TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Telangana SCERT 10th Class Biology Study Material Telangana 8th Lesson Heredity and Evolution Textbook Questions and Answers.

TS 10th Class Biology 8th Lesson Questions and Answers Telangana – Heredity and Evolution

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

  • Differences in characters within very closely related groups of organisms are referred to as variations.
  • Variations develop during reproduction in organisms.
  • Sexual reproduction and errors in DNA copying leads to variations in offsprings in a population.
  • Variations are passed from parent to offspring through heredity.
  • Thus the variations accumulate over the generations.
  • Beneficial variations are selected by the nature in evolution.
  • These variations increase the survival chance of the organisms.
  • These variations help the organisms to adopt to their environments.
  • 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.
  • Accumulated variations gradually lead to evolution.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 2.
One student (researcher) wants to cross pure tall plant(TT) with pure dwarf(tt) plant, what would be the F1 and F2 generations? Explain.
Answer:

  • When a pure tall plant (TT) is crossed with pure dwarf plant (tt), all the offsprings in F1 generation are tall.
  • Pure tall plant has both the factors of the same type ‘TT’.
  • Pure dwarf plant has both the factors of the same type ‘tt’.
  • The breed after cross pollination will have one of the factors from pure breed tall (TT) and one from pure breed dwarf (tt).
  • Thus all the plants will have the factor pair “Tt”.
  • So all the plants are heterozygous tall, as ‘T’ is the dominating factor.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 1

  • On self-pollination of these, the new breed can have any combination of T and t.
  • It can be TT, Tt, tT or tt. All of them are equal.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 3

  • But any plant that has a T factor will be tail.
  • So in F2 generation 75% of plants are tall and 25% of plants are dwarf. Thus the phenotype ratio is 3: 1.
  • Among 75% of tall plants, only 25% plants are pure tall (TT) or homozygous tall, remaining 50% plants are heterozygous tall (Tt, tT).
  • The remaining 25% dwarf plants are pure or homozygous dwarf (tt).
  • So the genotype ratio is 1: 2: 1.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

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:

  • If the tails of parent rats were cut, their offsprings will have normal tails.
  • This is because the bodily changes which may occur due to environment won’t be passed to its offspring.
  • Cutting of tail will not change the DNA of the germ cells, it is a bodily change. Therefore loss of tail is not a trait that can be inherited by progeny of tailless rats.
  • Augustus Weisemann did this experiment on rats to test the theory of “Inheritance of acquired characters” proposed by Lamarck.
  • He removed tails of parental rats.
  • He observed its offsprings which have normal tails.
  • He has done it again for twenty two generations but offsprings are with normal tails.
  • Thus he proved that the bodily changes which may occur due to environment won’t be passed to its offspring.

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 pest free. Is it possible to create new mango tree which the farmer wants? Can you explain how it is possible?
Answer:

  • It is possible to create new mango tree which one the farmer wanted with full of mango fruits and pest free.
  • It is possible if he crosses a mango tree with full of mango fruits and pests with another mango tree without pests but with less mango fruits.
  •  In F1 generation, he can get plants with full of mango fruits and without pests. Such plants are called hybrid plants.
  • They can be self pollinated and desired plants can be selected from the mixed population of F2 generation.
  • Otherwise, they can be vegetatively propagated to get these plants in a large number.

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

  • Cross pollinating a pure breed of tall (TT) and dwarf (tt) plants gave, F1 generation in which all the plants are heterozygous tall.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 4

  • These plants on self pollination gave F2 generation in which 75% of plants are tall and 25% of plants are dwarf.
  • Out of 75% tall plants 25% of plants are homozygous tall (TT) and remaining 50% are heterozygous tall (Tt, tT).
  • The remaining 25% dwarf plants are homozygous dwarf (tt).

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 5

  • So the phenotype ratio in F, generation is 3: 1, whereas genotype ratio is 1: 2: 1.
  • These plants on self pollination gave F3 generation, where a set of 25% tall plants gave only tall plants, rest of the tall plants gave 75% tall and 25% dwarf plants and a set of dwarf plants gave only dwarf plants.
  • With this experiment we can understand two laws of inheritance. One is law of dominance and the second one is law of segregation.
  • As only one trait is expressed in the offsprings of first generation crosses, we can assume that, among a pair of alleles for a character, only one expresses itself in the first generation one of the allele is dominant over the other. This is what Mendet called law of Dominance.
  • The law of segregation states that every individual possesses a pair of alleles for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

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, the factors for each pair of characters assorts independently of the other pairs. This is known as “Law of independent assortment”.

2. When we cross two sets of ‘pure’ pea plants, one with yellow seeds with smooth skin and second is green seeds with wrinkled cover, in the F1 generation, we will get the seeds which are yellow and smooth. Each pea will now have factors YyRr.
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 6

3. On self pollination of these seeds we will get some seeds smooth yellow (YyRr or YYRR), some seeds smooth and green (yyRR or yyRr), some seeds were wrinkled and yellow (Yyrr or Yyrr) and some seeds were wrinkled and green (yyrr).

4. In the above, dihybrid cross parents produced offspring containing the actors of characters of yellow (YY), round (RR), and wrinkled (rr), green (yy) appeared independently mixing with each other in F generation.

5. RRYY, RRYy, RrYY, Rr Yy, RRYy, RrYY, RrYy, RrYy and RrYy are round and yellow.

6. RRyy, Rryy, Rryy are round and green.

7. rrYy, rrYy, rrYY are wrinkled and yellow.

8. rryy are wrinkled and green.

9. From the above results it can be concluded that the factors for each character or trait remains separate and maintains its identity in the gametes.

10. The factors are independent to each other passes to its offspring. This shows the “Law of independent assortment”.

Question 7.
Explain the Darwin’s theory of evolution ‘Natural selection’ with an example?
Answer:

  • Darwin proposed the theory of “Natural selection”, means nature only selects or decides which organism should survive or perish in nature.
  • The organisms with useful traits will survive, and the organisms having harmful traits are going to be perished or eliminated from its environment.
  • Let us consider group of beetles that live in bushes on green leaves.
  • Their population will grow by sexual reproduction. So they generate variations in their population.
  • Let us assume crows eat these red beetles. if the crows eat more red beetles their population slowly reduces.
  • Let us consider one colour variation arises during reproduction so that there is a beetle that is green in colour instead of red.
  • Moreover this green colour beetle passes its colour to its offspring, 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 of beetle “green” gave a survival advantage to “green beetles” than red beetles. In other words it was naturally selected.

Question 8.
What are variations? Explain with a suitable example.
Answer:

  • Differences in characters within very closely related groups of organisms are referred to as variations.
  • Often a new character in a group may lead to variations that are inherited.
  • If we observe parents and offsprings, there will be some similar features in the offspring of the parents.
  • At the same time we find differences between parents and offspring in their features.
  • These differences are an example of variations.
  • Variations are quite apparent among closely related groups of organisms.
  • If we take roses as an another example, we observe number of varieties in them.
  • But we can still find some characters similar to all plants.
  • 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.
  • These differences in features are variations.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 9.
What variations generally have you observed in the species of cow?
Answer:
In the species of cow the following contrasting variations can be observed:

  • White coloured — spotted
  • Long horns — short horns
  • Height (tall) — dwarf
  • Long tail — short tail
  • Elongated face — stunted face
  • More milk giving — less milk giving, etc.

Question 10.
What are the characters Mendel selected for his experiments on pea plant’?
Answer:
Mendel selected the following seven characters for his experiments on pea plant:

  • Flower colour — Purple and White
  • Flower position — Axil and Terminal
  • Seed colour — Yellow and Green
  • Seed shape — Round and Wrinkled
  • Pod shape — Inflated and Constricted
  • Pod colour — Green and Yellow
  • Stem length — Tall and Dwarf

Question 11.
In what way Mendel used the word ‘Traits’- explain with an example.
Answer:

  • Trait is a separate variant of an organism.
  • Mendel hypothesized that characters were carried as traits.’
  • An organism always carried a pair of factors for a character.
  • He also hypothesized that distinguishing traits of the same character were present in the population of an organism.
  • He assumed that the traits shown by the pea plants must be in the seeds that produce them.
  • The seeds must have obtained these traits from the parent plants.
  • The factors which are responsible for character or trait of an organism, are now named as “genes”.
  • 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.
  • For example, height is a character of pea plant while the tallness is a trait expressed by a pair of factors either vr or Tt and dwarfness is another trait expressed by a pair of factors tt.

Question 12.
What differences Mendel identified 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.

 

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 13.
Male is responsible for sex determination of baby – do you agree? If so write your answer with a flow chari
Answer:
I agree with the statement that male is responsible for sex determination of baby.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 16

  • There are two types of sex chromosomes in human beings, one is ‘X’ and other is ‘Y’.
  • Females have two ‘X’ chromosomes in their cells (XX) whereas males have one ‘X’ and one ‘Y’ chromosomes in their cells (XY).
  • All the gametes produced by woman (ovum) will be with only X chromosomes.
  • The gametes produced by man (sperm) will be of two types one with X chromosomes and other Y chromosomes.
  • If the sperm carries X chromosome and fertilizes the ovum, the resultant baby will have XX condition. So the baby will be a gril.
  • II the sperm carries Y chromosome and fertilizes the ovuni, the resultant baby will have XY condition. So the baby will be a boy.
  • So the gamete produced by the male is the deciding factor for sex determination of the baby.

Question 14.
Write a brief note on analogous organs.
Answer:

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

Question 15.
How do scientists utilise the information about fossils?
Answer:

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

Question 16.
Mendel selected a pea plant for his experiments. Mention the reasons in your point of view.
Answer:
Mendel selected pea plant for his experiments because

  • Pea plants have short life cycle, they reproduce fast and mature right away.
  • They exhibit seven pairs of contrasting characters which are easily recognizable such as smooth or wrinkled seeds, short or tall, height, etc.
  • Hybrids and their offspring are fertile, that is continuous cross and self fertilizations were possible.
  • They are highly naturally self pollinated because the reproductive parts of the flower are covered by the keel (petals) which only opens after pollination has been completed.
  • Although the cross pollination methods are somewhat complicated, the results are largely successful.
  • These plants are easy to grow either on the ground or its pots.
  • These plants have short maturity and can produce large number of seeds in a single generation.

Question 17.
If the theory of inheritance of acquired characters proposed by Lamark was true how will the world be?
Answer:
If the theory of inheritance of acquired characters proposed by Lamarck was correct.

  • All the organisms which lost some of their body parts should give birth to the offsprings without the lost parts.
  • Rat which lost their tail should give birth to tail less rats.
  • A handicapped who lost their legs in an accident should give birth to babies without legs.
  • Women having holes in ears, should give birth to babies with holes in their ears.
  • A body builder’s children should be body builders.
  • But all these are not happening because bodily changes won’t be passed to its offspring.

Question 18.
Collect information on the inherited traits in your family members and write a note on it.
Answer:

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

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 19.
Observe flowering plants in your surroundings? Write similarties and differences between them?
Answer:
The flowering plants in my surroundings are sun flower and Dandelion.
Similarites:

Sun flower Dandelion
1. Growing conditions of sunlight

2. Best time to plant

3. Kingdom

4. Subkingdom

5. Division

6. Order

7. Class

8. Family

Full sun

Spring

Plantae

Trac heobionta

Magnoliophyta

Asterales

Magnoliopsida

Asteraceae

Full sun

Spring

Plantae

Tracheobionta

Magnollophyta

Asterales

Magnoliopsida

Asteraceae

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 8

Question 20.
With the help of given information write your corninent on evidences of evolution. Mammals have four 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:

  • The given information gives the evidences of evolution.
  • Mammals, birds, reptiles and amphibians all these have forelimbs which have similar basic structure.
  • But they are modified to perform different functions.
  • The internal structure of forelimb of mammals such as whale, bat, horse, mole and man have common pattern in the arrangement of bones, even though their external form and functions are different.
  • It 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.
  • In case of bat (mammal) and bird the designs of the two wings, their structure and components are different.
  • They look similar because they have common use for flying, but their origins are not common.
  • These organs which are structurally different but functionally similar are known as ‘Analogous organs’. This type of evolution is called “convergent evolution”.
  • 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.
Answer:

  • Carbon dating is the method used to calculate the age of rocks, minerals or fossils.
  • 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.
  • Archaeologists use the exponential, radioactive decay of carbon 14 to estimate the death dates of organic material.
  • The earth’s atmosphere contains various isotopes of carbon, roughly in constant proportions.
  • These include the main stable isotope 12C and an unstable isotope 14C.
  • Through photosynthesis, plants absorb both forms from carbon dioxide in the atmosphere.
  • When an organism dies, it contains the standard ratio of 14C to D12C.
  • But as the 14C decays with no possibility of replenishment, the proportion of carbon 14 decreases at a known constant rate.
  • The time taken for it to reduce by half is known as the half-life of 14C, which is 5730.
  • The measurement of the remaining proportion of 14C in organic matter thus gives an estimation of its age.
  •  Formula to calculate how old a sample is by carbon – 14 dating is
    \(t=\left[\frac{I_n\left(\frac{N_f}{N_0}\right)}{-0.693}\right] \times t_{1 / 2}\)
    where I is the natural logarithm, is the percent of carbon – 14 in the sample. Compared to the amount in living tissue, – 0.693 is the rate of decay for C – 14, t1/2 is the half life of C – 14 (5,700 years).
  • As the half life of carbon-14 is 5,700 years, it is useful for dating objects up to about 60,000 years old.

Question 22.
Draw a checker board show the law of independent assortment with a flow chart and explain the ratio.
Answer:
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 10

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 7

  • The ratio is 9:3:3: 1.
  • RRYY, RRYy, RrYy, RrYy, RRYy, RrYy, RrYy, RrYY and RrYy are round and yellow. (9)
  • RRyy, Rryy, Rryy are round and green. (3)
  • rrYY, rrYy, rrYy are wrinkled and yellow. (3)
  • rryy are wrinkled and green. (1)

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 inheritance of more than one pair of characters the factors for each pair of characters assorts independently of the other pairs. This is known as “Law of independent assortment”.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

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

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 11

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 12

Question 24.
Prepare a flow chart showing evolution of man through ages.
Answer:
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 13

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 25.
Nature selects only desirable characters. Prepare a cartoon.
Answer:
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 14

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

  • Nature favours only useful variations.
  • Each species tends to produce large number of offspring.
  • They compete with each other for food, space, mating and other species.
  • In this struggle for existence only the fittest can survive.
  • When cat tries to catch some rats, the rats which can run fast and hide in its hole card survive and which is slow can become prey for the cat. Same way in the forest those deers will survive which can run fast and escape from predators.
  • When we spray some insecticide on insects, most of them will die hut few which can withstand that chemical will escape.
  • When a pest attacks our garden plants. most of them may die but which can with stand the pest can survive.
  • 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 evolution of a man to perform a stage show on the theatre day in your school.
Answer:
Hai, I am human being. I am going to recall what had happened to me so far, how had evolved, simply my journey from my origIn to till now. Nearly 1.6 – 2.5 million years ago, during the gelasian pleistocene period, I used to wander in the forest, It is believed that, I evolved from apes, Then I was short and had disproportionately long arms like this.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 15

I used tools made of stone flakes. I was not the master hunter and I had a less specialized diet. I used to communicate through glusters. 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 believed that I travelled over oceans using rafts.

There was some possible evidence for that I had used fire. But my food was mostly raw meat and nuts, berries, fruits without cooking. Then I was not capable of producing sounds comparable to modern human speech. So I used to communicate through proto-language.

Around 1,00,000 – 40,000 thousand years ago I evolved into Homo sapiens neanderthalensis. I was stronger than present in those days. I was known for my large cranial capacity. I made advanced tools. I had language to communicate, and lived in complex social groups. I built my dwellings using animal bones.

I was largely carnivore and apex predator but I had cooked vegetables also in my diet. My genes then matched nearly. At this stage I was more closely related to modern human being differing in DNA by only 0.15%. Around 10 thousand years ago, I reached the present form of human being, the modern humans known as homosapiens. I learnt cultivation, Construction of houses, cooking, etc.

I had invented various things that help me to live comfortably. I civilised and learnt leading a social life with family system. With the help of my wisdom, I had reached the top most position among the all living beings controlling the total biosphere. Certain activities of mine are causing great harm to the nature also. But till today, I am the master of the world.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

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 characters or traits 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. Humans have ……………. pairs of autosomes and …………….. pair of sex chromosomes.
7. The population grows in …………. progression whereas food sources grow in …………… progression.
8. A goat which can’t walk 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:

Question 1.
Which of the following is not a variation in rose plant?
A. Coloured petals
B. Spines
C. Tendrils
D. Leaf margin
Answer:
C. Tendrils

Question 2.
According to Mendel, alleles have the following character.
A. Pair of genes
B. Responsible for character
C. Production of Gametes
D. Recessive factors
Answer:
A. Pair of genes

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 3.
Natural selection means
A. Nature selects desirable characters
B. Nature rejects undesirable characters
C. Nature reacts with an organism
D. A, B
Answer:
D. A, B

Question 4.
Palaeoutologists deal with ………..
A. Embryological evidences
B. Fossil evidences
C. Vestigial organ evidences
D. All
Answer:
B. Fossil evidences

TS 10th Class Biology 8th Lesson Heredity and Evolution Intext Questions

1 Mark Question and Answers :

Question 1.
What will happen if the sperm containing X chromosomes fertilizes the ovum?
Answer:

  • All the ovum produced by women have only X chromosomes.
  • So if the sperm containing X chromosomes fertilizes the ovum, the baby will have XX condition.
  • So the baby will be a girl.

Question 2.
Were all your traits similar to that of your parents?
Answer:

  • No, all my traits are not similar to my parents.
  • There are certain traits which differ from my parents.
  • This is due to genetical recombination during reproduction.

Question 3.
Does the embryological evidences indicate that frogs have evolved from ancestors of lslz?
Answer:

  • Tadpole of frog resembles more the fish than the frog.
  • It indicates that frogs have evolved from fish ancestors.

Question 4.
Does the life history of every individual exhibit the structural features of its ancestors?
Answer:

  • There are remarkable similarities in the embryos of different animals from fish to man.
  • The resemblance is so close at an early stage.
  • This indicates that every individual exhibits the structural features of its ancestors.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

2 Mark Question and Answers :

Question 1.
Is variation all about apparent differences ? or is it about some subtle differences as well that we most often overlook?
Answer:

  • Variations are no4 always apparent differences.
  • Sometimes these may be subtle differences that we most often overlook.
  • When these subtle differences accumulate together they may become apparent.

Question 2.
How do parent plants pass on their traits to the seeds?
Answer:

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

Question 3.
Will the seeds from tall plants always produce new tall plants?
Answer:

  • No. Tall plants may or may nut produce tail plants again.
  • ibis is because tallness Is a dominant character in most of the plants especially in peas.
  • So tail plant may be homozygous tall (iT) or heterozygous tall (TI).
  • If the parental plant Is homozygous tall (pure breed), then they always produce new tall plants.
  • If the parental plant Is heterozygoux tall plant, then they produce the tail and dwarf plants In the ratio of 3 1.

Question 4.
Who decides the sex of the baby – mother or father?
Answer:

  • Sex determination of the baby depends on the sex chromosome carried by the sperm, as the ovum always carries X chromosome only.
  • If the sperm with X chromosome fuses with ovum, the baby will have XX condition. So ‘he baby will be a girl.
  • If the sperm with Y chromosome fuses with ovum, the baby will have XY condition. So the baby will be a boy.
  • So the sperms that come from father decides the sex of the baby.
  • In fact It is by mere chance and the chance for any sex formation is 50% as the male produces both sperms with X spernis with Y are produced in saine number.

Question 5.
How does the evolution of organisms take place7
Answer:

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

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Question 6.
Think why ancient human beings travelled from one place to other and how they travelled.
Answer:

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

4 Mark Question and Answers :

Question 1.
How does evolution take place?
Answer:

  • Evolution takes place through the accumulation of new characters or variations in a species of organisms.
  • 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.
  • So this happens over a long period of time, sometimes several generations may pass.
  • Hence it happens in a slow and steady manner.
  • It is not just about change but producing something new and different.
  • It is about the formation of new species and their adaptation to their environments.

Question 2.
Is the sex also a character or trait ? Does it follow Mendel’s law of dominance?
Answer:

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

Question 3.
Are birds and bats more closely related to each other than to squirrels or lizards?
Answer:

  • No, bats are mammals whereas birds belong to aves.
  • Squirrels are mammals and lizards are reptiles.
  • So bats are more closely related to squirrels and lizards than birds.
  • But bats and birds resemble more as they have wings.
  • These wings are structurally different but functionally similar formed to have a common use of flying.
  • But their origin is not common, so not closely related.
  • These type of organs are called Analogous organs.
  • This type of evolution is called Convergent evolution.

TS 10th Class Biology 8th Lesson Heredity and Evolution Activities

Activity – 1.

Think of your own family, what simüa rifles do you share with your father and mother?
OR
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.
Compare your traits with the traits of your parents, brother, sister and grandparents by drawing a table as gwen below In your note book.
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 17
Answer:
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 18

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Q. Is there any character in you similar to that of your mother as well as your grandma?
Answer:
3 Characters:

  • Colour of eye (Iris)
  • Colour of hair
  • Type of earlobe

Q. Is there any character in you similar only to that of your grandma?
Answer:
2 Characters:

  • Shape of face
  • Inner thumb marking

Q. How do you think these characters may have been inherited by you from grandma?
Answer:
Passing of characters or traits from parent to child.

Q. Is there any character that is not present in grandma but present in your mother and you ?
Answer:
2 Characters:

  • Shape of nose
  • Type of hair

Q. 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.
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 19
Answer:
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 20

A. 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.

B. 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.

C. Do you think that your differences from parents are more or less than 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 genera lisation.

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

B. What makes them vary?
Answer:

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

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

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

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Activity – 4.

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

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 21

Method: Prepare a chart with 2 x 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 4 strips (2 long and 2 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 n 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.

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

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

C. What is the number of short strip pairs?
A. There are four short strip pairs.

D. What. is the percentage of each type ?Also find their ratios.
A. 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.

E. Whatcan you conclude fromthis game?
Aswer:
From this game I have concluded that:

  • Every individual possesses a pair of alleles, for any particular trait.
  • Each parent passes a randomly selected copy (allele) of these to an offspring.
  • The offspring then receives its own pair of alleles for that trait one each from both parents.
  • 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.
  • The genotype ratio is 1: 2: 1.

Activity – 5.

Observe the below diagram showing variation in beetle population and its impact.
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 24
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 3 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.
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 25

Moreover this green coloured beetle passes it’s colour to it’s 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 numher.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 beetle can lass its colour to its progeny. So that all its progeny are blue.
TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 26

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 rio 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.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution

Let us think of another situation:

Situation-3 : In this case beetles population is increasing, hut 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.

TS 10th Class Biology Study Material 8th Lesson Heredity and Evolution 27

Let us observe different stages of development of vertebrate embryos. Try to find out similarities and differences and discuss with your friends.
Answer:

  • There are remarkable similarities in the embryos of different animals from fish to man.
  • The resemblance is so close at an early stage.
  • Gradually the similarities are decreased when they become babies.

Activity – 6.

Let us observe different stages of development of vertebrate embryos. Try to find out similarities and differences and discuss with your friends. (iMà
Answer:

  • There are remarkable similarities in the embryos of different animals from fish to man.
  • The resemblance ¡s so close at an early stage.
  • Gradually the similarities are decreased when they become babies.

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