Lakhmir Singh Class 10 Biology 4th Chapter Heredity And Evolution Solution

Lakhmir Singh Class 10 Biology 4th Chapter Heredity And Evolution Solution

Lakhmir Singh Manjit Kaur Biology Solution: Heredity And Evolution Chapter 4. Here you get easy Solutions of Lakhmir Singh Class 10 Biology Solution Chapter 4. Here we have given Chapter 4 all Solution of Class 10. Its help you to complete your homework.

  • Board – CBSE
  • Text Book – Biology
  • Class – 10
  • Chapter – 04

Lakhmir Singh Class 10 Biology 4th Chapter Solution

Very Short Answer Type Question

 1.) Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings?

ANS-Sex cells involve in sexual reproduction brings about maximum variation in the offspring hence sexual reproduction which shows variation.

2.) Name one variation in humans connected with ears.

ANS- Free Earlobes makes variation in human connected to ears.

3.) What constitutes the link between one generation and the next?

ANS-The heredity information is present in the sex cells or gametes, thus gametes constitute the link between one generation to the next generation.

4.) If the trait A exists in 10% of a population of an asexually reproducing species and a trait B exits in 60% of the same population, which trait is likely to have arisen earlier?

ANS- Trait B exist in 60% as shown above hence it arisen earlier.

5.) Mendel said that the characteristics or traits of organisms are carried from one generation to the next by internal factors which occur in pairs. What is the modern name for these factors?

ANS-Genes are the heredity unit which carried character from one generation to the next by internal factor which always works in pairs.

6.) Some plants occur in one of the two sizes: tall or dwarf. This characteristic is controlled by one pair of genes. Tallness is dominant to dwarfness. Choose suitable letters for this gene pair.

ANS- T represents Tall character which is dominating genes, hence all character of these genes control by T genes. t shows dwarf character in these gene so the combination of both genes get Tt gene where T controls character.

7.) What are the chromosomes XY and XX known as?

ANS-Chromosomes XY present in male gender and chromosome XX shows female gender hence both chromosomes know as sex chromosomes.

8.) Which two, sperm or ovum, decides the sex of a child?

ANS- Ovum is a female sex cell which contain XX chromosome where as sperm is male sex cell containing XY chromosome. X&Y is different than each other hence whenever they passes to next generation decides gender of the child that is the main reason sperm decides sex of child.

9.) State whether the following statement is true or false:

The sex of an infant is not a case of inheritance of characteristics.

ANS-False

10.) A new born child has an XY pair of chromosomes. Will it be baby boy or a baby girl?

ANS- Chromosomes XY present in male gender hence new born child has an XY pair of chromosome will be baby boy.

11.) Which of the following combinations of sex chromosomes produce a male child: XX or XY?

ANS- XY chromosome represent male child.

12.) Name the first scientist who studied the inheritance of traits from one generation to the next.

ANS- Gregor Mendel is the first scientist who studied on inheritance of traits.

13.) What type of plants were used by Mendel for conducting his experiments on inheritance?

ANS- Mendel is the first scientist who did study on patterns of inheritants by using Pea plant.

14.) The gene for red hair is recessive to the gene for black hair. What will be the hair color of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father?

ANS- If we assume that r represent red hair which is recessive gene whereas B represent dominating gene with black hair hence the progeny born with black hair(because it is dominating gene).

15.) What are the four blood groups in humans?

ANS- A, B, AB, O is the main blood group found in humans.

16.) Name one reptile in each case where higher incubation temperature leads to the development of: (a) male progeny, (b) female progeny.

ANS- High incubation temperature lead to development of (a) male progeny – Lizard (b) Female progeny – Turtle.

17.) Fill in the following blanks with suitable words:

ANS- (a) Pairs

(b) Recessive, Dominant

(c) Free, attached

(d) 23,46

(e) Four

(f) Sex, Female, Male

Short Answer Type Questions

18.) Which of the following represent tall plants and which represent short plants ( or dwarf plants)?

(a) Tt.   (b) tt.    (c)  TT

ANS- (a)- T represents dominant gene and t is the recessive gene where T is controlled the character of progenyhence Tt plant is tall in nature.

(b) t represents recessive gene hencett plant is dwarf in nature.

(c) T represents dominant gene, hence TT plant is tall in nature.

19.) A man having blood group O marries a woman having blood group B and they have a daughter. What will be the blood group of the daughter?

ANS-

The blood group O is receives both gene that we called ii. Therefore, it has genotype of I and B blood group has Iᵇi.  hence the daughter has equal chances for blood type B and O.

20.) (a) name the scientist who gave the laws of inheritance.

 (b) name an animal in which individuals can change sex. What does this indicate?

ANS-(a) Gregor Mendel is the scientist who gave the laws of inheritance.

(b) In some animal sex determination is controlled by environment where some animal like Snail, can change their sex hence their sex is not determined genetically.

21.) Explain with an example how genes control the characteristics ( or traits).

ANS- Definition of gene- Gene is basic unit if heredity which transfer characteristics from parent to their offspring during reproduction.

1) Gene is always work in pair, generally the character which inherited in progeny that was coming from dominant gene for ex. The gene for tallness is represented by the letter T whereas the gene for dwarfness is represented by the letter t. The letter T and t actual represents two forms of the same gene.

2) Gene is the section of DNA on chromosome which shows the formation of protein controlling a specific character of organism. Suppose a plant progeny has gene for green color and if that gene is dominating then it instructs to plant cell to make lot of plant with green in color.

3) Character of gene cross over during sexual reproduction which is always transmit with the help of chromosome. Character of genes is usually representing in the term genotype

Example- If we take green pea with genotype GG, Gg and yellow pea with genotype gg. Progeny of these above genotypes shown below.

In above diagram G is representing dominating gene character that is green and g is representing recessive character that is yellow. Whereas G gene combines with g which hides g characters such a way we conclude that genes is always control characters.

22.) (a) State one advantage of variation to a species.

(b) What are sex chromosomes?  How many sex chromosomes and there? Name them.

ANS- (a) Sexual reproduction shows maximum variation then asexual reproduction. During cell division DNA get multiplies and make many copies. In asexual reproduction slight variation seen in new DNA copies but in sexual reproduction more change seen in DNA copies which responsible for variation.

Advantage-  1.) Due to variation, found in different characters of organisms can born (which are comes under the same species) with much tolerance against trans environment so the survival rate of species get enhance.

2.) Species with variation adapts environment change can help to sustain species life ultimately species does not come under endangered or extent species.

(b) Sex chromosomes means the chromosomes which represent sex of the individual. For example, XY is the male sex chromosomes and XX is a female sex chromosome so basically X and Y is the sex chromosomes.

23.) Explain how sex is determined in human babies.

1.) The process by which the sex of person is determined is called sex determination. A male has one X chromosomes and one Y chromosomes and female have X chromosome these means male gametes or half the sperms will have X chromosomes and others have Y chromosomes.

2.) Whenever female chromosomes and male chromosomes cross over that time the gender of progeny depends on male sex chromosomes. Male father passes either X or Y to the next progeny which is shown below

Above image shows that male sex chromosome secretes X chromosome to the next generation so zygote get X chromosomes from male father and X chromosomes from female mother. So zygote is born with XX chromosomes which is female child.

Above image shows that male sex chromosome secretes Y chromosome to the next generation so zygote get Y chromosomes from male father and X chromosomes from female mother. So zygote is born with XY chromosomes which is male child.

24.) What do the following symbols used in the topic on heredity represent?

 (a) TT.        (b) tt.      (c). XX.     (d)XY

ANS- Capital letters generally used for dominant character and small letters used for recessive character hence (a) TT used for tall character (b) tt used for dwarf character.

XX and XY are sex chromosomes hence (c) XX is female sex chromosomes (d) XY is male sex chromosome.

25.) (a) what will you get in the

 F1 and F2 generations in the following cross?

Pure tall pea plant x pure dwarf pea  plant

(b) is it an example of monohybrid cross or dihybrid cross?

ANS- (a) Pure tall plant represent TT genotype and pure dwarf plant represent tt genotype if they cross their gene then we get all tall plant in F1 generation.

In below diagram we cross F2 generation genotype where tall plant represent Tt. After crossing tall plants gene we get three tall plant and one dwarf plant in F2 generation.

In below figure 1:3 ratio represents phenotype it means three tall one dwarf.

(b) Above example contain one phenotype character hence it shows mono hybrid cross .Example- Pure tall plant cross with pure dwarf plant

26.) In in the F2 generation of across progeny having different traits are produced in the ratio 3:1 . State whether it is a monohybrid cross or dihybrid cross? Give one example of such a cross.

ANS- If we cross two individuals with their single character then we get 3:1 ratio in their F2 generation. Hence it is called monohybrid cross. Example- if we cross pure tall plant’s with pure dwarf plant then all progeny will be tall (Tt) in F1 generation. And when it further cross with each other in F2 generation then we found 3:1 ratio means 3 tall plants and one dwarf plant.

27.) (a) What is the genotype of dwarf plants which always produced dwarf offspring?

(b) What is the genotype of tall plants which always produced tall offspring?

 (c) What is the genotype of (i) dwarf  plants and (ii) tall plants whose parent cross always produces tall offspring?

ANS- From the above question we assume that T is gene of tall plant which we consider as dominant gene whereas t is a dwarf plant which we consider as recessive gene so, (a) If offspring is dwarf then genotype of offspring should be tt. (b) TT is genotype of tall pants which always produce tall offspring because it is dominant gene.

(c)

(i) dwarf plant-tt (ii) TT

28) (a) If a normal human cell has 46 chromosomes, how many chromosomes will be there in a human (i) sperm cell and (ii) zygote?

(b) What sizes of plants are produced in both parents have genes Tt?

ANS- (a) Normal human cell contain 46 chromosomes but due to meiotic division sex cell of human being contain half of the chromosomes. It means ova and sperm contain 23 chromosomes.

i) Sperm cell is sex cell of male gender hence it contain 23 chromosomes.

ii) During sexual reproduction in human being sperm cell combines with ova where sperm cell carry 23 chromosome and ova carries 23 chromosome. Hence when zygote is originate that time it born with 46 chromosomes.(23 Male + 23 Female )

(b)

If parents are with Tt gene which crosses their gene for next generation that time we get three tall plant Tt, Tt, TT and one dwarf planttt.

29.) In human, how many chromosomes are present in:

(a) a brain cell?

(b) a sperm in the testes?

(c) an egg which has just been produced by the ovary?

 (d) a skin cell?

 (e) fertilize egg?

ANS- (a) Brain cell contain 46 chromosome.

(b) Sperm is the male sex cell due to meiotic division it converts into haploid cell hence it carries 23 chromosomes.

(c) Egg is female se cell which produce by ovary after meiotic division therefore egg carries 23 chromosomes.

(d)  46 chromosomes present in skin cells.

(e) When sperm is contacted with egg that time egg gets fertilized hence it shows 46 chromosomes (23 from sperm + 23 from egg).

30.) Gregor Mendel’s first law of genetics states “Of a pair of contrasted characters, only one can be represented in a gamete by its internal ‘factor’.

(a) Give the loser name for this ‘factor’.

 (b) State where these factors are found in gametes.

ANS-(a) A pair of contrasted character which can be represented in gamete by its internal factors which is now known as Genes.

(b) Genes is the section of DNA which is found on chromosomes in gamete.

31.) Does genetic combination of mother play a significant role in determining the sex of a new born baby?

ANS- Mother carry XX pair of chromosome whereas father carries XY pair of chromosome so, mother can be produced only X chromosomes in next generation but father have two different chromosome which able to produce either X as well Y chromosome in next generation that is the main reason gender of new born baby is determine by the secretion of male chromosome so, it is purely depend on father chromosomes hence mother cannot determine the sex of new born baby.

32.) Give the contrasting traits of the following characters in pea plants and mention which is dominant and which is recessive:

(a) Yellow seed.   (b) Round seed

ANS- (a) Yellow is dominant gene and green is recessive hence Yellow seed get due to yellow is dominant over green.

(b) Round is dominant gene and wrinkled is recessive gene hence round seed get due to round is dominant over wrinkle.

Long Answer Type Questions

33.) (a) What is meant by ‘heredity’? What are the units of heredity?

(b) State Mendel’s first law of inheritance.

ANS- (a) (i) Heredity means the transmission of character from the one generation to the next generation here two parents get involved in sexual reproduction where the two different sex cells fuse together by forming zygote. The heredity information is present these sex cells of the parents. Hence gamete shows link between one generation to the next generation that is the main reason offspring is born with paternal and maternal character which we called heredity.

(ii) The particular type of hereditary character present in smallest unit called gene. Gene is always staying in pair which shows genotype of species.

(b) According to Mendel’s first law of inheritance the characteristic of an organism is determined by the pair of factors, only one pair of factors can be present in single gamete. It is also known as Law of segregation for Example- Pure tall Pea plant has two factors TT which shows tallness of plant whereas pure dwarf plant shows two factor tt for their dwarfness.

If we apply first Mendel law to this example then TT gets separate or segregate for the transmission of character to progeny. TT gets segregate as T and T and tt factors segregate as t and t.

34.) (a) Why did Mendel choose pea plants for considering his experiments on inheritance?

(b) State Mendel’s second law of inheritance.

ANS- (a) Mendel was the first scientist to make schematic study of pattern of inheritance which involved the transfer of characteristics from parent to progeny.

For that he studied inheritance of pea plant because pea plant has clear cut differences. For ex- (a) Pea plant is tall (long stem) (b) dwarf pea plant (short stem).

Pea plant production done in short time span. Hence many more observation found for study of inheritance.

It cannot choose animal species because study of plea plant is much simpler.

(b) Mendel’s first law unable to justify dihybrid cross hence he formulated second law of inheritance which is called Law of Independent Assorted. According to Mendel’s law of inheritance: of more than one pair of traits in cross simultaneously, the factors responsible for each pair of traits are distributed independently to the gametes.

35.) (a) What do you understand by the term ‘variation’?

(b) Name two human traits which show variation.

ANS- (a) Variation –

(i) In sexual reproduction DNA get replicate and multiply in daughter cell where some differences occur in DNA copying hence the individual grow from that daughter cell is different than parent. The differences found in character between the parent and offspring is called variation which is happened in same species.

ii) Due to variation any species, easily able to survive hence it cannot extinct in future. Example- In 19s London experiences pollution which shows affect on living species. Due to pollution plant become dark. The white moth which living on trees get easily captured by predators because they are in white color and their background is dark due to pollution. That is the main reason in 19s white moth started to extinct but after many years they adapt environment and they seems like grey. In these above case DNA of white moth get changed and shows variations hence color of white moth converts into grey.

(b) The differences in character of human being can easily seen by physical appearances. For example- (i) Difference in human height, some peoples are very tall some peoples are very less tall.

(ii) Another example of variation in human being seen in lowest part of our ear which we generally call earlobe in most of the people earlobe is hanging in some people earlobe is closely attached to the side of head. These two variation mostly found in human being.

36.) (a) What are genes? Where are they located in our body?

(b) What is meant by dominant genes and recessive genes? Give one example of each.

 (c) Explain how, characteristic (or traits) are inherited through genes.

ANS- (a) Gene- Gene is the basic unit of heredity which transfer character from parent to offspring’s during reproduction or we say a gene is a unit of DNA on a chromosome which synthesis protein and control particular character in the organism. Gene is present on DNA thread.

Location of Gene- Every single cell has one controlling cell organelle called as Nucleus. Nucleus contain Nucleic material called chromosomes. Chromosome is thread like structure which is made up of DNA. And Gene is a smallest part of DNA or chromosome.

(b) Gene controlling character which present in organism. Two type of gene passes character from parent to offspring these two types of gene known as dominant gene and recessive gene.

(i) Dominant Gene- The gene which decide the appearance of organism even in the presence of alternative gene is known as dominant gene. Dominant gene is always represent in capital letter for example- One plant has two character tall and dwarf where tall is dominant gene then its denotation should be capital letter (T-Tall).

(ii) The gene which can show its own appearance only in presence of its identical gene is called as recessive Gene. Recessive gene is always represented in small letter for Example- One plant has two character tall and dwarf where dwarf is recessive gene then its denotation should be Small letter(t-Dwarf).

(c) (i) Genes are responsible for characteristics feature present in organism. The characteristics of parent are transmitted to their progeny through gene present on their chromosome during the process of sexual reproduction. Every character is shown by gene which is always in two form like dominant character and recessive character.

(ii) In sexual reproduction two parents takes part for produce sex cell where chromosomes are present. Each parent possesses a pair of gene on chromosome. Parent only give one gene from the pair to the next generation. When male gamete fuses with female gamete by forming zygote.

(iii) Zygote shows  only those physical and genetical appearances that coming from dominant gene of parent.

Example-

In above diagram T is for tall plant and small t is for dwarf plant. We cross Both hybrid species which made by Tt. Whenever T gene  found which hides other gene character. Tt is always shows tall nature because T is dominant in nature.

37.) (a) How do Mendel’s experiments show that traits may be dominant or recessive?

 (b) How do Mendel’s experiments show that traits are inherited independently?

ANS- a) Mendel’s is the first scientist who study of patterns of inheritance which involved the transfer of characteristics from parents to progeny. For that study Mendel choose the pea plant which is more convenient plant for study by the many aspects.

i) In this experiment Mendel’s study, the monohybrid inheritance and the law of segregation: for that he chooses pure bred pea plant differing in these traits. He crossed pure bred tall plant and pure-bred dwarf plant where it gets F1 generation.

Conclusion-From the above cross he concludes that F1 cross showed the traits of only one of the parent plants that is tall character. Other dwarf plant cannot show its character in progeny.

(b) Then Mendel’s further choose the F1 species and crosses them. Mendel’s got all Tt tall plant in F1 generation. When he further crosses those Tt plant to each other then he gets F2 generation with 3:1 phenotype ratio ( three tall plant and one dwarf plant) and 1:2:1 genotype ratio ( Tt Tt TT tt)

Conclusion- from the above diagram in F2 generation T and t is independently inherited. tt shows its own character in pea plant even it is recessive gene it inherited independently.

Very Short Answer Type Questions

1.) What name is given to the sequence of gradual changes over millions of years in which new species are produced?

ANS- Organisms experiences gradual changes in body and habitat over millions of years and forms new species is called evolution.

2.) Name the scientist who gave the theory of evolution.

ANS- Charles Robert Darwin gave the theory of evolution which was wrote in their book ‘the origin of species’.

3.) State whether the following statement is true or false:

Human beings have evolved from chimpanzees.

ANS- False

4.) State one characteristic which shows that the birds are very closely related to dinosaurs.

ANS- birds has wings like structure and also dinosaur’s fossils both found with feather it may be ancestral link that shows they are closely related to each other.

5.) Name an animal having rudimentary eyes.

ANS-A flatworm (planaria) has rudimentary eye.

6.) Name the ancestor of the following:

Brocolli, Kohlrabi, Kale

ANS- Brocolli, Kohlrabi, Kale is originated from ancestor wild cabbage, in this case evolution done by artificial selection.

7.) Where did life originate on earth?

ANS-According theoretical consideration earth is originated from sea water because first primitive cell is born from the water.

8.) Write the names of at least three inorganic molecules which helped in the origin of life on the earth.

ANS-Early earth atmosphere which was suppose to consist of gaseous like methane, ammonia, and hydrogen sulphate etc. These are inorganic molecule.

9.)  Name the famous book written by Charles Robert Darwin.

ANS- Charles Robert Darwin gave the theory of evolution which was wrote in their book ‘the origin of species’.

10.) The forelimbs of a frog, a bird and man show the same basic design (or basic structure) of bones. What name is given to such organs?

Ans-. The forelimbs of a frog, a bird have same basic bone structure but its function is different hence that organ is comes under homologues organ.

11.) Name two organisms which are now extinct and studied from their fossil.

ANS- Dinosaurs, Fern type leaf, Archaeopteryx, Ammonite are extinct organism which fossils are found.

12.) Out of the wing of a bird, wing of an insect and the wing of bat:

(a) which two are homologous organs?

(b) which two are analogous organs?

ANS- (a) 1. Forelimb of humans, frog ,lizards are homologous organ.

2.) forelimb of bird and bat are homologous organ

(b) wing of insects and wing of birds are analogous organ.

13.) Why are human beings who look so different from each other in terms of size, color and looks said to belong to the same species?

ANS- human beings who look so different from each other in terms of size, color and looks because human beings are reproduce sexually, hence there were we found variation in character where it can inter breed that is why coming progeny is born with more different appearances.

14.) Name five varieties of vegetables which have been produced from wild cabbage by the process of artificial selection.

ANS- Cabbage, Broccoli, Cauliflower, Kohlrabi and Kale are produces from wild cabbage by the process of artificial selection.

15.) Choose the one term from the following which includes the other three:

brocolli, wild cabbage, cauliflower, cabbage

ANS- wild cabbage is ancestor of broccoli, cauliflower and cabbage.

16.) Fill in the following blanks with suitable words:

ANS-

(a) Homologous: Analogous

(b) Stages

(c) Homo sapiens

(d) Wild Cabbage

(e) Darwin

Short Answer Type Questions

17.)  Match the terms given in column 1 with those given in column 2:

ANS-

(i) – (c) Petrified remains of prehistoric life

(ii) – (b) Survival of the forest

(iii) –(e) Archaeopteryx

(iv) –(a) A famous evolutionist

(v) – (d) Father of genetics

18.) What is meant by acquired and inherited traits? Explain with one example each.

ANS-Acquired traits-A trait or characters of an organisms which is not inherited but develops in response to the environment is called as acquired trait.

1.) It is habitat which acquire by organisms for living in environment those habits is not coming from parent.

Example- 1.) The cut tail of mouse is the acquired trait of mouse.

2.) Man acquire skill to swim in water

3.) Man acquire skill to speak French language or any other language

Inherited traits-A traits of an organisms which is caused by change in its genes (DNA) is called inherited traits.

1.) inherited traits can be passed on to the progeny of the organisms because they have originated from genes.

Example-1. Color of red beetle change into green because green color is inherited trait it is happened due to changes occurs in gene (DNA) of its reproductive cell.

2.) children’s of the same parents looks like different it is also genetic change occurs during reproduction.

19.) Why are the traits acquired during the lifetime of an individual not inherited?

ANS- 1.) Inherited trait means a trait of an organisms which is caused by change in its genes (DNA) it is happen when zygote is formed.

2.) But in case of acquired trait, the organisms are acquires some habits or traits as according to situation. those traits are not originated due to gene at sexual reproduction.  That is the main reason acquired traits are not found in or not pass into progeny.

3.) it may happen is that the progeny also acquires some different trait than parent for survival and life progress.

20.) Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?

ANS-  Homologous organ is that organ which having same structure but different functions. Butterfly and Bat uses their wing for fly but their structure of wing is very different than each other. Hence wing of butterfly and wing of bat not consider as homologous organ.

21.) Name two animals having homologous organs and two having analogous organs. Name these organs.

ANS- Homologous organs-1.Forelimb of humans, frog ,lizards are homologous organ.

2.) forelimb of bird and bat are homologous organ

Analogous organs- Wing of insects and wing of birds are analogous organ.

22.) What are fossils ? Giving one example, explain how fossils provide evidence for evolution.

ANS- Fossils- Fossils is the remaining or impressions of dead organism that lived in past are known as fossils. Examples- Fossil of ammonite, Fossil of dinosaur skull, Fossil of dead ferns, Fossil of Archaeopteris.

1.) The fossils provide evidences for evolution.

2) Fossils provide the evidences that the present animals have originated from the previously existing ones through the process of evolution.

3) For Example Archaeopteris looks like a bird but it has many other features which is found like reptiles. a) Archaeopteryx has feather wings like bird b) Archaeopteris has teeth and tail like retile.

4) Conclusion- Due to dual nature of Archaeopteryx we conclude that it may be connecting link between reptile and birds which is clarifies that the bird has evolved from the reptile.

23.) Give an example of characteristics being used to determine how close two species are in evolutionary terms.

ANS-1.) During reproduction cell division occurred that time DNA get copied to the divided cells which is further grow as individual. Those DNA change affect the characteristics of organism.

2.) The organism which present in same species have same DNA code hence they looks similar but during DNA copying some changes occurs. If that changes less or small then those two species is determined for their characters which we usually call homologous characters and if that change is large then evolution occurs.

3.) So the relative closeness of DNA of two species determine the how close two species are in evolutionary term.

24.) In what way are homologous organs evidence for evolution?

ANS-1. Homologous organs means the organ which have the same basic structure but different functions.

2.) So, the homologous organ shows the evolutionary link between different organism for example- Forelimb of human and forelimb of lizard is the example of homologous organ. They may originated from the same ancestor hence their forelimb organ is looks like same but due to evolution and for survival their function is different.

25.) Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?

ANS- 1.) Some species may completely die out or it comes under extinct species or endangered species for example-Dodo and Tiger.

2.) If the any species is getting extinct then their genes also extinct with them.

3.) Causes if Tiger get extinct- (i) Gene of Tiger is completely disappear from the fauna.

(ii) Next generation will be might be completely unaware for tigers.

(iii) Tiger is major animal of the ecosystem hence if it will extinct in future then whole ecosystem get affected.

26.) Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Give reason for your answer.

ANS- 1. Asexual reproduction occurs due to one parent. Whereas sexual reproduction happen with the help of two different parents.

2.) The geographical isolation leads to reproductive isolation due to which there is no flow of gene between separate group of population. If the speciation done in any species then geographical isolation affects on the flow of gene between isolated population or speciation that is only happen in sexual reproduction. Hence geographical isolation cannot be a major factor in speciation of an Asexual reproducing organism because asexual reproduction requires only one parent.

27) Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.

ANS- For tracing evolutionary relationship human being used various tools 1. Excavating

2.) Carbon dating

3.) Studying Fossils

4.) Determining DNA sequence.

28.) Out of bacteria, spider, fish and chimpanzee , which organism have a better body design in evolutionary terms? Give reason for your answer.

ANS- When earth is originating that time, before the human being born primitive cell were born. After many years that primitive cell get evolved more and higher organisms also born. For example, human being. So from bacteria, spider, fish and chimpanzee single celled bacteria is made evolution in future. So, bacteria is the organism which body design is favorable for evolutionary change.

29.) With the help of an example, explain how variation leads to evolution.

ANS-

1.) Variations-the organisms which shows sexual reproduction can experiences variation. Because during sexual reproduction or cell division DNA get copied and that time some codes of DNA change where the variation occurs.

2.) evolution is gradual change in organisms where the physical as well as genetical change also happened. Physical appearance are depends on genetics of parents as well environment hence variation and evolution are both terms are inter related to each other.

3.) evolution occurs after the variation happens in species.

4.) for example-1. When earth is originating that time, before the human being born primitive cell were born. After many genetical changes means variations occurs in that primitive cells and many lower organisms developed. Further those organisms get evolved according to environmental change and genetical change results many higher organisms get born including human being.

2.) chimpanzees are evolved such way that at last human beings are originate. Change is happened due 1) some variations in gene

2) some change in habits according to environment.

30.) (a) What is meant by a species? Give two examples of plant species and two of animals.

 (b) State the various factors which could lead to the formation of new species.

ANS-(a) definition of species-A species is a population of plants and animals which are similar individuals where they did interbreed and produces their next progeny.

Example- 1. Animals-human, tiger, dog, cat, homo sapience comes under one species where it interbreeds and form daughter and sons

2.) plants-wheat, paddy, sunflower, lotus, mango

(b) speciation is the evolutionary change process where the new species is born from existing species. When any species get separate and lived with different group and different environment then adopt this culture and evolved as new species.

Factors effects on speciation-

1.) Geographical isolation-when any group of species grow in different environment which we called geographically isolation. The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.

2.) genetic drift- it is the drastic changes in the frequencies of particular genes Which happen by chance.

3.) Variations happened in individual’s speciesbecause they change their habits, appearance response to nature which we called natural selection.

31.) What evidence do we have for the origin of life from inorganic matter (lifeless matter)?

ANS- For checking of evidences of origin of life from inorganic matter Stanley L. Miller and Harold C. Urey made one experiment in 1953.

They set a experiment which was may be previously happened by many years ago

PROCEDURE-

Step 1. They assembled an apparatus to create an early earth atmosphere which was supposed to consist of gases like ammonia, methane and hydrogen sulphide, but no oxygen) over water.

2.) maintained temperature in assembly at below 100C

3.) electric sparks were passed through the mixture of gases to stimulate lightning.

OBSERVATION- At the end of a week, they found that 15% of the carbon (from methane) had been converted to simple compounds of carbon including amino acids which make up protein molecules.

CONCLUSION- According to this experiment they conclude that when life was originated that time protein molecule were first form.

32.) Does geographical isolation of individuals of a species lead to the formation of a new species? Provide with suitable explanation for your answer.

ANS-Yes, Geographical isolation of individual of species leads to the formation of new species.

Reason- 1. In these isolation species get isolated in the particular geographical environment where the gene flow in their species getting cutoff.

2.) The groups which lived under the particular area is acquires some changes and habits in response to environment. Those changes inherits two next generation for its own survival where the variation happens. Due to the variation happened in each generation, leads to birth of new species.

33.) Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria? Explain your answer.

ANS- According to study of origin of earth and organism, primitive cells were developed first due to mixing of inorganic molecule . Primitive cells have been progressively evolved and convert into multiple cells forming organisms which is further evolved into higher organisms having proper organ system.

Example- Primitive cells to human being

1) Bacteria is single cell organism which does not have proper DNA function. According to theory of origin of earth it less evolves by inner body structure but it is shows good response towards harsh conditions.

2) Human being is multicellular organism which evolved more than bacteria by internally because it have proper cell, organ and organ system.

But, according to habits it cannot lived in harsh condition.

Long Answer Type Questions

34.) (a) Name the scientist who gave the theory of origin of life on earth. What is this theory?

(b) How are those species which are now extinct studied?

ANS-(a)

1) the theory of origin of life proposed by Halden.

2) According to his theory, origin of life is started from inorganic molecule like methane, ammonia, hydrogen sulphide etc.. after many years some chemical reactions occurs and inorganic molecule developed. Those simple inorganic molecules convert into complex organic molecule. Whenever these two molecules joined together then first primitive cell born.

(b) Species which are extinct by many years ago those studied by using their fossils were they found in the earth by digging. For Example- Fossils of ammonite, fossils of dyno sour skull found in soil which can studied by carbon dating method.

35.) What do you understand by the term evolution? State Darwin’s theory of evolution.

ANS- Evolution is gradual change happened in species from pre-existing organism it is slow and steady process if these evolutionary change happens in living organism then its called organic evolution.

Charles Robert Darwin gave theory of evolution in his famous book. The origin of species and he put forth theory of evolution proposed by Darwin is known as the theory of natural selection. Darwin theory of evolution can be described as follows-

1) Darwin describe that in any population we found natural variation. Some individuals are more favorable then others.

2) Even though all species produce a large no. of offspring population remain fairly constant naturally.

3) This is due to the struggle between members of the same species and different species for food and space.

4) The struggle for survival within population eliminates the unfit individual. The fit individual possessing favorable variation survive and reproduce. This is called Natural Selection.

5) The individuals having favorable variations pass on these variation to their progeny from generation to generation.

6) These variation when accumulated over a long period of time lead to the origin of new species.

36.) (a) Explain the terms analogous organs and homologous organs with examples.

(b) In what way are analogous organs evidence for evolution?

ANS- (a) Definition of Homologous organ- The organs which have same basic structure but different functions are called homologous organ

Example-1. Forelimb of humans, frog ,lizards are homologous organ.

2.) forelimb of bird and bat are homologous organ

Definition of Analogous organ- The organs which have different basic structure but have same function are called analogous organ.

Example- Wing of insects and wing of birds are analogous organ.

(b) Analogous organ mean the organism having different structural organ but these organ does same function such type of organ is known analogous of organ.

For Example- Wing of insect and bird have different structure. Wing of insect consist by fold membrane and few muscles. But the wing of bird consist of feather, flesh and Skelton.

1.) Birds and insects have different structure of wing hence here it proves that they both are born by different ancestor.

2.)  the presence of analogous organisms shows evolution where we say that even the organisms with different structural organ they are adopt same similar function.

3.) due to analogous organs different animals provide evidence of evolution by showing giving us information about they are not born by same ancestor.

37.) (a) Define speciation. Explain how specification occurs.

(b) Will geographical isolation be a major factor in the specification of a self pollinating plant species? Give reason for your answer.

ANS-(a) 1. a species is the group of population of organism which made up of similar individual , can breed together and produce fertile offspring.

2.) speciation is the process which always seen in particular type of species.

3.) definition of speciation-it is process by which new species developed from the existing species known as speciation.

4.) new species formed when same species get splits into separate and they isolate from each other by geographically.

(b) In self pollinating species, pollen grain is transfer from anther to the stigma of same flower, hence if it can geographically isolate then also its gene pool and reproduction cannot stop because they did not depend on other species for reproduction that is the main reason geographically isolation cannot affect in the speciation of self-pollinating plant.

38.) (a) Define natural selection.

(b) “Only variations that consider an advantage to an individual organism will survive in a population.” Do you agree with this statement ? Give reason for your answer.

ANS-(a) Definition of natural selection- natural selection is the process of evolution where the particular character of species helps to survive and that character passes to that offspring is called natural selection.

Example- One theory is put forth by scientist based on natural selection in many years ago dinosaurs and short trees of fern get destroyed. Those ferns are the food of giraffe. So, they were die due to starvation, that time only tall plant are alive with green leaves so giraffe tried to grab those leaves for food hence their neck became long.

(b) variation- In sexual reproduction DNA get replicate and multiply in daughter cell where some differences occur in DNA copying hence the individual grow from that daughter cell is different than parent. The differences found in character between the parent and offspring is called variation which is happened in same species.

1.) variation creates difference in individuals hence both individuals from same species are looks different.

2.)  variation happens due to the genetical change and which is depends on environment as well habits of species

For example- 1. In 19s London experiences pollution which shows affect on living species. Due to pollution plant become dark. The white moth which living on trees get easily captured by predators because they are in white color and their background is dark due to pollution. That is the main reason in 19s white moth started to extinct but after many years they adapt environment and they seems like grey. In these above case DNA of white moth get changed and shows variations hence color of white moth converts into grey.

Variation is the process which survives organisms in  very harsh conditions.

Lakhmir Singh Manjit Kaur Class 10 Biology Solution


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