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Friday, June 10, 2022

AP Board Class 10 Biology Chapter 8 Heredity Textbook Solutions PDF: Download Andhra Pradesh Board STD 10th Biology Chapter 8 Heredity Book Answers

AP Board Class 10 Biology Chapter 8 Heredity Textbook Solutions PDF: Download Andhra Pradesh Board STD 10th Biology Chapter 8 Heredity Book Answers
AP Board Class 10 Biology Chapter 8 Heredity Textbook Solutions PDF: Download Andhra Pradesh Board STD 10th Biology Chapter 8 Heredity Book Answers


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Andhra Pradesh Board Class 10th Biology Chapter 8 Heredity Textbooks Solutions PDF

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Andhra Pradesh State Board Class 10th Biology Chapter 8 Heredity Books Solutions

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AP Board Class 10th Biology Chapter 8 Heredity Textbooks Solutions with Answer PDF Download

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10th Class Biology 8th Lesson Heredity Textbook Questions and Answers

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Question 1.
What are variations? How do they help organisms?
Answer:

  1. Differences in characters within very closely related groups of organisms are referred to as variations.
  2. Variations develop during reproduction in organisms.
  3. Variations are passed from parent to offspring through heredity.
  4. Beneficial variations are selected by the nature in evolution.
  5. Variations increase the survival chance of the organisms.
  6. These variations help the organisms to adapt to their environments.
  7. For example, green colour in the beetles is a variation that gave a survival advantage to the beetles as they cannot be seen by the crows.
  8. Some variations do not help organisms to survive. For example, colour variation occurs in red beetles and some blue beetles are produced instead of red beetles as they are eaten by crows easily.

Question 2.
One student (researcher) wants to cross pure tall plant (TT) with pure dwarf (tt) plant, what would be the Fj and F2 generations? Explain.
Answer:

  1. Pure tall plant has both the factors of the same type ‘TT’.
  2. Pure dwarf plant has both the factors of the same type ‘tt’.
  3. When a pure tall plant (TT) is crossed with pure dwarf plant (tt), all the offsprings in Fj generation are tall (Tt).
  4. So all the plants are heterozygous tall, as ‘T’ is the dominating factor.
  5. On self pollination of these F1 generation plants the new breed can have any combination of T and t like TT, Tt, Tt or tt.
  6. So in F2 generation 75% of plants are tall and 25% of plants are dwarf. Thus the phenotype ratio is 3 : 1.
  7. Among 75% of tall plants 25% are pure tall (TT) or homozygous tall, remaining 50% are heterozygous tall (Tt, tT).
  8. The remaining 25% dwarf plants are pure or homozygous dwarf (tt).
  9. So the genotype ratio is 1 : 2 : 1.

Question 3.
One experimenter cut the tails of parent rats, what could be the traits in offsprings? Do the daughter rats contain tails or not? Explain your argument.
Answer:

  1. If the tails of parent rats were cut, their offsprings will have normal tails.
  2. Daughter rats do not contain tails because the bodily changes are not inherited.
  3. So the change would not be passed to their offsprings.
  4. This was proved experimentally by Augustus Weisemann and rejected the theory ‘inheritance of acquired characters’ proposed by Lamarck.

Question 4.
In a mango garden a farmer saw one mango tree with full of mango fruits but with a lot of pests. He also saw another mango tree without pests but with few mangoes. But the farmer wants the mango tree with full of mango fruits and pests free. Is it possible to create new mango tree which the farmer wants? Can you explain how it is possible?
Answer:

  1. Yes, it is possible to create new mango tree which one the former wants with full of mango fruits and pests free.
  2. The former can cross two plants one with full of mangoes and pests and another plant with less mango fruits and without pests,
  3. In F1 generation he may get plants with full of mango fruits and without pests. Such plants are called hybrid plants.
  4. The F1 generation plants can be self pollinated and desired plants can be selected from the mixed population of F2 generation.
  5. The plant with desirable characters can be vegetatively propagated to get required number of plants.

Question 5.
ExplaIn monohybrid experiment with an example. Which law of inheritance can we understand? Explain.
Answer:

  1. We can understand the law of inheritance with an example of monohybrid cross between pure yellow pea seeds with pure green pea seeds.
  2. A pure breed (parental) yellow will have both the factors which denote them by ‘YY’ and pure breed (parental) green seed will have both the factors denote them by ‘yy’.
  3. During reproduction one factor (genes) from each parent is taken to form a new pair in the progeny (off spring).
  4. In F1 generation all pea plants are Yellow.
  5. F1 generation pea plants are self pollinated.
  6. In F2 generation 75% of the plants produced were Yellow seeds and the remaining 25% produced were green seed. It can be represented as

    In F2 generation the produced plants are YY, Yy; yY or yy.
    From the above example of monohybrid cross we can understand the following laws of inheritance.

1) When pure breed Yellow (YY) and green (yy) seeds were crossed, only Yellow seeds were expressed phenotypically in the F1 generation. It indicates that Yellow seed character is dominent over green seed characters.
This is “LAW OF DOMINANCE”.

2) When F1 plants are self pollinated each parent passes randomly selected allele (Y or y) of one of these factor to offsprings. This is segregation of alleles or genes during production of gametes.
This is “LAW OF SEGREGATION”.

Question 6.
What is the law of independent assortment? Explain with an example.
Answer:

  1. In the inheritance of more than one pair of characters (traits), the factors for each pair of characters assorts independently of the other pairs. This is known as “Law of independent assortment”.
  2. If pea plants with two different pairs of characteristics (eg. : Round / yellow and green wrinkled) are breed with each other, the F1 progeny plants would have all round and yellow seeds.
  3. This implies that round and yellow seeds are dominant characters over green and wrinkled seeds.
  4. In F2 progeny there would be some plants with round and yellow seeds and some with green and wrinkled seeds.
  5. However, there would be some plants with mixed characters – yellow and wrinkled seeds and green and round seeds.
  6. This depicts that round/wrinkled trait and yellow / green trait are inherited independent of each other (law of independent assortment).
    The following punnet square explains this.
  7. The different combination of characters resulted from dihybrid cross.
    a) RRYY, RRYy, RrYy, RrYY, RRYy, RrYy, RrYy, RrYY, RrYy are having round and yellow seeds.
    b) RRyy, Rryy, Rryy have round and green seeds.
    c) rrYy, rrYy, rrYY have wrinkled and yellow seeds.
    d) rryy have wrinkled and green seeds.
  8. From the result, it can be concluded that the factors for each character or trait remains separate and maintain its identity in the gametes. This is known as “Law of independent assortment”.

Question 7.
How does sex determination take place in human?
(OR)
Explain sex determination in humans with the help of flow chart.
Answer:

  1. Each human cell contains 23 pairs (46) of chromosomes.
  2. Out of 23 pairs, 22 pairs of chromosomes are called autosomes.
  3. Remaining one pair is called allosomes or sex chromosomes.
  4. There are two types of sex chromosomes – one is ‘X’ and the other is ‘Y’.
  5. These two chromosomes determine the sex of an individual.
  6. Females have two ‘X’ chromosomes in their cells (XX).
  7. Males have one ‘X’ and one ‘Y’ chromosomes in their cells (XY).
  8. All the gametes produced by women (ovum) will be with only X chromosomes.
  9. The gametes produced by man (sperm) will be of two types, one with X chromosomes and other with Y chromosomes.
  10. If the sperm carries X chromosome and fertilizes with the ovum, the resultant baby will have XX condition. So the baby will be a girl.
  11. If the sperm carries Y chromosome and fertilises with the ovum, the resultant baby will have XY condition. So the baby will be a boy.

Question 8.
Explain Darwin’s theory of ‘Natural selection’ with an example.
(OR)
What do you understand by the term Natural selection? Write Darwin’s theory of evolution.
Answer:

  1. Darwin proposed the theory of Natural selection.
  2. Nature only selects or decides which organism should survive or perish in nature.
  3. The organism with useful traits will survive and the organisms having harmful traits are going to perished or eliminated from its environment.
  4. For example, a group of twelve red beetles live in a bush of green leaves.
  5. They will grow their population by sexual reproduction.
  6. So they generate variations in their population. Let us assume crows eat the red beetles more the population of red beetles slowly reduced.
  7. Crows eat these red beetles and their population slowly reduces.
  8. During this time a colour variation arises by the sexual reproduction.
  9. So that there appears one beetle that is green in colour instead of red.
  10. Moreover this green colour beetle passes its colour to its offsprings; so that all its progeny are green.
  11. Crows cannot see the green coloured beetles on green leaves of the bushes and therefore crows cannot eat them.
  12. The crows can see the red beetles and eat them as a result, there are more and more green beetles than red ones which decrease in their number.
  13. The variation of green colour beetle gave a survival advantage to green beetles’ than red beetles. They were naturally selected.

Question 9.
What are variations? Explain with a suitable example.
Answer:

  1. Differences in characters within very closely related groups of organisms are referred to as variations.
  2. Often a new character in a group may lead to variations that are inherited.
  3. If we observe parents and offsprings, there will be some similar features in the offspring of the parents.
  4. At the same time we find differences between parents and offspring in their features.
  5. These differences are an example of variations.
  6. Variations are quite apparent among closely related groups of organisms.
  7. If we take roses as an another example, we observe number of varieties in them.
  8. But we can still find some characters similar to all plants.
  9. Thus rose plants have similar physical features, at the same time they have differences in characters like flower colour, number of petals, leaf size, stem, spines, etc.
  10. These differences in features are variations.

Question 10.
What variations generally have you observed in the species of cow?
Answer:
In the species of cow the following contrasting variations can be observed:

  1. White coloured – spotted
  2. Longhorns – short horns
  3. Height – dwarf
  4. Long-tail – short tail
  5. Elongated face – stunted face
  6. More milk giving – less milk giving, etc.

Question 11.
What are the characters that Mendel selected for his experiments on pea plants
(OR)
Write the seven pairs of contrasting characters in pea plant identified by Mendel and mention their traits.
Answer:
Mendel selected the following characters on pea plants for his experiment. They are:

Character Description
1. Colour of the flower 1. Purple or white.
2. Position of the flower 2. Axial or terminal in position
3. Colour of the seed 3. Either yellow or green.
4. Shape of the seed 4. Either round or wrinkled.
5. Shape of the pod 5. Inflated and constricted
6. Colour of the pod 6. Yellow or green.
7. Length of the stem 7. Tall and dwarf.

Question 12.
In what way Mendel used the word ‘Traits’? Explain with an example.
Answer:

  1. Trait is a separate variant of an organism.
  2. Mendel hypothesized that characters were carried as traits.
  3. An organism always carried a pair of factors for a character.
  4. He also hypothesized that distinguishing traits of the same character were present in the population of an organism.
  5. He assumed that the traits shown by the pea plants must be in the seeds that produce them.
  6. The seeds must have obtained these traits from the parent plants.
  7. The factors which are responsible for the character or trait of an organism, are now named as “genes”.
  8. By all these we can assume that Mendel used the word ‘traits’ for indicating the variant of an organism expressed by a pair of factors or genes.
  9. For example, height is a character of pea plant while the tallness is a trait expressed by a pair of factors either TT or Tt and dwarfness is another trait expressed by a pair of factors tt.

Question 13.
What are the differences that Mendel observed between parent and F2 generation?
Answer:
Mendel identified the following differences between parent and F2 generation.

Parent F2 Generation
1. They are pure breeds. 1. They consist of mixed population.
2. They consist of homozygous alleles. 2. They consist of homozygous alleles in some plants and heterozygous alleles in some other plants.
3. They have some fixed characteristic features. 3. New combination of characters will appear.

Question 14.
Male is responsible for sex determination of baby – do you agree? If so write your answer with a flow chart.
Answer:

  1. Yes, I agree with the statement that male is responsible for sex determination of baby.
  2. There are two types of sex chromosomes in human beings, one is ‘X’ and other is ‘Y’.
  3. Females have two ‘X’ chromosomes in their cells (XX) whereas males have one ‘X’ and one ‘Y’ chromosomes in their cells (XY).
  4. All the gametes produced by woman (ovum) will be with only X chromosomes.
  5. The gametes produced by man (sperm) will be of two types one with X chromosomes and other Y chromosomes.
  6. If the sperm carrying X chromosome fertilizes the ovum, the resultant baby will have XX condition. So the baby will be a girl.
  7. If the sperm carrying Y chromosome fertilizes the ovum, the resultant baby will have XY condition. So the baby will be a boy.
  8. So the gamete produced by the male is the deciding factor for sex determination of the baby.

Question 15.
Write a brief note on analogous organs.
(OR)
What are analogous organs?
Answer:

  1. The organs which are structurally different but functionally similar are known as ‘Analogous organs’.
  2. Wings of birds and bats is the example for analogous organs.
  3. The wings of bats are skin folds stretched mainly between elongated fingers.
  4. But the wings of birds are a feathery covering all along the arm.
  5. The designs of the two wings, their structure and components are different.
  6. They look similar because they have common use for flying, but their origins are not common.
  7. This makes the ‘analogous’ characteristics.
  8. This type of evolution is called convergent evolution.

Question 16.
How do scientists utilise information about fossils?
(OR)
“Fossils are valuable material that nature had preserved to know about ancient organisms.” Write the information you have collected about fossils.
Answer:

  1. Fossils are evidence of ancient life forms or ancient habitats which have been preserved by natural processes.
  2. The scientific study of fossils is called ‘Palaeontology’.
  3. Scientists utilise information about fossils to understand the evolutionary history of life.
  4. This information is also useful to study ecology and environmental history, such as ancient climates.
  5. This also helps to find out how old that certain layer of earth is.
  6. This information is also utilized as indicators of possible fossil fuel deposits which are of great interest to humanity.
  7. Thus scientists utilize the information on fossils to learn more about the earth’s past.

Question 17.
Mendel selected a pea plant for his experiments. Mention the reasons for the selection as these plants.
(OR)
Why did Mendel select the pea plant for his experiment? (OR)
Which characters in the pea plant are selected by Mendel, for his experiments?
What are the reasons for selecting pea plant by Mendel to conduct his experiments?
Answer:
Mendel chose the pea plant (Pisum sativam) for his breeding experiments for the following reasons.

  1. It is sexually reproducing.
  2. Flowers are bisexual.
  3. Predominantly self-pollinated.
  4. Predominantly self-fertilization.
  5. Well developed characters.
  6. Early hybridization.
  7. It is an annual plant.
  8. These plants have short maturity and can produce large number of seeds in a single generation.
  9. Pea plants have short life cycle.
  10. These plants can easy to grow either on the ground or in pots.

Question 18.
If the theory of inheritance of acquired characters proposed by Lamarck was true, how will the world be?
Answer:
If the theory of inheritance of acquired characters proposed by Lamarck was correct,

  1. All the organisms which lost some of their body parts should give birth to the offsprings without the lost parts.
  2. Rat which lost their tail should give birth to tail less rats.
  3. A handicapped who lost their legs in an accident should give birth to babies v without legs.
  4. A body builder’s children should be body builders.
  5. But all these are not happening because bodily changes won’t be passed to its offspring.

Question 19.
Collect information on the inherited traits in your family members and write a note on it.
Answer:

  1. My grandfather and father- had curling hair. I too have curling hair. So it’s an inherited trait in family.
  2. My mother and I both have long noses which appear similar. It’s another inherited trait.
  3. Eyes of my grandmother, my brother and mine are similar. It’s another inherited trait.
  4. Ear lobes of my father, brother and mine are similar. This is another inherited trait.

Question 20.
With the help of given information write your comment on evidences of evolution.

Mammals have fore limbs as do birds, reptiles and amphibians. The basic structure of the limbs is similar, though it has been modified to perform different functions.

Answer:

  1. The given information gives the evidences of evolution.
  2. Mammals. birds, reptiles and amphibians all these have forelimbs which have similar basic structure.
  3. But they are modified to perform different functions.
  4. This indicates that all the vertebrates have evolved from a common ancestor. These organs are called homologous organs. This type of evolution is called divergent evolution.
  5. In case of bat (mammal) and bird the designs of the two wings, their structure and components are different.
  6. They look similar because they have common use for flying, but their origins are not common.
  7. These organs which are structurally different but functionally similar are known as ‘Analogous organs’. This type of evolution is called “convergent evolution”.
  8. There are remarkable similarities in the embryos of above mentioned animals even in their limb formation. These are called embryological evidences.

Question 21.
Collect information about carbon dating method. Discuss with your physical science teacher.
(OR)
Write about the carbon dating method from the information collected by you.
Answer:

  1. Carbon dating is the method used to calculate the age of rocks, minerals or fossils.
  2. The breakdown of radioactive isotopes of certain elements such as carbon, uranium and potassium takes place at a known rate. So the age of rock or mineral containing isotopes can be calculated.
  3. Archaeologists use the exponential, radioactive decay of carbon 14 to estimate the death dates of organic material.
  4. The earth’s atmosphere contains various isotopes of carbon, roughly in constant proportions.
  5. These include the main stable isotope 12C and an unstable istope 14C.
  6. Through photosynthesis, plants absorb both forms from carbon dioxide in the atmosphere.
  7. When an organism dies, it contains the standard ratio of 14C to 12C.
  8. But as the 14C decays with no possibility of replenishment, the proportion of carbon 14 decreases at a known constant rate.
  9. The time taken for it to reduce by half is known as the half-life of 14C, which is 5730.
  10. The measurement of the remaining proportion of 14C in organic matter thus an estimation of its age.
  11. As the half life of carbon – 14 is 5,700 years, it is useful for dating objects up (o about 60,000 years old.

Question 22.
Draw a checker board, show the law of independent assortment with a flowchart and explain the ratio.
Answer:

  1. The phenotypic ratio is 9 : 3 : 3 : 1. i.e., 9 round and yellow seeds 3 round and green seeds, 3 wrinkled and green seeds and 1 wrinkled and green seed.
  2. RRYY, RRYy, RrYy, RrYy, RRYy, RrYy, RrYy, RrYY and RrYy are round and yellow seeds.
  3. RRyy, Rryy, Rryy are round and green.
  4. rrYY, rrYy, rrYy are wrinkled and yellow.
  5. rryy are wrinkled and green.

From the above result, it can be concluded that factors for each character or trait remains separate and maintains its identity in the gametes. Thus in the inheritance of more than one pair of characters, the factors for each pair of characters assort independently of the other pairs. This is known as “Law of independent assortment”.

Question 23.
Explain the process to understand the monohybrid cross of Mendel experiment with a checker board.
Answer:

Question 24.
Prepare a chart showing the evolution of man through ages.
Answer:

Question 25.
Nature selects only desirable characters. Prepare a cartoon.
Answer:
Nature selects only desirable characters

Question 26.
What is your understanding about survival of the fittest? Give some situations or examples that you observe in your surroundings.
Answer:

  1. Nature favours only useful variations.
  2. Each species tends to produce a large number of offspring.
  3. They compete with each other for food, space, mating and other species.
  4. In this struggle for existence only the fittest can survive.
  5. When cat tries to catch some rats, the rats which can run fast and hide in its hole can survive and which is slow can become prey for the cat.
  6. When we spray some insecticide on insects, most of them will die but few which can withstand that chemical will escape.
  7. When a pest attacks our garden plants, most of them may die but Which can withstand the pest can survive.
  8. When the dog tries to catch chickens, the chickens which will run fast and escape can survive but the slower ones will become food for the dog.

Question 27.
Write a monologue on the evolution of a human to perform a stage show on the theatre day in your school.
Answer:

  1. Hai, I am a human being. I am going to recall what had happened to me so far, how I had evolved, simply my journey from my origin to till now.
  2. Nearly 1.6 – 2.5 million years ago, during the gelasian pleistocene period, I used to wander in the forest. It is belived that, I evolved from apes.
  3. Between 1-1.8 million years ago, I gradually evolved into Homo erectus. I lived in this stage throughout most of the pleistocene. I used more diverse and sophisticated stone tools than my predecessors and it is belived that I travelled over oceans using rafts.
  4. Around 1,00,000 – 40,000 thousand years ago I evolved into Homo sapiens neanderthalensis. I was stronger than present in those days. I made advanced tools. I had language to communicate.
  5. Around 40 thousand years ago, I reached the present form of human being, the modern humans known as Homo sapiens. I learnt cultivation, construction of houses, cooking, etc. I had invented various things that help me to live comfortably.
  6. But my journey did not stop. It is still continuing. Let us see what may happen? Where can I reach? What changes may come in me? Hope for the best.
    Thank you.

Fill in the blanks.

  1. The process of acquiring change is called ———–.
  2. Mendel’s experiment explains about ———–.
  3. The four characters observed in the experiments on law of independent assortment are ———–.
  4. If we cross pollinate red flower plant with white flower we will get percent of ———– recessive trait plants.
  5. TT or YY, Tt or Yy are responsible for a ———– character.
  6. Female baby having 23 pairs of autosomes at the age of 18 years, has ———– pair autosomes and ———– of sex chromosomes.
  7. The population grows in ———– progression whereas food sources grow in ———– progression.
  8. A goat which walks properly can’t live for a long time. According to Darwin, this represents ———–.
  9. Forelimb of whale is for swimming whereas in horse it is used for ———–.
  10. The study of fossils is called ———–.

Answer:

  1. evolution
  2. heredity
  3. Round, wrinkled, yellow, green
  4. 100
  5. dominant
  6. 22, one pair
  7. geometrical, arithmetic
  8. survival of the fittest
  9. running
  10. palaeontology

Choose the correct answer.

  1. Which of the following is not a variation in rose plant? [ ]
    A) Coloured petals
    B) Spines
    C) Tendrils
    D) Leaf margin
    Answer: C
  2. According to Mendel, alleles are [ ]
    A) Pair of genes , Responsible for character
    B) gene
    C) Production of Gametes
    D) Recessive factors
    Answer: B
  3. Natural selection means [ ]
    A) Nature selects desirable characters
    B) Nature rejects undesirable characters
    C) Nature reacts with an organism
    D) A, B
    Answer: A
  4. Palaeontologists deal with [ ]
    A) Fossilised Embryological evidences
    B) Fossil evidences
    C) Fossilised Vestigial organ evidences
    D) All
    Answer: D

10th Class Biology 8th Lesson Heredity InText Questions and Answers

10th Class Biology Textbook Page No. 166

Question 1.
How does evolution take place?
Answer:

  1. Evolution takes place through the accumulation of new characters or variations in a species of organisms.
  2. Accumulation of variations occurs only when new characters are passed on from one generation to other and much more new characters are added to the pre-existing once.
  3. So this happens oVer a kirig period of time, sometimes several generations may pass.
  4. Hence it happens in a slow and steady manner.
  5. It is not just about change but producing something new and different.
  6. It is about the formation of new species and their adaptation to their environments.

10th Class Biology Textbook Page No. 168

Question 2.
Is variation all about apparent differences? Or is it about some subtle differences as well that we most often overlook?
Answer:

  1. Variations are not always apparent differences.
  2. Sometimes these may be subtle differences that we most often overlook.
  3. When these subtle differences accumulate together they may become apparent.

10th Class Biology Textbook Page No. 171

Question 3.
How do parent plants pass on their traits to the seeds?
Answer:

  1. Every character or trait is controlled by a pair of factors called genes.
  2. At the time of sexual reproduction, one factor or each trait will pass to the gametes.
  3. By the fussion of male and female gametes zygote will form in which factors from both male and female parents get paired again.
  4. This zygote will develop into seed in the later stages.
  5. Thus parent plants pass on their traits to the seeds.

Question 4.
Will the seeds from tall plants always produce new tall plants?
Answer:

  1. No. Tall plants may or may not produce tall plants again.
  2. This is because tallness is a dominant character in most of the plants, especially in peas.
  3. So tall plant may be homozygous tall (TT) or heterozygous tall (Tt).
  4. If the parental plant is homozygous tall (pure breed), then they always produce new tall plants.
  5. If the parental plant is a heterozygous tall plant, then they produce the tall and dwarf plants in the ratio of 3 : 1.

10th Class Biology Textbook Page No. 175

Question 5.
What should be the percentage of each type of plants in F2 generation produced in dihybrid cross between pea plants with yellow, smooth seeds and green wrinkled seeds?
Answer:

  1. In F2 generation of dihybrid cross between pea plants with yellow, smooth seeds and green wrinkled seeds, new plants will produce with the following combination.
    i) Round and yellow
    ii) Round and green and
    iii) Wrinkled and green iv) Wrinkled and yellow
  2. They will produce in the ratio of 9 : 3 : 3 : 1 respectively.
  3. So 56 (56.25%) of plants should be with round and yellow seeds. 19 (18.75%) of plants should be with wrinkled and yellow seeds. 19 (18.75 %) of plants should be with round and green seeds and 6% (6. 25%) of plants should be with wrinkled and green seeds.

10th Class Biology Textbook Page No. 178

Question 6.
What will happen if the sperm containing X chromosomes fertilizes the ovum?
Answer:

  1. If the sperm containing X chromosomes fertilizes the ovum which has X chromosome, the baby will have XX condition.
  2. So the baby will be a girl.

Question 7.
Who decides the sex of the baby – mother or father?
Answer:
Father decides the sex of the baby.

Question 8.
Is the sex also a character or trait? Does It follow Mendels’ law of dominance?
Answer:

  1. Yes, sex is also a character or a trait.
  2. It has two contrasting characters male and female.
  3. Male character is represented by a pair of allosomes ‘XY‘ (heterozygous).
  4. In this, we can consider Y as dominant and X as recessive.
  5. In this, recessive character is expressed only when it is homozygous recessive, i.e. female.
  6. Homozygous dominant is not existing as reproduction occurs between male (heterozygous dominent XY) and female (homozygous recessive XX) only.
  7. As X is not exhibiting its nature when Y is present along with it. it follows Mendel’s law of dominance.

Question 9.
Were all your traits similar to that of your parents?
Answer:

  1. No, all my traits are not similar to my parents.
  2. There are certain traits which differ from my parents.

10th Class Biology Textbook Page No. 185

Question 10.
How does the evolution of organisms have taken place?
Answer:

  1. Variations which are beneficial are selected by nature and passed from parents to offspring through heredity.
  2. The same process happens with every new generation until the variation becomes common feature.
  3. As the environment changes, the organism within environment adopts and changes to the new living conditions.
  4. Over a long period of time, each species of organisms can acuumulate so many changes that it becomes a new species.
  5. Thus evolution of organisms took place from common pre-existing ancestors.

Question 11.
Are birds and bats more closely related to each other than to squirrels or lizards?
Answer:

  1. No, bats are mammals whereas birds belong to aves.
  2. Squirrels are mammals and lizards belong to reptiles.
  3. So bats and birds are not closely related to each other as they belong to two different groups.
  4. Both bats and birds have wings.

10th Class Biology Textbook Page No. 186

Question 12.
Do embryological evidences indicate that frogs have evolved from ancestors of fish?
Answer:
Yes the embryological evidences indicate that frogs have evolved from ancestors of fish.

Question 13.
Does the life history of every individual exhibit the structural features of their ancestors?
Answer:

  1. Yes. The life history of every individual exhibit the structural features of its ancestors.
  2. The resemblance is so close at an early stage.

10th Class Biology Textbook Page No. 189

Question 14.
Think why did ancient human beings travelled from one place to other and how did they travelled?
Answer:

  1. Ancient human beings travelled from one place to other in search of better living conditions such as availability of food, water shelter and other facilities.
  2. They did not travel in a single line.
  3. They went forwards and backwards with groups, sometimes separating from each other.
  4. This travel is responsible for the formation of races.

10th Class Biology Textbook Page No. 183

Question 15.
In a forest there are two types of deer, in which one type of deer can run very fast. Whereas second type of deer can not run as fast as the first one. Lions, Tigers hunt deer for their food. Imagine which type of deer are going to survive in the forest and which type of deer population is going to be eliminated? And why?
Answer:

  1. Deer that can run fast can survive in the forest. Because they can escape easily from lions and tigers, when compared to second type.
  2. Deer that run slowly are going to be eliminated. Because they can be caught easily by its predators. So the survival chance will decrease.

10th Class Biology 8th Lesson Heredity Activities

Activity – 1

Think of your own family, what similarities do you share with your father and mother? Draw a table to represent the similarities of some characters like colour of eye (cornea), colour of hair, shape of nose, shape of face, type of earlobe (attached or free), inner thumb markings, etc. Write your characters in one column and that of your parents in the other columns.
Table – 1

Characters In me In my Mother/Father In my Brother/Sister In my grandma/grandpa

Answer:

S.No. Characters In me In my Mother/Father In my Brother/Sister In my grandma/grandpa
1. Colour of eye Black Black Black Black
2. Colour of hair Black Black Black Black
3. Shape of nose Long Long Short Short
4. Shape of face Oval Round Oval Oval
5. Type of earlobe Free Free Free Free
6. Type of hair Curling Curling Straight Straight
7. Inner thumb marking Conical Round Round Conical
8. Skin colour Fair Fair Fair Fair

1. Is there any character in you similar to that of your mother as well as your grandma?
Answer:
There are four characters in me similar to my mother as well as my grandma. They are

  1. Colour of eye
  2. Colour of hair
  3. Type of earlobe and
  4. Skin colour.

2. Is there any character in you similar only to that of your grandma?
Answer:
Two characters are similar in me and in my grandma. They are

  1. Shape of face and
  2. Inner thumb marking.

3. How do you think these characters may have been inherited by you from grandma?
Answer:
These characters are hereditary from parent to child.

4. Is there any character that is not present in grandma but present in your mother and you?
Answer:
Two characters are not present in grandma which are only present in me and my mother. They are

  1. Shape of nose
  2. Type of hair

5. Think where from your mother got that character?
Answer:
This character is the result of inherited traits transmitted from parent to progeny.

Activity – 2
Observe some of your friends and note their characters in the following table. Fill in yours as well.
Table – 2

Name of your friend Colour of skin Earlobes Free / Attached Marking on inner side of thumb Length of forehead Colour of eyes (Cornea) Any other features

Answer:

Name of your friend Colour of skin Earlobes Free / Attached Marking on inner side of thumb Length of forehead Colour of eyes (Cornea) Any other features
Ravi Black Free Round Broad Blue Straight hair, long nose, and face, etc.
Ganesh Black Attached Conical Narrow Black Straight hair, short nose, oval face, etc.
Vi jay Fair Free Conical Broad Black Curling hair, short nose, round face, etc.
Karthik Fair Free Round Broad Black Straight hair, long nose, round face, etc.

1. Compare your characters to that of any one of your friend. How many characters did you find were similar among you and your friend?
Answer:
Only few characters such as black hair and black eye were similar among me and my friend.

2. Do you share more similar characters with your parents or with your friends?
Answer:
I share more similar characters with my parents than my friends.

3. Do you think that your differences from parents are same as differences from friends? Why / Why not?
Answer:
My differences from parents are not same as differences from friend. This is because the differences from parents are subtle as there is more genetic relation with parents but the differences from friends are apparent.

Activity – 3

Observe seeds in a pea or bean pod. You may observe several parts to arrive at a generalisation.

1. Can you find two similar seeds there?
Answer:
No, all the seeds are not similar. They had certain variations.

2. What makes them vary? even though they are in the same pod. (Hint: You know that seeds are formed from ovules).
Answer:

  1. They vary from one another because they are produced from different ovules.
  2. Ovules of a plant are female gametes.
  3. These gametes carry different factors (genes) for different characters randomly.

3. Why variations are important? How are variations useful for an organism or a population?
Answer:

  1. Variations perhaps help a certain group of organisms in a community when conditions would otherwise be unfavourable for other groups.
  2. Desirable variations can be selected by nature.
  3. Desirable variations increase the chance of survival of an organism.
  4. Accumulation of variations after a long period leads to formation of new species.

Activity – 4

Let us do the following activity to understand the Mendelian principles of Heredity. Materials required :
a) 3 cm length and 1cm breadth chart pieces – 4
b) 2 cm length and 1cm breadth chart pieces – 4
c) Red buttons – 4
d) White buttons – 4
e) Chart, scale, sketch pen, pencil, 2 bags.

Method: Prepare a chart with 2×2 boxes along with number and symbol as shown in the figure.

Game 1: Monohybrid cross (starting with hybrid parents)
To start with take 1, 2 or 3, 4 . In case you start 1, 2 pick all the 16 long and short pieces and prepare such pairs in each of which you have a long and short piece.

Take 4 pairs each of long and short strips and put them in two separate bags. Now each bag contains 8 strips (4 long and 4 short).One bag say ‘A’ represents male and the bag ‘B’ represents female. Now randomly pick one strip each from bag A and B and put them together in the 1 on the chart. Keep picking out the strips and arrange them in the same manner till your bags are empty. Same time your boxes in the chart are filled with pairs of strips. You might have got the following combinations, two long strips, one long and one short strip, two short strips.

1. What is the number of long strip pairs?
Answer:
There are four long strip pairs.

2. What is the number of one long and one short pairs?
Answer:
There are eight, one long and one short strip pairs.

3. What is the number of short strips pairs?
Answer:
There are four short strip pairs.

4. What is the percentage of each type? Also find their ratios.
Answer:
The percentage of long strip pairs, one long and one short strip pairs and short strip pairs are 25%, 50% and 25% respectively and the ratio is 1 : 2 : 1.

5. What can you conclude from this game?
Answer:
From this game I have concluded that:

  1. Every individual possesses a pair of alleles, for any particular trait.
  2. Each parent passes a randomly selected copy (allele) of these to an offspring.
  3. The offspring then receives its own pair of alleles for that trait one each from both parents.
  4. If the long strip is considered as dominant 75% exhibit dominant and 25% exhibit recessive character. Thus the phenotype ratio is 3 : 1 in monohybrid cross.
  5. The genotype ratio is 1 : 2 : 1.

Activity – 5

Observe the below diagram showing variation in beetle population and its impact.
Let us consider a group of twelve beetles. They live in bushes on green leaves. Their population will grow by sexual reproduction. So they were able to generate variations in population. Let us assume crows eat these red beetles. If the crows eat more Red beetles, their population is slowly reduced. Let us discuss the above three different situations in detail.
Answer:
Situation-1: In this situation, a colour variation arises during reproduction. So that there appears one beetle that is green in colour instead of red.
Moreover, this green coloured beetle passes its colour to Its offspring (Progeny). So that all its progeny are green. Crows cannot see the green coloured beetles on green leaves of the bushes and therefore crows cannot eat them. But crows can see the red beetles and eat them. As a result there are more and more green beetles than red ones which decrease in their number.

The variation of colour in beetle ‘green’ gave a survival advantage to’green beetles’ than red beetles. In other words it was naturally selected. We can see that the ‘natural selection’ was exerted by the crows. The more crows there are, the more red beetles would be eaten and the more number of green beetles in the population would be. Thus the natural selection is directing evolution in the beetle population. It results in adaptation in the beetle population to fit in their environment better.

Let us think of another situation.
Situation-2: In this situation a colour variation occurs again in its progeny during reproduction, but now it results in ‘blue’ colour beetles instead of ‘red’colour beetle. This blue colour beetled can pass its colour to its progeny. So that all its progeny are blue.
Crows can see blue coloured beetles on the green leaves of the bushes and the red ones as well. And therefore crows can eat both red and blue coloured beetles. In this case there is no survival advantage for blue coloured beetles as we have seen in case of green coloured beetles.

What happens initially in the population, there are a few blue beetles,but most are red. Imagine at this point an elephant comes by and stamps on the bushes where the beetles live. This kills most of the beetles. By chance the few beetles survived are mostly blue. Again the beetle population slowly increases. But in the beetle population most of them are in blue colour.

Thus sometimes accidents may also result in changes in certain characters of the population. Characters as we know are governed by genes. Thus there is change in the frequency of genes in small populations. This is known as “Genetic drift’, which provides diversity in the population.

Let us think of another situation :
Situation-3: In this case beetles population is increasing, but suddenly bushes were affected by a plant disease in which leaf material were destroyed or in which leaves are affected by this beetles got less food material.
So beetles are poorly nourished. So the weight of beetles decrease but no changes take place in their genetic material (DNA). After a few years the plant disease are eliminated. Bushes are healthy with plenty of leaves.

What do you think will be condition of the beetles?
Answer:
The weight of beetles will increase once again as they get plenty of food material again.

Activity – 6

Let us observe different stages of development of vertebrate embryos. Try to find out similarities and differences and discuss with your friends.
(OR)
What do you infer about the embroyological evidences of various organisms?
Answer:

  1. There are remarkable similarities in the embryos of different animals from fish to man.
  2. The resemblance is so close at an early stage.
  3. Gradually the similarities are decreased when they become babies.
  4. The embryological evidences give us an idea that all the organisms have evolved from a common ancestors.

AP Board Textbook Solutions PDF for Class 10th Biology


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