ts scert 10th class Biology Lesson 8 Heredity and Evolution

Chapters

Solutions
Important Question
Question Papers / Notes Download
Videos

Solutions

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

Improve your learning

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
Variations are passed from parent to offspring through heredity
Beneficial variations are selected by the nature in evolution
Variations increase the survival chance of the organisms
These variations help the organisms to adapt 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
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:

Pure tall plant has both the factors of the same type TT
Pure dwarf plant has both the factors of the same type tt
When a pure tall plant (TT) is crossed with pure dwarf plant (tt), all the offsprings in Fj generation are tall (Tt)
So all the plants are heterozygous tall, as T is the dominating factor

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.
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 25% are pure tall (TT) or homozygous tall, remaining 50% are heterozygous tall (Tt, tT)
The remaining 25% dwarf plants are pure or homozygous dwarf (tt)
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:

If the tails of parent rats were cut, their offsprings will have normal tails
Daughter rats do not contain tails because the bodily changes are not inherited
So the change would not be passed to their offsprings
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:

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

We can understand the law of inheritance with an example of monohybrid cross between pure yellow pea seeds with pure green pea seeds
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
During reproduction one factor (genes) from each parent is taken to form a new pair in the progeny (off spring)
In F1 generation all pea plants are Yellow.
F1 generation pea plants are self pollinated
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

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".

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:

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"
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
This implies that round and yellow seeds are dominant characters over green and wrinkled seeds
In F2 progeny there would be some plants with round and yellow seeds and some with green and wrinkled seeds
However, there would be some plants with mixed characters - yellow and wrinkled seeds and green and round seeds
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

The different combination of characters resulted from dihybrid cross
RRYY, RRYy, RrYy, RrYY, RRYy, RrYy, RrYy, RrYY, RrYy are having round and yellow seeds
RRyy, Rryy, Rryy have round and green seeds
rrYy, rrYy, rrYY have wrinkled and yellow seeds
rryy have wrinkled and green seeds
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?

Answer:

Each human cell contains 23 pairs (46) of chromosomes
Out of 23 pairs, 22 pairs of chromosomes are called autosomes
Remaining one pair is called allosomes or sex chromosomes
There are two types of sex chromosomes - one is X and the other is Y
These two chromosomes determine the sex of an individual
Females have two X chromosomes in their cells (XX)
Males have one X and one Y chromosomes in their cells (XY)

All the gametes produced by women (ovum) will be with only X chromosomes
The gametes produced by man (sperm) will be of two types, one with X chromosomes and other with Y chromosomes
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
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 Darwins theory of Natural selection with an example?

Answer:

Darwin proposed the theory of Natural selection
Nature only selects or decides which organism should survive or perish in nature
The organism with useful traits will survive and the organisms having harmful traits are going to perished or eliminated from its environment
For example, a group of twelve red beetles live in a bush of green leaves
They will grow their population by sexual reproduction
So they generate variations in their population. Let us assume crows eat the red beetles more the population of red beetles slowly reduced
Crows eat these red beetles and their population slowly reduces
During this time a colour variation arises by the sexual reproduction
So that there appears one beetle that is green in colour instead of red
Moreover this green colour beetle passes its colour to its offsprings; 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
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
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:

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

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:

White coloured - spotted
Longhorns - short horns
Height - dwarf
Long-tail - short tail
Elongated face - stunted fac
More milk giving - less milk giving, etc

Question 11. What are the characters that Mendel selected for his experiments on pea plants?

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:

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 the 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 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:

Yes, I agree with the statement that male is responsible for sex determination of baby
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 carrying X chromosome fertilizes the ovum, the resultant baby will have XX condition. So the baby will be a girl
If the sperm carrying Y chromosome fertilizes the ovum, 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 15. 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 is the example 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 16. How do scientists utilise 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 Palaeontology
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 earths past

Question 17. Mendel selected a pea plant for his experiments. Mention the reasons for the selection as these plants?

Answer: Mendel chose the pea plant (Pisum sativam) for his breeding experiments for the following reasons

It is sexually reproducing
Flowers are bisexual
Predominantly self-pollinated
Predominantly self-fertilization
Well developed characters
Early hybridization
It is an annual plant
These plants have short maturity and can produce large number of seeds in a single generation
Pea plants have short life cycle
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

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 v without legs
A body builders children should be body builders
But all these are not happening because bodily changes wont be passed to its offspring

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

Answer:

My grandfather and father- had curling hair. I too have curling hair. So its an inherited trait in family
My mother and I both have long noses which appear similar. Its another inherited trait
Eyes of my grandmother, my brother and mine are similar. Its another inherited trait
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?

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
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
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 earths atmosphere contains various isotopes of carbon, roughly in constant proportions
These include the main stable isotope 12C and an unstable istope 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 12C
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 an estimation of its age
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:

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
RRYY, RRYy, RrYy, RrYy, RRYy, RrYy, RrYy, RrYY and RrYy are round and yellow seeds
RRyy, Rryy, Rryy are round and green
rrYY, rrYy, rrYy are wrinkled and yellow
rryy are wrinkled and green

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:

Nature favours only useful variations
Each species tends to produce a 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 can survive and which is slow can become prey for the cat
When we spray some insecticide on insects, most of them will die but few which can withstand that chemical will escape
When a pest attacks our garden plants, most of them may die but Which can withstand 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 the evolution of a human to perform a stage show on the theatre day in your school?

Answer:

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
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
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
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
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
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

Fill in the blanks?

The process of acquiring change is called ----
Mendels experiment explains about ----
The four characters observed in the experiments on law of independent assortment are ----
If we cross pollinate red flower plant with white flower we will get percent of ---- recessive trait plants
TT or YY, Tt or Yy are responsible for a ---- character
Female baby having 23 pairs of autosomes at the age of 18 years, has ---- pair autosomes and ---- of sex chromosomes
The population grows in ---- progression whereas food sources grow in ---- progression
A goat which walks properly cant live for a long time. According to Darwin, this represents ----
Forelimb of whale is for swimming whereas in horse it is used for ----
The study of fossils is called ----

Answer:

evolution
heredity
Round, wrinkled, yellow, green
100
dominant
22, one pair
geometrical, arithmetic
survival of the fittest
running
palaeontology

Which of the following is not a variation in rose plant? [ ] ?

Coloured petals
Spines
Tendrils
Leaf margin

Answer: C 2.

According to Mendel, alleles are [ ] ?

Pair of genes , Responsible for character
gene
Production of Gametes
Recessive factors

Answer: B 3.

Natural selection means [ ] ?

Nature selects desirable characters
Nature rejects undesirable characters
Nature reacts with an organism
A, B

Answer: A 4.

Palaeontologists deal with [ ] ?

Fossilised Embryological evidences
Fossil evidences
Fossilised Vestigial organ evidences
All

Answer: D

10th Class Biology 8th Lesson Heredity InText Questions 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 kirig 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 variation all about apparent differences? Or is it about some subtle differences as well that we most often overlook?

Answer:

Variations are not 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 3. 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 factor or each trait will pass to the gametes
By the fussion 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 4. Will the seeds from tall plants always produce new tall plants?

Answer:

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

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:

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
Round and yellow
Round and green and
Wrinkled and green iv) Wrinkled and yellow
They will produce in the ratio of 9 : 3 : 3 : 1 respectively
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

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

Answer:

If the sperm containing X chromosomes fertilizes the ovum which has X chromosome, the baby will have XX condition
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:

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 dominent XY) and female (homozygous recessive XX) only
As X is not exhibiting its nature when Y is present along with it. it follows Mendels law of dominance

Question 9. 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

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

Answer:

Variations which are beneficial are selected by nature and passed from parents to offspring through heredity
The same process happens with every new generation until the variation becomes common feature
As the environment changes, the organism within environment adopts and changes to the new living conditions
Over a long period of time, each species of organisms can acuumulate so many changes that it becomes a new species
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:

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

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:

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

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

Answer:

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
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

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:

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

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?

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

Answer:

Characters	In me	In my Mother/Father	In my Brother/Sister	In my grandma/grandpa
1	Colour of eye	Black	Black	Black
2	Colour of hair	Black	Black	Black	Black
3	Shape of nose	Long	Long	Short	Short
4	Shape of nose	Oval	Round	Ovel	Round
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

Colour of eye
Colour of hair
Type of earlobe and
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

Shape of face and
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

Shape of nose
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

Observe some of your friends and note their characters in the following table. Fill in yours as well?

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
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

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:

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

3. Why variations are 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

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

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

Observe the below diagram showing variation in beetle population and its impact?

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 togreen 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 redcolour 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

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
The embryological evidences give us an idea that all the organisms have evolved from a common ancestors

Important Question

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

1 Mark Questions:

Question 1.
When cross is done between pure yellow and pure green pea seed-producing plants the following results were obtained. (Y = yellow ; y = green)?

Answer: Answer the

Questions given below based on the above table.

Questioni.
Yy - indicates which colour of the seed?

Answer: Yy - indicates the Yellow colour of the seed

Questionii.
What is the Phenotypic ratio of the above cross?

Answer: Phenotypic ratio of the above cross is 3: 1

Question 2.
Observe the given How-chart and answer the

Question. Who decides the sex of the baby - mother or father? How?

Answer: Father decides the sex of the baby. Mother has XX chromosomes. Father has XY chromosomes. Y chromosome is determining factor. So father is responsible

Question 3.
What examples will you give to prove that Lamarcklsm is not correct?

Answer: Augustus Weismann, tested the theory proposed by Lamarck by experiments on rats. He removed tails of parental rats. He observed for twenty two generations but still off springs are normal with tails

Question 4.
Which chromosomes determine the sex in human beings?

Answer: Allosomes or Sex chromosomes. They are XX (girls) and XY (boys)

Question 5.
Why do we call appendix as a vestigial organ?

Answer:

Vestigial organ is the organ of our body which is smaller and simpler than those in related species they have lost their original function
Appendix is highly developed in ruminants which helps in the digestion of cellulose. But, in human beings the cellulose is eliminated as undigested food. Hence in human beings appendix has no role in cellulose digestion. So, we call it as a vestigial organ

Question 6.
What are variations?

Answer: Differences in characters within very closely related groups of organisms are referred to as "variations"

Question 7.
What is F1 generation?

Answer: F1 generation or first filial stands for offsprings of first generation parents

Question 8.
What is F2 generation?

Answer: F2 generation is the offsprings produced either by self hybridization or inbreeding from F1 individuals

Question 9.
What is F3 generation?

Answer: F3 generation represents the offsprings produced from the individuals of F2 generation

Question 10.
What is phenotyperatio?

Answer: The characters which can be seen is known as phenotype and their ratio is called "phenotype ratio". The phenotype ratio in F2 generation of monohybrid cross is 3: 1

Question 11.
What is genotype ratio?

Answer: The genetic makeup of an individual with reference to a specific character under consideration is called genotype and their ratio is called "genotype ratio". It indicates the internal factors. The genotype ratio in F2 generation of monohybrid cross is 1: 2: 1

Question 12.
State the law of Independent assortment?

Answer: In the inheritance of more than one pair of characters (traits), the factors for each pair of characters assort independently of the other pairs. This is known as law of independent assortment

Question 13.
What is allele?

Answer: The pair of genes which are responsible for character is called "allele"

Question 14.
Whatare genes?

Answer: Genes are the factors which are responsible for character or trait of an organism. These are the units of heredity that is transferred from a parent to offspring. These are the segments of nucleic acid called DNA which is present in the nucleus of every cell

Question 15.
What are homozygous alleles?

Answer: Homozygous alleles are the same alleles. Either both dominant are both recessive. Ex : TT, tt

Question 16.
What is heterozygous allele?

Answer: Heterozygous allele is that which has both dominant and recessive genes. Ex : Tt

Question 17.
What is law of dominance?

Answer: According to Mendel, among a pair of alleles for a character, only one expresses itself in the first generation as one of the allele is dominant over the other. This is known as law of dominance

Question 18.
State the law of segregation?

Answer: 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 of only one of these to its offspring

Question 19.
What are inherited traits?

Answer: The characters which pass from parents to children or from one generation to next generations are called "Inherited Traits" or "Inherited Characters"

Question 20.
What is heredity?

Answer: The process of acquiring characters or traits from parents is called "Heredity"

Question 21.
What is Inheritance?

Answer: The process in which traits are passed from one generation to another generation is called "Inheritance"

Question 22.
What are autosomes?

Answer: Chromosomes whose number and morphology do not differ between males and females of a species are called autosomes

Question 23.
What are allosomes?

Answer: Sex determining chromosomes are called allosomes or sex chromosomes. in humans there is a pair of allosomes. There are two types of allosomes in human, one is X and second one is Y

Question 24.
What are acquired characters?

Answer: Characters that are developed during the lifetime of an organism are called "acquired characters"

Question 25.
What is inheritance of acquired characters?

Answer: Lamarck proposed that the acquired characters are passed to its offspring. i.e. to next generation. This Is known as "Inheritance of acquired characters". For example elongation of neck and forelimbs in giraffe

Question 26.
What is meant by survival of the fittest?

Answer: Nature favours only useful variations. Each species tend 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. This is called survival of the fittest

Question 27.
What is micro evolution?

Answer: Small changes within the species is known as micro evolution

Question 28.
What is macro evolution or speclation?

Answer: The process of evolution through which new species are going to be formed is known as speciation or macro evolution

Question 29.
What are homologous organs?

Answer: Organs which have a common fundamental anatomical plan and similar embroyonic origin whatever varied functions they may perform are called homologous organs. Ex: Flippers of a whale, wing of a bat, forelimb of a horse, forelimb of human

Question 30.
What are analogous organs?

Answer: Analogous organs are those that perform similar functions but have entirely different embryonic origins. Ex : Wing of a bird and wing of a bat

Question 31.
What is embryology?

Answer: Embryology is the study of the development of an organism from egg to adult stage

Question 32.
What are fossils?

Answer: Fossils are evidence of ancient life forms or ancient habitats which have been preserved by natural processes

Question 33.
What is Palaeontology?

Answer: The study of fossil is called "Palaeontology"

Question 34.
What is the method used to determine the age of the fossil?

Answer: Carbon dating is the method used to determine the age of the fossil

Question 35.
What is human evolution?

Answer: Human evolution is the evolutionary process leading up to the appearance of modern human beings

Question 36.
How do variations occur?

Answer: Variations dey lop during reproduction In organisms. Sexual reproduction and errors in DNA copying lead to variations in offspring in a population

Question 37.
What is divergent evolution?

Answer: The evolutionary process through which homologous organs develop is called divergent evolution

Question 38.
What is convergent evolution?

Answer: The evolutionary process through which analogous organs develop is called convergent evolution

Question 39.
Where were the fossils of dinosaurs collected in our state from?

Answer: The fossils of dinosaurs and ketosaurs were collected from Yamanapalli in Adilabad district in Telangana state

Question 40.
What are vestigial organs?

Answer: Organs which are not useful in animal are called vestigial organs

Question 41.
Who was the first person to propose the theory of evolution?

Answer: Jean Baptist Lamarck was the first person to propose the theory of evolution

Question 42.
Who proposed the theory of Inheritance of acquired characters?

Answer: Jean Baptist Lamarck proposed the theory of Inheritance of acquired characters

Question 43.
Who proved that the bodily changes which may occur due to environment wont be passed to its offsprings?

Answer: Augustus Weismann proved that the bodily changes which may occur due to environment wont be passed to its offspring

Question 44.
Who proposed the theory of Natural selection?

Answer: Charles Darwin proposed the theory of Natural selection

Question 45.
What does the theory of Natural selection state?

Answer: The theory of Natural selection states that nature only selects which organism should survive or perish in nature. The organisms with useful traits will survive. The organisms having harmful traits are perished or eliminated from its environment

Question 46.
How many vestigial organs are there in human beings?

Answer: There are nearly 180 vestigial organs in human beings

Question 47.
Give some examples for vestigial organs in man?

Answer: Pinna, hair on skin, mammary glands in man, appendix, etc. are the examples for vestigial organs

Question 48.
Which organism is said to be a moving museum of vestigial organs?

Answer: Human being is said to be a moving museum of vestigial organs

Question 49.
How can one change adopted perform different functions?

Answer: The study of evolution reveals one change occurred initially is used to perform other function. For example initially feathers were evolved for warmth, later they were adapted for flight

Question 50.
Why are traits acquired during the lifetime of an individual not inherited?

Answer: Any change in somatic cells cannot be passed to DNA of germ cells. Hence these traits are not inheritable

Question 51.
What factors could lead to rise of a new species?

Answer:

Genetic variation
Natural selection
Genetic drift

Question 52.
Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?

Answer: No, though the function of wings in both the cases is same they are structurally different and their origin is also different. They are analogous organs

Question 53.
If the sperm bearing Y chromosome fertilizes the egg, the child born will not be entirely like his father, why is it so?

Answer: It is because the other sex chromosome, i.e. X- chromosome also has its effect on the fertilized egg

2 Mark Questions:

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 not 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 factor or each trait will pass to the gametes
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 not produce tall plants again
This is because tallness is a dominant character in most of the plants especially in peas
So tall plant may be homozygous tall (TT) or heterozygous tall (Tt)
If the parental plant is homozygous tall (pure breed), then they always produce new tall plants
If the parental plant is heterozygous tall plant, then they produce the tall 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 and sperms with Y are produced in same number

Question 5.
How does the evolution of organisms take place?

Answer:

Variations which are beneficial are selected by the nature and passed from parents to offspring through heredity
The same 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

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

Question 7.
Explain the theory of "inheritance of acquired characters" with an example?

Answer:

Jean Baptist Lamarck proposed the theory of inheritance of acquired characters
According to this theory the new character that are developed during the life time of an organism are passed to next generation
For example initially giraffee was equal to deer. Due to shortage of food materials and to reach the lower branches of tree giraffee started stretching its neck
Because of continuous stretchness of neck after several generations giraffee developed long neck
Such character that are developed during the life time of an organism are called acquired characters. These acquired characters are passed to next generation

Question 8.
Who decides the sex of the baby, mother or father Explain with a flow chart?

Answer: Father decides the sex of the baby. (Or) Draw a flow - chart showing the sex determination in human beings.

Question 9.
Define the terms phenotype and genotype?

Answer: Phenotype: The observable properties of an organism that are produced by the interaction of the genotype and the environment. These characters can be seen. Genotype : The genotype is the genetic make-up an individual usually with reference to a specific characteristic consideration

Question 10.
What

Questions you will ask a palaeontologist about fossils?

Answer:

What are fossils
How do they preserve
What can be the actual remains
How do they form
What do we call the study of fossil
Can you tell some examples of fossils
Flow do the palaeontologists determine the age of fossils
What are dinosaurs and ketosaurs ? In which years they belong
Where did they collect the fossil of dinosaurs ? What is the length of this fossil
Where did they preserve the fossil of dinosaurs

Question 11.
Observe the checker board and answer the following

Questions?

Write phenotypic ratio of monohybrid cross
How many heterozygous plants are present in the checker board

Answer:

Phenotypic ratio 3: 1
Two heterozygous plants

Question 12.
How does the embryological evidences support that Evolution has taken place?

Answer: Evidences:

Remarkable similarities in the Embryos of different animals from fish to man
Tadpole of frog resembles the fish more than the frog
Life history of every individual exhibits the structural features of their ancestors
The resemblance is so close at an early stage, it is difficult to distinguish one embryo from other

Question 13.
What happens if there is no evolution?

Answer:

Evolution is a continuous and comprehensive process
If it does not take place, there is no formation of new species
Variations do not take place and hence desirable traits are not developed
All the Earth would be with the primitive species without any changes

Question 14.
If you cross a plant with pure yellow seeds (YY) with a plant with pure green seeds (yy), what would be the colour of the seeds in F2 generation ? Show in a checker board?

Answer: All pea plants are yellow in F1 generation on self pollination in F1 generation In F2 generation, we can observe that 75% are yellow seed producing pea plants and 25% are green ones. Hence the phenotypic ratio is 3: 1 the genotypic ratio is 1: 2: 1

4 Mark Questions:

Question 1.
Explain sex determination in humans with the help of flow chart?

Answer:

Each human cell contains 23 pairs (46) of chromosomes
Out of 23 pairs, 22 pairs of chromosomes are called autosomes
Remaining one pair is called allosomes or sex chromosomes
There are two types of sex chromosomes - one is X and the other is Y
These two chromosomes determine the sex of an individual
Females have two X chromosomes in their cells (XX)
Males have one X and one Y chromosomes in their cells (XY)
All the gametes produced by women (ovum) will be with only X chromosomes
The gametes produced by man (sperm) will be of two types, one with X chromosomes and other with Y chromosomes
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
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 2.
What are Mendels laws of inheritance? What are the reasons to choose pea plant for his experiment?

Answer: Mendels Laws of inheritance

Law of Dominance : Among a pair of closely related alleles or factors, only one expresses itself. In the first generation as one of the allele is dominant over the other. This is called as Mendels Law of dominance
Law of Seggregation : The law of seggregation states that every individual possesses a pair of alleles for any particular trait that each parent posses a randomly selected copy only one of these to its off-spring
Law of Independent assortment: In the inheritance of more than one pair of characters (traits), the factors for each pair of characters assort independently of the other pairs. This is known as Law of Independent assortment

Mendel has chosen garden pea as material for his experiment because:

It has well developed characters
It is a bisexual flower
Predominently self pollinating
Suitable for cross pollination
It is an annual plant

Question 3. What is Phenotype and Genotype? Explain them with the help of Mendels Monohy brid cross?

Answer: Phenotype: Expression of visible character of an individual is called phenotype. Genotype: Genetic constitution of an individual for any character is called Genotype or Probable nature of factors is known as genotype. Cross Pollinating a pure breed of yellow coloured pea seeds (YY) and green coloured pea seeds (yy) give F1 generation. All pea seeds were yellow in F1 generation. So, yellow colour is phenotype. Yy is genotype of all pea seeds in F1 generation. F2 Generation: Self pollination of F1 pea plants Yy Phenotype Ratio is 3:1 Genotype Ratio is 1:2:1

Question 4.
Explain in brief any two evidences of Evolution?

Answer: Some of the evidences of evolution are

Homologous and analogous organs

Evidences from embryology and

Evidences from fossils

I. Homologous and analogous organs:

Organs which have common fundamental anatomical plan and similar embryonic origin, whatever varied functions they may perform are regarded as homologous organs

For example forelimb of a whale, wing of bat, leg of leopord, claw of mole and hand of man

They indicate that all the vertebrates are evolved from common ancestor

Organs which are structurally different but functionally similar are known as "Analogous organs"

For example wings of bats and wings of birds

The designs of the two wings, their structure and components are different but they look similar because they have a common use for flying but their origin is not common

II. Evidences from embryology:

There are remarkable similarities in the embryos of different animals from fish to man

The resemblance is so close that at an early stage even an experienced embryologist would find difficulty to distinguish one embryo from the other

This strengthens the view of the existence of a common ancestor from which all these have evolved

III. Evidences from fossils:

Fossils are evidences of ancient life forms or ancient habitats which have been
preserved by natural processes
Palaeontologists determine the age of fossils by using carbon dating method

These fossils provide evidences of presence of extinct animals like dinosaurs and how the evolution occurred on the earth, etc

Question 5.
Observe the given flow-chart and answer the following
Questions?

Questioni.
Name the chromosomes that determine the sex of an individual?

Answer: Y Chromosome of father

Questionii.
Show given Information in the form of Checker Board?

Answer:

Questioniii.
In this situation, which principle of Mendel Is applicable?

Answer: Law of dominance

Questioniv.
"Mother determines the sex of the baby". Is this statement correct or not? Why?

Answer: The statement is not correct. Because the sperm of father that carries Y chromosome fertilize with ovum of mother that contains X chromosome the resultant will be XY - Male baby
I. Conceptual Understanding
Question 1.
Keep in mind Mendels experiments and write what you know about the following?

Pure breed

Phenotype

Genotype

Alleles

Answer:

Pure breed : These are such kind of plants that expresses a selected character, over several generations. Such plants according to Mendel were pure breed for that character

Phenotype: The characters which can be seen is known as phenotype. We cannot determine the internal factors by phenotype. It tells about only the dominating characters which express externally. The phenotype ratio in monohybrid cross is 3: 1

Genotype : The genetic make up of an individual is known as genotype. Genotype itself is the indication of internal factors. It tells about both dominant and recessive characters present within. The genotype ratio in monohybrid cross is 1: 2: 1

Alleles: Alleles are corresponding pairs of genes located at specific positions in chromosomes. Together they determine the genotype of their host organism. Every individual possesses a pair of alleles for any particular trait and that each parent passes a rondomly selected copy of only one of these to an offspring. The offspring then receive their own pair of alleles for that trait one each from both parents

Question 2.
What is natural selection? How does it direct the evolution ? Explain with an example?

Answer:

Natural selection states that 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 a group of red beetles which live in bushes on green leaves and grow by sexual reproduction

Let us assume crows eat these red beetles

Let us consider one colour variation arises during reproduction so that there is abeetle 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 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 by means of 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

Question 3.
What is genetic drift ? Explain how it provides diversity in the population?

Answer:

Changes in the frequency of genes in small populations, due to accidents is known as "Genetic drift"

Let us consider a colour variation occurred in red colour beetles which are living on green coloured leaves of bushes

It results in "blue" colour beetles instead of red colour beetles and passed its colour to its progeny

Initially in the population, there are 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 but by chance a 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 genetic drift provides diversity in the population

Question 4.
Write the main points in the Darwin theory of evolution in a nutshell?

Answer: Darwins theory of evolution in a nutshell

Any group of population of an organism contains variations and not all members of group are identical

Variations are passed from parent to offspring through heredity

The natural selection over abundance of offspring leads to a constant struggle for their survival in any population

Individual organisms with variations that help them to survive and reproduce tend to live longer and have more offsprings than organisms with less useful features

The offsprings of survivors inherit the useful variations, and the same process happens with every new generation until the variation becomes a common feature

As the environment changes, the organism within the environment adapts and changes to the new living conditions

Over a long period of time, each species of organism can accumulate so many changes that it becomes a new species, similar to, but distinctly different from the original species. All species on the earth arise in this way

Evolution is a slow and continuous process

Question 5.
How are new species evolved?

Answer:

Sexual reproduction and errors in DNA copying leads to variations in offspring in a population

Organisms contain variations that help to adapt to its environment going to be survived more efficiently

But in the same population, the organisms which contain the trait which may not help to adopt in its environment may be perished or eliminated slowly

These small changes within the population due to variations is called micro evolution

When organisms of the same species with variations are separated by some cause for long years, lot of variations may take place in these years

These accumulated variations make them unable to mate and produce new offsprings

Thus new species form and this is known as speciation or macro evolution

Question 6.
What are fossils ? Write a short note on their formation?

Answer:

Fossils are evidence of ancient life forms or ancient habitats which have been preserved by flatural processes

Fossil evidence is typically preserved within sediments deposited beneath water and land

II. Asking Questions And Making Hypothesis
Question 1.
What is meant by law of dominance ? To know more about law of dominance, what kind of
Questions will you ask?

Answer:

Out of a pair of contrasting characters present together only one is able to express itself while the other remain suppressed is known as law of dominance

I will ask following
Questions to know more about law of

dominance:

Who proposed law of dominance

Which plant Mendel took for his experiments

Why he (Mendel) took pea plant for his experiments

How many contrasting characters he choose in pea plant

How can you correlate law of dominance in daily life situation

Tall / dwarf - which one is dominant character
(You can add some more
Questions related to concept )

Question 2.
What are the hypothesis assumptions and outcomes of Mendels experiments with pea plants?

Answer: Regarding his experiments with pea plants, Mendel hypothesised that

Characters were carried as traits and an organism always carried a pair of factors for a character

The distinguishing traits of the same charater were present in the population of an organism

The traits shown by the pea plants must be in the seeds that produced them

The seeds must have obtained by the traits from the parent plants

His assumptions made to explain his observations are: Assumption 1: Every pea plant has two factors which are responsible for producing a particular property or trait. Assumption 2: During reproduction one factor from each parent is taken to form a new pair in the progeny. Assumption 3: One of these will always dominate the other if mixed together
Laws made from his experiments:

Law of Dominance : Among a pair of alleles for a character, only one expresses itself in the first generation as one of the allele is dominant over the other

Law of Segregation : Every individual possesses a pair of alleles for any particular trait and that each parent passes a randomly selected copy of only one of these to its offspring

Law of Independent Assortment: In the inheritance of more than one pair of characters the factors for each pair of characters assorts independently of the other pairs

III. Experimentation And Field Investigation
Question 1.
The cross between Hybrid tall (Tt) and dwarf (tt), what will be F1 generation progency. Write phenotypic and genotypic ratio?

Answer: Phenotype ratio 1: 1 Genotype ratio 1: 1

Question 2.
What will be phenotypic and genotypic ratio if cross between pure Red (RR) and Hybrid Red (Rr)?

Answer: Parents are RR and Rr. Phenotypic ratio 2 : 0 Genotypic ratio 1: 1: 0
V. Communication Through Drawing, Model Making
Question 1.
Draw the diagram of monohybrid cross and explain it?

Answer: A cross-pollination between a pure breed of yellow seed bearing plant and green seed bearing plant gave the following results: First Filial / F1-generation : (Filial means progeny) All pea seeds were Yellow. On self-pollination of these pea plants the following results were obtained : All pea seeds were yellow

Second Filial / F2-generation : The F2 generation had about 75% of yellow seeded pea plants and 25% of green seeded pea plants, i.e. they appear in 3: 1 ratio

Adding to above results, Mendel made following observations:

A set of peas (about 25%) obtained in F2 generation are yellow seeded plants (Hornozygous dominant)

A Set of peas (about 50%) obtained in F2 generation are heterozygous yellow and give yellow and green seeds in 3:1 on self pollination

A set of peas (about 25%) obtained in F2 generation are green seeded. On self-pollination they keep producing green seeded plants (Homozygous recessive)

VI. Apprecition Andthetic Sense, Values
Question 1.
How will you appreciate Mendels work?

Answer:

Mendel laid foundation to hybrid varies in plants

Because his works and laws (Mendels laws) became guide to later generation scientist

So many plants with desirable characters created, which are helpful to mankind

His works help the scientist to find new varieties of species in animals

Ultimately more desirable plants and animals came into existence

Question 2.
How would you appreciate Gregor Johann Mendels contribution to the genetics?

Answer:

Gregor Johann Menclel worked on the problem of how variations were passed from one generation to the other

As he was a monk, he did his experiments with interest in the garden of the monastery

He worked for over seven years alter which he presented conclusions from his experimental data in a form of a detailed research paper

Mendel made many careful observations of pea plants and asked himself
Questions about what he observed and then planned and designed experiments to find the answers

He had worked on nearly 10,000 pea plants of 34 different varieties choosing 7 distinguishing forms of characters

His experimental outcomes gave the idea how the variations were passed on from one generation to another

He was an exemplary person for his observation, planning, patience and experimental skills

His efforts to know the secrets of nature was really appreciable

Question 3.
How would you appreciate Charles Robert Darwin for his work on evolution?

Answer:

Charles Darwin voyaged for five years, just when he was 22 years old

In the world survey ship H.M.S. Beagle, he visited number of places including Galapagos Islands

He keenly observed the flora and fauna of these places

He gathered a lot of information and evidences

He was influenced by the book "Principles of Geology" written by Sir Charles Lyell and "Maithus theory written in "An essay on the principles of population"

Darwin proposed the theory of "Natural selection", means nature only selects or decides which organism should survive or perish in nature

This theory remained a milestone in the studies of evolution

Everyone should appreciate him for his observations and analytical abilities which revealed the secret from where we come from

VII. Application To Daily Life, Concern To Biodiversity
Question 1.
Write a small essay supporting fila t genes are the cause to form to different characters in organisms?

Answer: A gene is the section of DNA on a chromosome which controlls a specific characteristic of the organism. A gene is a unit of DNA on a chromosome which governs the synthesis of one protein that controls a specific characteristic of an organism. There are thousands of genes on a chromosome which control various characteristics of an organism

Genes are actually units of heredity which transfer characteristics from parents to their offsprings (luring reproduction. Genes work in pairs. Genes controlling the same characteristics are given the same letters. For example the gene for tallness is represented by the latter T whereas the gene for dwarfness is represented by the letter t

Genes for controlling the same characteristics of an organism can be of two types dominant or recessive. The gene which decider the appearance of an organism even in the presence of an alternative gene is known as dominant gene. The gene which can decide the appearance of an organism only in the presence of another identical gene called recessive gene

Question 2.
Sujathas in-laws worried for having daughter in her second delivery. How will you make them agree that she is not all responsible for having daughter?

Answer:

Sujatha is not responsible for giving birth to female child. Men are responsible for the birth of male / female child

Each human cell contains 23 pairs of chromosomes. Out of 23 pairs, 22 pairs of chromosomes are autosomes

The remaining pair is called allosomes or sex chromosome. These are two types; one is X and the other is Y. These two chromosomes determine the sex of individual

Females have two X chromosomes in their cells (XX). Males have one X and one Y chromosome in their cells (XY)

All the gametes produced by woman have only X chromosomes. The gametes produced by a man are of two types one with X chromosome and other with Y chromosome

If the sperm carries Y chromosome and fertilizes the OVU (X chromosome). Then the baby will have XY condition. So the baby will be a boy

Question Papers / Notes Download

Videos

Heredity and Evolution

Improve your learning

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

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?

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?

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

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

Question 7. How does sex determination take place in human?

Question 8. Explain Darwins theory of Natural selection with an example?

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

Question 10. What variations generally have you observed in the species of cow?

Question 11. What are the characters that Mendel selected for his experiments on pea plants?

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

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

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

Question 15. Write a brief note on analogous organs?

Question 16. How do scientists utilise information about fossils?

Question 17. Mendel selected a pea plant for his experiments. Mention the reasons for the selection as these plants?

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

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

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

Question 21. Collect information about carbon dating method. Discuss with your physical science teacher?

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

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

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

Question 25. Nature selects only desirable characters. Prepare a cartoon?

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

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

Fill in the blanks?

Which of the following is not a variation in rose plant? [ ] ?

According to Mendel, alleles are [ ] ?

Natural selection means [ ] ?

Palaeontologists deal with [ ] ?

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

Question 1. How does evolution take place?

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

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

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

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?

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

Question 7. Who decides the sex of the baby - mother or father?

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

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

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

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

Question 12. Do 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?

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

Activity - 1

1. Is there any character in you similar to that of your mother as well as your grandma?

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

3. How do you think these characters may have been inherited by you from grandma?

4. Is there any character that is not present in grandma but present in your mother and you?

5. Think where from your mother got that character?

Observe some of your friends and note their characters in the following table. Fill in yours as well?

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?

2. Do you share more similar characters with your parents or with your friends?

3. Do you think that your differences from parents are same as differences from friends? Why / Why not?

1. Can you find two similar seeds there?

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

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

1. What is the number of long strip pairs?

2. What is the number of one long and one short pairs?

3. What is the number of short strips pairs?

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

5. What can you conclude from this game?

Observe the below diagram showing variation in beetle population and its impact?

What do you think will be condition of the beetles?

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

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

Question 1. When cross is done between pure yellow and pure green pea seed-producing plants the following results were obtained. (Y = yellow ; y = green)?

Questions given below based on the above table.

Questioni. Yy - indicates which colour of the seed?

Questionii. What is the Phenotypic ratio of the above cross?

Question 2. Observe the given How-chart and answer the

Question. Who decides the sex of the baby - mother or father? How?

Question 3. What examples will you give to prove that Lamarcklsm is not correct?

Question 4. Which chromosomes determine the sex in human beings?

Question 5. Why do we call appendix as a vestigial organ?

Question 6. What are variations?

Question 1.
When cross is done between pure yellow and pure green pea seed-producing plants the following results were obtained. (Y = yellow ; y = green)?

Questioni.
Yy - indicates which colour of the seed?

Questionii.
What is the Phenotypic ratio of the above cross?

Question 2.
Observe the given How-chart and answer the

Question 3.
What examples will you give to prove that Lamarcklsm is not correct?

Question 4.
Which chromosomes determine the sex in human beings?

Question 5.
Why do we call appendix as a vestigial organ?

Question 6.
What are variations?

Question 7.
What is F1 generation?

Question 8.
What is F2 generation?

Question 9.
What is F3 generation?

Question 10.
What is phenotyperatio?

Question 11.
What is genotype ratio?

Question 12.
State the law of Independent assortment?

Question 13.
What is allele?

Question 14.
Whatare genes?

Question 15.
What are homozygous alleles?

Question 16.
What is heterozygous allele?

Question 17.
What is law of dominance?

Question 18.
State the law of segregation?

Question 19.
What are inherited traits?

Question 20.
What is heredity?

Question 21.
What is Inheritance?

Question 22.
What are autosomes?

Question 23.
What are allosomes?

Question 24.
What are acquired characters?

Question 25.
What is inheritance of acquired characters?

Question 26.
What is meant by survival of the fittest?

Question 27.
What is micro evolution?

Question 28.
What is macro evolution or speclation?

Question 29.
What are homologous organs?

Question 30.
What are analogous organs?

Question 31.
What is embryology?

Question 32.
What are fossils?

Question 33.
What is Palaeontology?

Question 34.
What is the method used to determine the age of the fossil?

Question 35.
What is human evolution?

Question 36.
How do variations occur?

Question 37.
What is divergent evolution?

Question 38.
What is convergent evolution?

Question 39.
Where were the fossils of dinosaurs collected in our state from?

Question 40.
What are vestigial organs?

Question 41.
Who was the first person to propose the theory of evolution?

Question 42.
Who proposed the theory of Inheritance of acquired characters?

Question 43.
Who proved that the bodily changes which may occur due to environment wont be passed to its offsprings?