A British scientist, J.B.S. Haldane, suggested that life originated from simple inorganic molecules. He believed that when the earth was formed, it was a hot gaseous mass containing elements such as nitrogen, oxygen, carbon, hydrogen, etc. These elements combined to form molecules like water (H2O),Read more
A British scientist, J.B.S. Haldane, suggested that life originated from simple inorganic
molecules. He believed that when the earth was formed, it was a hot gaseous mass
containing elements such as nitrogen, oxygen, carbon, hydrogen, etc. These elements
combined to form molecules like water (H2O), carbon dioxide (CO2), methane (CH4),
ammonia (NH3), etc.
After the formation of water, slowly the earth surface cooled and the inorganic molecules
interacted with one another in water to form simple organic molecules such as sugars,
fatty acids, amino acids, etc. The energy for these reactions was provided by solar
radiations, lightning, volcanic eruptions, etc.
This was proved by the experiment of Stanley L. Miller and Harold C. Urey in 1953. They
took a mixture of water (H2O), methane (CH4), ammonia (NH3), and hydrogen gas (H2) in
a chamber and sparks were passed through this mixture using two electrodes. After one
week, 15% of the carbon from methane was converted into amino acids, sugars, etc.
These organic molecules are polymerized and assembled to form protein molecules that
gave rise to life on earth.
Fossils are the remains of the organism that once existed on earth. They represent the ancestors of the plants and animals that are alive today. They provide evidences of evolution by revealing the characteristics of the past organisms and the changes that have occurred in these organisms to give riRead more
Fossils are the remains of the organism that once existed on earth. They represent the
ancestors of the plants and animals that are alive today. They provide evidences of
evolution by revealing the characteristics of the past organisms and the changes that have
occurred in these organisms to give rise to the present organisms. Let us explain the
importance of fossils in deciding evolutionary history with the help of the following
example.
Around 100 million years ago, some invertebrates died and were buried in the soil in that
area. More sediment accumulated on top of it turning it into sedimentary rock. At the same
place, millions of years later, some dinosaurs died and their bodies were buried on top of
the sedimentary rock. The mud containing dinosaurs also turned into a rock.
Then, millions of years later, some horse-like creatures died in that area and got fossilized
in rocks above the dinosaur fossils.
Sometime later, due to soil erosion or floods in that area, the rocks containing horselike
fossils are exposed.
If that area is excavated deeper, then the dinosaur and invertebrates fossils can also be
found. Thus, by digging that area, scientists can easily predict that horse-like animals
evolved later than the dinosaurs and the invertebrates.
Thus, the above example suggests that the fossils found closer to the surface of the earth
are more recent ones than the fossils present in deeper layers.
Homologous organs are similar in origin (or are embryologically similar) but perform different functions. For example, the forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar. It means that their origin is similar (as wings in birds are modifiRead more
Homologous organs are similar in origin (or are embryologically similar) but perform
different functions. For example, the forelimbs of humans and the wings of birds look
different externally but their skeletal structure is similar. It means that their origin is
similar (as wings in birds are modifications of forearm) but functions are different – the
wings help in flight whereas human forearm helps in various activities.
Analogous organs, on the other hand, have different origin but perform similar functions.
For example, the wings of a bird and a bat are similar in function but this similarity does
not mean that these animals are more closely related. If we carefully look at these
structures, then we will find that the wings of a bat are just the folds of skin that are
stretched between its fingers whereas the wings of birds are present all along the arm.
Therefore, these organs are analogous organs.
Classification involves grouping of organism into a formal system based on similarities in internal and external structure or evolutionary history. Two species are more closely related if they have more characteristics in common. And if two species are more closely related, then it means they have aRead more
Classification involves grouping of organism into a formal system based on similarities in
internal and external structure or evolutionary history.
Two species are more closely related if they have more characteristics in common. And if
two species are more closely related, then it means they have a more recent ancestor.
For example, in a family, a brother and sister are closely related and they have a recent
common ancestor i.e., their parents. A brother and his cousin are also related but less
than the sister and her brother. This is because the brother and his cousin have a common
ancestor i.e., their grandparents in the second generation whereas the parents were from
the first generation.
With subsequent generations, the variations make organisms more different than their
ancestors.
This discussion clearly proves that we classify organisms according to their resemblance
which is similar to creating an evolutionary tree.
Let us assume that children with light - coloured eyes can either have LL or Ll or ll genotype. If the children have LL genotype, then their parents will also be of LL genotype. LL × LL ↓ LL If the children with light-coloured eyes have ll genotype, then their parents will also have ll genotype. llRead more
Let us assume that children with light – coloured eyes can either have LL or Ll or ll
genotype. If the children have LL genotype, then their parents will also be of LL genotype.
LL × LL
↓
LL
If the children with light-coloured eyes have ll genotype, then their parents will also have
ll genotype.
ll × ll
↓
ll
Therefore, it cannot be concluded whether light eye colour is dominant or recessive.
What evidence do we have for the origin of life from inanimate matter?
A British scientist, J.B.S. Haldane, suggested that life originated from simple inorganic molecules. He believed that when the earth was formed, it was a hot gaseous mass containing elements such as nitrogen, oxygen, carbon, hydrogen, etc. These elements combined to form molecules like water (H2O),Read more
A British scientist, J.B.S. Haldane, suggested that life originated from simple inorganic
molecules. He believed that when the earth was formed, it was a hot gaseous mass
containing elements such as nitrogen, oxygen, carbon, hydrogen, etc. These elements
combined to form molecules like water (H2O), carbon dioxide (CO2), methane (CH4),
ammonia (NH3), etc.
After the formation of water, slowly the earth surface cooled and the inorganic molecules
interacted with one another in water to form simple organic molecules such as sugars,
fatty acids, amino acids, etc. The energy for these reactions was provided by solar
radiations, lightning, volcanic eruptions, etc.
This was proved by the experiment of Stanley L. Miller and Harold C. Urey in 1953. They
took a mixture of water (H2O), methane (CH4), ammonia (NH3), and hydrogen gas (H2) in
a chamber and sparks were passed through this mixture using two electrodes. After one
week, 15% of the carbon from methane was converted into amino acids, sugars, etc.
These organic molecules are polymerized and assembled to form protein molecules that
gave rise to life on earth.
For more answers visit to website:
See lesshttps://www.tiwariacademy.com/ncert-solutions/class-10/science/chapter-9/
Explain the importance of fossils in deciding evolutionary relationships.
Fossils are the remains of the organism that once existed on earth. They represent the ancestors of the plants and animals that are alive today. They provide evidences of evolution by revealing the characteristics of the past organisms and the changes that have occurred in these organisms to give riRead more
Fossils are the remains of the organism that once existed on earth. They represent the
ancestors of the plants and animals that are alive today. They provide evidences of
evolution by revealing the characteristics of the past organisms and the changes that have
occurred in these organisms to give rise to the present organisms. Let us explain the
importance of fossils in deciding evolutionary history with the help of the following
example.
Around 100 million years ago, some invertebrates died and were buried in the soil in that
area. More sediment accumulated on top of it turning it into sedimentary rock. At the same
place, millions of years later, some dinosaurs died and their bodies were buried on top of
the sedimentary rock. The mud containing dinosaurs also turned into a rock.
Then, millions of years later, some horse-like creatures died in that area and got fossilized
in rocks above the dinosaur fossils.
Sometime later, due to soil erosion or floods in that area, the rocks containing horselike
fossils are exposed.
If that area is excavated deeper, then the dinosaur and invertebrates fossils can also be
found. Thus, by digging that area, scientists can easily predict that horse-like animals
evolved later than the dinosaurs and the invertebrates.
Thus, the above example suggests that the fossils found closer to the surface of the earth
are more recent ones than the fossils present in deeper layers.
For more answers visit to website:
See lesshttps://www.tiwariacademy.com/ncert-solutions/class-10/science/chapter-9/
Explain the terms analogous and homologous organs with examples.
Homologous organs are similar in origin (or are embryologically similar) but perform different functions. For example, the forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar. It means that their origin is similar (as wings in birds are modifiRead more
Homologous organs are similar in origin (or are embryologically similar) but perform
different functions. For example, the forelimbs of humans and the wings of birds look
different externally but their skeletal structure is similar. It means that their origin is
similar (as wings in birds are modifications of forearm) but functions are different – the
wings help in flight whereas human forearm helps in various activities.
Analogous organs, on the other hand, have different origin but perform similar functions.
See lessFor example, the wings of a bird and a bat are similar in function but this similarity does
not mean that these animals are more closely related. If we carefully look at these
structures, then we will find that the wings of a bat are just the folds of skin that are
stretched between its fingers whereas the wings of birds are present all along the arm.
Therefore, these organs are analogous organs.
How are the areas of study – evolution and classification – interlinked?
Classification involves grouping of organism into a formal system based on similarities in internal and external structure or evolutionary history. Two species are more closely related if they have more characteristics in common. And if two species are more closely related, then it means they have aRead more
Classification involves grouping of organism into a formal system based on similarities in
internal and external structure or evolutionary history.
Two species are more closely related if they have more characteristics in common. And if
two species are more closely related, then it means they have a more recent ancestor.
For example, in a family, a brother and sister are closely related and they have a recent
common ancestor i.e., their parents. A brother and his cousin are also related but less
than the sister and her brother. This is because the brother and his cousin have a common
ancestor i.e., their grandparents in the second generation whereas the parents were from
the first generation.
With subsequent generations, the variations make organisms more different than their
ancestors.
This discussion clearly proves that we classify organisms according to their resemblance
which is similar to creating an evolutionary tree.
For more answers visit to website:
See lesshttps://www.tiwariacademy.com/ncert-solutions/class-10/science/chapter-9/
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
Let us assume that children with light - coloured eyes can either have LL or Ll or ll genotype. If the children have LL genotype, then their parents will also be of LL genotype. LL × LL ↓ LL If the children with light-coloured eyes have ll genotype, then their parents will also have ll genotype. llRead more
Let us assume that children with light – coloured eyes can either have LL or Ll or ll
genotype. If the children have LL genotype, then their parents will also be of LL genotype.
LL × LL
↓
LL
If the children with light-coloured eyes have ll genotype, then their parents will also have
ll genotype.
ll × ll
↓
ll
Therefore, it cannot be concluded whether light eye colour is dominant or recessive.
For more answers visit to website:
See lesshttps://www.tiwariacademy.com/ncert-solutions/class-10/science/chapter-9/