Accumulation of variation during reproduction" refers to the process where offspring inherit a combination of genetic traits from their parents, resulting in diversity within a species over time. This variation is crucial for evolution and adaptation
Over many generations, these accumulated variations can lead to new traits or characteristics in a population. In this way different species evolve and adapt to their environments.
Thus, Diversity within a species increases the chances of survival and long-term success
Creating variations in a species is essential for promoting survival because it enhances a population's ability to adapt to changing environments and challenges.
Over many generations, these accumulated variations can lead to new traits or characteristics in a population. In this way different species evolve and adapt to their environments.
Thus, Diversity within a species increases the chances of survival and long-term success
Creating variations in a species is essential for promoting survival because it enhances a population's ability to adapt to changing environments and challenges.
- Survival in Changing Environments: Environments can change due to factors like climate, predators, and available food sources. When a species has a wide range of variations in its genetic makeup, some individuals may possess traits that are better suited to the new conditions. These individuals are more likely to survive and reproduce, passing on their advantageous traits to the next generation.
- Resisting Diseases: Variations also play a role in resisting diseases. If all individuals in a population have the same genetic makeup, a single disease could wipe out the entire population. However, when there is genetic diversity, some individuals may have immunity or resistance to the disease, ensuring that the population continues to thrive.
- Competition for Resources: Within a species, there's often competition for resources like food, water, and mates. Variations can lead to different strategies for obtaining these resources. Some individuals may be better at finding food or attracting mates, giving them a competitive edge.
- Response to Predators: Predators are constantly adapting their hunting strategies. Variations in a prey species can make it more challenging for predators to target them consistently. Some individuals may have features that make them less vulnerable to predation.
- Long-Term Survival: Variations accumulate over many generations. This means that a species is better prepared for long-term survival and can adapt to various challenges over time. Without variations, a species might become stagnant and vulnerable to extinction if faced with a sudden change.
- Genetic Information: Every living organism, including humans, has a set of instructions for how their body should develop and function. These instructions are stored in a molecule called DNA, which is found in cells. DNA is like a biological "instruction manual."
- Inheritance from Parents: When living things reproduce, they pass on a copy of their DNA to their offspring. Offspring inherit a combination of genetic material from both parents. This is why children often resemble their parents in various ways, such as eye color, height, and hair type.
- Variation: While offspring inherit traits from their parents, they don't inherit an exact copy of their parents' traits. Instead, there can be variations or differences in these traits. These variations are due to the mixing of genetic information from both parents and can lead to unique combinations of traits in each individual.
- Mendel's Laws: The study of heredity is often associated with Gregor Mendel, an Austrian scientist known as the "Father of Genetics." He discovered fundamental principles of heredity, including the laws of segregation and independent assortment, which explain how traits are inherited.
- Dominant and Recessive Traits: Some traits are dominant, meaning that if an individual inherits even one copy of the dominant gene, that trait will be expressed. Others are recessive, and an individual needs to inherit two copies of the recessive gene to express the trait.
- Punnett Squares: In genetics, Punnett squares are used to predict the probability of offspring inheriting specific traits based on the genetic makeup of their parents. This tool helps illustrate how genetic information is passed down from one generation to the next.
- Role in Evolution: Heredity is a critical concept in understanding evolution. Over long periods of time, variations in traits within a population can lead to the development of new species, as those with advantageous traits are more likely to survive and reproduce.
Gregor Mendel's contributions to the understanding of the inheritance of traits laid the foundation for modern genetics. Here are some of the key rules and principles of inheritance based on Mendel's work
1.Law of Segregation: Mendel's first law, the Law of Segregation, states that an individual inherits two alleles (gene variants) for each trait, one from each parent. These alleles segregate or separate during the formation of gametes (sperm and egg cells), so each gamete carries only one allele for each trait.
Genotype and Phenotype: Mendel introduced the terms "genotype" and "phenotype." The genotype represents an individual's genetic makeup (the combination of alleles they carry), while the phenotype is the physical or observable expression of those genetic traits. (#Dominant and #Recessive)
2. Independent Assortment: Mendel's second law, the Law of Independent Assortment, states that alleles for different traits segregate independently during gamete formation. This means that the inheritance of one trait does not influence the inheritance of another trait
Hereditary Factors: Mendel proposed that traits are controlled by "factors" (now known as genes) that are inherited from parents and segregate in predictable ways. He also proposed that these factors come in pairs, with one from each parent
1.Law of Segregation: Mendel's first law, the Law of Segregation, states that an individual inherits two alleles (gene variants) for each trait, one from each parent. These alleles segregate or separate during the formation of gametes (sperm and egg cells), so each gamete carries only one allele for each trait.
Genotype and Phenotype: Mendel introduced the terms "genotype" and "phenotype." The genotype represents an individual's genetic makeup (the combination of alleles they carry), while the phenotype is the physical or observable expression of those genetic traits. (#Dominant and #Recessive)
2. Independent Assortment: Mendel's second law, the Law of Independent Assortment, states that alleles for different traits segregate independently during gamete formation. This means that the inheritance of one trait does not influence the inheritance of another trait
Hereditary Factors: Mendel proposed that traits are controlled by "factors" (now known as genes) that are inherited from parents and segregate in predictable ways. He also proposed that these factors come in pairs, with one from each parent
What happens when pea plants showing same characteristics are bred with each other?
Offspring Uniformity: When two pure breeding pea plants with the same characteristics are crossed, all of their offspring will also have the same characteristic. This is because each parent can only contribute one type of allele for that trait.
Useful for Establishing Dominance: Pure breeding experiments are valuable for determining whether a trait is dominant or recessive. If offspring consistently display the same trait as the parents in multiple generations of pure breeding, it suggests dominance. If there is a consistent change in the trait when different pure breeding plants are crossed, it indicates excessiveness.
Useful for Establishing Dominance: Pure breeding experiments are valuable for determining whether a trait is dominant or recessive. If offspring consistently display the same trait as the parents in multiple generations of pure breeding, it suggests dominance. If there is a consistent change in the trait when different pure breeding plants are crossed, it indicates excessiveness.
What happens when pea plants showing two different characteristics, rather than just one, are bred with each other?
The offspring display a wide range of trait combinations due to the independent assortment of alleles for each trait. This type of genetic analysis helps scientists understand how genes for different traits are inherited together and how they interact in the offspring's phenotype.
Each parent plant has a combination of alleles for two different traits. For example, one parent might have the genotype "PPSS" (purple flowers and smooth seeds), while the other might have "ppss" (white flowers and wrinkled seeds). Each letter represents a different gene pair.
The offspring inherit one allele for each trait from each parent, resulting in four possible allele combinations for each trait. For the flower color trait, offspring can inherit "PP" (purple) or "pp" (white). For the seed texture trait, they can inherit "SS" (smooth) or "ss" (wrinkled).
As a result of the independent assortment of alleles, offspring from a dihybrid cross exhibit various combinations of the two traits (9:3:3:1)). For example, some offspring may have purple flowers and smooth seeds ("PPSS"), while others may have white flowers and wrinkled seeds ("ppss"). Additionally, there will be combinations like "PPss" and "ppSS."
The offspring inherit one allele for each trait from each parent, resulting in four possible allele combinations for each trait. For the flower color trait, offspring can inherit "PP" (purple) or "pp" (white). For the seed texture trait, they can inherit "SS" (smooth) or "ss" (wrinkled).
As a result of the independent assortment of alleles, offspring from a dihybrid cross exhibit various combinations of the two traits (9:3:3:1)). For example, some offspring may have purple flowers and smooth seeds ("PPSS"), while others may have white flowers and wrinkled seeds ("ppss"). Additionally, there will be combinations like "PPss" and "ppSS."
How traits are passed from one generation to the next
Traits are passed from one generation to the next through the transmission of genetic information from parents to offspring. This process involves the inheritance of alleles, genetic recombination during meiosis, fertilization, and the expression of traits in the phenotype
Traits are passed from one generation to the next through the transmission of genetic information from parents to offspring. This process involves the inheritance of alleles, genetic recombination during meiosis, fertilization, and the expression of traits in the phenotype
How is the sex of a newborn individual determined?
XX (Female) Offspring: If a sperm carrying an X chromosome fertilizes the egg (which also has an X chromosome), the resulting combination is XX. This combination typically leads to the development of a female individual.
XY (Male) Offspring: If a sperm carrying a Y chromosome fertilizes the egg (with an X chromosome), the combination is XY. This combination usually leads to the development of a male individual.
Thus, the sex of the children will be determined by what they inherit from their father
XX (Female) Offspring: If a sperm carrying an X chromosome fertilizes the egg (which also has an X chromosome), the resulting combination is XX. This combination typically leads to the development of a female individual.
XY (Male) Offspring: If a sperm carrying a Y chromosome fertilizes the egg (with an X chromosome), the combination is XY. This combination usually leads to the development of a male individual.
Thus, the sex of the children will be determined by what they inherit from their father
Class 10 - Chapter - 8
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Board Based Questions with answers: Class 10 Chapter: Heredity and Evolution
Q. Why did Mendel chosen pea plant for his experiments?
Answer: Mendel chose pea plant for his experiments because it is:
(a) Easy to grow (b) Short lifespan (c) Easily distinguishable characters (d) Larger size of flower (e) Self-pollinated.
Q. What is heredity?
Ans:- Heredity refers to the transmission of characters or traits from the parents to their offspring.
Q. What do you understand by evolution?
Ans:-Evolution is the sequence of gradual changes which takes place in the primitive organisms over million of years in which new species are produced.
Q. What is a gene?
Ans:- Gene is a small segment of DNA on a chromosome occupying specific position in which is a hereditary determinant or unit of a biological function.
Q. With the help of suitable examples, explain why certain traits cannot be passed on to the next generation. What are such traits called?
Solution: The traits which are acquired during the lifetime of a person are called acquired traits. These traits involve changes in non reproductive cells (somatic cells) which are not transferred to germ cells. So, these traits cannot be passed on to the next generation. For example: Learning skills like swimming, dancing, cooking, body building, etc are acquired traits and cannot be passed on to the next generation.
Q. "A trait may be inherited, but may not be expressed." Justify this statement with the help of a suitable example.
Ans: When a tall plant was crossed with a short plant, the first (F1) generation plants were all tall. But when the F1 generation plants were crossed, the second (F2) generation plants were not all tall: there were both tall and short plants.
This shows that the F1 plants had inherited their trait from the short plants but did not express it in the presence of the tallness, and had transferred it to the next generation.
Q. 'It is a matter of chance whether a couple will give birth to a male child or a female child." Justify this statement with the help of a flow chart showing the fusion of sex chromosomes.
Ans: Sex is determined at the time of fertilization and the two sexes are produced in approximately equal numbers. A human male has XY sex-chromosomes and produces two types of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.
A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with X-chromosomes.
Parents Male Female
Gametes X Y X
Progeny XX XY
Female (50%) Male (50%)
Q. What are homologous organs? How do they provide evidence in support of evolution?
Ans:- Homologous organs are those organs which have the same basic structure and developmental origin but have different functions and appearance.
Homologous organs support evolution:
(i) The similarities of structure and origin of organs indicate that all vertebrates had common ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale for swimming and in bat for flying.
(ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology, which indicate towards common ancestry. Thus, homologous point that organic evolution has taken place.
Q. What is a retrovirus?
Ans:- A virus having RNA (Ribonucleic acid) as genetic (heredity) material is called Retrovirus. For example, Human immunodeficiency virus (HIV) is a retrovirus.
Q. Who provided the evidence of DNA as a genetic material? Write the names of components of DNA?
Ans:- Griffith, Avery , McLeod and McCarty established that DNA is the genetic material.
Components of DNA: A DNA molecule consists of two polynucleotide chains. Each nucleotide consists of (a) nitrogenous base (Adenine/guanine/Thymine or Cytosine) , a pentose sugar(deoxyribose) and a phosphate group.
Q. How many types of nitrogenous bases are present in DNA? Name them.
Ans:-In DNA two types of nitrogenous bases are present. These are
(i)PURINES which are adenine and guanine (ii)PYRIMIDINES which are Thymine and cytosine.
Q. How do embryological studies provide evidence for evolution?
Ans:- The similarities in embryonic development reinforce the idea of evolution from common ancestors. The sequence of embryonic development in different vertebrates shows striking similarities. Notochord and gill clefts appear in the embryos of all vertebrates.
Q. What are transgenic organisms? Which property of DNA is used as a tool in genetic engineering?
Ans:-The organisms that contain a segment of foreign DNA are known as transgenic organisms. The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic engineering.
Q. Name the two homologous structures in vertebrates. Why are they so called? How do such organs help in understanding an evolutionary relationship?
Ans: Limbs of birds, reptiles and humans are all the examples of homologous structures in the vertebrates. They are called so as the basic structure of the limbs is similar. Though it has been modified to perform different functions in various vertebrates.
These are organs which are inherited from a common ancestor. Such a homologous characteristic helps to identify an evolutionary relationship between apparently different species.
Q. What are the different ways in which individuals with a particular trait may increase in a population?
Ans : The different ways in which individuals with a particular trait may increase in a population, are :
Genetic drift ; Geographical isolation ; Natural selection and Artificial selection
Q. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?
Ans : If they all die out became extinct, tiger gene will be lost forever and the coming generation will not be able to see tiger at all.
Q. Will geographical isolation be a major factor in the speciation of a self-pollination plant species? Why or why not?
Ans: No, In asexually reproducing organisms pass on the parent DNA to offspring that leaves no chance of speciation
Q. What is the evolutionary significance of the fossil archaeopteryx?
Ans: Archaeopteryx serves as a connecting link between birds and reptiles. It is the fossil evidence to show that birds have evolved from reptiles.
Q. Give the evidence that bird have been evolved from reptile?
Ans: They both lay eggs, have scales on feet and soft anatomy such as musculature, brain, heart.
Q. What are vestigial organs? Name any two vestigial organs in man and name organ which is vestigial in man but not in birds.
Ans: Organs that are well developed and functional in many organisms and are very much reduced and functionless in other organisms is called vestigial organs. Nictitating membrane in the eye and vermiform appendix attached to the intestine are two such examples of vestigial organs in man.
Nictitating membrane provides protection of eyes in birds, but in humans it remains as a small fold of skin.
Q. Variation is useful for the survival of species overtime but the variants have unequal chances of survival. Explain the statement.
Ans: If organisms are suited to a particular environment there is chances of survival but drastic changes in environment could wipe out that population
(i) If some variations are there, few individuals might survive
(ii) Depending on whether the variations are useful to the change in the environment some variants survive whereas others do not
Q. a) Why do we see different variety of organisms around us? b) In which type of reproduction
(i) Off springs are identical? (ii) Exact similar offspring‘s are not produced?
Ans: (a) Due to inaccuracies in DNA copying (i) asexual (ii)sexual reproduction
Q. How do species of two isolated sub populations become two different species?
Ans: Together, the processes of genetic drift and natural selection will result in these two isolated sub-populations and thus species of two isolated sub populations become two different species
Q. How does sexual reproduction leads to similarities as well as variations ?
Ans: Similarities and variations are dependent on the type of allele combination an offspring will get from their parents. If a child get dominant alleles from father then he will look quite similar to his father and quit different from his mother. If he got a combination of dominant alleles from both the parents then he will be quite different from both the parents.
Q.All dead organisms do not leave their fossil records, but in some cases their fossils are formed. How do these fossils records form a direct evidence of past happenings?
Ans: There are two components to this estimation. One is relative. If we dig into the earth and start finding fossils, it is reasonable to suppose that the fossils we find closer to the surface are more recent than the fossils we find in deeper layers. The second way of dating fossils is by detecting the ratios of different isotopes of the same element in the fossil material.
Q. Evolution is a process in which simple life forms change into complex life forms by gradual changes. But, there is a difference between chemical and organic evolution. Differentiate by giving three points.
Ans: The formation of organic molecules from inorganic molecules is known as chemical evolution. Around four billion years ago, earth’s atmosphere consisted of chemicals such as water vapour, methane, ammonia, hydrogen, Sunlight, heat from volcanoes and lightning caused these molecules to combine in the shallow seas and produce various organic molecules such as sugars. Slowly, these organic molecules combined to form big molecules which include proteins and simple RNA and DNA molecules.
The enzymes, proteins, RNA and DNA once formed constituted a self-replicating system enclosed in a selectively
Permeable, protective lipid sphere which further evolved into membrane bound proto cells and finally into living
Cells. This is known as organic evolution. It includes the changes from the simplest unicellular forms of life to the most complex multicellular forms.
Q. There are a number of ways by which the genes enter a population. Explain briefly the three ways
Ans: Gene flow refers to the transfer of alleles from one population to another as a result of interbreeding between members of two populations.
Mutation: are the sudden changes that take place in the DNA sequence of an organism.
Migration: Migration will change gene frequencies by bringing in more copies of an allele already in the population or by bringing in a new allele that has arisen by mutation.
Q. why more complex organisms cannot give rise to new individuals through regeneration?
Ans: Complex organisms have highly differentiated tissues and organs. In this case regeneration of complex individual organism is difficult from a small piece.
Q. Why are the small number of surviving tigers a cause of worry from the point of view of genetics?
Ans: Decrease in population; decreases the chances of recombination and variation which impacts the gene pool. As a result, there is a loss of genes. Thus they become extinct
Q: shibu's father is a wrestler and has a robust body. His son was thin
(a) Is it true that a wrestles son should also have heavy muscles
(b) What type of character is it - acquired or inherited?
(c) If you are shibu's friend how will you convinced him that he is normal
Answer: (a) It is not true that wrestlers son also have heavy muscles.
(b) Having heavy muscles is an acquired trait. Heavy muscles can be made by regular exercising.
(c) As Shibu's friend can convince him by telling him that traits like heavy muscles are not inherited but are acquired in the lifetime. So he can start exercising on a regular basis to be like his father. If he is not as strong as his father, there is also a possibility that he may have more traits from her mother .
More solved question is added soon............................
Q. Why did Mendel chosen pea plant for his experiments?
Answer: Mendel chose pea plant for his experiments because it is:
(a) Easy to grow (b) Short lifespan (c) Easily distinguishable characters (d) Larger size of flower (e) Self-pollinated.
Q. What is heredity?
Ans:- Heredity refers to the transmission of characters or traits from the parents to their offspring.
Q. What do you understand by evolution?
Ans:-Evolution is the sequence of gradual changes which takes place in the primitive organisms over million of years in which new species are produced.
Q. What is a gene?
Ans:- Gene is a small segment of DNA on a chromosome occupying specific position in which is a hereditary determinant or unit of a biological function.
Q. With the help of suitable examples, explain why certain traits cannot be passed on to the next generation. What are such traits called?
Solution: The traits which are acquired during the lifetime of a person are called acquired traits. These traits involve changes in non reproductive cells (somatic cells) which are not transferred to germ cells. So, these traits cannot be passed on to the next generation. For example: Learning skills like swimming, dancing, cooking, body building, etc are acquired traits and cannot be passed on to the next generation.
Q. "A trait may be inherited, but may not be expressed." Justify this statement with the help of a suitable example.
Ans: When a tall plant was crossed with a short plant, the first (F1) generation plants were all tall. But when the F1 generation plants were crossed, the second (F2) generation plants were not all tall: there were both tall and short plants.
This shows that the F1 plants had inherited their trait from the short plants but did not express it in the presence of the tallness, and had transferred it to the next generation.
Q. 'It is a matter of chance whether a couple will give birth to a male child or a female child." Justify this statement with the help of a flow chart showing the fusion of sex chromosomes.
Ans: Sex is determined at the time of fertilization and the two sexes are produced in approximately equal numbers. A human male has XY sex-chromosomes and produces two types of sperms (heterogametic). Either with X-chromosome or with Y-chromosome.
A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with X-chromosomes.
Parents Male Female
Gametes X Y X
Progeny XX XY
Female (50%) Male (50%)
Q. What are homologous organs? How do they provide evidence in support of evolution?
Ans:- Homologous organs are those organs which have the same basic structure and developmental origin but have different functions and appearance.
Homologous organs support evolution:
(i) The similarities of structure and origin of organs indicate that all vertebrates had common ancestors. For example, the forelimbs of humans, whale and bat show structural similarities but functional dissimilarities. Forelimbs in humans used for grasping or holding the things, in whale for swimming and in bat for flying.
(ii) All the organs and systems of the vertebrates show fundamental similarities i.e. homology, which indicate towards common ancestry. Thus, homologous point that organic evolution has taken place.
Q. What is a retrovirus?
Ans:- A virus having RNA (Ribonucleic acid) as genetic (heredity) material is called Retrovirus. For example, Human immunodeficiency virus (HIV) is a retrovirus.
Q. Who provided the evidence of DNA as a genetic material? Write the names of components of DNA?
Ans:- Griffith, Avery , McLeod and McCarty established that DNA is the genetic material.
Components of DNA: A DNA molecule consists of two polynucleotide chains. Each nucleotide consists of (a) nitrogenous base (Adenine/guanine/Thymine or Cytosine) , a pentose sugar(deoxyribose) and a phosphate group.
Q. How many types of nitrogenous bases are present in DNA? Name them.
Ans:-In DNA two types of nitrogenous bases are present. These are
(i)PURINES which are adenine and guanine (ii)PYRIMIDINES which are Thymine and cytosine.
Q. How do embryological studies provide evidence for evolution?
Ans:- The similarities in embryonic development reinforce the idea of evolution from common ancestors. The sequence of embryonic development in different vertebrates shows striking similarities. Notochord and gill clefts appear in the embryos of all vertebrates.
Q. What are transgenic organisms? Which property of DNA is used as a tool in genetic engineering?
Ans:-The organisms that contain a segment of foreign DNA are known as transgenic organisms. The complimentary property of the nucleotides of DNA.is the most powerful tool in genetic engineering.
Q. Name the two homologous structures in vertebrates. Why are they so called? How do such organs help in understanding an evolutionary relationship?
Ans: Limbs of birds, reptiles and humans are all the examples of homologous structures in the vertebrates. They are called so as the basic structure of the limbs is similar. Though it has been modified to perform different functions in various vertebrates.
These are organs which are inherited from a common ancestor. Such a homologous characteristic helps to identify an evolutionary relationship between apparently different species.
Q. What are the different ways in which individuals with a particular trait may increase in a population?
Ans : The different ways in which individuals with a particular trait may increase in a population, are :
Genetic drift ; Geographical isolation ; Natural selection and Artificial selection
Q. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?
Ans : If they all die out became extinct, tiger gene will be lost forever and the coming generation will not be able to see tiger at all.
Q. Will geographical isolation be a major factor in the speciation of a self-pollination plant species? Why or why not?
Ans: No, In asexually reproducing organisms pass on the parent DNA to offspring that leaves no chance of speciation
Q. What is the evolutionary significance of the fossil archaeopteryx?
Ans: Archaeopteryx serves as a connecting link between birds and reptiles. It is the fossil evidence to show that birds have evolved from reptiles.
Q. Give the evidence that bird have been evolved from reptile?
Ans: They both lay eggs, have scales on feet and soft anatomy such as musculature, brain, heart.
Q. What are vestigial organs? Name any two vestigial organs in man and name organ which is vestigial in man but not in birds.
Ans: Organs that are well developed and functional in many organisms and are very much reduced and functionless in other organisms is called vestigial organs. Nictitating membrane in the eye and vermiform appendix attached to the intestine are two such examples of vestigial organs in man.
Nictitating membrane provides protection of eyes in birds, but in humans it remains as a small fold of skin.
Q. Variation is useful for the survival of species overtime but the variants have unequal chances of survival. Explain the statement.
Ans: If organisms are suited to a particular environment there is chances of survival but drastic changes in environment could wipe out that population
(i) If some variations are there, few individuals might survive
(ii) Depending on whether the variations are useful to the change in the environment some variants survive whereas others do not
Q. a) Why do we see different variety of organisms around us? b) In which type of reproduction
(i) Off springs are identical? (ii) Exact similar offspring‘s are not produced?
Ans: (a) Due to inaccuracies in DNA copying (i) asexual (ii)sexual reproduction
Q. How do species of two isolated sub populations become two different species?
Ans: Together, the processes of genetic drift and natural selection will result in these two isolated sub-populations and thus species of two isolated sub populations become two different species
Q. How does sexual reproduction leads to similarities as well as variations ?
Ans: Similarities and variations are dependent on the type of allele combination an offspring will get from their parents. If a child get dominant alleles from father then he will look quite similar to his father and quit different from his mother. If he got a combination of dominant alleles from both the parents then he will be quite different from both the parents.
Q.All dead organisms do not leave their fossil records, but in some cases their fossils are formed. How do these fossils records form a direct evidence of past happenings?
Ans: There are two components to this estimation. One is relative. If we dig into the earth and start finding fossils, it is reasonable to suppose that the fossils we find closer to the surface are more recent than the fossils we find in deeper layers. The second way of dating fossils is by detecting the ratios of different isotopes of the same element in the fossil material.
Q. Evolution is a process in which simple life forms change into complex life forms by gradual changes. But, there is a difference between chemical and organic evolution. Differentiate by giving three points.
Ans: The formation of organic molecules from inorganic molecules is known as chemical evolution. Around four billion years ago, earth’s atmosphere consisted of chemicals such as water vapour, methane, ammonia, hydrogen, Sunlight, heat from volcanoes and lightning caused these molecules to combine in the shallow seas and produce various organic molecules such as sugars. Slowly, these organic molecules combined to form big molecules which include proteins and simple RNA and DNA molecules.
The enzymes, proteins, RNA and DNA once formed constituted a self-replicating system enclosed in a selectively
Permeable, protective lipid sphere which further evolved into membrane bound proto cells and finally into living
Cells. This is known as organic evolution. It includes the changes from the simplest unicellular forms of life to the most complex multicellular forms.
Q. There are a number of ways by which the genes enter a population. Explain briefly the three ways
Ans: Gene flow refers to the transfer of alleles from one population to another as a result of interbreeding between members of two populations.
Mutation: are the sudden changes that take place in the DNA sequence of an organism.
Migration: Migration will change gene frequencies by bringing in more copies of an allele already in the population or by bringing in a new allele that has arisen by mutation.
Q. why more complex organisms cannot give rise to new individuals through regeneration?
Ans: Complex organisms have highly differentiated tissues and organs. In this case regeneration of complex individual organism is difficult from a small piece.
Q. Why are the small number of surviving tigers a cause of worry from the point of view of genetics?
Ans: Decrease in population; decreases the chances of recombination and variation which impacts the gene pool. As a result, there is a loss of genes. Thus they become extinct
Q: shibu's father is a wrestler and has a robust body. His son was thin
(a) Is it true that a wrestles son should also have heavy muscles
(b) What type of character is it - acquired or inherited?
(c) If you are shibu's friend how will you convinced him that he is normal
Answer: (a) It is not true that wrestlers son also have heavy muscles.
(b) Having heavy muscles is an acquired trait. Heavy muscles can be made by regular exercising.
(c) As Shibu's friend can convince him by telling him that traits like heavy muscles are not inherited but are acquired in the lifetime. So he can start exercising on a regular basis to be like his father. If he is not as strong as his father, there is also a possibility that he may have more traits from her mother .
More solved question is added soon............................
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