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NCERT Solutions for Class 12 Biology Chapter 7
Evolution Class 12
Chapter 7 Evolution Exercise Solutions
Exercise : Solutions of Questions on Page Number : 142
Q1 :
Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Answer :
Darwinian selection theory states that individuals with favourable variations are better adapted than individuals with
less favourable variation. It means that nature selects the individuals with useful variation as these individuals are
better evolved to survive in the existing environment. An example of such selection is antibiotic resistance in bacteria.
When bacterial population was grown on an agar plate containing antibiotic penicillin, the colonies that were sensitive
to penicillin died, whereas one or few bacterial colonies that were resistant to penicillin survived. This is because
these bacteria had undergone chance mutation, which resulted in the evolution of a gene that made them resistant to
penicillin drug. Hence, the resistant bacteria multiplied quickly as compared to non-resistant (sensitive) bacteria,
thereby increasing their number. Hence, the advantage of an individual over other helps in the struggle for existence.
Q2 :
Find out from newspapers and popular science articles any new fossil discoveries or controversies about
evolution.
Answer :
Fossils of dinosaurs have revealed the evolution of reptiles in Jurassic period. As a result of this, evolution of other
animals such as birds and mammals has also been discovered. However, two unusual fossils recently unearthed in
China have ignited a controversy over the evolution of birds.Confuciusornis is one such genus of primitive birds that
were crow sized and lived during the Creataceous period in China.
Q3 :
Attempt giving a clear definition of the term species
Answer :
Species can be defined as a group of organisms, which have the capability to interbreed in order to produce fertile
offspring.
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Q4 :
Try to trace the various components of human evolution (hint: brain size and function, skeletal structure,
dietary preference, etc.)
Answer :
The various components of human evolution are as follows.
(i) Brain capacity
(ii) Posture
iii. Food / dietary preference and other important features
Name Brain Posture Food Features
capacity
1. Dryopithecus --- Knuckle walker, Soft fruit and Canines large, arms and legs are of
africans walked similar to leaves equal size
gorillas and
chimpanzees (was
more ape-like)
2. Ramapithecus --- Semi-erect (more Seeds, nuts Canines were small while molars
man-like) were large.
3. Australopithecus 450 cm 3
Full erect posture, Herbivorous Hunted with stone weapons, lived
africanus height (1.05 m) (ate fruits) at trees, canines and incisors were
small
4. Homo habilis 735cm 3
Fully erect posture, Carnivorous Canines were small. They were
height (1.5 m) first tool makers.
5. Homo erectus 800-1100 Fully erect posture, Omnivorous They used stone and bone tools for
cm 3
height(1.5-1.8 m ) hunting games.
6. Homo 1300- Fully erect posture, Omnivorous Cave dwellers, used hides to
neanderthalnsis 1600 cm height (1.5-1.66 m)
3
protect their bodies, and buried
their dead
7. Homo sapiens 1650 cm Fully erect posture Omnivorous They had strong jaw with teeth
3
fossilis with height (1.8 m) close together. They were cave
dwellers, made paintings and
carvings in the caves. They
developed a culture and were
called first modern men.
8. Homo sapiens 1200- Fully erect posture, Omnivorous They are the living modern men,
sapiens 1600 cm height (1.5-1.8 m )
3
with high intelligence. They
developed art, culture, language,
www.ncrtsolutions.in
NCERT Solutions for Class 12 Biology Chapter 7
Evolution Class 12
Chapter 7 Evolution Exercise Solutions
Exercise : Solutions of Questions on Page Number : 142
Q1 :
Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
Answer :
Darwinian selection theory states that individuals with favourable variations are better adapted than individuals with
less favourable variation. It means that nature selects the individuals with useful variation as these individuals are
better evolved to survive in the existing environment. An example of such selection is antibiotic resistance in bacteria.
When bacterial population was grown on an agar plate containing antibiotic penicillin, the colonies that were sensitive
to penicillin died, whereas one or few bacterial colonies that were resistant to penicillin survived. This is because
these bacteria had undergone chance mutation, which resulted in the evolution of a gene that made them resistant to
penicillin drug. Hence, the resistant bacteria multiplied quickly as compared to non-resistant (sensitive) bacteria,
thereby increasing their number. Hence, the advantage of an individual over other helps in the struggle for existence.
Q2 :
Find out from newspapers and popular science articles any new fossil discoveries or controversies about
evolution.
Answer :
Fossils of dinosaurs have revealed the evolution of reptiles in Jurassic period. As a result of this, evolution of other
animals such as birds and mammals has also been discovered. However, two unusual fossils recently unearthed in
China have ignited a controversy over the evolution of birds.Confuciusornis is one such genus of primitive birds that
were crow sized and lived during the Creataceous period in China.
Q3 :
Attempt giving a clear definition of the term species
Answer :
Species can be defined as a group of organisms, which have the capability to interbreed in order to produce fertile
offspring.
www.ncrtsolutions.in
, www.ncrtsolutions.in
Q4 :
Try to trace the various components of human evolution (hint: brain size and function, skeletal structure,
dietary preference, etc.)
Answer :
The various components of human evolution are as follows.
(i) Brain capacity
(ii) Posture
iii. Food / dietary preference and other important features
Name Brain Posture Food Features
capacity
1. Dryopithecus --- Knuckle walker, Soft fruit and Canines large, arms and legs are of
africans walked similar to leaves equal size
gorillas and
chimpanzees (was
more ape-like)
2. Ramapithecus --- Semi-erect (more Seeds, nuts Canines were small while molars
man-like) were large.
3. Australopithecus 450 cm 3
Full erect posture, Herbivorous Hunted with stone weapons, lived
africanus height (1.05 m) (ate fruits) at trees, canines and incisors were
small
4. Homo habilis 735cm 3
Fully erect posture, Carnivorous Canines were small. They were
height (1.5 m) first tool makers.
5. Homo erectus 800-1100 Fully erect posture, Omnivorous They used stone and bone tools for
cm 3
height(1.5-1.8 m ) hunting games.
6. Homo 1300- Fully erect posture, Omnivorous Cave dwellers, used hides to
neanderthalnsis 1600 cm height (1.5-1.66 m)
3
protect their bodies, and buried
their dead
7. Homo sapiens 1650 cm Fully erect posture Omnivorous They had strong jaw with teeth
3
fossilis with height (1.8 m) close together. They were cave
dwellers, made paintings and
carvings in the caves. They
developed a culture and were
called first modern men.
8. Homo sapiens 1200- Fully erect posture, Omnivorous They are the living modern men,
sapiens 1600 cm height (1.5-1.8 m )
3
with high intelligence. They
developed art, culture, language,
www.ncrtsolutions.in
