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Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and  lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.
In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs  forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings,  and human hands .  They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA – just the concentration of these special molecules varied corresponding to the desired structure.
The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates ("fish") to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence  that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaalik’s limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture. 
In the context of the passage, why was the discovery of the Tiktaalik important? 
  • a)
    It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.
  • b)
    It proved the reason why the architecture of limbs in various organisms was optimized for the organism’s corresponding functional needs. 
  • c)
    It provided the reason for commonality of skeletal architecture described earlier in the passage.
  • d)
    It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.
  • e)
    It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
Despite radical differences in what limbs do and what they look like, ...
Passage is factual ,so author has no role here
the qn is why he took example of one species,
the answer lies in why nature doesn't develope optimised version of the present structure..
it's just a question to the answer
option c is correct
option B is opposite
A is nonsense
D is specific to Qn but why we share dna is not mentioned
E this is absolutely rubbish
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Community Answer
Despite radical differences in what limbs do and what they look like, ...
Importance of the Discovery of Tiktaalik
The discovery of Tiktaalik was important because it provided the reason for the commonality of skeletal architecture described earlier in the passage.

Common Ancestry
- The Tiktaalik fossil served as a crucial transitional species between non-tetrapod vertebrates (fish) and early tetrapods, showing a common ancestry for all land-based organisms with limbs.
- This common ancestry explains why the underlying blueprint of all limbs in land-based animals is the same, despite the radical differences in their appearance and function.

Utilization of Ancient Genes
- By tracing our ancestral heritage back to Tiktaalik, the discovery showed that the genetic material used to develop limbs in various organisms has been conserved over evolutionary time.
- This supports the idea that ancient genes, such as those involved in the development of Tiktaalik's limbs, have been repurposed and modified to create the diverse array of limb structures seen in different species today.

Explanation for Diversity in Shapes
- The discovery of Tiktaalik helps explain how the same genetic toolkit can be used to generate structures as diverse as wings in birds, flippers in penguins, and hands in humans.
- It highlights that the diversity in limb shapes is a result of utilizing ancient genetic material in new ways rather than the origin of entirely new DNA.
In conclusion, the discovery of Tiktaalik not only provided evidence for the common ancestry of all land-based organisms with limbs but also offered insights into the mechanisms behind the diversity of limb structures while maintaining a common underlying architecture.
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Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer?
Question Description
Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer? for GMAT 2024 is part of GMAT preparation. The Question and answers have been prepared according to the GMAT exam syllabus. Information about Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer? covers all topics & solutions for GMAT 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer?.
Solutions for Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for GMAT. Download more important topics, notes, lectures and mock test series for GMAT Exam by signing up for free.
Here you can find the meaning of Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer? defined & explained in the simplest way possible. Besides giving the explanation of Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer?, a detailed solution for Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer? has been provided alongside types of Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. Can you explain this answer? theory, EduRev gives you an ample number of questions to practice Despite radical differences in what limbs do and what they look like, the underlying blueprint of all limbs in land based animals, whether those limbs are wings in birds, flippers in penguins, or hands in humans, is the same - one bone, the humerus in the arm or the femur in the leg, articulates with two bones, which attach to a series of small blobs, which connect with the fingers or toes. Want to make a bat wing? Make the fingers really long. Want to make a horse? Elongate the middle fingers and toes and lose the outer ones. The differences between creatures lie in differences in the shapes and sizes of the bones and the numbers of blobs, fingers, and toes.In the 1950s and 1960s a number of biologists, including Edgar Zwilling and John Saunders, did extraordinarily creative experiments on chicken eggs to understand how skeletal structure of limbs forms and uncovered some of the key mechanisms that build limbs that have the same architecture but are as different as bird wings, lizards webbings, and human hands . They discovered that two little patches of tissue essentially control the development of the pattern of bones inside limbs. These patches of tissue were named the zone of polarizing activity (ZPA). The cells in the ZPA made special molecules that then spread across the limb to instruct cells to make femur, articulates, and connecting toes. The concentration of these molecules was the important factor and decided the length of femur, articulates, connecting toes, and even the length of individual toe fingers. Later experiments with other animals such as the bat, frog, etc. proved that the mechanism to form limbs remained the same - formation of limbs in every creature was controlled by the ZPA just the concentration of these special molecules varied corresponding to the desired structure.The reason for this inherent commonality in architecture still remained a conundrum for decades. Why did nature not develop architectures better optimized to the functional needs of various organisms? The discovery of Tiktaalik, a transition between non-tetrapod vertebrates (fish) to early tetrapods solved this mystery, providing evidence that all land based creatures that have limbs, hands, etc. share a common ancestor. The fact that our DNA and that of all land based animals can be traced back to Tiktaalik further provided evidence that all appendages, whether they are hands or limbs, are built by similar kinds of genes and that this great evolutionary transformation did not involve the origin of new DNA: much of the shift likely involved using ancient genes, such as those involved in development of Tiktaaliks limbs, in new ways to make wings in birds or various sized limbs with fingers and toes, explaining the diversity in shapes while maintaining the similarity in architecture.In the context of the passage, why was the discovery of the Tiktaalik important?a)It proved beyond doubt and without the need of experimentation the commonality of skeletal architectures of all land based organisms.b)It proved the reason why the architecture of limbs in various organisms was optimized for the organisms corresponding functional needs.c)It provided the reason for commonality of skeletal architecture described earlier in the passage.d)It traced our ancestral heritage to the fish, providing the reason why we share majority of our DNA with aquatic animals.e)It showed how ancient genes could be used in new ways for structures as diverse as wings in birds and fins in sharks.Correct answer is option 'C'. 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