the cellular nucleus of living organisms  
 carries hereditary characters?
2. What do we call to the process of transfer of physical and   
 mental  characters from parents to the progeny?
3. Which are the components the DNA molecule?
Heredity and hereditary changes
 You know that heredity is the transfer of biological characters from one generation to 
another via genes. Gregor Johann Mendel is pioneer of the modern genetics. It took a long 
time to understand the conclusions of his research about heredity.  In 1901, the reasons behind 
the sudden changes were understood due to the mutational theory of Hugo de Vries. Meanwhile 
in 1902, Walter Sutton observed the paired chromosomes in the cells of grasshopper; until 
then it was not known to anyone. Research started in the direction of finding the nature of 
genetic material when it was proved that genes are carried via chromosomes. Through which 
1944, trio of scientists Oswald Avery, Mclyn McCarty and Colin McLeod proved that except 
viruses, all living organisms have DNA as genetic material.
 In 1961, the French geneticists Francois Jacob and Jack Monod proposed a model for 
process of protein synthesis with the help of DNA in bacterial cells. It helped to uncover the 
genetic codes hidden in DNA. Thereby, the technique of recombinant DNA technology 
emerged which has vast scope in the field of genetic engineering.
 The science of heredity is useful for diagnosis, treatment and prevention of hereditary 
disorders, production of hybrid varieties of animals and plants and in industrial processes in 
which microbes are used.
Transcription, Translation and Translocation
 With the help of RNA, the genes present in the form of DNA participate in the functioning 
of cell and thereby control the structure and functioning of the body. Information about protein 
synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is 
necessary for body. These proteins are synthesized by DNA through the RNA. This is called 
as ‘Central Dogma’. mRNA is produced as per the sequence of nucleotides on DNA. Only one 
of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being 
produced is always complementary to the DNA strand used for synthesis. Besides, there is 
uracil in RNA instead of thymine of DNA.  This process of RNA synthesis is called as 
‘transcription’.
Can you tell?
Can you recall?
1.  Sketch and explain the structure of DNA and various types of RNA.
2.  Explain the meaning of genetic disorders and give names of some      
  disorders.
1. Heredity and Evolution 
Ø Heredity and Hereditary Changes   Ø   Transcription, Translation & 
                      Translocation
Ø	Evolution       Ø 	Evidences of Evolution
Ø   Darwin’s Theory of Natural Selection   Ø 	Lamarckism
Ø Speciation      Ø 	Human Evolution
2
` The mRNA formed in nucleus comes in 
cytoplasm. It brings in the coded message 
from DNA. The message contains the codes 
for amino acids. The code for each amino 
acid consists of three nucleotides. It is called 
as ‘triplet codon’. 
 Dr Har Govind Khorana, a scientist of 
Indian origin has made an important 
contribution in discovery of triplet codons 
for 20 amino acids. For this work, he has 
been awarded with the Nobel Prize in 1968, 
along with two other scientists. 
 Each mRNA is made up of thousands of 
triplet codons. As per the message on mRNA, 
amino acids are supplied by the tRNA. For 
this purpose, tRNA has ‘anticodon’ having 
complementary sequence to the codon on 
mRNA. This is called as ‘translation’. The 
amino acids brought in by tRNA are bonded 
together by peptide bonds with the help of 
rRNA. During this process, the ribosome 
keeps on moving from one end of mRNA to 
other end by the distance of one triplet codon. 
This is called as ‘translocation’. Such many 
chains come together to form complex 
proteins. These proteins control various 
functions in the body of living organisms 
and their appearance too.
 Living organisms can produce new 
individuals like themselves due to genes 
only and some of those genes are transmitted 
to the next generation without any changes. 
Due to this, some of the characters of parents 
are transmitted to their offsprings. However, 
sometimes sudden changes occur in those 
genes. Sometimes, any nucleotide of the 
gene changes its position that causes a minor 
change which is nothing but the ‘mutation’. 
1.2  Translation & Translocation
1.1  Transcription 
1.3  Mutation
RNA Polymerase
RNA Nucleotides  
Transcription 
Main Sequence 
Replacement
 Some mutations may be minor but some may be considerable. Ex. Mutation may cause 
the genetic disorders like sickle cell anaemia.   
Nucleus
Amino Acid 
Ribosome 
Codon
mRNA
tRNA
mRNA
3
1. What is the function of the appendix of our digestive system?
2. Are our wisdom teeth really useful for chewing the food?
3. Why did the huge animals like dinosaur become extinct?
4. Why are many species of animals and birds getting extinct?
 3.5 billion years ago, life had been non 
existent on the Earth. At the beginning, there 
may have been only simple elements in the 
ocean on the Earth and simple type of organic 
and inorganic compounds may have been 
formed from those. Complex compounds like 
proteins and nucleic acids may have formed 
over the long period from those simple 
compounds. First primitive type of cells may 
have been formed from the mixture of different 
types of organic and inorganic compounds. 
Number of those cells may have increased at 
the cost of surrounding chemicals. There may 
had been some differences among those cells 
and according to the principle of natural 
selection, some may have shown good growth 
and some may have perished which could not 
adjust with the surrounding.
 At present, crores of species of plants and 
animals with huge diversity regarding shape 
and complexity are present on the Earth. 
Animal diversity ranges from the unicellular 
Amoeba and Paramecium to man and giant 
whale. The plant diversity consists of various 
species ranging from unicellular Chlorella to 
the huge banyan tree. The life exists on Earth 
everywhere from equator to both the poles. 
Organisms are present at all the places like 
air, water, land, rock, etc. Humans have 
shown curiosity about origin of life and 
reasons for such a great diversity in life 
present on the Earth since ancient period. 
Different theories about origin and evolution 
of life have been proposed till today of which 
theory of 'Gradual development of living 
organisms is accepted.
A peek into History
Many philosophers and religious scholars 
have written their views about formation of 
life. There seems to be a thorough discussion 
over the formation of Universe, in various 
cultures like Indian, Chinese, Roman, 
Greek, etc. Various cultures have noted 
different type of information about planets, 
stars, the ‘panchmahabhuta’, living 
organisms, etc. in the form of poetry, stories 
and religious / sacred books.
Evolution  
 Evolution is the gradual change occurring in living organisms over a long duration.  This is 
a very slow-going process through which development of organisms is achieved. All the stages 
in changes occurred in various components ranging from stars and planets in space to the 
biosphere present on the Earth should be included in the study of evolution. Formation of new 
species due to changes in specific characters of several generations of living organisms as a 
response to natural selection, is called as evolution.
Internet is my friend
 Collect the information from internet 
about Big-Bang theory related with the 
formation of stars and planets and present it 
in your class.
Can you recall?
Theory of Evolution:
According to this theory, first living material 
(protoplasm) has been formed in ocean. In 
due course of time, unicellular organism was 
formed. Gradually, changes occurred in the 
unicellular organisms from which larger and 
more complex organisms were formed. All 
those changes were slow and gradual. Duration 
of all these changes is at most 300 crore years. 
Changes and development in living organisms 
had been all round and multi-dimensional 
and this led to evolution of different types 
of organisms. Hence, this overall process is 
called as evolution which is organizational. 
Progressive development of plants and animals 
from the ancestors having different structural 
and functional organization is called evolution.
4
Observe the following images and note the similarities between given 
 animal images and plant images.
1.4  Morphological evidences
2. Anatomical Evidences
 If you carefully observe the 
pictures, there doesn’t seem any 
superficial similarity between human 
hand, foreleg of ox, flipper of whale 
and patagium of bat. Similarly, use of 
each of those structures is different in 
respective animals. However, there is 
similarity in structure of bones and 
joints in organs of each of those 
animals. This similarity indicates that 
those animals may have common 
ancestor.
1.5  Structure of bones
Human        foreleg         Patagium          Flipper
  hand            of ox             of Bat          of Whale           
1. Which are the different organs in body of organisms?
2.  Is each of the organs useful to organism?
Use of ICT  :  
      Collect the information of geological dating and Present it classroom.  
Evidences of evolution 
 Collective thinking upon all above mentioned theories implies that evolution 
is everlasting process of changes. However, it needs proof to prove it. Following are 
various proofs available in support of the theories mentioned above.
1. Morphological Evidences 
Try this
 Various similarities like 
structure of mouth, position of 
eyes, structure of nostrils and 
ear pinnae and thickly 
distributed hairs on body are 
seen in animals whereas 
similarities in characters like 
leaf shape, leaf venation, leaf 
petiole, etc. occur in case of 
plants. This indicates that there 
are some similarities in those 
groups and hence it proves that 
their origin must be same and 
must have common ancestors
Can you tell?
5
 Appendix, which is useless to human, is useful and 
fully functional organ in ruminants. Similarly, muscles of 
ear pinna, which are useless to human, are useful in 
monkeys for movement of ear pinna.  Various vestigial 
organs like tail-bone (coccyx), wisdom teeth, and body 
hairs are present in body of human being.
 Find how the 
vestigial organs in 
certain animals are 
functional in others. 
Present the 
information in your 
class and send it to 
others. 
Use of  ICT 
1.7 Some fossils
Appendix   
 Large
 Intestine 
Small 
Intestine 
3. Vestigial Organs 
 Degenerated or underdeveloped useless organs of organisms are called as vestigial 
organs. In living organisms, sudden development of new tissues or organs for living in 
changing environment is not possible. Instead, existing organs undergo gradual changes. 
Mostly, a specific structure in the body is useful under certain situation. However, same 
structure under different situation may become useless or even harmful. Such structure begins 
to degenerate under such situation as per the principle of natural selection. It takes thousands 
of years for a structure to disappear. Such organs are seen in different phases of disappearance 
in different animals. Such organ, though non-functional in certain organisms, it may be 
functional in other organisms i.e. it is not vestigial in other organisms.
Tail bone 
(Coccyx)
4. Palaeontological Evidences
 A question may arise in your mind that which organisms existed millions of years 
ago? How can we tell this? Now this secret has been hidden in the Earth. Large number of 
organisms get buried due to disasters like flood, earthquake, volcano, etc. Remnants and 
impressions of such organisms remain preserved underground. These are called as fossils. 
Study of fossils is an important aspect of study of evolution.
Observe the following pictures. 
Observe and discuss.
Ear 
muscles 
1.6 Vestigial organs  
Wisdom teeth